Blog archive

Thu

21

Mar

2019

Latest research in football - week 7 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Ankle Structures of Professional Soccer (Football) Players With Proximal Diaphyseal Stress Fractures of the Fifth Metatarsal
Reference: J Foot Ankle Surg. 2019 Feb 11. pii: S1067-2516(18)30428-9. doi: 10.1053/j.jfas.2018.09.024. [Epub ahead of print]
Authors: Kizaki K, Yamashita F, Mori D, Funakoshi N
Summary: Despite a high incidence of proximal diaphyseal stress fractures of the fifth metatarsal (zone 3) in soccer (football) players, studies that examine risk factors of the fractures in professional soccer players are scarce; in particular, ankle structures have not yet been investigated. This study was designed to investigate ankle structures of professional soccer players with proximal diaphyseal stress fractures of the fifth metatarsal. We reviewed the ankle radiographs of 100 professional soccer players (stress fractures n = 15; controls n = 85) and measured the medial malleolar slip angle (MMSA), the ratio of the medial malleolar length to the width of the talar dome (MML:TD ratio), the ratio of the lateral malleolar length to the width of the TD (LML:TD ratio), and the ratio of the MML to the LML (MML:LML ratio). The MMSA (p < .01: 28.7° ± 5.8° versus 23.0° ± 4.9°) in the stress fractures was significantly wider and the MML:TD ratio (p = .08: 0.49 ± 0.08 versus 0.52 ± 0.07) had a trend to be smaller compared with the values of the controls. Logistic regression analysis revealed that a wider malleolar slip angle became a factor associated with stress fractures in professional soccer players (p < .01: odds ratio 1.27, 95% confidence interval 1.110 to 1.463). Receiver operating characteristic curve with MMSA for the stress fractures was depicted with an area under the curve of 0.778, and the suitable cut-off point was set at MMSA >27° with a positive likelihood ratio of 3.67 (95% confidence interval 2.173 to 6.188). Our study results show that a wide MMSA was associated with proximal diaphyseal stress fractures of the fifth metatarsal in professional soccer players.


#2 The acute effects of a short technique-intense training period on side-foot kick performance among elite female soccer players
Reference: J Sports Med Phys Fitness. 2019 Feb 13. doi: 10.23736/S0022-4707.19.09449-0. [Epub ahead of print]
Authors: Carlsson M, Isberg J, Nilsson J, Carlsson T
Summary: Previously, it was shown that elite soccer teams were 24% more likely to win matches if their passing effectiveness were increased by 1%. However, research interventions aiming to improve passing performance are scarce. The current study aimed to investigate the effect of a short technique-intense training period on side-foot kick performance among elite female soccer players. Four side-foot kick tests were completed before and after a training period: kicking a stationary ball using match-relevant (SBRS) and maximal ball speed (SBMS), passing the ball on the move using match-relevant ball speed (RBRS), and repeated side-foot kicks onto a rebound-box with continuously increasing passing distance (RRB). The players were assigned to either the intervention group or the control group. The training intervention consisted of six 55-min training sessions with five side-foot kick exercises. Within-group and between-group differences were investigated using paired-samples t-test and Mann-Whitney U test, respectively. The intervention group improved the performance in the RBRS and RRB tests (both P < 0.05), but no differences were found for the SBRS and SBMS tests (both P > 0.05). No improvements were found for the control group independent of test condition (all P > 0.05). Significant between-group differences were found for the RBRS and RRB tests (both P < 0.05), whereas no differences were found for the SBRS and SBMS tests (both P > 0.05). The fundamental soccer skill of passing a moving ball was improved in elite female soccer players by a short technique-intense training period.


#3 Head Injury in Soccer: From Science to the Field; summary of the head injury summit held in April 2017 in New York City, New York
Reference: Br J Sports Med. 2019 Feb 13. pii: bjsports-2018-100232. doi: 10.1136/bjsports-2018-100232. [Epub ahead of print]
Authors: Putukian M, Echemendia RJ, Chiampas G, Dvorak J, Mandelbaum B, Lemak LJ, Kirkendall D
Summary: There has been an increased focus and awareness of head injury and sport-related concussion (SRC) across all sports from the medical and scientific communities, sports organisations, legislators, the media and the general population. Soccer, in particular, has been a focus of attention due to the popularity of the game, the frequency of SRC and the hypothesised effects of repetitive heading of the ball. Major League Soccer, US Soccer and the National Women's Soccer League jointly hosted a conference entitled, 'Head Injury in Soccer: From Science to the Field', on 21-22 April 2017 in New York City, New York. The mission of this conference was to identify, discuss and disseminate evidence-based science related to the findings and conclusions of the fifth International Conference on Concussion in Sport held by the Concussion in Sport Group and apply them to the sport of soccer. In addition, we reviewed information regarding the epidemiology and mechanism of head injuries in soccer at all levels of play, data regarding the biomechanics and effects of repetitive head impacts and other soccer-specific considerations. We discussed how to release the information raised during the summit to key stakeholders including athletes, parents, coaches and healthcare providers. We identified future areas for research and collaboration to enhance the health and safety of soccer (football) players.


#4 The use of adaptive neuro-stimulation for rebalancing posture and muscular tone in a soccer team
Reference: J Sports Med Phys Fitness. 2019 Feb 12. doi: 10.23736/S0022-4707.19.09311-3. [Epub ahead of print]
Authors: Barassi G, Bellomo RG, Porreca A, Giannuzzo G, Giannandrea N, Pezzi L, Crudeli M, Visciano C, Saggini R
Summary: Posture and somatic structure could positively influence athletic gestures for their biomechanical implications. Working on neuromuscular activity, offers the possibility of intervention on postural control. The aim is demonstrating the possibility of interacting with the human body system through the spinal reflex pathway, starting from the stimulation of cutaneous receptors. In this study, developed inside the Chair in Physical and Rehabilitative Medicine, at G. d'Annunzio University, twenty soccer players were recruited. Males between 25.5 ± 10.6 years old participated in this study. Patients were divided using a single-blind criterion into two groups, each containing ten subjects. The experimental group was treated with 2 pre-set programs 4 times a week with an Adaptive Neuro-Stimulation (ANS) able to interact with cutaneous receptors through an ENF Physio® device with a range of electrical frequency of about 15-350 Hz; the placebo-controlled group received the treatment with the device switched off. Patients performed a myometric evaluation with the MyotonPRO® system and a postural one with the Rarog system at T0 before the treatment and at T1 after the four-week treatment. After our intervention, we identified an improvement in muscular tone, in particular in the hamstring muscles (17.69%, R p<0.01 / L p<0.05 ) and a rebalancing of the principal bone points in the postural system (shoulder 71%, p<0.05, hips 65.6%, p=0.056, sagittal "AP" and frontal "LL" centre of gravity, respectively 40%, p<0.05 and 52.7%, p=0.01 ). In conclusion, we could hypothesise the usefulness of an Adaptive Neuro-Stimulation to act on these parameters. Clinical rehabilitation impact - Adaptive Neuro-Stimulation could be used not only for treatment of injuries but also in the field of prevention.


#5 Plantar pressures in male adolescent soccer players and its associations with bone geometry and strength
Reference: J Sports Med Phys Fitness. 2019 Feb 12. doi: 10.23736/S0022-4707.19.09267-3. [Epub ahead of print]
Authors: Lozano-Berges G, Matute-Llorente Á, Gómez-Bruton A, Alfaro-Santafé V, González-Agüero A, Vicente-Rodríguez G, Casajús JA
Summary: Mechanical loads exerted by soccer-specific actions increase bone remodeling activity. Nevertheless, little is known about the relationship between plantar pressure and bone structure. Therefore, the aim of this study was to compare bone geometry and strength between soccer players who exhibited different maximum values of the average pressures (MP) when performing a combination of soccer-specific tasks. Forty male adolescent soccer players (mean age 13.20.5 y) and 13 controls (mean age 13.10.9 y) participated in this study. Biofoot system was used to measure MP at the non-dominant foot during a circuit of soccer-specific tasks. Cluster analysis was performed to classify players into groups of similar MP profiles resulting two different groups as follows: 15 players with high MP (SOC-HP; mean MP: 392.768.2 kPa) and 25 with low MP (SOC-LP; mean MP: 261.049.6 kPa). Total and cortical volumetric bone mineral content (Tt.BMC/Ct.BMC), cross-sectional area (Tt.Ar/Ct.Ar), cortical thickness (Ct.Th), fracture load in X-axis, and polar strength index (SSIp) were measured at 38% of the non-dominant tibia by peripheral quantitative computed tomography. Bone geometry and strength comparisons between SOC-HP and SOC-LP were performed using analyses of covariance controlling by weight and tibia length. Greater Tt.BMC, Ct.BMC and Tt.Ar. were found in SOC-HP compared to CG (Tt.BMC: 3.22vs2.95 g, Ct.BMC: 2.95vs2.68 g, Ct.Ar: 280vs253 mm2; p<.05). Nevertheless, no significant bone geometry and strength differences were found between soccer groups and between SOC-LP and CG (p>.05). Developing high MP when training and playing soccer might be favourable to bone development.


#6 Sex-Related Hip Strength Measures Among Professional Soccer Players
Reference: J Strength Cond Res. 2019 Feb 7. doi: 10.1519/JSC.0000000000003003. [Epub ahead of print]
Authors: Hedt CA, Pearson JM, Lambert BS, McCulloch PC, Harris JD
Summary: Lower-extremity musculoskeletal injuries in soccer are common among sexes. However, it remains unknown whether differences between sexes exist with regard to absolute or relative hip strength and how these differences may relate to injury. In the current study, we performed a retrospective cross-sectional analysis of pre-season data from male (♂n = 21) and female (♀n = 19) professional United States soccer organizations. Two years of pre-season data were collected for peak strength of lower extremity and hip musculature (no duplicates used). A 2 × 2 multivariate analysis of variance was used to detect differences in hip strength between sexes and dominant compared with nondominant legs. For all significant multivariate effects indicated by Wilks lambda and follow-up univariate analysis, a Tukey's post hoc test was used for pairwise univariate comparisons. A 2-tailed independent-samples T-test was used for comparison of height, body mass, body mass index (BMI), mean leg length, and strength ratios between dominant and nondominant limbs between sexes. Type I error was set at α = 0.05 for all analyses. Height (♂183.1 ± 6.8 cm, ♀170.0 ± 5.5 cm), body mass (♂79.0 ± 8.7 kg, ♀65.1 ± 5.6 kg), BMI (♂23.5 ± 1.3 kg·m, ♀22.5 ± 1.4 kg·m), and mean leg length (♂95.5 ± 4.34 cm, ♀ 88.3 ± 3.24 cm) differed between groups (p < 0.05). Sex differences (p < 0.05) were also found for hip abduction (dominant ♂19.5 ± 3.6 kg, ♀17.3 ± 2.2 kg; nondominant ♂18.5 ± 3.7 kg, ♀16.0 ± 2.3 kg), adduction (dominant ♂19.8 ± 3.0 kg, ♀16.7 ± 2.3 kg; nondominant ♂20.1 ± 2.9 kg, ♀17.6 ± 2.9 kg), external rotation (dominant ♂21.7 ± 3.4 kg, ♀17.7 ± 2.4 kg; nondominant ♂21.6 ± 3.9 kg, ♀16.8 ± 2.1 kg), and dominant hamstring strength (♂27.9 ± 6.5 kg, ♀23.0 ± 4.9 kg). The ratio of hip internal to external rotation strength differed in the nondominant leg (♂1.1 ± 0.2, ♀0.9 ± 0.2, p < 0.05). No significant differences were found between males and females when measures were normalized to body mass. These findings provide baseline pre-season normative data for professional soccer athletes and indicate that strength differences can be expected among different sexes, but are attenuated with attention to body mass. Further research should indicate how pre-season strength measures relate to injury.


#7 Prevalence of Hamstring Strain Injury Risk Factors in Professional and Under-20 Male Football (Soccer) Players
Reference: J Sport Rehabil. 2019 Feb 12:1-23. doi: 10.1123/jsr.2018-0084. [Epub ahead of print]
Authors: Ribeiro-Alvares JB, Dornelles MP, Fritsch CG, de Lima-E-Silva FX, Medeiros TM, Severo-Silveira L, Marques VB, Baroni BM
Summary: Hamstring strain injury (HSI) is the most prevalent injury in football (soccer), and a few intrinsic factors have been associated with higher injury rates. The purpose was to describe the prevalence of the main intrinsic risk factors for HSI in professional and under-20 football players. One-hundred and one football players (52 professionals; 49 under-20) participated in this study. Anamnesis, hamstrings ultrasonography, passive straight-leg raise test, functional movement screen, and isokinetic dynamometry were performed. Eleven HSI risk factors for each leg were assessed, besides the player's age as a systemic risk factor. Reports were delivered to the coaching staff. Professionals had greater prevalence of HSI history compared to under-20 players (40% vs. 18%). No between-group differences were found for the other screening tests. Altogether, thirty percent of players had already sustained at least one HSI; 58% had history of injuries in adjacent regions; 49% had short biceps femoris fascicles; 66% and 21% had poor passive and active flexibility, respectively; 42% and 29% had deficits in functional movements and core stability, respectively; 7% and 26% presented bilateral imbalance for hamstring concentric and eccentric strength, respectively; 87% and 94% obtained low values for hamstring-to-quadriceps conventional and functional ratios, respectively. Two-thirds of players had 3 to 5 risk factors per leg. None of the players was fully free of HSI risk factors. Most football players present multiple risk factors for sustaining an HSI. Hamstring weakness is the most prevalent risk factor, but the teams should also be aware of deficits in flexibility, core stability, functional movements, and hamstring fascicle length.


#8 Hydrothermally Modified Corn Starch Ingestion Attenuates Soccer Skill Performance Decrements in the Second Half of a Simulated Soccer Match
Reference: Int J Sport Nutr Exerc Metab. 2019 Feb 12:1-26. doi: 10.1123/ijsnem.2018-0217. [Epub ahead of print]
Authors: Quinones MD, Lemon PWR
Summary: Hydrothermally modified non-GMO corn starch (HMS) ingestion may enhance endurance exercise performance via sparing carbohydrate oxidation. To determine whether similar effects occur with intermittent, high intensity exercise we investigated the effects of HMS ingestion prior to and at half time on soccer skill performance and repeated sprint ability during the later stages of a simulated soccer match. Eleven, male, university varsity, soccer players (177.7±6.8 cm, 77.3±7.9 kg, 22±3 y, 12.8±4.9 %BF, V̇O2max = 57.1±3.9 ml∙kg BM-1∙min-1) completed the match with HMS (8% CHO containing a total of 0.7 g∙kg BM-1∙h-1; 2.8 kcal∙kg BM-1∙h-1) or isoenergetic dextrose (DEX). Blood glucose was lower (p<0.001) with HMS at 15 (5.3 vs 7.7 mmol∙L-1) and 30 min (5.6 vs 8.3 mmol∙L-1) following ingestion, there were no treatment differences in blood lactate, and the respiratory exchange ratio was lower with HMS at 15 (0.84 vs 0.86, p = 0.003), 30 (0.83 vs 0.85, p = 0.004) and 45 min (0.83 vs 0.85, p = 0.007) of the first half. Repeated sprint performance was similar for both treatments (p>0.05) but soccer dribbling time was slower with DEX vs baseline (15.63 s vs 14.43 s, p < 0.05) but not so with HMS (15.04 vs 14.43 s, p > 0.05). Further, during the passing test, penalty time was reduced (4.27 s vs 7.73 s, p = 0.004) with HMS. During situations where glycogen availability is expected to become limiting, HMS ingestion pre-match and at half time could attenuate the decline in skill performance often seen late in contests.


#9 Are Soccer Players Older Now Than Before? Aging Trends and Market Value in the Last Three Decades of the UEFA Champions League
Reference: Front Psychol. 2019 Jan 28;10:76. doi: 10.3389/fpsyg.2019.00076. eCollection 2019.
Authors: Kalén A, Rey E, de Rellán-Guerra AS, Lago-Peñas C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6360147/pdf/fpsyg-10-00076.pdf
Summary: The aims of the current study were to analyze the evolution of players' age in the UEFA Champions League since the start of its modern-day format in 1992-1993 up until 2017-2018 and to determine how the players' age relates to their market value. The sample consisted of all players participating in the UEFA Champions League from the 1992-1993 to 2017-2018 seasons (n = 16062). The following variables were used in this study: players' age, number of seasons in the club, number of Champions Leagues won, team performance, and market value of the player in the season. Data were examined using a one-way ANOVA and a linear regression. The main finding of the current study is that an aging trend has occurred in the last three decades in the Champions League. A significant increase in average players' age (>1.6 years) was observed, rising from an age of 24.9 to 26.5 years. Goalkeepers and Center Backs tend to peak later than attackers, and their peak performance can last until an age of about 31 years. Finally, an inverted-U curve defines the association between market value and age, with peak value appearing in the 26-30 age range. These results provide useful information regarding at which age soccer players are likely to perform at the highest level, as well as the age they are likely to have the highest market value.


#10 Young Soccer Players With Higher Tactical Knowledge Display Lower Cognitive Effort
Reference: Percept Mot Skills. 2019 Feb 11:31512519826437. doi: 10.1177/0031512519826437. [Epub ahead of print]
Authors: Cardoso FDSL, González-Víllora S, Guilherme J, Teoldo I
Summary: The present study aimed to investigate whether the form and amount of declarative tactical knowledge (DTK) and procedural tactical knowledge (PTK) influence cognitive effort during soccer performance among young players. We assessed 36 male players from a Brazilian first-division soccer club; participants averaged 14.89 ( SD = 1.42) years of age. We evaluated DTK from video simulation tests and PTK through the System of Tactical Assessment in Soccer. We assessed cognitive effort by measures of pupil diameter using Mobile Eye Tracking-XG while players viewed soccer video scenes and made game-related play decisions. After the assessment of tactical knowledge, we categorized the sample according to players' tactical knowledge into participants with higher and lower PTK and higher and lower DTK. Subsequently, we examined the both PTK and DTK groups on cognitive effort. Our results suggest that tactical knowledge influences cognitive effort in that players with higher PTK and DTK displayed less cognitive effort during soccer performance tasks. In conclusion, we observed that PTK and DTK influenced the cognitive effort younger soccer players expended while viewing soccer scenes and making soccer performance decisions.


#11 Differences in Acceleration and High-Intensity Activities Between Small-Sided Games and Peak Periods of Official Matches in Elite Soccer Players
Reference: J Strength Cond Res. 2019 Feb 6. doi: 10.1519/JSC.0000000000003081. [Epub ahead of print]
Authors: Dalen T, Sandmæl S, Stevens TGA, Hjelde GH, Kjøsnes TN, Wisløff U
Summary: The purpose of this study was to compare whether the physical performance of players during 4 vs. 4 + goalkeeper (4 vs. 4) and 6 vs. 6 + goalkeeper (6 vs. 6) small-sided games (SSGs) is equivalent to those experienced during the most intense 5-minute period of soccer match play. Twenty-six male soccer players from an elite Norwegian league team took part. Players were monitored during 18 matches, 56 SSGs: twenty-eight 4 vs. 4 and twenty-eight 6 vs. 6 games. The ZXY Sport Tracking System was used to measure for each player the total distance covered, high-intensity running distance, sprint distance, number of accelerations, and player load (all expressed per minute). To compare the physical performance variables on players during the SSGs formats and match play, a 1-way analysis of variance with repeated measures was used. Players performed the same number of accelerations and player load in 4 vs. 4 (1.7 and 248, respectively) as in peak match (1.6 and 227, respectively), whereas in 6 vs. 6, there were 63% fewer accelerations and 15% lower player load (1.2 and 198, respectively), than in peak match. High-intensity running and sprint distance were significantly lower than mean match values in both 4 vs. 4 (4.1 and 0.2 m vs. 8.2 and 1.7 m) and 6 vs. 6 games (2.7 and 0.21 m vs. 8.2 and 1.7 m) (p < 0.05). In conclusion, only 4 vs. 4 SSGs are highly valuable, and in that, they elicit player load and accelerations to a level that is (at least) equivalent with peak periods of official match play.


#12 Effects of Plyometric Training on Physical Performance of Young Male Soccer Players: Potential Effects of Different Drop Jump Heights
Reference: Pediatr Exerc Sci. 2019 Feb 8:1-8. doi: 10.1123/pes.2018-0207. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, García-Pinillos F, Gentil P, Moran J, Pereira LA, Loturco I
Summary: The purpose was to compare the effects of plyometric drop jump (DJ) training against those induced by regular soccer training and assess the transference effect coefficient (TEC) of DJs ("trained exercises") performed from 20- (DJ20) and 40-cm (DJ40) height boxes with respect to different physical qualities (jumping, linear and change of direction speed, kicking, endurance, and maximal strength) in youth male soccer players. Participants were randomly divided into a control group (n = 20; age: 13.5 [1.9] y) and a DJ training group (n = 19; age: 13.2 [1.8] y), and trained for 7 weeks. A 2-way analysis of variance for repeated measures with the within-subject factor time (preintervention and postintervention) and between-subject factor group (intervention vs control) was performed. To calculate the TECs between the trained exercises (DJ20 and DJ40) and the physical tests, the ratio between the "result gains" (effect size [ES]) in the analyzed physical qualities and the result gains in the trained exercises were calculated. The TECs were only calculated for variables presenting an ES ≥ 0.2. Significant improvements (ES = 0.21-0.46; P < .05) were observed in the DJ training group, except in linear sprint performance. The control group improved only the maximal strength (ES = 0.28; P < .05). Significant differences were observed in all variables (ES = 0.20-0.55; P < .05) in favor of the DJ training group, except for maximal strength (group × time interaction). A plyometric training scheme based on DJs was able to significantly improve the physical performance of youth male soccer players. Overall, greater TECs were observed for DJ40 (0.58-1.28) than DJ20 (0.55-1.21).


#13 Vitamin D Supplementation and Physical Activity of Young Soccer Players during High-Intensity Training
Reference: Nutrients. 2019 Feb 6;11(2). pii: E349. doi: 10.3390/nu11020349.
Authors: Skalska M, Nikolaidis PT, Knechtle B, Rosemann TJ, Radzimiński Ł, Jastrzębska J, Kaczmarczyk M, Myśliwiec A, Dragos P, López-Sánchez GF, Jastrzębski Z
Download link: https://www.mdpi.com/2072-6643/11/2/349/pdf
Summary: The aim of this study was to confirm that vitamin D supplementation of young soccer players during eight-week high-intensity training would have a significant effect on their motion activity. The subjects were divided into two groups: the experimental one, which was supplemented with vitamin D (SG, n = 20), and the placebo group (PG, n = 16), which was not supplemented with vitamin D. All the players were subjected to the same soccer training, described as High-Intensity Interval Training (HIIT). The data of the vitamin D status, time motion parameters and heart rate were collected just before and after the intervention. A significant increase in 25(OH)D concentration (119%) was observed in the supplemented group, while the non-supplemented group showed a decrease of 8.4%. Based on the obtained results, it was found that physical activity indicators in the players were significantly improved during small-sided games at the last stage of the experiment. However, taking into account the effect of supplementation with vitamin D, there were no statistically significant differences between the placebo and the supplemented groups; thus, the effect size of the conducted experiment was trivial.

Mon

18

Mar

2019

Latest research in football - week 6 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Design, Validation, and Reliability of an Observation Instrument for Technical and Tactical Actions of the Offense Phase in Soccer
Reference: Front Psychol. 2019 Jan 24;10:22. doi: 10.3389/fpsyg.2019.00022. eCollection 2019.
Authors: Ortega-Toro E, García-Angulo A, Giménez-Egido JM, García-Angulo FJ, Palao JM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353797/pdf/fpsyg-10-00022.pdf
Summary: The use of observational methodology in the sports context provides coaches and other sports professionals with flexible tools that adapt to their needs. In collective sports, the use of these instruments is common for the technical and tactical analysis of the game. Based on the importance of data quality in these instruments, the purpose was to design, validate, and test the reliability of a mixed observational instrument of field formats and category systems to analyze technical and tactical actions in the offense phase in soccer. The instrument collects information regarding the actions with the ball, moment of the play (start, development, and end), and contextual situation for the offensive team and for the goalkeeper. The instrument design, validation, and reliability calculation were done in four stages: (a) review of the literature, (b) design the first draft of the instrument, (c) experts' qualitative and quantitative review of the instrument, and (d) observer training test (reliability calculation). The content validity was established by 12 experts (Ph.D. in sports science or soccer coach with at least of 10 years of coaching experience). The Delphi methodology was used. Experts did a quantitative (scale 0-10) and qualitative evaluation. Experts were asked about: (a) comprehension of the criteria, categorical cores, degree of openness, and their definitions, (b) pertinence of categorical cores and degree of openness, and (c) whether to include other categorical cores or degree of openness in the observation instrument. The lowest Aiken's V index was 0.91 for the categorical core "numerical situation with opponent goalkeeper." The inter- and intra-observer reliability presented good levels of agreement. The lowest Kappa index was 0.96 for the inter-reliability in the categorical core "defensive pressing lines" and was 0.98 for the intra-reliability in the categorical core "ball height (start of ball possession)," "distance of the defensive player," "ball height (end of ball possession)," "numerical situation," and "defensive pressing lines." The coefficients of the generalizability analysis showed a high level of accuracy, validity and reliability of the instrument. The results show that the instrument allows to obtain objective, valid and reliable information about the offensive phase in soccer.


#2 Change-of-direction, speed and jump performance in soccer players: a comparison across different age-categories
Reference: J Sports Sci. 2019 Feb 6:1-7. doi: 10.1080/02640414.2019.1574276. [Epub ahead of print]
Authors: Loturco I, Jeffreys I, Abad CCC, Kobal R, Zanetti V, Pereira LA, Nimphius S
Summary: This study examined the age-specific development of vertical jump height, straight and change-of-direction (COD) speed, and COD deficit in one-hundred and eighty-two elite soccer players from different age-categories (U15, U17, U20, and Senior). All participants were players of two distinct clubs and were undertaking different training routines, as planned by their technical staff members. For this purpose, the soccer players performed: (1) squat and countermovement jumps; (2) a maximal 20-m linear sprint speed test, and (3) the Zigzag COD test. The magnitude-based inference approach and standardized differences were used to compare the age-groups. Sprint speed at longer distances (20-m) increased progressively across the age-ranges. In contrast, speed and acceleration performances at shorter distances (5-m) were better in U15 than in the other age-categories. The COD speed did not change throughout the younger categories but presented a meaningful decrease in the Senior category. Surprisingly, despite the progressive increase in volume and intensity of neuromuscular training from younger to older categories, the COD deficit presented a gradual increase across the age-groups. It is possible that simple modulation of the strength-power training program during the maturation process is not sufficient to produce faster adult players with enhanced ability to change direction. Therefore, coaches are strongly encouraged to implement specific COD training practices to tolerate braking at increasing running speeds and appropriate volume and intensity of soccer specific training throughout the players' specialization process.


#3 Prevalence of labrum and articular cartilage injuries of the hip on 3T magnetic resonance imaging of asymptomatic elite soccer players
Reference: Rev Esp Cir Ortop Traumatol. 2019 Feb 2. pii: S1888-4415(18)30173-5. doi: 10.1016/j.recot.2018.10.008. [Epub ahead of print] [Article in English, Spanish]
Authors: Márquez WH, Gómez-Hoyos J, Gallo JA, Espinosa B, Rivas N, Llano JF, Osorio J, Martin HD
Summary: The purpose was to establish the prevalence of lesions of the labrum and articular cartilage of the hip in asymptomatic elite soccer players by performing 3T magnetic resonance imaging. Eighty-four asymptomatic hips of 42 professional soccer players were evaluated. Male subjects older than 18 years were included. Cam and pincer deformity were defined as an alpha angle greater than 55 degrees and a lateral centre edge angle greater than 39 degrees, respectively. Labral injuries were classified with the Czerny classification and cartilage damage was classified with the Outerbridge classification. Specific statistical tests were used to establish the relationship between anatomical variances of the hip and the presence of chondral and labral injuries. FAI morphology prevalence was 25%. Abnormalities such as cam (22.5%) and labral injuries (33.8%) were found. Those cases with reported labral injury were predominantly intrasubstance damage (18.8%). Anatomical features of FAI were found to be related to lesions of the femoral cartilage (P<.001), chondrolabral damage (P=.042), or both injuries (P<.001). Asymptomatic labral or cartilaginous injuries of the hip were reported in 25% of the included professional soccer players. These injuries were associated with anatomical features of FAI.


#4 Effects of playing position, pitch location, opposition ability and team ability on the technical performance of elite soccer players in different score line states
Reference: PLoS One. 2019 Feb 5;14(2):e0211707. doi: 10.1371/journal.pone.0211707. eCollection 2019.
Authors: Redwood-Brown AJ, O'Donoghue PG, Nevill AM, Saward C, Sunderland C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0211707&type=printable
Summary: The purpose of this study was to investigate the effects of playing position, pitch location, team ability and opposition ability on technical performance variables (pass, cross, corner, free kick accuracy) of English Premier League Soccer players in difference score line states. A validated automatic tracking system (Venatrack) was used to code player actions in real time for passing accuracy, cross accuracy, corner accuracy and free kick accuracy. In total 376 of the 380 games played during the 2011-12 English premier League season were recorded, resulting in activity profiles of 570 players and over 35'000 rows of data. These data were analysed using multi-level modelling. Multi-level regression revealed a "u" shaped association between passing accuracy and goal difference (GD) with greater accuracy occurring at extremes of GD e.g., when the score was either positive or negative. The same pattern was seen for corner accuracy away from home e.g., corner accuracy was lowest when the score was close with the lowest accuracy at extremes of GD. Although free kicks were not associated with GD, team ability, playing position and pitch location were found to predict accuracy. No temporal variables were found to predict cross accuracy. A number of score line effects were present across the temporal factors which should be considered by coaches and managers when preparing and selecting teams in order to maximise performance. The current study highlighted the need for more sensitive score line definitions in which to consider score line effects.


#5 Age-related differences in flexibility in soccer players 8-19 years old
Reference: PeerJ. 2019 Jan 29;7:e6236. doi: 10.7717/peerj.6236. eCollection 2019.
Authors: Cejudo A, Robles-Palazón FJ, Ayala F, De Ste Croix M, Ortega-Toro E, Santonja-Medina F, Sainz de Baranda P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357869/pdf/peerj-07-6236.pdf
Summary: Muscle flexibility is a main component of health-related fitness and one of the basic components of fitness for the performance in some sports. Sport and health professionals require the flexibility profile of soccer to define quantitative aims in the training of flexibility. The aim of this study was to identify age-related differences in lower extremity flexibility in youth soccer players. Seventy-two young male soccer players (age: 13.0 ± 3.1 y; body mass: 50.5 ± 15.3 kg; stature 158.2 ± 16.8 cm; BMI: 19.6 ± 2.6 kg/m2) completed this study. Measures of eleven passive hip (hip extension (HE), hip adduction with hip flexed 90°(HAD-HF90°), hip flexion with knee flexed (HF-KF) and extended (HF-KE), hip abduction with hip neutral (HAB) and hip flexed 90°(HAB-HF90°), hip external (HER) and internal (HIR) rotation), knee (knee flexion (KF)) and ankle dorsiflexion (ankle dorsiflexion with knee flexed (ADF-KF) and extended (ADF-KE)) ranges of motion (ROM) were taken. Descriptive statistics were calculated for hip, knee and ankle ROM measured separately by leg (dominant and non-dominant) and age-group (U10, U12, U14, U16 and U19). The data was analysed using a one-way analysis of variance (ANOVA) to examine the interaction of 11 ROM in the different players' age-group. Generally, U10 and/or U12 soccer players obtain the highest mean value in almost all ROM evaluated (U10: HAD-HF [39.6° ± 4.3°], ADF-KE [32.3° ± 4.1°], HER [63.5° ± 5.6°] and HAB-HF90°[64.1° ± 7.5°]; U12: HE [17.7° ± 6.2°], HAB [35.6° ± 3.0], HIR [60.8° ± 4.7°] and KF [133.8° ± 7.1°]). Nonetheless, significant differences between the players' age-groups are just found in HAD-HF90°(p = .042; ES = .136), HAB (p = .001; ES = .252), HIR (p = .001; ES = .251), HER (p < .001; ES = .321) and HAB-HF90°(p < .001; ES = .376) ROM, showing a progressive and irregular decrease in these ROM until the U19 team. The findings of this study reinforce the necessity of prescribing exercises aimed at improving HAD-HF90°  ROM in U16, HAB ROM in U14, HIR ROM in U16 and U19, HER ROM in U12 and U19, and HAB-HF90°  ROM in U16 and U19 players within everyday soccer training routines.


#6 Effects of the long-term consumption of hydrogen-rich water on the antioxidant activity and the gut flora in female juvenile soccer players from Suzhou, China
Reference: Med Gas Res. 2019 Jan 9;8(4):135-143. doi: 10.4103/2045-9912.248263. eCollection 2018 Oct-Dec.
Authors: Sha JB, Zhang SS, Lu YM, Gong WJ, Jiang XP, Wang JJ, Qiao TL, Zhang HH, Zhao MQ, Wang DP, Xia H, Li ZW, Chen JL, Zhang L, Zhang CG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352569/pdf/MGR-8-135.pdf
Summary: Expending a considerable amount of physical energy inevitably leads to fatigue during both training and competition in football. An increasing number of experimental findings have confirmed the relationship between the generation and clearance of free radicals, fatigue, and exercise injury. Recently, hydrogen was identified as a new selective antioxidant with potential beneficial applications in sports. The present study evaluated the effect of 2-month consumption of hydrogen-rich water on the gut flora in juvenile female soccer players from Suzhou. As demonstrated by enzyme linked immunosorbent assay and 16S rDNA sequence analysis of stool samples, the consumption of hydrogen-rich water for two months significantly reduced serum malondialdehyde, interleukin-1, interleukin-6, tumour necrosis factor-α levels; then significantly increased serum superoxide dismutase, total antioxidant capacity levels and haemoglobin levels of whole blood. Furthermore, the consumption of hydrogen-rich water improved the diversity and abundance of the gut flora in athletes. All examined indices, including the shannon, sobs, ace, and chao indices, were higher in the control group than those proposed to result from hydrogen-rich water consumption prior to the trial, but these indices were all reversed and were higher than those in the controls after the 2-month intervention. Nevertheless, there were some differences in the gut flora components of these two groups before the trial, whereas there were no significant changes in the gut flora composition during the trial period. Thus, the consumption of hydrogen-rich water for two months might play a role modulating in the gut flora of athletes based on its selective antioxidant and anti-inflammatory activities.


#7 Effects of a multifactorial injuries prevention program in young Spanish football players
Reference: J Sports Med Phys Fitness. 2019 Feb 5. doi: 10.23736/S0022-4707.19.09219-3. [Epub ahead of print]
Authors: Chena M, Rodríguez ML, Bores AJ, Ramos-Campo DJ
Summary: The high injury rate in football has highlighted the need to research strategies that allow the modification of the dynamic risk factors. Most of the preventive proposals have focused on standardized protocols. However, the aim of this study was to evaluate the effect of a multifactorial injuries prevention program (MC-7) in Spanish football players. A total of 219 Spanish football male players aged 16-23 were studied. The study was conducted over two consecutive seasons (2012-2013, 2013-2014). The first season was the control season (SC) and the second one was the experimental season (ES). Injuries were recorded prospectively during the two seasons in accordance with the criteria established by the consensus statement. During CS the injuries were just observed, while during ES, the players participated in the MC-7: training methodology, specific warm-up protocol (FIFA 11+), basic injury recovery strategies, continuous training of coaches, conferences for parents/family and education sessions for players. The frequency of injuries was significantly reduced by 63.8% in the ES. Muscle-tendon and joint injuries were reduced by 65% and 56.7% respectively, with a significant decrease in the lower-limbs injuries. The incidence of injuries was reduced by 71.4%, with significant differences in the typology, location and severity of injuries. The rate of injury in football is reduced when multifactorial strategies are applied. Reducing the frequency and severity of injuries allowed players to greatly increase their available for sports practice.


#8 ACTN3 single nucleotide polymorphism is associated with non-contact musculoskeletal soft-tissue injury incidence in elite professional football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Feb 5. doi: 10.1007/s00167-019-05381-x. [Epub ahead of print]
Authors: Clos E, Pruna R, Lundblad M, Artells R, Esquirol Caussa J
Summary: Muscle injuries are common in professional football, even though prevention protocols are being implemented. Genetics constitutes a novel field for studying intrinsic injury risks and performance. Since previous studies involving single nucleotide polymorphisms (SNPs) have shown that SNPs influence muscle injury rate, injury severity and recovery time, the aim was to study the association the SNP of ACTN3 has with those parameters in professional football players. The medical staff team recorded non-contact musculoskeletal soft-tissue injuries in 43 professional football players in 7 different seasons (2007-2012 and 2015-2016). Injury rate, injury severity and injury recovery times were established. Players were genotyped by extracting DNA from a blood sample and using a polymerase chain reaction. Injury rate was associated with the SNP of ACTN3 (p = 0.003). The 577R allele was more frequent in subjects than in a normal population by showing presence in 93% of the subjects and suggesting that it could influence football performance. No statistically significant differences in injury severity and recovery time were associated with the SNP of ACTN3. Genetics is gaining in importance when assessing injury risk and performance in professional football. ACTN3 can be regarded as a biomarker of injury susceptibility in this discipline. Identifying those players with the highest injury susceptibility through genetics could lead football teams to individualise workloads and prevention protocols.


#9 Relationships between Anxiety, Emotional Intelligence, and Motivational Climate among Adolescent Football Players
Reference: Sports (Basel). 2019 Feb 1;7(2). pii: E34. doi: 10.3390/sports7020034.
Authors: Castro-Sánchez M, Zurita-Ortega F, Ubago-Jiménez JL, González-Valero G, Chacón-Cuberos R
Summary: Emotional and motivational factors are fundamental in the context of sport, as they directly relate to sports performance and anxiety. The present study aimed to analyze the relationships between motivational climate (MC), emotional intelligence (EI), and anxiety within a sample of footballers playing at a low level. The sample was composed of 282 registered football players aged between 16 and 18 years old (16.96 ± 0.77), playing in the lower tier in the province of Jaen (Spain). Data were self-reported, with participants responding to the Perceived Motivational Climate in Sport Questionnaire (PMCSQ-2), the Schutte Self-Report Inventory (SSRI), and the State Trait Anxiety Inventory (STAI). The results showed that footballers who reported higher levels of state anxiety and trait anxiety also demonstrated lower EI and more negatively perceived and regulated their emotions. Moreover, an ego-oriented climate was associated with higher levels of anxiety, while a task-oriented climate was related to lower levels of anxiety and higher levels of EI. No relationship was identified between the emotional aspects of young footballers and holding a motivational orientation toward an ego climate. Football players who more greatly perceived a task-oriented climate had higher EI and usually reported lower levels of anxiety related to sport performance. It is therefore important to promote intrinsic motivations and develop the capacity of footballers to regulate their own emotions.


#10 A Brazilian Football Player Still on the Pitch After 10 Years of Parkinson's Disease with Severe Freezing of Gait
Reference: Mov Disord Clin Pract. 2014 Dec 6;2(1):43-44. doi: 10.1002/mdc3.12110. eCollection 2015 Mar.
Authors: Vale TC, Pedroso JL, Barsottini OG, Lees AJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353400/pdf/MDC3-2-43.pdf

Sun

03

Mar

2019

Latest research in football - week 5 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Immediate effects and one-week follow-up after neuromuscular electric stimulation alone or combined with stretching on hamstrings extensibility in healthy football players with hamstring shortening
Reference: J Bodyw Mov Ther. 2019 Jan;23(1):16-22. doi: 10.1016/j.jbmt.2018.01.017. Epub 2018 Feb 2.
Authors: Espejo-Antúnez L, Carracedo-Rodríguez M, Ribeiro F, Venâncio J, De la Cruz-Torres B, Albornoz-Cabello M
Summary: The purpose was to assess the immediate and mid-term (after 7 days) effects of electric current combined with simultaneous muscle stretching (EME technique) per comparison to the isolated use of the same current (without applying simultaneous muscle stretching), over the hamstring extensibility in football players with hamstring shortening, and to estimate the clinical benefit of the interventions according to the muscular extensibility. Forty-eight participants were randomized to receive one session of EME technique (n = 26) or one session of the electrical current (EC) alone (n = 22). The measurement of the hamstrings extensibility through the active knee test was carried out before and immediately after each intervention and one week later. A significant interaction group x time was observed (F2,84 = 7.112, p = 0.001; partial eta squared = 0.145). The hamstrings extensibility changed significantly immediately after the EME technique (147.3° ± 16.4° to 153.5° ± 14.2°, p < 0.05), but not after the EC only (144.2 ± 10.2° to 141.7 ± 7.8°, p > 0.05). One week after the intervention no significant differences were found to the baseline values in both groups. The number needed to treat to prevent one new case of hamstring shortening was 3. The combination of electric current with simultaneous stretching is an effective technique to acutely increase the hamstring extensibility of football players with hamstring shortness.


#2 Sudden cardiac death in football players: Towards a new pre-participation algorithm
Reference: Exp Ther Med. 2019 Feb;17(2):1143-1148. doi: 10.3892/etm.2018.7041. Epub 2018 Nov 30.
Authors: Mavrogeni SI, Tsarouhas K, Spandidos DA, Kanaka-Gantenbein C, Bacopoulou F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6327574/pdf/etm-17-02-1143.pdf
Summary: Athletic pre-participation screening is essential for minimizing the risk for sudden cardiac death (SCD) in athletes participating in either competitive or leisure sporting activities. The primary causes of SCD in young athletes (<35 years of age) include hypertrophic cardiomyopathy, congenital anomalies of the coronary artery and arrhythmogenic right ventricular cardiomyopathy. Other abnormalities, such as malignant arrhythmia due to blunt trauma to the chest (commotio cordis), myocarditis, valvular disease, aortic rupture (in Marfan syndrome) and ion channelopathies (catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, long or short QT syndrome), also contribute to a lesser degree to SCD. Currently, clinical assessment, electrocardiogram (ECG) and echocardiography are the cornerstones of the pre-participation athletic evaluation. However, their low sensitivity raises queries as regards the need for the application of more sophisticated modalities, such as cardiovascular magnetic resonance (CMR). CMR offers precise biventricular assessment and is greatly reproducible without the inherent limitations of echocardiography; i.e., low quality of images due to the lack of appropriate acoustic window or operator's experience. Furthermore, myocardium replacement fibrosis, indicative of patients' increased risk for future cardiac events, can be effectively detected by late gadolinium enhanced (LGE) images, acquired 15 min post-contrast injection. Finally, diffuse myocardial fibrosis not identified by LGE, can also be detected by pre-contrast (native) T1, post-contrast T1 mapping and extracellular volume images, which provide detailed information about the underlying pathophysiologic background. Therefore, CMR is recommended in all football players with a positive family or personal history of syncope or SCD, abnormal/doubtful ECG or echocardiogram.


#3 Asthma and youth soccer: an investigation into the level of asthma awareness and training among youth soccer coaches
Reference: Open Access J Sports Med. 2019 Jan 15;10:17-31. doi: 10.2147/OAJSM.S182178. eCollection 2019.
Authors: Sadasivan C, Cave A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339450/pdf/oajsm-10-017.pdf
Summary: Asthma is the most common chronic disease among children. Exercise-induced bronchoconstriction which is common in asthmatic patients also occurs in individuals with no prior asthma diagnosis. Despite this and the fact that soccer is a high ventilation sport, there are no validated asthma management protocols in place for soccer coaches. This study aims to address 1) soccer coaches' current knowledge on asthma, 2) whether there is a need for asthma-related training, and 3) any barriers to administration of such training. A total of 2,300 volunteer youth soccer coaches from the Edmonton Minor Soccer Association (EMSA) were invited to participate in completing a 22-question online survey. The survey was open for 1 month from June 8, 2018, to July 8, 2018. There was a response rate of 22% (513 of 2,300). Respondents were on average, inexperienced coaches, coached younger age groups, and approximately one-third of respondents had personal experience with asthma (either themselves or their child had asthma). 93% of respondents had not received any asthma-related training at any coaching level, whether it be from EMSA or the Alberta Soccer Association. Coaches had strong knowledge on how to treat asthma attacks, but mixed levels of knowledge on asthma attack prevention. Experienced coaches were better at identifying the number of players with asthma on their team and the number of asthma-related incidents they had encountered as coaches. Coaches demonstrated a receptive attitude toward receiving asthma-related training, with 91% of respondents saying training would be beneficial and 69% of respondents saying training should be mandatory. The results of this study indicate that soccer coaches have limited knowledge regarding asthma management, acknowledge a need for asthma-related training, and are willing to participate in and could benefit from educational interventions as it pertains to their roles as coaches.


#4 Electrocardiographic and echocardiographic evaluation of a large cohort of peri-pubertal soccer players during pre-participation screening
Reference: Eur J Prev Cardiol. 2019 Jan 29:2047487319826312. doi: 10.1177/2047487319826312. [Epub ahead of print]
Authors: Calò L, Martino A, Tranchita E, Sperandii F, Guerra E, Quaranta F, Parisi A, Nigro A, Sciarra L, Ruvo E, Casasco M, Pigozzi F
Summary: The early diagnosis of cardiac abnormalities in young athletes may be helpful not only to identify subjects potentially at risk of sudden cardiac death but also to prevent stress-related cardiac dysfunction and cardiovascular events during the life of these subjects. The aim of our study was to investigate the prevalence of cardiac abnormalities in a population of young male soccer players undergoing pre-participation screening through electrocardiogram and trans-thoracic echocardiography. All consecutive male football players undergoing pre-participation screening comprehensive of medical history, physical examination, 12-lead electrocardiogram and trans-thoracic echocardiography at the FMSI Sport Medicine Institute in Rome between January 2008-March 2009 were enrolled in the study. Overall, 2261 consecutive young athletes aged 12.4 ± 2.6 years were evaluated. Training-unrelated electrocardiogram abnormalities were observed in 65 (2.9%) athletes. Abnormal trans-thoracic echocardiography was observed in 102 athletes (4.5%), including two cases of hypertrophic cardiomyopathy, eight of mild left ventricular hypertrophy, six of mild left ventricular dilation and 17 of bicuspid aortic valve. An abnormal electrocardiogram was associated with anomalous trans-thoracic echocardiography in 11/65 (16.9%) cases. All athletes requiring sport disqualification were identified by electrocardiogram. Notably, among 2216 athletes with a normal electrocardiogram, 91 had abnormal trans-thoracic echocardiography, including six cases of left ventricular dilation and six of ventricular hypertrophy. In a wide population of peri-pubertal male athletes, evaluation of the electrocardiogram identified all cardiac diseases requiring sport disqualification. Trans-thoracic echocardiography alone allowed the identification of cardiac abnormalities potentially leading to cardiomyopathies or major cardiovascular events over time.


#5 Ecological and Construct Validity of a Repeated Sprint Test in Male Youth Soccer Players
Reference: J Strength Cond Res. 2019 Jan 23. doi: 10.1519/JSC.0000000000003047. [Epub ahead of print]
Authors: Fernandes-Da-Silva J, Castagna C, Teixeira AS, Carminatti LJ, Francini L, Póvoas SCA, Antonacci Guglielmo LG
Summary: This study aimed to examine the relationship between a repeated sprint ability (RSA) test (5 bouts of 30-m sprints interspersed by 30 seconds of recovery) and match-related physical performance in male youth soccer players. Although 60 outfield players were evaluated, only data from players who participated in the full matches (n = 39) were retained (8 central defenders, 7 external defenders, 8 central midfielders, 8 external midfielders, and 8 forwards). To verify the ecological validity of this RSA protocol, the association between the best (RSAbest) and mean (RSAmean) sprint time in the 5 × 30-m and physical match performance during friendly youth soccer games was examined. Physical match demands were assessed using global positioning system technology (10 Hz) considering distance covered in selected arbitrary speed categories. The absolute speed thresholds were the same for all the players. Players were categorized into 2 groups based on the 5 × 30-m performance: RSAmean times below (i.e., faster) and above (i.e., slower) the median value. Players with faster RSAmean times covered significantly more distance sprinting during friendly matches (606 ± 204 m, +47.0%; t = 4.953; effect size = 1.88, 1.24; 2.52, p ≤ 0.001) compared to their slower counterparts (322 ± 145 m). A large negative correlation (r = -0.63, -0.77; -0.44, p ≤ 0.001) was found between RSAbest time (4.59 ± 0.27 seconds) and match sprint distance (457 ± 229 m). Likewise, RSAmean time (4.76 ± 0.25 seconds) was also largely associated (r = -0.60, -0.75; -0.39; p ≤ 0.001) with in-game sprinting performance. The results of this study provided evidence to support the construct and ecological validity of the 5 × 30-m protocol in male youth soccer players. Furthermore, differences in 5 × 30-m performance explained the amount of sprinting activity performed during the match.


#6 Accuracy of Anthropometric Equations to Estimate DXA-Derived Skeletal Muscle Mass in Professional Male Soccer Players
Reference: J Sports Med (Hindawi Publ Corp). 2019 Jan 1;2019:4387636. doi: 10.1155/2019/4387636. eCollection 2019.
Authors: González-Mendoza RG, Gaytán-González A, Jiménez-Alvarado JA, Villegas-Balcázar M, Jáuregui-Ulloa EE, Torres-Naranjo F, López-Taylor JR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6332936/pdf/JSM2019-4387636.pdf
Summary: Several anthropometric equations that estimate skeletal muscle mass (SMM) have been published, but their applicability and accuracy among athletes are still uncertain. The purpose was to assess the accuracy of different anthropometric equations that estimate SMM in professional male soccer players, as compared to dual-energy X-ray absorptiometry (DXA) as the reference method. In this cross-sectional study, we evaluated 179 professional male soccer players aged between 18 and 37 years. Anthropometric measurements (height, body weight, skinfold thicknesses, and girths) and a DXA whole body scan were performed the same day for each participant, and SMM was estimated with nine anthropometric equations (Heymsfield, Martin, Doupe, Kerr, Drinkwater, Lee, De Rose, and two equations published by Kuriyan). To determine differences between SMM estimated with anthropometric equations and SMM evaluated with DXA, a Kruskal-Wallis test was performed using Dunn's test as post hoc. The significance level was set at p < 0.05. We calculated the mean difference and 95% limits of agreement for the analyzed equations (Equation - DXA). Only Heymsfield's and Lee's equations showed no significant differences with DXA. Heymsfield's equation had the smallest mean difference (-0.17 kg), but wider limits of agreement with DXA (-6.61 to 6.94 kg). Lee's equation had a small mean difference (1.10 kg) but narrower limits of agreement with DXA (-1.83 to 4.03 kg). In this study, the prediction equation published by Lee et al. showed the best agreement with DXA and is able to estimate SMM accurately in professional male soccer players.


#7 Management of concussion in soccer
Reference: Acta Neurochir (Wien). 2019 Jan 28. doi: 10.1007/s00701-019-03807-6. [Epub ahead of print]
Authors: Hubertus V, Marklund N, Vajkoczy P
Summary: When participating in contact sports, (mild) head trauma is a common incident-observed in both professional and amateur sports. When head trauma results in transient neurological impairment, a sports-related concussion has occurred. Acute concussion, repetitive concussions, as well as cumulative "sub-concussive" head impacts may increase the risk of developing cognitive and behavioral deficits for athletes, as well as accelerated cerebral degeneration. While this concept has been well established for classic contact sports like American Football, Rugby, or Boxing, there is still an awareness gap for the role of sports-related concussion in the context of the world's most popular sport-Soccer. Here, we review the relevance of sport-related concussion for Soccer as well as its diagnosis and management. Finally, we provide insight into future directions for research in this field. Soccer fulfills the criteria of a contact sport and is characterized by a high incidence of concussion. There is ample evidence that these events cause functional and structural cerebral disorders. Furthermore, heading, as a repeat sub-concussive impact, has been linked to structural brain changes and neurocognitive impairment. As a consequence, recommendations for the diagnosis and management of concussion in soccer have been formulated by consensus groups. In order to minimize the risk of repetitive concussion in soccer the rapid and reliable side-line diagnosis of concussion with adoption of a strict remove-from-play protocol is essential, followed by a supervised, graduated return-to-play protocol. Recent studies, however, demonstrate that adherence to these recommendations by players, coaches, clubs, and officials is insufficient, calling for stricter enforcement. In addition, future research to solidify the pathophysiological relevance of concussion for soccer athletes seems to be needed. Advanced neuroimaging and neurochemical biomarker analyses (e.g. S100β, tau and neurofilament light (NfL)) may assist in detecting concussion-related structural brain changes and selecting athletes at risk for irreversible damage. Sports-related concussion represents a genuine neurosurgical field of interest. Given the high socioeconomic relevance, neurosurgeons should get involved in prevention and management of concussion in soccer.


#8 Training Loads and RSA and Aerobic Performance Changes During the Preseason in Youth Soccer Squads
Reference: J Hum Kinet. 2018 Dec 31;65:235-248. doi: 10.2478/hukin-2018-0032. eCollection 2018 Dec.
Authors: Cetolin T, Teixeira AS, Netto AS, Haupenthal A, Nakamura FY, Guglielmo LGA, da Silva JF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341967/pdf/hukin-65-235.pdf
Summary: The aims of this study were to compare the internal training load (ITL) in soccer players of two competitive age groups (under-15 [U-15] and under-19 [U-19]) during an 8-week preseason training period and compare the associated changes in physical performance measures. Eighteen U-15 and twelve U-19 players were monitored over an 8-week period during the preseason phase. The ITL was monitored using the session rating of perceived exertion (RPE) method. Before and after the preseason period, physical performance was assessed by best (RSAbest) and mean (RSAmean) times in a repeated sprint ability (RSA) test and peak velocity derived from the Carminatti test (PVT-CAR). Total weekly ITL increased with age (U-15: 13770 ± 874 AU vs. U-19: 33584 ± 2506 AU; p < 0.001). In addition, U-19 players perceived training sessions as heavier than U-15 players (6.1 ± 0.3 vs. 5.3 ± 0.3 AU, respectively; p < 0.001). After the preseason period, very likely to almost certainly positive changes were observed for all performance measures in both age groups. However, the U-15 group had possibly superior gains in RSAbest (+1.40%, 90%CL -0.29 to 3.05, with ES = 0.35) and likely higher effects in RSAmean (+1.89%, 90%CL 0.04 to 3.70, with ES = 0.53) and PVT-CAR (+2.71%, 90%CL 0.35 to 5.01, with ES = 0.37) compared to the U-19 group. In conclusion, our findings demonstrate that the U-19 group accumulate higher total weekly ITLs than the U-15 group during the preseason phase due to longer and heavier training sessions. However, the U-15 group obtained superior gains in soccer-specific physical abilities while accumulating half the total ITLs during lighter training sessions.


#9 Relative Age Effect and Long-Term Success in the Spanish Soccer and Basketball National Teams
Reference: J Hum Kinet. 2018 Dec 31;65:197-204. doi: 10.2478/hukin-2018-0027. eCollection 2018 Dec.
Authors: López de Subijana C, Lorenzo J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341957/pdf/hukin-65-197.pdf
Summary: The aims of this study were: i) to analyze whether relative age effect occurs in the athletes of the junior national teams and professional athletes in Spain in general and in soccer and basketball, and ii) to compare the long-term success of the players selected for the junior national team between these sports. The samples for this study were Spanish professional soccer (n = 461) and basketball (n = 250) players in the 2013-2014 premier league and players from the junior Spanish soccer (i.e., n = 273; U-17: n = 107; U-19: n = 166) and basketball (i.e., n = 240; U-18: n = 120, U-16: n = 120) teams that classified to play in the European Championships (from 2004 to 2013). Junior players (42.3%) were more frequently born in the 1st quarter of the year than the professional players (30.7%) (χ2(3) = 30.07; p = .001; Vc = .157). This was found in both basketball (χ2(3) = 12.2.; p = .007; Vc = .158) and soccer (χ2(3) = 20.13; p < .001; Vc = .166). Long-term success is more frequent in soccer, where 59.9% of the juniors selected for the national team played later in the premier league, while in basketball that percentage was 39.6% (χ2(1) = 14.64; p < .001; Vc = .201). On the other hand, 79.4% and 39.8% of the professional soccer and basketball players had been previously selected for junior national teams (χ2(1) = 60.2; p < .001; Vc = .386), respectively. The talent selection process should be reviewed as players born in the second half of the year have fewer opportunities to stand out.


#10 Effects of the Pitch Surface on Displacement of Youth Players During Soccer Match-Play
Reference: J Hum Kinet. 2018 Dec 31;65:175-185. doi: 10.2478/hukin-2018-0046. eCollection 2018 Dec.
Authors: Brito Â, Roriz P, Silva P, Duarte R, Garganta J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341947/pdf/hukin-65-175.pdf
Summary: The aim of this study was to analyze the effect of different pitch surfaces (artificial turf, natural turf and dirt field) on positioning and displacement of young soccer players (age: 13.4 ± 0.5 yrs; body height: 161.82 ± 7.52 cm; body mass: 50.79 ± 7.22 kg and playing experience: 3.5 ± 1.4 yrs). Data were collected using GPS units which allowed to calculate spatial distribution variability, assessed by measuring entropy of individual distribution maps (ShannEn). Ellipsoidal areas (m2) representing players' displacement on the pitch, centred on the average players' positional coordinates, were also calculated, with axes corresponding to the standard deviations of the displacement in the longitudinal and lateral directions. Analysis of variance (ANOVA) was used to evaluate differences between pitch surfaces and across players' positions. There was significant effect in positioning (η2 = 0.146; p < 0.001) and displacement (η2 = 0.063; p < 0.05) by the players between pitch surfaces. A dirt field condition induced an increase in the players' movement variability, while players' displacement was more restricted when playing on artificial turf. Also, there were significant effects on positioning (η2 = 0.496; p < 0.001) and displacement (η2 = 0.339; p < 0.001) across players' positions. Central midfielders presented the greatest movement variability and displacement while fullbacks showed the lowest variability. Subsequently, the results may contribute to implement strategies that optimise players' performance in different surface conditions.


#11 Work-rate Analysis of Substitute Players in Professional Soccer: Analysis of Seasonal Variations
Reference: J Hum Kinet. 2018 Dec 31;65:165-174. doi: 10.2478/hukin-2018-0025. eCollection 2018 Dec.
Authors: Padrón-Cabo A, Rey E, Vidal B, García-Nuñez J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341962/pdf/hukin-65-165.pdf
Summary: The aims of this study were to evaluate physical performance of substitute players versus those replaced or completing the entire match, determine physical performance of substitute players across different playing positions and examine variations in match-related running performance in substitute players throughout the entire competitive season. The sample was composed of 943 observations of professional players who participated in the first division of the Spanish League (La Liga) during the 2014-2015 season. The players were divided into three different groups: players who completed the entire match (n = 519), players who were replaced (n = 212) and substitute players (n = 212). Substitute players covered greater distances at medium and high intensity compared to the players who played the entire match and those who were replaced. Position-specific trends indicated that attackers and central midfielder increased the distance covered at high-intensity running compared to their peers who played the whole match. During the competitive season, it was observed that substitute players attained greater match running performance during the mid-season period, allowing them to cover more distance for different variables of running performance compared to the start and end of the season.


#12 Analysis of elite soccer players' performance before and after signing a new contract
Reference: PLoS One. 2019 Jan 25;14(1):e0211058. doi: 10.1371/journal.pone.0211058. eCollection 2019.
Authors: Gómez MÁ, Lago C, Gómez MT, Furley P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347186/pdf/pone.0211058.pdf
Summary: The aim of the current study was to analyse performance differences of football players 2-years prior and the year after signing a new contract (the following year) while taking playing position, nationality, player's role, team ability, and age into account. The sample was comprised of 249 players (n = 109 defenders, n = 113 midfielders; and n = 27 forwards) from four of the major European Leagues (Bundesliga, English FA Premier League, Ligue 1, and La Liga) during the seasons 2008 to 2015. The dependent variables studied were: shooting accuracy, defense (the sum of defensive actions, tackles, blocks, and interceptions), yellow cards, red cards, passing accuracy, tackle success, and minutes played per match. Two-step cluster analysis allowed classifying the sample into three groups of defenders (national important, foreign important, and less important players) and four groups of midfielders and forwards (national important, foreign important, national less important, and foreign less important players). Magnitude Based Inference (MBI) was used to test the differences between player's performances during the years of analyses. The main results (very likely and most likely effects) showed better performance in the year prior to signing a new contract than the previous year for foreign important defenders (decreased number of red cards), national important midfielders (increased number of minutes played), foreign important forwards (increased minutes played and defense), and national important forwards (increased minutes played). In addition, performance was lower the year after signing the contract compared to the previous one for less important defenders (decreasing defense), national less important midfielders (decreased minutes played), and foreign less important forwards (decreased defense). On the other hand, the players showed better performance in defense and more minutes played the year after signing the contract for less important defenders, national less important midfielders, and foreign less important forwards. These results may assist coaches to decide on when a new contract should be signed or the duration of the contract.


#13 Assessing the Validity of the MyJump2 App for Measuring Different Jumps in Professional Cerebral Palsy Football Players: An Experimental Study
Reference: JMIR Mhealth Uhealth. 2019 Jan 30;7(1):e11099. doi: 10.2196/11099.
Authors: Coswig V, Silva AACE, Barbalho M, Faria FR, Nogueira CD, Borges M, Buratti JR, Vieira IB, Román FJL, Gorla JI
Download link: https://mhealth.jmir.org/2019/1/e11099/pdf
Summary: Vertical jumps can be used to assess neuromuscular status in sports performance. This is particularly important in Cerebral Palsy Football (CP Football) because players are exposed to high injury risk, but it may be complicated because the gold standard for assessing jump performance is scarce in field evaluation. Thus, field techniques, such as mobile apps, have been proposed as an alternative method for solving this problem. This study aims to evaluate the reliability of the measures of the MyJump2 app to assess vertical jump performance in professional CP Football. We assessed 40 male CP Football athletes (age 28.1 [SD 1.4] years, weight 72.5 [SD 6.2] kg, and height 176 [SD 4.2] cm) through the countermovement jump (CMJ) and squat jump (SJ) using a contact mat. At the same time, we assessed the athletes using the MyJump2 app. There were no significant differences between the instruments in SJ height (P=.12) and flight time (P=.15). Additionally, there were no significant differences between the instruments for CMJ in jump height (P=.16) and flight time (P=.13). In addition, it was observed that there were significant and strong intraclass correlations in all SJ variables varying from 0.86 to 0.89 (both P<.001), which was classified as "almost perfect." Similar results were observed in all variables from the CMJ, varying from 0.92 to 0.96 (both P ≤.001). We conclude that the MyJump2 app presents high validity and reliability for measuring jump height and flight time of the SJ and CMJ in CP Football athletes.


#14 Does the Environment Influence the Frequency of Concussion Incidence in Professional Football?
Reference: Cureus. 2018 Nov 23;10(11):e3627. doi: 10.7759/cureus.3627.
Authors: Haider S, Kaye-Kauderer HP, Maniya AY, Dai JB, Li AY, Post AF, Sobotka S, Adams R, Gometz A, Lovell MR, Choudhri TF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347446/pdf/cureus-0010-00000003627.pdf
Summary: Background Sports-related concussion is a major cause of mild traumatic brain injury (mTBI). It is possible that environmental factors, such as temperature, humidity, and stadium's altitude, may influence the overall incidence of concussions during a game. Purpose To examine the impact of environmental factors, such as temperature, humidity, barometric pressure, and dew point, on concussion incidence. Methods Public Broadcasting Service (PBS) FRONTLINE Concussion Watch was used to collect injury data on 32 NFL teams during regular season games from 2012 to 2015. Weather data points were collected from Weather Underground. Concussion incidence per game, the probability of a concussion during a game, and a difference in mean game-day temperature, humidity, dew point, and barometric pressure between concussion and concussion-free games were calculated. Our analysis included t-tests, analysis of variance (ANOVA), multivariate correlation tests, and logistic and Poisson regression.  Results Overall, 564 concussions were reported. There were 411 games with concussions and 549 games without concussions. We observed a significant decrease in concussion incidence with increasing temperature, both when the temperature was divided into 20oF increments or into quartiles (p = 0.005 and p = 0.002, respectively). We identified a statistically significant lower mean-game day temperature in concussion games compared to concussion-free games (p < 0.0006). We also observed a significant decrease in the incidence of concussion per game with increasing dew point. There was no significant difference in concussion incidence in barometric pressure and humidity. The logistic regression model predicted a decrease in the probability of a concussion in games with higher temperatures and dew points. Conclusions National Football League (NFL) players experienced an increased risk of concussion during football games played in colder temperatures and at lower dew points. Further research on environmental effects on concussions may aid in improving player safety in football leagues.

Sat

02

Mar

2019

Latest research in football - week 4 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Head impact magnitudes that occur from purposeful soccer heading depend on the game scenario and head impact location
Reference: Musculoskelet Sci Pract. 2019 Jan 24;40:53-57. doi: 10.1016/j.msksp.2019.01.009. [Epub ahead of print]
Authors: Harriss A, Johnson AM, Walton DM, Dickey JP
Summary: This study quantified the linear and angular kinematics that result from purposeful heading during youth soccer games, and the influence of game scenario and head impact location on these magnitudes. This observational study recruited thirty-six female soccer players (13.4 ± 0.9 years old) from three elite youth soccer teams (U13, U14, U15) and followed for an entire soccer season. Players wore wireless sensors during each game to quantify head impact magnitudes. A total of 60 regular season games (20 games per team) were video recorded, and purposeful heading events were categorized by game scenario (e.g. throw in), and head impact location (e.g. front of head). Game scenario had a statistically significant effect on the linear head acceleration, and rotational head velocity, that resulted from purposeful headers. Rotational velocity from purposeful headers varied significantly between head impact locations, with impacts to the top of the head (improper technique) resulting in larger peak rotational velocities than impacts to the front of the head (proper technique); this was also the case for the linear acceleration for punts. Our findings suggest that the magnitude for both linear and angular head impact kinematics depend on the game scenario and head impact location. Headers performed with the top of the head (improper technique) result in larger rotational velocities compared to the front of the head (proper technique). Accordingly, youth players should be educated on how to execute proper heading technique to reduce head impact accelerations.


#2 Jumping Asymmetries Are Associated With Speed, Change of Direction Speed, and Jump Performance in Elite Academy Soccer Players
Reference: J Strength Cond Res. 2019 Jan 30. doi: 10.1519/JSC.0000000000003058. [Epub ahead of print]
Authors: Bishop C, Brashill C, Abbott W, Read P, Lake J, Turner A
Summary: The aim of this study was to establish interlimb asymmetries across different age groups in elite academy male soccer players and to examine any relationships between asymmetry and measures of physical performance. Fifty-one players from an English Premier League soccer academy were split into under-23 (n = 21), under-18 (n = 14), and under-16 (n = 16) groups and performed bilateral and unilateral countermovement jumps, 5-, 10-, and 20-m sprints, and a 505 change of direction speed tests. All tests showed low variability (coefficient of variation ≤ 2.5%) and good to excellent reliability (intraclass correlation coefficient = 0.80-0.99). A 1-way analysis of variance showed that the under-23 group was significantly faster than the under-16 group during the 20-m sprint (2.90 vs. 2.98 s; p = 0.02; effect size = 0.94). No other significant differences were present between groups. Interlimb asymmetry was quantified from the single-leg countermovement jump, and no significant differences in the magnitude of asymmetry were present between groups. However, multiple significant correlations were present in each age group between asymmetry and physical performance tests, all of which were indicative of reduced athletic performance. Results from this study show that although interlimb asymmetry scores are comparable across age groups in elite academy soccer players, differences as low as 5% are associated with reduced physical performance during jumping, sprinting, and change of direction speed tasks. This study suggests the importance of monitoring jump height asymmetries in elite academy soccer players.


#3 Coaching Efficacy, Player Perceptions of Coaches' Leadership Styles, and Team Performance in Premier League Soccer
Reference: Res Q Exerc Sport. 2019 Feb 1:1-9. doi: 10.1080/02701367.2018.1563277. [Epub ahead of print]
Authors: Keatlholetswe L, Malete L
Summary: The coaching competency research has demonstrated the role of coaching efficacy and coaching behaviors on various athlete outcomes. However, athlete perceptions of these relationships and how they affect performance are less understood. This study examined if coaching efficacy is predictive of player perceptions of coaches' leadership styles, team atmosphere, and team performance in a soccer season. Fifteen male premier league soccer coaches (Mage = 45.27, SD = 6.07) and 226 players (Mage = 25.66, SD = 3.96) from Botswana participated in the study. All participants completed a background information questionnaire. Coaches completed the Coaching Efficacy Scale. Players rated their coaches' leadership styles using the Revised Leadership Scale for Sports as well as team atmosphere. Team performance was based on position in the league log and player ratings of the teams' performance. Findings showed that coaches' self-ratings on technique efficacy predicted player perceptions of the coaches' use of all six leadership styles. Game strategy efficacy predicted higher team atmosphere and team performance. Motivation efficacy was not significantly associated with player perceptions of the coaches' use of any of the leadership styles, while character building efficacy was negatively associated with the various leadership styles. Findings provide support to previous research evidence linking higher coaching efficacy, leadership styles, and team outcomes. The study expands the emergent research within the coaching competency literature that examines player perceptions of coaches' behaviors and leadership styles.


#4 The Effect of In-Season Traditional and Explosive Resistance Training Programs on Strength, Jump Height, and Speed in Recreational Soccer Players
Reference: Res Q Exerc Sport. 2019 Feb 1:1-8. doi: 10.1080/02701367.2018.1563276. [Epub ahead of print]
Authors: Griffiths B, Grant J, Langdown L, Gentil P, Fisher J, Steele J
Summary: Resistance training is often performed in a traditional training style using deliberate relatively longer repetition durations or in an explosive training style using maximal intended velocities and relatively shorter repetition durations. Both improve strength, "power" (impulsivity), and speed. This study compared explosive and traditional training over a 6-week intervention in 30 healthy young adult male recreational soccer players. Full body supervised resistance training was performed 2 times a week using 3 sets of each exercise at 80% of one repetition maximum to momentary failure. Outcomes were Smith machine squat 1 repetition maximum, 10 meter sprint time, and countermovement jump. Both groups significantly improved all outcomes based on 95% confidence intervals not crossing zero. There were no between-group differences for squat 1 RM (TRAD = 6.3[5.1 to 7.6] kg, EXP = 5.2[3.9 to 6.4] kg) or 10 meter sprint (TRAD = -0.05[-0.07 to -0.04] s, EXP = -0.05[-0.06 to -0.03] s). Explosive group had a significantly greater increase in countermovement jump compared to the traditional group (TRAD = 0.7[0.3 to 1.1] cm, EXP = 1.3[0.9 to 1.7] cm). Both the traditional training and explosive training performed to momentary failure produced significant improvements in strength, speed, and jump performance. Strength gains are similar independent of intended movement speed. However, speed and jump performance changes are marginal with resistance training.


#5 A match-day analysis of the movement profiles of substitutes from a professional soccer club before and after pitch-entry
Reference:  PLoS One. 2019 Jan 31;14(1):e0211563. doi: 10.1371/journal.pone.0211563. eCollection 2019.
Authors: Hills SP, Barrett S, Feltbower RG, Barwood MJ, Radcliffe JN, Cooke CB, Kilduff LP, Cook CJ, Russell M
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0211563&type=printable
Summary: Whilst the movement demands of players completing a whole soccer match have been well-documented, comparable information relating to substitutes is sparse. Therefore, this study profiled the match-day physical activities performed by soccer substitutes, focusing separately on the pre and post pitch-entry periods. Seventeen English Championship soccer players were monitored using 10 Hz Micromechanical Electrical Systems (MEMS) devices during 13 matches in which they participated as substitutes (35 observations). Twenty physical variables were examined and data were organised by bouts of warm-up activity (pre pitch-entry), and five min epochs of match-play (post pitch-entry). Linear mixed modelling assessed the influence of time (i.e., 'bout' and 'epoch'), playing position, and match scoreline. Substitutes performed 3±1 rewarm-up bouts∙player-1∙match-1. Compared to the initial warm-up, each rewarm-up was shorter (-19.7 to -22.9 min) and elicited less distance (-606 to -741 m), whilst relative total distances were higher (+26 to +69 m∙min-1). Relative total (+13.4 m∙min-1) and high-speed (+0.4 m∙min-1) distances covered during rewarm-ups increased (p <0.001) with proximity to pitch-entry. Players covered more (+3.2 m; p = 0.047) high-speed distance per rewarm-up when the assessed team was losing compared with when winning at the time of pitch-entry. For 10 out of 20 variables measured after pitch-entry, values reduced from 0-5 min thereafter, and substitutes covered greater (p ˂0.05) total (+67 to +93 m) and high-speed (+14 to +33 m) distances during the first five min of match-play versus all subsequent epochs. Midfielders covered more distance (+41 m) per five min epoch than both attackers (p ˂0.001) and defenders (p = 0.016). Acknowledging the limitations of a solely movement data approach and the potential influence of other match-specific factors, such findings provide novel insights into the match-day demands faced by substitute soccer players. Future research opportunities exist to better understand the match-day practices of this population.


#6 Effect of Heavy Resisted Sled Sprint Training During the Competitive Season on Sprint and Change-of-Direction Performance in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Jan 31:1-25. doi: 10.1123/ijspp.2018-0592. [Epub ahead of print]
Authors: McMorrow BJ, Ditroilo M, Egan B
Summary: Resisted sled sprinting (RSS) is an effective tool for improving sprint performance over short distances, but the effect on change-of-direction (COD) performance is largely unknown. The present study investigated the effect of heavy RSS training during the competitive season on sprint and COD performance in professional soccer players. Over six weeks in-season, a RSS training group (n=6) performed RSS at a sled load of 30% of body mass for a total programme running distance of 800 m, while an unresisted sprint (URS) training group (n=7) performed the same distance of unresisted sprinting. A 20 m maximal sprint with split times measured at 5, 10 and 20 m, and the sprint 9-3-6-3-9 m with 180° turns COD test were performed before and after the intervention. Sprint performance (mean; 95% confidence limits; qualitative inference) was improved in both groups over 5 m (URS, 5.1%; -2.4, 12.7; likely moderate; RSS, 5.4%; 0.5, 10.4; likely moderate), 10 m (URS, 3.9%; -0.3, 8.1; very likely moderate; RSS, 5.0%; 1.8, 8.0; very likely large), and 20 m (URS, 2.0%; -0.6, 4.5; likely moderate; RSS (3.0%; 1.7, 4.4; very likely moderate). COD was improved in both groups (URS, 3.7%; 2.2, 5.2; most likely large; RSS, 3.3%; 1.6, 5.0; most likely moderate). Between-group differences were unclear. Heavy RSS or URS training matched for running distance were similarly effective at improving sprint and COD performance in professional soccer players when performed in the competitive phase of the season.


#7 Predicting Future Perceived Wellness in Professional Soccer: The Role of Preceding Load and Wellness
Reference: Int J Sports Physiol Perform. 2019 Jan 31:1-25. doi: 10.1123/ijspp.2017-0864. [Epub ahead of print]
Authors: Jaspers A, De Beéck TO, Brink MS, Frencken WGP, Staes F, Davis JJ, Helsen WF
Summary: The influence of preceding load and perceived wellness on the future perceived wellness of professional soccer players is unexamined. This paper simultaneously evaluates the external and internal load for different time frames in combination with pre-session wellness to predict future perceived wellness using machine learning techniques. Training and match data were collected from a professional soccer team. The external load was measured using global positioning system technology and accelerometry. The internal load was obtained using the RPE multiplied by duration. Predictive models were constructed using gradient boosted regression trees (GBRT) and one naive baseline method. The individual predictions of future wellness items (i.e., fatigue, sleep quality, general muscle soreness, stress levels, and mood) were based on a set of external and internal load indicators in combination with pre-session wellness. The external and internal load was computed for acute and cumulative time frames. The GBRT model's performance on predicting the reported future wellness was compared to the naive baseline's performance by means of absolute prediction error and effect size. The GBRT model outperformed the baseline for the wellness items fatigue, general muscle soreness, stress levels and mood. Additionally, only the combination of external load, internal load, and pre-session perceived wellness resulted in non-trivial effects for predicting future wellness. Including the cumulative load did not improve the predictive performances. The findings may indicate the importance of including both acute load and pre-session perceived wellness in a broad monitoring approach in professional soccer.


#8 A tactical comparison of the 4-2-3-1 and 3-5-2 formation in soccer: A theory-oriented, experimental approach based on positional data in an 11 vs. 11 game set-up
Reference: PLoS One. 2019 Jan 30;14(1):e0210191. doi: 10.1371/journal.pone.0210191. eCollection 2019.
Authors: Memmert D, Raabe D, Schwab S, Rein R
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0210191&type=printable
Summary: The presented field experiment in an 11 vs. 11 soccer game set-up is the first to examine the impact of different formations (e.g. 4-2-3-1 vs. 3-5-2) on tactical key performance indicators (KPIs) using positional data in a controlled experiment. The data were gathered using player tracking systems (1 Hz) in a standardized 11 vs. 11 soccer game. The KPIs were measured using dynamical positioning variables like Effective Playing Space, Player Length per Width ratio, Team Separateness, Space Control Gain, and Pressure Passing Efficiency. Within the experimental positional data analysis paradigm, neither of the team formations showed differences in Effective Playing Space, Team Separateness, or Space Control Gain. However, as a theory-based approach predicted, a 3-5-2 formation for the Player Length per Width ratio and Pressure Passing Efficiency exceeded the 4-2-3-1 formation. Practice task designs which manipulate team formations therefore significantly influence the emergent behavioral dynamics and need to be considered when planning and monitoring performance. Accordingly, an experimental positional data analysis paradigm is a useful approach to enable the development and validation of theory-oriented models in the area of performance analysis in sports games.


#9 Time Trends of Head Injuries Over Multiple Seasons in Professional Male Football (Soccer)
Reference: Sports Med Int Open. 2019 Jan 28;3(1):E6-E11. doi: 10.1055/a-0808-2551. eCollection 2019 Jan.
Authors: Beaudouin F, der Fünten KA, Tröß T, Reinsberger C, Meyer T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6349547/pdf/10-1055-a-0808-2551.pdf
Summary: The present study aimed to investigate time trends of head injuries and their injury mechanisms since a rule change as monitoring may help to identify causes of head injuries and may advance head injury prevention efforts. Based on continuously recorded data from the German football magazine "kicker Sportmagazin ® " as well as other media sources, a database of head injuries in the 1 st German male Bundesliga was generated comprising 11 seasons (2006/07-2016/17). Injury mechanisms were analysed from video recordings. Injury incidence rates (IR) and 95% confidence intervals (95% CI) were calculated. Time trends were analysed via linear regression. Two hundred thirty-eight match head injuries occurred (IR 1.77/1000 match hours, 95% CI 1.56-2.01). There were no significant seasonal changes, expressed as annual average year-on-year change, in IRs over the 11-year period for total head injuries (p=0.693), facial/head fractures (p=0.455), lacerations/abrasions (p=0.162), and head contusions (p=0.106). The annual average year-on-year increase for concussion was 6.4% (p=0.004). Five head injury mechanisms were identified. There were no seasonal changes in injury mechanisms over the study period. The concussion subcategory increased slightly over the seasons, which may either be a result of increasing match dynamics or raised awareness among team physicians and players.

Thu

14

Feb

2019

Latest research in football - week 3 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Resisted Sprint With Changes of Direction Training Through Several Relative Loads on Physical Performance in Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Jan 24:1-20. doi: 10.1123/ijspp.2018-0702. [Epub ahead of print]
Authors: Rodríguez-Osorio D, Gonzalo-Skok O, Pareja-Blanco F
Summary: The purpose was to compare the effects of resisted change of direction (COD) movements, using several relative loads, on soccer players' physical performance. Fifty-four male soccer players were randomly assigned to one of the following 3 groups, which differed only in the magnitude of the external load used during the COD training: COD training without external load (COD-0; n = 16); COD training with a 12.5% body mass (BM) external load (COD-12.5; n = 19); and COD training with a 50% BM external load (COD-50; n = 19). Participants performed the specific COD training twice per week for 6 weeks. Before and after the training period a battery of tests was completed: countermovement jump (CMJ); 30 m running sprint (time in 10-m [T10], 20-m [T20] and 30-m [T30]); L-RUN test; and V-CUT test. Within-group comparisons showed substantial improvements in CMJ and T10 (likely) in COD-0, whereas CMJ, T10 and T20 were substantially enhanced (possibly to likely) in COD-50. COD-12.5 induced substantial improvements in all analyzed variables (likely to most likely). Between-groups comparisons showed better effects on all analyzed variables for COD-12.5 compared to COD-0 group (possibly to very likely), whereas COD-50 only showed possibly better effects than COD-0 on T10. In addition, COD-12.5 induced a better effect on L-RUN and V-CUT tests than COD-50 (possibly to likely). These results indicate that COD training, especially moderate load (12.5% BM) resisted COD training, may have a positive effect on COD skills, running sprint performance and jumping ability in young soccer players.


#2 The Arrowhead Agility Test: Reliability, Minimum Detectable Change, and Practical Applications in Soccer Players
Reference: J Strength Cond Res. 2019 Jan 22. doi: 10.1519/JSC.0000000000002987. [Epub ahead of print]
Authors: Rago V, Brito J, Figueiredo P, Ermidis G, Barreira D, Rebelo A
Summary: Four independent studies were conducted to examine the utility of the arrowhead agility test (AAT) to measure change of direction (COD) capacity in soccer players, specifically, (a) intersession reliability and minimum detectable change (n = 24); (b) power-dependent abilities associated with AAT performance (n = 56); and (c) fatigue sensitivity (n = 20); differences between competitive levels and age groups (n = 264). Irrespective of the AAT outcome measure (skillful side, less-skillful side, sum of both), intersession reliability and the ability to detect changes in performance were good (ICC = 0.80-0.83; CV = 1.25-2.21%; smallest worthwhile change, 0.06-0.12 >SEM, 0.01-0.03) except for the asymmetry index. A 15-m sprint explained a significant amount of variance in COD (p < 0.01; R = 0.42). Arrowhead agility test performance did not change from the prematch toward half time (p = 0.21). However, reduced COD performance was observed after an intense period in the second half and after the game, compared with prematch and half-time performance (p < 0.05; effect size [ES] = -0.85 to 0.42). Irrespective of age group, national players were more agile than regional players (p < 0.05; ES = -1.97 to -0.36). Moreover, independently of their competitive level, senior and U18 players had a better performance than U16 (p < 0.05; ES = -2.33 to -0.84), whereas no significant differences were observed between senior and U18. Percentiles were also reported in the results. The AAT is reliable to measure COD in soccer players. The test may simultaneously encompass 15-m sprint testing but should be implemented independently to countermovement jump. Furthermore, the test is sensitive to match-induced fatigue during the second half and discriminates players from different competitive levels.


#3 External Cueing Influences Drop Jump Performance in Trained Young Soccer Players
Reference: J Strength Cond Res. 2019 Jan 22. doi: 10.1519/JSC.0000000000002935. [Epub ahead of print]
Authors: Oliver JL, Barillas SR, Lloyd RS, Moore I, Pedley J
Summary: Drop jump (DJ) characteristics provide insight on power production and injury risk. The purpose of this study was to investigate the effect of external cueing on DJ characteristics in young male soccer players. Fourteen academy soccer players performed DJs with 4 different conditions, control (CONT), contact cue (CC), height cue (HC), and quiet cue (QC). Performance measures were reactive strength index (RSI), jump height, ground contact time (GCT), and take-off impulse, with injury risk reflected by impact peak, impact timing, and landing impulse. Contact cue showed a very large significant reduction in GCT (effect size [ES] > 2.0, p < 0.05), and moderate to large increase in RSI, landing impulse, and push-off impulse (ES 0.70-1.55, p < 0.05) compared with all other conditions. Contact cue also moderately increased impact peak when compared with HC and QC (ES ≥ 0.78, p < 0.05). Height cue led to a significant increase in jump height that was moderately greater than other external cues (ES ≥ 0.87, p < 0.05), but with only a small nonsignificant increase compared (ES 0.54, p > 0.05) with CONT. The data showed that all cues provided a specific response; CC reduced GCT and increased RSI, HC increased jump height, and QC reduced outcomes associated with injury risk. Height cue may be advantageous for young soccer players with a low training age because it shows a small to moderate increase in jump height without increasing injury risk. Young players may need to be safely progressed to be able to use a CC to facilitate high reactive strength without being exposed to undue injury risk.


#4 Measuring the Hip Adductor to Abductor Strength Ratio in Ice Hockey and Soccer Players: A Critically Appraised Topic
Reference: J Sport Rehabil. 2019 Jan 24:1-18. doi: 10.1123/jsr.2018-0250. [Epub ahead of print]
Author: Rodriguez R
Summary: Ice hockey and soccer are both dynamic sports that involve continuous, unpredictable play. These athletes consistently demonstrate higher rates of groin strains compared to other contact sports. Measuring the hip adductor/abductor ratio has the potential to expose at-risk players, reduce injury rates, and preserve groin health in players with chronic strains. What is the clinical utility of measuring the hip adductor/abductor ratio for pre-season and in-season ice hockey and soccer players? Three studies, all of which were prospective cohort designs, were included. One study involved assessing preseason strength and flexibility as a risk factor for adductor strains in professional ice hockey players. Another study performed in the same professional hockey team used preseason hip adductor/abductor strength ratios to screen for those players who would benefit from a strengthening intervention aimed at reducing the incidence of adductor strains. The final study, which was performed in elite U17 soccer players, assessed the effectiveness of monthly in-season strength monitoring as a guide to trigger in-season interventions to decrease injury incidence. Measuring the hip adductor/abductor strength ratio in hockey and soccer players can be a beneficial pre-season and in-season tool to predict future groin strain risk and screen for athletes who might benefit from a strengthening intervention. Evidence exists to support monitoring the hip adductor/abductor strength ratio to assess and reduce the risk of adductor strains in ice hockey and soccer players.


#5 Realistic Soccer-Specific Virtual Environment Exposes High-Risk Lower Extremity Biomechanics
Reference: J Sport Rehabil. 2019 Jan 24:1-23. doi: 10.1123/jsr.2018-0237. [Epub ahead of print]
Authors: DiCesare CA, Kiefer AW, Bonnette SH, Myer GD
Summary: Laboratory-based biomechanical analyses of sport-relevant movements such as landing and cutting have classically been used to quantify kinematic and kinetic factors in the context of injury risk, which are then used to inform targeted interventions designed to improve risky movement patterns during sport. However, the non-contextual nature of standard assessments presents challenges for assessing sport-relevant skill transfer. It may be more effective to examine injury-risk biomechanics on individuals performing sport-specific tasks within the actual sport environment, or more feasibly, within a simulated sport environment using virtual reality (VR). The purpose of this study was to examine biomechanical differences exhibited by athletes during a jump-landing task performed as part of both a standard biomechanical assessment and a sport-specific VR-based assessment.  22 female adolescent soccer athletes (age = 16.0 ± 1.4 years; height = 165.6 ± 4.9 cm; weight = 60.2 ± 11.4 kg) participated in this study. The landing performance of was analyzed for a drop vertical jump task and a VR-based, soccer-specific corner-kick scenario in which the athletes were required to jump to head a virtual soccer ball and land. Hip, knee and ankle joint kinematic differences in the frontal and sagittal planes were used as main outcome measures. Athletes exhibited reduced hip and ankle flexion, hip abduction, and frontal plane ankle excursion during landing in realistic sport scenario compared to the standard drop vertical jump task. VR-based assessments can provide a sport-specific context in which to assess biomechanical deficits that predispose athletes for lower extremity injury and offer a promising approach to better evaluate skill transfer to sport which can guide future injury prevention efforts.


#6 Associations Between Selected Training Stress Measures and Fitness Changes in Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Jan 24:1-23. doi: 10.1123/ijspp.2018-0462. [Epub ahead of print]
Authors: Rabbani A, Kargarfard M, Castagna C, Clemente FM, Twist C
Summary: The purpose of this study was to investigate the relationship of accumulated Global Positioning System (GPS)-accelerometer-based and heart rate (HR)-based training metrics to changes in high-intensity intermittent running capacity during an in-season phase in professional soccer players. Eleven male professional players (mean ± SD, age: 27.2 ± 4.5 years) performed the 30-15 Intermittent Fitness Test (30-15IFT) before and after a five-week in-season training phase, and the final velocity (VIFT) was considered as players' high-intensity intermittent running capacity. During all sessions, Edwards' training impulse (Edwards' TRIMP), Banister's TRIMP, Z5 TRIMP, training duration, total distance covered, New Body Load (NBL), high-intensity running performance (distance covered above 14.4 km·h-1), and very high-intensity running performance (distance covered above 19.8 km·h-1) were recorded. The players' VIFT showed a most likely moderate improvement (+4.3%, 90% confidence limits [3.1; 5.5%], effect size ES, 0.70 [0.51; 0.89]). Accumulated NBL, Banister's TRIMP and Edwards' TRIMP showed large associations (r = 0.51 to 0.54) with changes in VIFT. Very large relationship was also observed between accumulated Z5 TRIMP (r= 0.72) with changes in VIFT. Large-to-nearly perfect within-individual relationships were observed between NBL and some of the other training metrics (i.e., Edwards' TRIMP, Banister's TRIMP, training duration, and total distance) in 10 out of 11 players. HR-based training metrics can be used to monitor high-intensity intermittent running capacity changes in professional soccer players. The dose-response relationship is also largely detected using accelerometer-based metrics (i.e., NBL) to track changes in high-intensity intermittent running capacity of professional soccer players.


#7 Learning to Rate Player Positioning in Soccer
Reference: Big Data. 2019 Jan 23. doi: 10.1089/big.2018.0054. [Epub ahead of print]
Authors: Dick U, Brefeld U
Summary: We investigate how to learn functions that rate game situations on a soccer pitch according to their potential to lead to successful attacks. We follow a purely data-driven approach using techniques from deep reinforcement learning to valuate multiplayer positionings based on positional data. Empirically, the predicted scores highly correlate with dangerousness of actual situations and show that rating of player positioning without expert knowledge is possible.


#8 Match Running Performance in Young Soccer Players: A Systematic Review
Reference: Sports Med. 2019 Jan 22. doi: 10.1007/s40279-018-01048-8. [Epub ahead of print]
Authors: Palucci Vieira LH, Carling C, Barbieri FA, Aquino R, Santiago PRP
Summary: To date, athletic performance has been extensively assessed in youth soccer players through laboratory and field testing. Only recently has running performance via time-motion analysis been assessed during match play. Match running data are often useful in a practical context to aid game understanding and decision making regarding training content and prescriptions. A plethora of previous reviews have collated and appraised the literature on time-motion analysis in professional senior players, but none have solely examined youth players. The aim of the present systematic review was to provide a critical appraisal and summary of the original research articles that have evaluated match running performance in young male soccer players. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, literature searches were performed in four databases: PubMed, ISI Web of Science, SPORTDiscus and SciELO. We used the following descriptors: soccer, football, young, youth, junior, physical performance, running performance, match running performance, movement patterns, time-motion analysis, distances covered, activity profile, work rate, match analysis, and match performance. Articles were included only if they were original articles written in the English language, studied populations of male children and/or adolescents (aged ≤ 20 years), were published/ahead of print on or before 31 December 2017 and showed at least one outcome measure regarding match running performance, such as total distance covered, peak game speed or indicators of activities performed at established speed thresholds. A total of 5801 records were found. After duplicates were removed and exclusion and inclusion criteria applied, 50 articles were included (n = 2615 participants). Their outcome measures were extracted and findings were synthesized. The majority of the reviewed papers covered the European continent (62%) and used global positioning systems (GPS) (64%). Measurement error of the tools used to obtain position data and running metrics was systematically overlooked among the studies. The main aims of studies were to examine differences across playing positions (20%), age groups (26%) and match halves (36%). Consistent findings pointed to the existence of positional role and age effects on match running output (using fixed running speed thresholds), but there was no clear consensus about reductions in activity over the course of match play. Congested schedules negatively affected players' running performance. While over 32% of all studies assessed the relationships between match running performance and physical capacity, biochemical markers and body composition, ~ 70% of these did not account for playing position. This review collated scientific evidence that can aid soccer conditioning professionals in understanding external match loads across youth categories. Coaches working with youth development programs should consider that data derived from a given population may not be relevant for other populations, since game rules, match format and configuration are essentially unstandardized among studies for age-matched players. Despite limited evidence, periodization training emphasizing technical-tactical content can improve match running performance. Occurrence of acute and residual impairments in the running performance of young soccer players is common. Prescription of postmatch recovery strategies, such as cold water immersion and spa treatment, can potentially help reduce these declines, although additional research is warranted. This review also highlighted areas requiring further investigation, such as the possible influence of environmental and contextual constraints and a more integrative approach combining tactical and technical data.


#9 Drop Jump Asymmetry is Associated with Reduced Sprint and Change-of-Direction Speed Performance in Adult Female Soccer Players
Reference: Sports (Basel). 2019 Jan 21;7(1). pii: E29. doi: 10.3390/sports7010029.
Authors: Bishop C, Turner A, Maloney S, Lake J, Loturco I, Bromley T, Read P
Download link: https://www.mdpi.com/2075-4663/7/1/29/pdf
Summary: Studies that examine the effects of inter-limb asymmetry on measures of physical performance are scarce, especially in adult female populations. The aim of the present study was to establish the relationship between inter-limb asymmetry and speed and change-of-direction speed (CODS) in adult female soccer players. Sixteen adult players performed a preseason test battery consisting of unilateral countermovement jump (CMJ), unilateral drop jump (DJ), 10 m, 30 m, and 505 CODS tests. Inter-limb asymmetry was calculated using a standard percentage difference equation for jump and CODS tests, and Pearson's r correlations were used to establish a relationship between asymmetry and physical performance as well as asymmetry scores themselves across tests. Jump-height asymmetry from the CMJ (8.65%) and DJ (9.16%) tests were significantly greater (p < 0.05) than asymmetry during the 505 test (2.39%). CMJ-height asymmetry showed no association with speed or CODS. However, DJ asymmetries were significantly associated with slower 10 m (r = 0.52; p < 0.05), 30 m (r = 0.58; p < 0.05), and 505 (r = 0.52⁻0.66; p < 0.05) performance. No significant relationships were present between asymmetry scores across tests. These findings suggest that the DJ is a useful test for detecting existent between-limb asymmetry that might in turn be detrimental to speed and CODS performance. Furthermore, the lack of relationships present between different asymmetry scores indicates the individual nature of asymmetry and precludes the use of a single test for the assessment of inter-limb differences.


#10 Hip Arthroscopic Management Can Improve Osteitis Pubis and Bone Marrow Edema in Competitive Soccer Players With Femoroacetabular Impingement
Reference: Am J Sports Med. 2019 Jan 21:363546518819099. doi: 10.1177/0363546518819099. [Epub ahead of print]
Authors: Saito M, Utsunomiya H, Hatakeyama A, Nakashima H, Nishimura H, Matsuda DK, Sakai A, Uchida S
Summary: There is a dearth of knowledge regarding the correlation between femoroacetabular impingement (FAI) and osteitis pubis (OP) among symptomatic soccer players. The purpose was to elucidate whether arthroscopic FAI correction is effective for young competitive soccer players with FAI combined with OP or perisymphyseal pubic bone marrow edema (BME). A total of 577 consecutive patients who underwent arthroscopic FAI correction were retrospectively reviewed with a minimum 2-year follow-up. Competitive soccer players who were professional, college, and high school athletes were included. The authors assessed the modified Harris Hip Score and Nonarthritic Hip Score preoperatively and at 6 months, 1 year, and 2 years after surgery. In addition, players were divided into groups according to radiographic evidence of OP and BME (2 groups each). Clinical outcomes, return to play, and radiographic assessments were compared between groups. Twenty-eight hips met the inclusion criteria. The median modified Harris Hip Score significantly improved after hip arthroscopy (81.4, preoperatively; 95.7 at 6 months, P = .0065; 100 at 1 year, P = .0098; 100 at 2 years, P = .013). The median Nonarthritic Hip Score also significantly improved (75.0, preoperatively; 96.3 at 6 months, P = .015; 98.8 at 1 year, P = .0029; 100 at 2 years, P = .015). Furthermore, 92.0% of players returned to play soccer at the same or higher level of competition at a median 5.5 months (range, 4-15 months); 67.8% had radiological confirmation of OP; and 35.7% had pubic BME. The alpha angle was significantly higher in pubic BME group than the no-pubic BME group (64.8° vs 59.2°, P = .027), although there was no significant difference between the OP and no-OP groups. The prevalence of tenderness of the pubic symphysis significantly decreased preoperatively (32.1%) to postoperatively (3.6%). Magnetic resonance imaging findings confirmed that pubic BME disappeared in all players at a median 11 months (range, 6-36) after initial surgery. Arthroscopic management for FAI provides favorable clinical outcomes, a high rate of return to sports, and, when present, resolution of pubic BME among competitive soccer players.


#11 Effects of Combined Surfaces vs. Single-Surface Plyometric Training on Soccer Players' Physical Fitness
Reference: J Strength Cond Res. 2019 Jan 17. doi: 10.1519/JSC.0000000000002929. [Epub ahead of print]
Authors: Ramirez-Campillo R, Álvarez C, García-Pinillos F, García-Ramos A, Loturco I, Chaabene H, Granacher U
Summary: The aim of this study was to compare the effects of a 8-week plyometric jump training (PJT) performed on different surfaces (grass, land-dirt, sand, wood, gym mat, and tartan-track) vs. a single-surface PJT (grass) on components of physical fitness (muscle power, speed, and change-of-direction speed [CODS] tasks) and sport-specific performance (i.e., maximal kicking velocity [MKV]) in male soccer players aged 11-14 years. Athletes were randomly assigned to a combined surfaces PJT (PJTc, n = 8), a single-surface PJT (PJTs, n = 8), or an active control (CON, n = 7). Although the PJT group trained on grass, the PJTc trained on 6 different surfaces and equally distributed the total jump volume according to the surface. Pre-post tests were conducted on grass. Significant main effects of time were observed for the countermovement jump, the standing-long-jump, the 20-cm drop jump, 30-m sprint time, CODS, and MKV (all p < 0.001; d = 0.53-0.87). Group × time interactions were identified for all jump tests, MKV, 30-m sprint time, and CODS (all p < 0.001; d = 0.58-0.71) in favor of PJTc. No significant pre-post changes were observed in the CON (all p > 0.05; d = 0.07-0.1). In conclusion, PJT is effective in improving physical fitness in young soccer players when conducted in combination with regular soccer training. Although general fitness testing and PJTs were performed on grass, larger physical fitness improvements were found after PJTc. Thus, PJTc is recommended, as it provides a better overload stimulus compared with more conventional training overload (e.g., increase in training volume or intensity). Future studies still have to address the underlying physiological adaptations after PJTc.


#12 Effect of deep oscillation as a recovery method after fatiguing soccer training: A randomized cross-over study
Reference: J Exerc Sci Fit. 2018 Dec;16(3):112-117. doi: 10.1016/j.jesf.2018.10.004. Epub 2018 Oct 16.
Authors: von Stengel S, Teschler M, Weissenfels A, Willert S, Kemmler W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6323303/pdf/main.pdf
Summary: In soccer the recovery time between matches is often not long enough for complete restoration. Insufficient recovery can result in reduced performance and a higher risk of injuries. The purpose of this study was to evaluate the potential of Deep Oscillation (DO) as a recovery method. In a randomized crossover study including 8 male soccer players (22 ± 3.3 years) the following parameters were evaluated directly before and 48 h after a fatiguing soccer-specific exercise: Maximum isokinetic strength of the leg and hip extensors and flexors (Con-Trex® Leg Press, Physiomed, Germany), rating of perceived exertion (RPE) during isokinetic testing (Borg scale 6-20), creatine kinase (CK) serum levels and Delayed Onset Muscle Soreness (DOMS; visual analogue scale 1-10). By random allocation, half of the group performed a DO self-treatment twice daily (4 applications of 15min each), whilst the other half received no intervention. 4 weeks later a cross-over was conducted. Two-way repeated measures analysis of variance was used to compare treatment versus control. A significant treatment effect was observed for maximum leg flexion strength (p = 0.03; DO: 125 ± 206 N vs. CG: -115 ± 194; p = 0.03) and for RPE (DO: -0.13 ± 0.64; vs. CG: +1.13 ± 1.36; p = 0.03). There was a trend to better recovery for maximum leg extension strength (DO: -31 ± 165 N vs. CG: -138 ± 212; p = 0.028), CK values (DO: 72 ± 331 U/ml vs. CG: 535 ± 797 U/ml; p = 0.15) and DOMS (DO: 3.4 ± 1.5 vs. CG: 4.1 ± 2.6; p = 0.49). In the present study we found significant effects of DO on maximum leg flexion strength and perceived rate of exertion. Other variables showed a consistent trend in favour of DO compared with the control without significance. DO seems to be a promising method to accelerate the time-course of peripheral recovery of muscle which should be addressed in larger studies in future.


#13 In season adaptations to intense intermittent training and sprint interval training in sub-elite football players
Reference: Scand J Med Sci Sports. 2019 Jan 24. doi: 10.1111/sms.13395. [Epub ahead of print]
Authors: Hostrup M, Gunnarsson TP, Fiorenza M, Mørch K, Onslev J, Pedersen KM, Bangsbo J
Summary: This study investigated the in-season effect of intensified training comparing the efficacy of duration-matched intense intermittent exercise training with sprint interval training in increasing intermittent running performance, sprint ability, and muscle content of proteins related to ion handling and metabolism in football players. After the first two weeks in the season, 20 sub-elite football players completed either 10 weeks of intense intermittent training using the 10-20-30 training concept (10-20-30, n=12) or sprint interval training (SIT, n=10; work/rest-ratio: 6-s/54-s) three times weekly, with a ~20% reduction in weekly training time. Before and after the intervention, players performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) and a 30-m sprint test. Furthermore, players had a muscle biopsy taken from the vastus lateralis. Yo-Yo IR1 performance increased by 330 m (95%CI: 178-482, P≤0.01) in 10-20-30, whereas no change was observed in SIT. Sprint time did not change in 10-20-30, but decreased by 0.04 s (95%CI: 0.00-0.09, P≤0.05) in SIT. Muscle content of HADHA (24%, P≤0.01), PDH-E1α (40%, P≤0.01), complex I-V of the electron transport chain (ETC) (51%, P≤0.01) and Na+ ,K+ -ATPase subunits α2 (33%, P≤0.05) and β1 (27%, P≤0.05) increased in 10-20-30, whereas content of DHPR (27%, P≤0.01) and complex I-V of the ETC (31%, P≤0.05) increased in SIT. Intense intermittent training, combining short sprints and a high aerobic load, is superior to regular sprint interval training in increasing intense intermittent running performance during a Yo-Yo IR1 test and muscle content of PDH-E1α and HADHA in sub-elite football players.

Wed

13

Feb

2019

Latest research in football - week 2 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Impact of Sports-Related Subconcussive Injuries in Soccer Players
Reference: Semin Speech Lang. 2019 Feb;40(1):57-64. doi: 10.1055/s-0038-1676365. Epub 2019 Jan 7.
Authors: Díaz-Rodríguez YI, Salvatore AP
Summary: Sports-related subconcussive impacts to the head are receiving increased interest. Recent evidence indicates that subconcussive impacts will have greater relevance across time because of the number of repetitive impacts. Soccer players are at risk of receiving at least one impact during a soccer game. The authors review the cognitive-communication functioning following subconcussive head injuries in youth and recommendations for baseline assessments and cognitive-communication dysfunctions after subconcussive impacts in youth. The review is followed by a description and discussion of a study that assessed the cognitive-communicative dysfunction in young soccer players prior to and following a series of soccer matches and recommendations for monitoring recovery of cognitive-communication.


#2 Practical Torso Cooling During Soccer-Specific Exercise in the Heat
Reference: J Athl Train. 2018 Nov;53(11):1089-1097. doi: 10.4085/1062-6050-417-17. Epub 2019 Jan 7.
Authors: Parris K, Tyler CJ
Summary: Precooling and midevent cooling of the torso using cooling vests can improve exercise performance in the heat with or without physiological changes; however, the effects of such cooling during intermittent exercise in the heat are unknown. The objective of the study was to investigate the effects of torso cooling during intermittent exercise in the heat (35°C, 50% relative humdity) on sprint performance and the physiological and perceptual responses to the exercise. Ten non-heat-acclimated, male soccer players (age = 25 ± 2 years, height = 1.77 ± 0.06 m, mass = 72.9 ± 7.6 kg) participated in this study. Two 90-minute bouts of soccer-specific intermittent running in the heat: 1 trial with a cooling vest worn during the exercise and 1 trial without a cooling vest. Each trial comprised two 45-minute periods separated by approximately 15 minutes of seated rest in cool conditions (approximately 23°C, 50% relative humdity). Peak sprint speed, rectal temperature (Tr), mean-weighted skin temperature (Tsk), heart rate (HR), rating of perceived exertion (RPE), and thermal sensation (TS) were measured every 5 minutes. Peak sprint performance was largely unaffected by the cooling vest. The Tr, Tsk, HR, RPE, and TS were unaffected in the cooling-vest trial during the first 45 minutes, but Tr rose at a slower rate in the cooling-vest trial (0.026°C.min-1 ± 0.008°C.min-1) than in the no-vest trial (0.032°C.min-1 ± 0.009°C.min-1). During the second 45-minute period, Tr, Tr rate of rise, Tsk, RPE, and TS were lower in the cooling-vest trial (Hedges g range, 0.55-0.84), but mean HR was unaffected. Wearing a cooling vest during soccer-specific intermittent running in the heat reduced physiological and perceptual strain but did not increase peak sprint speed.


#3 Bone quality in young adults with intellectual disability involved in adapted competitive football
Reference: Eur J Sport Sci. 2019 Jan 9:1-10. doi: 10.1080/17461391.2018.1563633. [Epub ahead of print]
Authors: Lizondo V, Caplliure-Llopis J, Escrivá D, De La Rubia JE, Barrios C
Summary: The objective of this study was to analyse bone quality parameters of football players with intellectual disability (ID) participating in adapted competitive football. Sixty-seven male football players with ID were studied: 22 with Down syndrome (DS) and 45 without DS. The average age was 26 years (range: 16 ̶ 50 years). A group of 25 age-matched sedentary individuals with ID (11 DS and 14 non-DS) and another group of 20 healthy participants of the same age group not involved in competitive football were comparatively analysed. There were no differences in the bone quality parameters when the healthy sedentary individuals were compared with both the sedentary and the football players with ID. However, the speed of sound (SOS), T-score, and estimated bone mineral density (BMD) were of higher values in the football players with ID than in the sedentary ID group (p < 0.05). On comparing the football players with non-DS ID with the sedentary non-DS individuals, significant differences were noted in SOS (p < 0.01), T-scores (p < 0.01), and estimated BMD (p < 0.01). Four of the 45 non-DS (8.9%) and none of the football players with DS had T-scores less than -1.5. Two of the 14 sedentary non-DS participants (14.3%) had T-scores indicating osteoporosis. In summary, the ID population actively involved in football showed higher values of bone mass parameters than their sedentary ID and healthy peers. The participants with non-DS ID showed a higher prevalence of osteoporosis than the football players with DS. Participation in sports seems to prevent bone loss in individuals with ID.


#4 Dual Kinect v2 system can capture lower limb kinematics reasonably well in a clinical setting: concurrent validity of a dual camera markerless motion capture system in professional football players
Reference: BMJ Open Sport Exerc Med. 2018 Dec 17;4(1):e000441. doi: 10.1136/bmjsem-2018-000441. eCollection 2018.
Authors: Kotsifaki A, Whiteley R, Hansen C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307561/pdf/bmjsem-2018-000441.pdf
Summary: The purpose was to determine whether a dual-camera markerless motion capture system can be used for lower limb kinematic evaluation in athletes in a preseason screening setting. Thirty-four (n=34) healthy athletes participated. Three dimensional lower limb kinematics during three functional tests: Single Leg Squat (SLS), Single Leg Jump, Modified Counter-movement Jump. The tests were simultaneously recorded using both a marker-based motion capture system and two Kinect v2 cameras using iPi Mocap Studio software. Excellent agreement between systems for the flexion/extension range of motion of the shin during all tests and for the thigh abduction/adduction during SLS were seen. For peak angles, results showed excellent agreement for knee flexion. Poor correlation was seen for the rotation movements. This study supports the use of dual Kinect v2 configuration with the iPi software as a valid tool for assessment of sagittal and frontal plane hip and knee kinematic parameters but not axial rotation in athletes.


#5 Don't Turn Blind! The Relationship Between Exploration Before Ball Possession and On-Ball Performance in Association Football
Reference: Front Psychol. 2018 Dec 10;9:2520. doi: 10.3389/fpsyg.2018.02520. eCollection 2018.
Authors: McGuckian TB, Cole MH, Jordet G, Chalkley D, Pepping GJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6295565/pdf/fpsyg-09-02520.pdf
Summary: Visual exploratory action - scanning movements expressed through left and right rotation of the head - allows perception of a surrounding environment and supports prospective actions. In the dynamically changing football environment, the extent to which exploratory action benefits a player's subsequent performance with the ball is likely influenced by how and when the exploratory action occurs. Although few studies have examined the relationship between visual exploration and on-pitch football performance, it has been reported that a higher frequency of exploratory head movement up to 10-s before receiving the ball increases the likelihood of successful performance with the ball. This study investigated the relationship between head turn frequency and head turn excursion, and how and when exploratory head movement - within 10-s before ball possession - is related to performance with the ball in 11v11 match-play. Thirty-two semi-elite football players competed in 11v11 match-play. Head turn frequency and head turn excursion before ball possession were quantified with wearable inertial measurement units, and actions with the ball were coded via notational analysis. Odds ratio calculations were conducted to determine the associations between exploration variables and on-ball performance outcomes. A total of 783 actions with the ball were analyzed. Results revealed a strong relationship between head turn frequency and head turn excursion. Further, a higher than average head turn frequency and head turn excursion before receiving the ball resulted in a higher likelihood of turning with the ball, playing a pass in the attacking direction, and playing a pass to an area that is opposite to which it was received from. The strength of these outcomes varied for different time periods before receiving the ball. When players explored their environment with higher than average head turn frequency and excursion, they used more complex action opportunities afforded by the surrounding environment. Considerations for future research and practical implications are discussed.


#6 Use of viscosupplementation for the recovery of active football players complaining of knee pain
Reference: Open Access J Sports Med. 2018 Dec 24;10:11-15. doi: 10.2147/OAJSM.S164693. eCollection 2019.
Authors: Migliore A, Giannini S, Bizzi E, Massafra U, Cassol M, Abilius MJM, Boni G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307486/pdf/oajsm-10-011.pdf
Summary: The aim of this study is to investigate the effect of intra-articular hyaluronic acid administration in active football players complaining of knee pain after sports activity. Efficacy and safety profiles of intra-articular hyaluronic acid and time needed for football players to recover and restart sports activity were examined. Clinical data of active football players reporting knee pain after sports activity were included in this retrospective study. All patients who received an intra-articular injection at time 0 and after 2 weeks were included in the study. Patients underwent laboratory examination, knee X-ray, ultrasound, and clinical examination before receiving the intra-articular injection. Effusions or cysts were drained before injections. Lequesne index score, pain visual analog scale (VAS) score, and patient's global assessment score were recorded at time 0 (day of the first injection), 1 and 2 days after the first injection, at 2 weeks (day of the second injection), and at follow-up visits. Only data from patients completing the follow-up were analyzed. Data from 17 patients were analyzed: 16 males and one female, of which three were professional players (two males and one female) and 14 were nonprofessional players. The mean age of patients was 39.8±11.8 years. Two patients (one male and one female) showed joint effusion. Two patients reported relevant joint pain after injection that regressed without any medication. At the first week, all parameters examined indicated improvement that was maintained until the end of follow-up. One day after the first and second injection, patients reported a slight increase in pain VAS score, which was not statistically significant, and the pain resolved after 1 day. All patients successfully restarted playing after the first injection within 3.1±2.0 days and kept playing after the second injection following our indication (1 day of break). The use of a medium-molecular weight hyaluronic acid in football players affected by knee osteoarthritis seems efficacious and safe and resulted, in our experience, a stable improvement of symptoms; moreover, it allowed a rapid restart of sports activity. Larger studies on larger populations are needed to confirm these findings.


#7 The value of tibial mounted inertial measurement units to quantify running kinetics in elite football (soccer) players. A reliability and agreement study using a research orientated and a clinically orientated system
Reference: J Electromyogr Kinesiol. 2019 Jan 7;44:156-164. doi: 10.1016/j.jelekin.2019.01.001. [Epub ahead of print]
Authors: Hughes T, Jones RK, Starbuck C, Sergeant JC, Callaghan MJ
Summary: In elite football, measurement of running kinetics with inertial measurement units (IMUs) may be useful as a component of periodic health examination (PHE). This study determined the reliability of, and agreement between a research orientated IMU and clinically orientated IMU system for initial peak acceleration (IPA) and IPA symmetry index (SI) measurement during running in elite footballers. On consecutive days, 16 participants performed treadmill running at 14kmph and 18kmph. Both IMUs measured IPA and IPA SI concurrently. All measurements had good or excellent within-session reliability (intraclass correlation coefficient (ICC2,1) range = 0.79-0.96, IPA standard error of measurement (SEM) range = 0.19-0.62 g, IPA SI SEM range = 2.50-8.05%). Only the research orientated IMU demonstrated acceptable minimal detectable changes (MDCs) for IPA at 14kmph (range = 7.46-9.80%) and IPA SI at both speeds (range = 6.92-9.21%). Considering both systems, between-session IPA reliability ranged from fair to good (ICC2,1 range = 0.63-0.87, SEM range = 0.51-1.10 g) and poor to fair for IPA SI (ICC2,1 range = 0.32-0.65, SEM range = 8.07-11.18%). All MDCs were >10%. For IPA and SI, the 95% levels of agreement indicated poor between system agreement. Therefore, the use of IMUs to evaluate treadmill running kinetics cannot be recommended in this population as a PHE test to identify prognostic factors for injuries or for rehabilitation purposes.


#8 Premenstrual Syndrome, Inflammatory Status, and Mood States in Soccer Players
Reference: Neuroimmunomodulation. 2019 Jan 17:1-6. doi: 10.1159/000494559. [Epub ahead of print]
Authors: Foster R, Vaisberg M, Bachi ALL, Dos Santos JMB, de Paula Vieira R, Luna-Junior LA, Araújo MP, Parmigiano TR, Borges F, Di-Bella ZIKJ
Summary: The aim was to evaluate the relationship between the inflammatory profile and mood states in the different phases of the menstrual cycle in soccer players with and without premenstrual syndrome (PMS). Data on the menstrual cycle and mood states were collected using the Daily Symptom Report and the Brunel Mood Scale. Cytokine and stress hormone concentrations were measured in urine by flow cytometry before and after a game in the luteal phase and in the follicular phase of one menstrual cycle. In all, 59.6% of the athletes had PMS. The PMS group showed higher concentrations of interleukin (IL)-1β, IL-6, and IL-8 than the athletes without PMS. After the game, IL-6 decreased in the follicular phase and the luteal phase. The tumor necrosis factor-α levels were higher in the group without PMS during the post-game follicular phase than before the game. In the PMS group, tension was higher in the follicular phase before the game and depression was higher in the pre-game luteal phase than in the group without PMS. The PMS group also presented a negative correlation between depression and IL-10 levels in the pre-game follicular phase. Finally, in the pre-game luteal phase were found positive correlations between growth hormone and IL-10. PMS influences the inflammatory condition related to mood states and stress hormones in female soccer players.


#9 Nutrition-Related Considerations in Soccer: A Review
Reference: Am J Orthop (Belle Mead NJ). 2018 Dec;47(12). doi: 10.12788/ajo.2018.0100.
Authors: Keen R
Summary: Soccer is the world's most popular sport. As the sport has grown, so have the physical demands and the search for ways to edge out the competition with the use of sports science and nutrition. The demands, which include intense training, ≥90 minutes matches, congested fixtures, and travel, lead to increased energy and nutrient requirements, stress on the body, and risk of impaired sleep cycles. Identifying key areas to enhance a player's performance is an ongoing effort because of individual differences. Moreover, new information is being discovered via research, and advancing technology to measure performance is always evolving. This article focuses on the core nutrition principles known to lay the foundation for a better soccer player. These principles are obvious for some; however, nutrition and hydration are often undervalued, leaving the individual player with the responsibility to eat right. This review addresses the most applicable nutrition-related recommendations for soccer players.


#10 Limb Differences in Unipedal Balance Performance in Young Male Soccer Players with Different Ages
Reference: Sports (Basel). 2019 Jan 11;7(1). pii: E20. doi: 10.3390/sports7010020.
Authors: Muehlbauer T, Schwiertz G, Brueckner D, Kiss R, Panzer S
Download link: https://www.mdpi.com/2075-4663/7/1/20/pdf
Summary: In soccer, the dominant leg is frequently used for passing and kicking while standing on the non-dominant leg. Consequently, postural control in the standing leg might be superior compared to the kicking leg and is further enhanced with increasing age (i.e., level of playing experience). Unfortunately, leg differences in postural control are associated with an increased risk of injuries. Thus, we examined differences between limbs in unipedal balance performance in young soccer players at different ages. Performance in the Lower Quarter Y Balance Test (YBT-LQ) of the dominant and non-dominant leg and anthropometry was assessed in 76 young male soccer players (under-13 years [U13]: n = 19, U15: n = 14, U17: n = 21, U19: n = 22). Maximal reach distances (% leg length) and the composite scores were used for further analyses. Statistical analyses yielded no statistically significant main effects of leg or significant Leg × Age interactions, irrespective of the measure investigated. However, limb differences in the anterior reach direction were above the proposed cut-off value of >4 cm, which is indicative of increased injury risk. Further, statistically significant main effects of age were found for all investigated parameters, indicating larger reach distances in older (U19) compared to younger (U13) players (except for U15 players). Although reach differences between legs were non-significant, the value in the anterior reach direction was higher than the cut-off value of >4 cm in all age groups. This is indicative of an increased injury risk, and thus injury prevention programs should be part of the training of young soccer players.


#11 Recruiting Older Men to Walking Football: A Pilot Feasibility Study
Reference: Explore (NY). 2018 Dec 11. pii: S1550-8307(18)30194-0. doi: 10.1016/j.explore.2018.12.001. [Epub ahead of print]
Authors: McEwan G, Buchan D, Cowan D, Arthur R, Sanderson M, Macrae E
Summary: Walking football (soccer) has recently emerged as a physical activity option targeted at older males to enhance health and wellbeing. This pilot study aimed to examine the feasibility of recruiting and retaining males aged 50 years and over to an 8-week walking football programme in a professional football club. Participants were recruited via social media and assigned to an intervention group or a wait-list control group. The intervention group engaged in 1 h of walking football a week led by a community coach from the professional football club, followed by an optional social session in the club facility. Physiological and psychological outcome measures were obtained onsite at the football club facility (aiding compliance and retention) at baseline and following 8-weeks, from both groups. Semi-structured interviews were conducted after the 8-week programme and 1 year later, to explore motivations for engagement and the social impact. The opportunity to engage in football and the link to a professional football club were key attractions. All participants recruited were overweight, sedentary, exhibited blood pressures outside normal ranges, and all but two were hypertensive. Adherence to the programme was 90% over 8 weeks, and of the participants who were contacted after one year, all (n = 6) had maintained engagement in walking football. Walking football is therefore a feasible, cost-effective method of recruiting and retaining males aged 50 years and over to a physical activity programme, though attrition is to be expected.

Thu

07

Feb

2019

Latest research in football - week 1 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Visualizing a Team's Goal Chances in Soccer from Attacking Events: A Bayesian Inference Approach
Reference: Big Data. 2018 Dec 1;6(4):271-290. doi: 10.1089/big.2018.0071. Epub 2018 Dec 13.
Authors: Whitaker GA, Silva R, Edwards D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306690/pdf/big.2018.0071.pdf
Summary: We consider the task of determining the number of chances a soccer team creates, along with the composite nature of each chance-the players involved and the locations on the pitch of the assist and the chance. We infer this information using data consisting solely of attacking events, which the authors believe to be the first approach of its kind. We propose an interpretable Bayesian inference approach and implement a Poisson model to capture chance occurrences, from which we infer team abilities. We then use a Gaussian mixture model to capture the areas on the pitch a player makes an assist/takes a chance. This approach allows the visualization of differences between players in the way they approach attacking play (making assists/taking chances). We apply the resulting scheme to the 2016/2017 English Premier League, capturing team abilities to create chances, before highlighting key areas where players have most impact.


#2 Predicting the defensive performance of individual players in one vs. one soccer games
Reference: PLoS One. 2018 Dec 31;13(12):e0209822. doi: 10.1371/journal.pone.0209822. eCollection 2018.
Authors: Wilson RS, Smith NMA, Santiago PRP, Camata T, Ramos SP, Caetano FG, Cunha SA, Sandes de Souza AP, Moura FA
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209822&type=printable
Summary: The aim of this study was to use technical skill and physical performance and coaches' rankings to predict the defensive performance of junior soccer players. Twenty-one male players (mean age 17.2 years, SD = 1.1) were recruited from the Londrina Junior Team Football Academy in Brazil. Data were collected during regular training sessions. After participants had warmed up, players were asked to either dribble the ball or sprint through five custom circuits that varied in average curvature (0-1.37 radians.m-1). In addition, four coaches were asked to rank the players from best to worst in defensive ability. Dribbling, sprinting, and coaches' rankings were then compared with defending performance as assessed in the one vs. one competitions (N = 1090 paired-trials: 40-65 trials per individual), in which they acted as defender or attacker in turn. When defending, the objective was to steal the ball or prevent the attacker from running around them with the ball into a scoring zone. Testing occurred over three days. Overall, dribbling performance (r = 0.56; P = 0.008) and coaches' ranking (r = 0.59; P = 0.004) were significantly related to defensive ability; sprinting performance was not (r = 0.20; P = 0.38). Though dribbling performance and coaches' ranking each explained 30% and 37% of the variance in defensive performance, respectively, the two predictors were not related (r = 0.27; P = 0.23), so combined these traits explained more than half the variance in defensive performance. In conclusion, the current study demonstrates that including only one metric of closed-skill performance-dribbling speed-doubles the ability of coaches to identify their best defensive players in one vs. one scenarios.


#3 Patellar and Achilles Tendon Stiffness in Elite Soccer Players Assessed Using Myotonometric Measurements
Reference: Sports Health. 2019 Jan 2:1941738118820517. doi: 10.1177/1941738118820517. [Epub ahead of print]
Authors: Cristi-Sánchez I, Danes-Daetz C, Neira A, Ferrada W, Yáñez Díaz R, Silvestre Aguirre R
Summary: Tendon overuse injuries are an issue in elite footballers (soccer players) and may affect tendon function. Achilles and patellar tendinopathy are the most frequent pathologies. Tendon stiffness, the relationship between the force applied to a tendon and the displacement exerted, may help represent tendon function. Stiffness is affected by training and pathology. Nevertheless, information regarding this mechanical property is lacking for elite soccer athletes. Achilles and patellar tendon stiffness assessed using myotonometric measurements will be greater in elite soccer athletes than in control participants. Forty-nine elite soccer athletes and 49 control participants were evaluated during the 2017 preseason. A handheld device was used to measure Achilles and patellar tendon stiffness. Dominant and nondominant limbs were assessed for both groups. A significantly stiffer patellar tendon was found for both the dominant and the nondominant limb in the elite soccer athletes compared with the control group. Nevertheless, no differences were found in Achilles tendon stiffness between groups. When comparing between playing positions in soccer athletes, no significant differences were found for both tendons. Greater patellar tendon stiffness may be related to an improvement in force transmission during muscle contraction. On the other hand, it seems that after years of professional training, Achilles tendon stiffness does not change, conserving the storing-releasing function of elastic energy. The nonsignificant differences between positions may be attributable to the years of homogeneous training that the players underwent. The present study shows another technique for measuring mechanical properties of tendons in soccer athletes that could be used in clinical settings. In the future, this technique may help clinicians choose the best exercise protocol to address impairments in tendon stiffness.


#4 Examination of Physical Characteristics and Positional Differences in Professional Soccer Players in Qatar
Reference: Sports (Basel). 2018 Dec 31;7(1). pii: E9. doi: 10.3390/sports7010009.
Authors: Wik EH, Auliffe SM, Read PJ
Download link: https://www.mdpi.com/2075-4663/7/1/9/pdf
Summary: Physical characteristics in professional soccer differ between competition levels and playing positions, and normative data aid practitioners in profiling their players to optimize performance and reduce injury risk. Given the paucity of research in Arabic soccer populations, the purpose of this study was to provide position-specific normative values for professional players competing in the Qatar Stars League. One hundred and ninety-five players completed a musculoskeletal assessment as part of an annual periodic health examination. Tests included measures of range of motion (hip, ankle, and hamstring), bilateral and unilateral jump performance, and quadriceps/hamstring (isokinetic/NordBord), hip adduction/abduction (eccentric), and groin (isometric) strength. Descriptive data were examined, and positional differences were analyzed using a one-way analysis of variance (ANOVA). Goalkeepers were significantly heavier (p < 0.01), had a higher body mass index (p < 0.05) than outfield positions and demonstrated greater absolute strength. Defenders were the strongest relative to body mass, and these differences were significant (p < 0.05) versus goalkeepers and strikers. No meaningful between-group comparisons were apparent for jumping or range of motion tests. Compared to mean values from other professional leagues, soccer players in Qatar appear to be shorter, lighter and display inferior strength and jump capacities. These data can be used to tailor training and rehabilitation programs to the specifics of the league and position in which the athletes compete.


#5 Photobiomodulation therapy as a tool to prevent hamstring strain injuries by reducing soccer-induced fatigue on hamstring muscles
Reference: Lasers Med Sci. 2019 Jan 3. doi: 10.1007/s10103-018-02709-w. [Epub ahead of print]
Authors: Dornelles MP, Fritsch CG, Sonda FC, Johnson DS, Leal-Junior ECP, Vaz MA, Baroni BM
Summary: Muscle fatigue is a potential risk factor for hamstring strain injuries in soccer players. The aim of this study was to verify the effect of photobiomodulation therapy (PBMT) on the hamstrings' muscle fatigue of soccer players during a simulated match. Twelve male amateur soccer players (~ 25 years) participated in this randomized, crossover, double-blinded, placebo-controlled trial. The volunteers were evaluated in two sessions, with a minimum 7-day interval. At each session, volunteers received either PBMT (300 J per thigh) or placebo treatment on the hamstrings prior to the simulated soccer match. Muscle strength and functional capacity were evaluated through isokinetic dynamometry and countermovement jump (CMJ) tests, respectively, before and immediately after the simulated soccer match. Players had lower reductions on hamstring eccentric peak torque [4.85% (ES = 0.31) vs. 8.72% (ES = 0.50)], hamstring-to-quadriceps torque ratio [3.60% (ES = 0.24) vs. 7.75% (ES = 0.50)], and CMJ height [1.77% (ES = 0.09) vs. 5.47% (ES = 0.32)] when treated with PBMT compared to placebo. Magnitude-based inference supports that PBMT promoted 75%, 69%, and 53% chances for beneficial effects on hamstring eccentric peak torque, hamstring-to-quadriceps torque ratio, and CMJ height, respectively, compared to placebo treatment. In conclusion, PBMT applied before a simulated soccer match proved to be effective in attenuating the hamstrings' muscle fatigue. These findings support PBMT as a promising tool to prevent hamstring strain injury in soccer players.


#6 Accelerations - a new approach to quantify physical performance decline in male elite soccer?
Reference: Eur J Sport Sci. 2019 Jan 11:1-9. doi: 10.1080/17461391.2019.1566403. [Epub ahead of print]
Authors: Dalen T, Lorås H, Hjelde GH, Kjøsnes TN, Wisløff U
Summary: The aim of the current study was (1) to investigate whether the number of accelerations is a more precise estimate of performance decline in soccer compared to distances with high-speed running (HSR) and (2) to compare changes in the number of accelerations and HSR distances across playing positions in order to examine whether the match profiles of the physical measures are consistent or demonstrate high interposition variability. The dataset includes domestic home games (N = 34) over three full seasons (2012-2014) for a team in the Norwegian Elite League. The change in the number of accelerations throughout the match demonstrates a more clear pattern compared to the distance covered by HSR. In numbers of accelerations, a systematic and linear decrease can be observed throughout the match, with 34% less accelerations from the first to the last 5-minute period of the game (6.7 vs. 4.4 accelerations). This pattern of results captures the change in the number of accelerations across all positions. HSR distance had more variability during the match. All five positions investigated displayed a similar trend in accelerations and HSR profiles after the peak periods in each half. In contrast to the absolute number of accelerations, there were major positional differences in the mean HSR distance during the match. Our data suggest a more visible performance decline in the number of accelerations from the start to the end of the game, than the decline in the distance covered by HSR distance.


#7 A Nationwide Follow-up Survey on the Effectiveness of an Implemented Neuromuscular Training Program to Reduce Acute Knee Injuries in Soccer Players
Reference: Orthop J Sports Med. 2018 Dec 21;6(12):2325967118813841. doi: 10.1177/2325967118813841. eCollection 2018 Dec.
Authors: Åman M, Larsén K, Forssblad M, Näsmark A, Waldén M, Hägglund M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6304704/pdf/10.1177_2325967118813841.pdf
Summary: A cruciate ligament (CL) injury is a severe injury in soccer. Neuromuscular training programs have a well-documented preventive effect, but there are few studies on the effectiveness of such a program at a national level. The Swedish Knee Control Program (KCP) was found to be effective in preventing CL injuries in youth female soccer players. The KCP was implemented nationwide in Sweden in 2010. The purpose was to evaluate the effectiveness of the Swedish KCP in reducing acute knee injuries in soccer players at a nationwide level. All licensed soccer players in Sweden are covered by the same insurance company. Using this insurance database, around 17,500 acute knee injuries that were reported to the insurance company between 2006 and 2015 were included in the study. By matching the number of licensed soccer players with the number of reported injuries each year, the annual incidence of knee and CL injuries was able to be calculated. To evaluate the spread of the KCP nationally, a questionnaire was sent to all 24 Swedish district football associations (FAs) with questions regarding KCP education. The number of downloads of the KCP mobile application (app) was obtained. The incidence of CL injuries decreased during the study period for both male (from 2.9 to 2.4 per 1000 player-years) and female players (from 4.9 to 3.9 per 1000 player-years). The overall incidence of knee injuries decreased in both male (from 5.6 to 4.6 per 1000 player-years) and female players (from 8.7 to 6.4 per 1000 player-years). Comparing before and after the nationwide implementation of the KCP, there was a decrease in the incidence of CL injuries by 6% (rate ratio [RR], 0.94 [95% CI, 0.89-0.98]) in male players and 13% (RR, 0.87 [95% CI, 0.81-0.92]) in female players and a decrease in the incidence of knee injuries by 8% (RR, 0.92 [95% CI, 0.89-0.96]) and 21% (RR, 0.79 [95% CI, 0.75-0.83]), respectively (P < .01 for all). This trend corresponded to a reduction of approximately 100 CL injuries each year in Sweden. A total of 21 of 24 district FAs held organized KCP educational courses during the study period. The percentage of district FAs holding KCP courses was between 46% and 79% each year. There were 101,236 downloads of the KCP app. The KCP can be considered partially implemented nationwide, and the incidence of knee and CL injuries has decreased in both sexes at a nationwide level.


#8 Cardio respiratory response: Validation of new modifications of Bruce protocol for exercise testing and training in elite Saudi triathlon and soccer players
Reference: Saudi J Biol Sci. 2019 Jan;26(1):105-111. doi: 10.1016/j.sjbs.2017.05.009. Epub 2017 May 19.
Authors: Badawy MM, Muaidi QI
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6319022/pdf/main.pdf
Summary: The Bruce protocol is the traditional method used to assess maximal fitness level, although it may have limitations, such as its short duration and large work rate increases, with very high levels of exertion that consist of speed/incline combinations. Modifications have been added to elicit similar maximal fitness achievements. The authors of this experimental trial have proposed a new treadmill protocol that allows optimal test duration in conjunction with peak oxygen consumption 'VO2max', and with appropriate patient comfort and safety during both exercise testing and training. Twenty-two elite Saudi players, comprising eleven Saudi triathlon athletes, and eleven Saudi elite soccer players, BMI, body fat mass percentage, body fat free mass percentage. cardiovascular parameter; including, absolute and relative "VO2max" as well as maximal heart rate "HR max", were assessed during a graded treadmill running modified protocol, using a Quark Cardio Pulmonary Exercise Testing Unit (CPET). Descriptive statistics were used to obtain the anthropometric characteristics, including comparisons between the means, independent sample T-test and a regression analysis, to test the association of the protocol duration and the corresponding, dependent variables. It is often difficult to achieve a high cardiorespiratory response, VO2max, without an association to high values of HR max, and peak perceived exertion. This may lead to cardiovascular risk. Our new modifications can provide a practical, valid alternative protocol to be used comfortably both during exercise testing and training, rather than performance testing only, to achieve high VO2max with minimal cardiovascular stress.


#9 Knee Angle Affects Posterior Chain Muscle Activation During an Isometric Test Used in Soccer Players
Reference: Sports (Basel). 2019 Jan 4;7(1). pii: E13. doi: 10.3390/sports7010013.
Authors: Read PJ, Turner AN, Clarke R, Applebee S, Hughes J
Download link: https://www.mdpi.com/2075-4663/7/1/13/pdf
Summary: It has been suggested that altering the knee flexion angle during a commonly used supine isometric strength test developed with professional soccer players changes preferential hamstring muscle recruitment. The aim of this study was to examine the electromyography (EMG) knee joint-angle relationship during this test, as these data are currently unknown. Ten recreational male soccer athletes (age: 28 ± 2.4 years) were recruited and performed a supine isometric strength test on their dominant leg with the knee placed at two pre-selected flexion angles (30° and 90°). The surface EMG of the gluteus maximus, biceps femoris, semitendinosus, and medial gastrocnemius was measured, in addition to the within-session reliability (intraclass correlation coefficient (ICC) and coefficient of variation (CV)). Within-session reliability showed large variation dependent upon the test position and muscle measured (CV% = 8.8⁻36.1) Absolute mean EMG activity and percentage of maximum voluntary isometric contraction (MVIC) indicated different magnitudes of activation between the two test positions; however, significant mean differences were present for the biceps femoris only with greater activation recorded at the 30° knee angle (% MVIC: 31 ± 9 vs. 22 ± 7; p = 0.002). These differences (30% mean difference) were greater than the observed typical measurement error (CV% = 13.1⁻14.3 for the 90° and 30° test positions, respectively). Furthermore, the percentage MVIC showed a trend of heightened activation of all muscles with the knee positioned at 30°, but there was also more within-subject variation, and this was more pronounced for the gluteus maximus (CV% = 36.1 vs. 19.8) and medial gastrocnemius (CV% 31 vs. 22.6). These results indicate that biceps femoris and overall posterior chain muscle activation is increased with the knee positioned at 30° of flexion; however, the 90° angle displayed less variation in performance within individual participants, especially in the gluteus maximus and medial gastrocnemius. Thus, practitioners using this test to assess hamstring muscle strength should ensure appropriate familiarisation is afforded, and then may wish to prioritise the 30° knee position.


#10 Interpersonal Coordination in Soccer: Interpreting Literature to Enhance the Representativeness of Task Design, From Dyads to Teams
Reference: Front Psychol. 2018 Dec 11;9:2550. doi: 10.3389/fpsyg.2018.02550. eCollection 2018.
Authors: Santos R, Duarte R, Davids K, Teoldo I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6297834/pdf/fpsyg-09-02550.pdf
Summary: Interpersonal coordination in soccer has become a trending topic in sports sciences, and several studies have examined how interpersonal coordination unfolds at different levels (i.e., dyads, sub-groups, teams). Investigations have largely focused on interactional behaviors at micro and macro levels through tasks from dyadic (i.e., 1 vs. 1) to team (i.e., 11 vs. 11) levels. However, as the degree of representativeness of a task depends on the magnitude of the relationship between simulated and intended environments, it is necessary to address a discussion on the correspondence between competitive and practice/experimental settings in soccer. The aims of this paper are to: (i) provide a brief description of the main concepts underlying the subject of interpersonal coordination in sports teams; (ii) demonstrate, through exemplar research findings, how interpersonal coordination in soccer unfolds at different scales; and (iii), discuss how coaches and researchers may ensure representativeness for practice and experimental tasks. We observed that papers addressing the analysis of interpersonal coordination tendencies in soccer often resort to dyadic (one vs. one) or sub-group (many vs. many) experimental tasks, instead of full-sized (11 vs. 11) games. Consequently, the extent to which such patterns reflect those observed in competition is somewhat uncertain. The design of practice and/or experimental tasks that rely on sub-phases of the game (e.g., 1 vs. 1, 4 vs. 4) should ensure the preservation of players' behavior patterns in intended match conditions (11 vs. 11). This can be accomplished by measuring the level of action fidelity of the task, ensuring correspondence and successful transfer across contexts.


#12 Use of Saliva in Alternative to Serum Sampling to Monitor Biomarkers Modifications in Professional Soccer Players
Reference: Front Physiol. 2018 Dec 20;9:1828. doi: 10.3389/fphys.2018.01828. eCollection 2018.
Authors: Francavilla VC, Vitale F, Ciaccio M, Bongiovanni T, Marotta C, Caldarella R, Todaro L, Zarcone M, Muratore R, Bellia C, Francavilla G, Mazzucco W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306404/pdf/fphys-09-01828.pdf
Summary: We aimed to investigate the correlation between serum and salivary concentrations of steroid hormones and IgA, and the variation in concentrations of these biomarkers, across a soccer competitive season in a sample of players playing for an Italian major League team. Thirty-five elite male soccer players were recruited and assessed for salivary hormones (cortisol, testosterone, T/C‰ and DHEA-S) and IgA at three different time-points: (t1) after the pre-season period and 16 official matches played; (t2) after a winter break and three official matches played; (t3) 2 days after the final match of the championship and 19 matches played. Players were also tested for blood biomarkers (ser-C, ser-T, ser-T/C‰, ser-IgA, ACTH) at two detection times (t1 and t3). Blood samples were collected immediately after saliva sampling. The Spearman's rank correlation was used to explore the correlation between blood and salivary concentrations of cortisol, free testosterone and IgA in the different time points. One-way ANOVA and permutation test were performed to explore changes by time of hormones and IgA concentrations over the competitive season. We documented a positive correlation between serum and saliva concentrations for Cortisol at t1 (+58.2%; p-value = 0.002) and t3 (+54.2%; p-value = 0.018) and for Testosterone at t1 (+42.0%; p-value = 0.033). Moreover, a positive variation was documented across the season (D = t3-t1) for Cortisol (D = +6.83; SEM = ±2.70; Var% = +37.6; p-value = 0.032), Testosterone (D = +0.33; SEM = ±0.07; Var% = +27.3; p-value = 0.002) and DHEA-S (D = +44.48; SEM = ±18.54; Var% = +82.0; p-value = 0.042), while a decrease of sal-T/C ratio and no variation in salivary IgA concentrations were reported. In conclusion, our findings support for experimental use of saliva samples to monitor steroid hormones modifications in professional soccer players across a competitive season.

Wed

06

Feb

2019

Latest research in football - week 52 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Reliability and validity of field-based fitness tests in youth soccer players
Reference: Eur J Sport Sci. 2018 Dec 27:1-12. doi: 10.1080/17461391.2018.1556739. [Epub ahead of print]
Authors: Dugdale JH, Arthur CA, Sanders D, Hunter AM
Summary: This study aimed to establish between-day reliability and validity of commonly used field-based fitness tests in youth soccer players of varied age and playing standards, and to discriminate between players without ("unidentified") or with ("identified") a direct route to professional football through their existing club pathway. Three-hundred-and-seventy-three Scottish youth soccer players (U11-U17) from three different playing standards (amateur, development, performance) completed a battery of commonly used generic field-based fitness tests (grip dynamometry, standing broad jump, countermovement vertical jump, 505 (505COD) and T-Drill (T-Test) change of direction and 10/20 m sprint tests) on two separate occasions within 7-14 days. The majority of field-based fitness tests selected within this study proved to be reliable measures of physical performance (ICC = 0.83-0.97; p < .01). However, COD tests showed weaker reliability in younger participants (ICC = 0.57-0.79; p < .01). The field-based fitness testing battery significantly discriminated between the unidentified and identified players; χ2 (7) = 101.646, p < .001, with 70.2% of players being correctly classified. We have shown field-based fitness tests to be reliable measures of physical performance in youth soccer players. However, results from the 505COD and T-Test change of direction tests may be more variable in younger players, potentially due to complex demands of these tests and the limited training age established by these players. While the testing battery selected in this study was able to discriminate between unidentified and identified players, findings were inconsistent when attempting to differentiate between individual playing standards within the "identified" player group (development vs. performance).


#2 Factors influencing hydration status during a National Collegiate Athletics Association division 1 soccer preseason
Reference: J Sci Med Sport. 2018 Dec 14. pii: S1440-2440(18)31245-3. doi: 10.1016/j.jsams.2018.12.005. [Epub ahead of print]
Authors: Sekiguchi Y, Adams WM, Curtis RM, Benjamin CL, Casa DJ
Summary: The purpose was to investigate the roles that training load and environmental conditions have on fluid balance during a collegiate men's soccer preseason. Twenty-eight male collegiate soccer players (mean±SD; age, 20±1.7y; body mass (BM), 79.9±7.3kg; height, 180.9±6.8cm; body fat, 12.7±3.1%; VO2max, 50.7±4.3ml·kg-1·min-1) participated in this study. Prior to (PRE) and following (POST) each team session, BM, percent BM loss (%BML) and hydration status was measured. Participants donned a heart rate and GPS enabled monitor to measure training load. For all team activities, ambient temperature (TAMB) and relative humidity (RH) were obtained from the nearest local weather station. Participants consumed 500mL of water as part of the team-based hydration strategy before and after training session. Stepwise linear regression was used to identify the variables that predicted %BML. Significance was set a-priori p<0.05. Total distance covered predicted %BML during all preseason activities (r2=0.253, p<0.001), with TAMB and RH further adding to the model (r2=0.302, p<0.001). %BML never exceeded 2% of BM during any one session and daily variation in BM was <1% from baseline measures. Urine specific gravity was greater than 1.020 on 12/15days and UCOL was above 4 on 13/15days, indicating a state of hypohydration. Total distance covered was the best predictor for the extent of body water losses during a collegiate preseason. While the team-based hydration strategy during preseason was successful in minimizing fluid losses during activity, participants arrived hypohydrated 80% of the time, necessitating a greater focus on daily fluid needs.


#3 Assessing the validity of a video-based decision-making assessment for talent identification in youth soccer
Reference: J Sci Med Sport. 2018 Dec 21. pii: S1440-2440(18)30435-3. doi: 10.1016/j.jsams.2018.12.011. [Epub ahead of print]
Authors: Bennett KJM, Novak AR, Pluss MA, Coutts AJ, Fransen J
Summary: The aim was to investigate the construct and discriminant validity of a video-based decision-making assessment for talent identification in youth soccer. A total of 328 academy youth soccer players (tier one, tier two, and tier three) from three developmental stages (late childhood, early adolescence, and mid-adolescence) participated in this study. The control group consisted of 59 youth athletes with no soccer experience in the last five years. Players completed a video-based decision-making assessment on an iPad, with response accuracy and response time recorded for various attacking situations (2 vs. 1, 3 vs. 1, 3 vs. 2, 4 vs. 3, and 5 vs. 3). The video-based decision-making assessment showed some construct validity. Response times were significantly faster in early and mid-adolescent players when compared to those in the late childhood group. Furthermore, an overall decline in decision-making performance (i.e. decrease in response accuracy and increase in response time) was observed from the 2 vs. 1 to the 4 vs. 3 situations. The video-based decision-making assessment lacked discriminant validity as minimal differences between academies were evident for response accuracy and response time. Only response accuracy was able to discriminate youth academy soccer players from the control group to some extent. Coaches and sporting professionals should apply caution when interpreting data from practical, video-based decision-making assessments. There is currently limited conclusive evidence supporting the effectiveness of these assessments for talent identification.


#4 Influences of Synchronized Metronome Training on Soccer Players' Timing Ability, Performance Accuracy, and Lower-Limb Kinematics
Reference: Front Psychol. 2018 Dec 7;9:2469. doi: 10.3389/fpsyg.2018.02469. eCollection 2018.
Authors: Rönnqvist L, McDonald R, Sommer M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6292953/pdf/fpsyg-09-02469.pdf
Summary: Planning and performance of all complex movement requires timing, integration, and coordination between sensory-perception and motor production to be successful. Despite this, there is limited research into "if" and "how" timing training may influence movement performance in athletes. The aim of the present study was to investigate the effect of synchronized metronome training (SMT) on sensorimotor timing ability, and in view of that, if improved timing may be transferred to lower-limb movement planning, precision performance, and kinematics. The sample consisted of 24 female elite- and semi-elite soccer players, randomly assigned to receive SMT and a control group. The SMT group received 12 sessions of Interactive Metronome® (IM) training over 4 weeks. At pre- and post-test, timing-precision was assessed through hand and feet movement synchronization with rhythmic sound; and leg-movements performance accuracy, duration, and kinematics were recorded during embodied high cognitive-load stepping task (6 trials×20 s) by use of a optoelectronic motion capture system. Pre- to post-test comparisons showed significant timing improvements as an effect of the IM training. Significant pre- to post-test improvements on the stepping task performance were seen in an increasing number of accurate foot taps during the stepping task sequence and by shorter duration for the SMT-group only. No evident pre- to post-test effects of SMT on the kinematic parameters investigated were found. These findings signify that the guided attention and working-memory functioning may be positively affected by SMT training; thereby, resulting in better motor planning, performance, and movement precision. Still, independent of group and test-occasion, significant correlations were found between the participants' outcome performance differences and the kinematic parameters. It was found that a decreasing 3D movement distance and less segmented movements correlating negatively, and increasing velocity (speed) positively, with accuracy and performance duration, respectively. These findings are likely associated with inter-individual variations in the nature of higher-order cognitive processing capacity due to the highly cognitive demanding stepping task.


#5 Amyotrophic Lateral Sclerosis and soccer: an internet survey of 29 Italian players
Reference: Ann Ist Super Sanita. 2018 Oct-Dec;54(4):364-369. doi: 10.4415/ANN_18_04_14.
Authors: Vanacore N, Barbariol P, Caffari B, Lacorte E, Bacigalupo I, Spila Alegiani S
Download link: http://old.iss.it/binary/publ/cont/ANN_18_04_14.pdf
Summary: Previous epidemiological studies reported a significantly higher risk of Amyotrophic Lateral Sclerosis (ALS) in Italian male soccer players. As a consequence, sports newspapers and news agencies focused on this issue and spread the news of 51 male soccer players with a reported diagnosis of ALS. We searched news on male Italian national soccer players with a reported diagnosis of ALS quoted from January 1, 1950 to July 31, 2016 in at least two Internet web sites or in books by journalists. A total of 39 male soccer players with a reported diagnosis of ALS were identified. Subjects were born from 1905 to 1973, 32 were currently deceased, 6 were still living, while the status of 1 player was unknown. All gathered information was available for 29 soccer players. The group had a mean age at diagnosis of 45.3 ± 12.2 years, a mean age at onset of symptoms of 46.4 ± 12.1 years, and a mean age at death of 50.9 ± 12.3 years. A significant inverse correlation between year of birth and age at onset of symptoms was observed, with a younger age at onset of symptoms in soccer players born in more recent years (r = -0.65, p < 0.01). Italian male soccer players with a reported diagnosis of ALS have a significantly younger age at diagnosis when compared to other European patients with ALS. Results support a possible relationship between soccer and the risk of ALS. We believe that further research is urgently needed in this field.


#6 Dark Chocolate Intake Positively Modulates Redox Status and Markers of Muscular Damage in Elite Football Athletes: A Randomized Controlled Study
Reference: Oxid Med Cell Longev. 2018 Nov 21;2018:4061901. doi: 10.1155/2018/4061901. eCollection 2018.
Authors: Cavarretta E, Peruzzi M, Del Vescovo R, Di Pilla F, Gobbi G, Serdoz A, Ferrara R, Schirone L, Sciarretta S, Nocella C, De Falco E, Schiavon S, Biondi-Zoccai G, Frati G, Carnevale R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280237/pdf/OMCL2018-4061901.pdf
Summary: Intensive physical exercise may cause increase oxidative stress and muscular injury in elite football athletes. The aim of this study was to exploit the effect of cocoa polyphenols on oxidative stress and muscular injuries induced by intensive physical exercise in elite football players. Oxidant/antioxidant status and markers of muscle damage were evaluated in 24 elite football players and 15 controls. Furthermore, the 24 elite football players were randomly assigned to either a dark chocolate (>85% cocoa) intake (n = 12) or a control group (n = 12) for 30 days in a randomized controlled trial. Oxidative stress, antioxidant status, and muscle damage were assessed at baseline and after 30 days of chocolate intake. Compared to controls, elite football players showed lower antioxidant power and higher oxidative stress paralleled by an increase in muscle damage markers. After 30 days of dark chocolate intake, an increased antioxidant power was found in elite athletes assuming dark chocolate. Moreover, a significant reduction in muscle damage markers (CK and LDH, p < 0.001) was observed. In the control group, no changes were observed with the exception of an increase of sNox2-dp, H2O2, and myoglobin. A simple linear regression analysis showed that sNox2-dp was associated with a significant increase in muscle damage biomarker release (p = 0.001). An in vitro study also confirmed that polyphenol extracts significantly decreased oxidative stress in murine myoblast cell line C2C12-derived. These results indicate that polyphenol-rich nutrient supplementation by means of dark chocolate positively modulates redox status and reduced exercise-induced muscular injury biomarkers in elite football athletes.


#7 "Macro-structure" of developmental participation histories and "micro-structure" of practice of German female world-class and national-class football players
Reference: J Sports Sci. 2018 Dec 24:1-9. doi: 10.1080/02640414.2018.1558744. [Epub ahead of print]
Authors: Güllich A
Summary: The study examined the "micro-structure" of football practice and the "macro-structure" of participation history of female professional football players. Participants were 29 German 1st league (Bundesliga) players, 14 of whom played on the senior national team (Olympic Champion in 2016). A questionnaire recorded the players' positions, proportions of physical conditioning, drill-type skill exercises and playing forms within coach-led football practice, and the volume of coach-led practice and peer-led play, in both football and other sports, from childhood to adulthood. Analyses revealed that most athletes played various attacker and defender positions during development. National team players differed from their Bundesliga peers by less physical conditioning and greater proportions of playing forms within football practice. National team players also accumulated less total football practice until age 18 years, but more peer-led football and coach-led practice in other sports compared to their Bundesliga counterparts. Based on these variables, a binary logistic regression classified 93% of the national team and Bundesliga players correctly. Conclusion: A combination of long-term coach-led football practice involving a relatively large proportion of playing forms with considerable childhood/adolescent peer-led football play and coach-led practice in other sports may have facilitated adult performance among German female world-class football players.


#8 Comparison of head impact exposure in practice drills among multiple youth football teams
Reference: J Neurosurg Pediatr. 2018 Dec 21:1-9. doi: 10.3171/2018.9.PEDS18314. [Epub ahead of print]
Authors: Kelley ME, Espeland MA, Flood WC, Powers AK, Whitlow CT, Maldjian JA, Stitzel JD, Urban JE
Summary: Limiting contact in football practice can reduce the number of head impacts a player receives, but further research is needed to inform the modification of optimal drills that mitigate head impact exposure (HIE) while the player develops the skills needed to safely play the game. This study aimed to compare HIE in practice drills among 6 youth football teams and to evaluate the effect of a team on HIE. On-field head impact data were collected from athletes (ages 10-13 years) playing on 6 local youth football teams (teams A-F) during all practices using the Head Impact Telemetry System. Video was recorded and analyzed to verify and assign impacts to a specific drill. Drills were identified as follows: dummy/sled tackling, half install, install, install walk through, multiplayer tackle, Oklahoma, one-on-one, open field tackling, other, passing, position skill work, scrimmage, special teams, tackling drill stations, and technique. HIE was quantified in terms of impacts per player per minute (ppm) and peak linear and rotational head acceleration. Generalized linear models were used to assess differences in head impact magnitude and frequency among drills as well as among teams within the most common drills. Among 67 athlete-seasons, a total of 14,718 impacts during contact practices were collected and evaluated in this study. Among all 6 teams, the mean linear (p < 0.0001) and rotational (p < 0.0001) acceleration varied significantly among all drills. Open field tackling had significantly (p < 0.001) higher mean linear acceleration than all other drills. Multiplayer tackle had the highest mean impact rate (0.35 ppm). Significant variations in linear acceleration and impact rate were observed among teams within specific drills. Team A had the highest mean linear acceleration in install, one-on-one, and open field tackling and the highest mean impact rate in Oklahoma and position skill work. Although team A spent the greatest proportion of their practice on minimal- or no-player versus player contact drills (27%) compared to other teams, they had the highest median (20.2g) and 95th percentile (56.4g) linear acceleration in practice. Full-speed tackling and blocking drills resulted in the highest HIE. Reducing time spent on contact drills relative to minimal or no contact drills may not lower overall HIE. Instead, interventions such as reducing the speed of players engaged in contact, correcting tackling technique, and progressing to contact may reduce HIE more effectively.

Wed

30

Jan

2019

Latest research in football - week 51 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Pre-Practice Hydration Status in Soccer (Football) Players in a Cool Environment
Reference: Medicina (Kaunas). 2018 Dec 5;54(6). pii: E102. doi: 10.3390/medicina54060102.
Authors: Kiitam U, Voitkevica L, Timpmann S, Pontaga I, Ereline J, Unt E, Ööpik V
Download link: https://www.mdpi.com/1010-660X/54/6/102/pdf
Summary: Only a few studies have reported the pre-practice hydration status in soccer players (SPs) who train in a cool climate. The primary purpose of this study was to examine the hydration status of male semiprofessional SPs immediately before their regular training session in winter. The secondary purpose was to compare the urinary indices of the hydration status of Estonian and Latvian SPs. Pre-training urine samples were collected from 40 Estonian (age 22.1 ± 3.4 years, soccer training experience 13.7 ± 3.9 years) and 41 Latvian (age 20.8 ± 3.4 years, soccer training experience 13.3 ± 3.0 years) SPs and analyzed for urine specific gravity (USG). The average outdoor temperature during the sample collection period (January⁻March) was between -5.1 °C and 0.2 °C (Estonia) and -1.9 °C and -5.0 °C (Latvia). Results: The average pre-training USG of Estonian and Latvian SPs did not differ (P = 0.464). Pooling the data of Estonian and Latvian SPs yielded a mean USG value of 1.021 ± 0.007. Hypohydration (defined as a USG ≥ 1.020) was evident altogether in fifty SPs (61.7%) and one of them had a USG value greater than 1.030. Estonian and Latvian SPs do not differ in respect of USG and the prevalence of pre-training hypohydration is high in this athletic cohort. These findings suggest that SPs as well as their coaches, athletic trainers, and sports physicians should be better educated to recognize the importance of maintaining euhydration during the daily training routine in wintertime and to apply appropriate measures to avoid hypohydration.


#2 Injury Risk and Injury Burden Are Related to Age Group and Peak Height Velocity Among Talented Male Youth Soccer Players
Reference: Orthop J Sports Med. 2018 Dec 11;6(12):2325967118811042. doi: 10.1177/2325967118811042. eCollection 2018 Dec.
Authors: Bult HJ, Barendrecht M, Tak IJR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6293374/pdf/10.1177_2325967118811042.pdf
Summary: The relationship between injury risk (IR) in age groups and periods around peak height velocity (PHV) remains unclear. PHV is defined as the moment of the largest increase in body height. The purpose was to investigate injury risk and injury burden as functions of growth velocity (periods around PHV) and chronological age groupings (under 12 years [U12] to U19) in talented youth male soccer players. Cohort study; Level of evidence, 2. A total of 170 players from the youth academy of a Dutch soccer club (highest professional league: Eredivisie) were observed for 1 to 3 seasons. Injuries, exposure, PHV age, and chronological age were registered. The injury incidence density (IID) and injury burden per 1000 hours of soccer participation, with 95% CIs, were calculated for 5 PHV periods and 7 age groups. These were compared with the overall cohort results using incidence ratios (IRs) and burden ratios (BRs) with 95% CIs. The mean age at PHV was 14.4 ± 0.65 years (range, 12.8-16.5 years). The mean IID for the total cohort was 8.34 injuries per 1000 hours (95% CI, 7.71-9.02). Compared with the overall mean, a significantly higher IID was found for PHV period 4+5 (IR, 1.31 [95% CI, 1.00-1.71]; P = .049) and for the U15 group (IR, 1.49 [95% CI, 1.24-1.79]; P < .001). The overall injury burden was 58.37 injury days per 1000 hours (95% CI, 56.66-60.13). In PHV period 4+5, the injury burden was significantly higher (BR, 1.53 [95% CI, 1.39-1.68]; P < .001) when compared with the overall mean. Also, compared with the overall mean, the injury burden was higher in the U16 (BR, 1.48 [95% CI, 1.39-1.58]; P < .001), U15 (BR, 1.28 [95% CI, 1.19-1.38]; P < .001), and U17 groups (BR, 1.21 [95% CI, 1.13-1.31]; P < .001). Talented young soccer players were more prone to injuries during the 6 months after PHV (31% above overall mean) as well as in the U15 group (49% above overall mean). Based on the higher injury burden in the U16 (48%), U15 (28%), and U17 (21%) groups, we suggest that research on injury risk factors and preventive measures should primarily target these age groups. Additional interventions based on PHV may be of limited value from a screening perspective. Further research is needed on the interaction between age groups and PHV periods.


#3 Anthropometry, Physical and Movement Features, and Repeated-sprint Ability in Soccer Players
Reference: Int J Sports Med. 2018 Dec 17. doi: 10.1055/a-0781-2473. [Epub ahead of print]
Authors: Campa F, Semprini G, Júdice PB, Messina G, Toselli S
Summary: This study aimed to evaluate the associations of anthropometry, functional movement patterns (FMP) and physical performance characteristics with repeated-sprint ability (RSA) in male youth soccer players. Thirty six athletes (ages 16.6±0.5 years, BMI 22.0±1.3 kg/m2) completed the RSA test and other physical tests including countermovement jump with (CMJA) and without the help of arms (CMJ), 10-m and 20-m straight-line sprints, Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo), and functional movement screen (FMS). In addition, a battery of anthropometric variables was measured. RSA performance components such as best time (BT), mean time (MT) and sprint decrement were calculated. Results showed that measures of physical performance derived from horizontal plane in 10-m and 20-m sprints, were more strongly associated (p<0.01) with RSA performance than those obtained with CMJ or CMJA (p<0.05). High correlations (p<0.01) were found between MT, BT and Yo-Yo distance (r=-0.79, r=-0.67, respectively), as well as with FMS scores (r=-0.68, r=-0.58, respectively). Anthropometric measures, such as fat mass, upper fat area, thigh fat area, calf muscle area, and endomorphy were associated with RSA components (p<0.05). Predictors for the RSA performance identified in the stepwise multivariate analysis included Yo-Yo distance, time in sprints, FMP, and calf muscle area.


#4 Do male and female soccer players differ in helping? A study on prosocial behavior among young players
Reference: PLoS One. 2018 Dec 17;13(12):e0209168. doi: 10.1371/journal.pone.0209168. eCollection 2018.
Authors: Van Lange PAM, Manesi Z, Meershoek RWJ, Yuan M, Dong M, Van Doesum NJ
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209168&type=printable
Summary: Acting prosocially can be quite challenging in one of the most salient intergroup contexts in contemporary society: Soccer. When winning is the ultimate goal, balancing self-interest with helping a fellow player in distress can be a tough decision; yet it happens. To date, we know little about what motivates soccer players to offer such help in the heat of the game. We propose that sex and what is at stake will matter in such prosocial dilemma situations. A pilot study (N = 107) indicated that female players may be more likely to help than male players, but this difference was only observed when the players are close to scoring position rather than far away from the goal (midfield). The main study (N = 366) finds that young soccer players show elevated inclinations to help in low-stakes situations, for example when their team is winning or when the outcome of the game seems pretty much decided. Contrariwise, helping intentions decline in high-stakes situations, for example when one's own team is losing, when one is close to a scoring position in the offense (rather than at the midfield), or when the outcome of the game is still uncertain. Furthermore, female players show somewhat greater inclinations to help than their male counterparts. The current data point at some differences for male and female soccer players, albeit small in effect size. In contrast, we conclude that especially quick cost-benefit judgments regarding the stakes can play a major role in decisions to help or not to help another player on the soccer field.


#5 Internal and External Loads in Training Week Before the Competition in U19 High-Level Soccer Players
Reference: J Strength Cond Res. 2018 Dec 14. doi: 10.1519/JSC.0000000000002975. [Epub ahead of print]
Authors: Martín-López Á, Mendes RS, Castillo-Rodríguez A
Summary: Nowadays, the information about the load in training sessions (TRs) and the relationship of these TRs with official competition are necessary to gain the sport success in soccer. The aim of this study was to quantify the different loads in TRs according to days before the competition (P-4, P-2, and P-1) on soccer players U19 based on their playing position and their sport success. Twenty-four male Spanish high-level players (age: 16.5 ± 0.5 years; height: 1.69 ± 0.04 m; and body mass: 63.0 ± 6.3 kg) participated in the study. They were grouped according to their playing position: external defenders, internal defenders (ID), external midfielders, internal midfielders (IM), and forwards (FO). To conduct the study, global positioning system technology was used, and a 1-way analysis of variance and Pearson correlation were performed. The main results revealed that the highest physical and physiological responses in the TRs were shown by ID, IM, and players without sport success (p < 0.05), and during P-2. In addition, sport success is predicted by the mean heart rate (R = 0.33; p < 0.001). As conclusion, players covering central positions in the playing field performed higher physical and physiological demands than players covering exterior or forward positions. Furthermore, physical and physiological responses during the TRs P-2 may be similar to the responses produced in competition match and are notably different depending on the sport success of the soccer player.


#6 The team's influence on physical and technical demands of elite goalkeepers in LaLiga: a longitudinal study in professional soccer
Reference: Res Sports Med. 2018 Dec 16:1-15. doi: 10.1080/15438627.2018.1555755. [Epub ahead of print]
Authors: Serrano C, Paredes-Hernández V, Sánchez-Sánchez J, Gallardo-Pérez J, Da Silva R, Porcel D, Colino E, García-Unanue J, Gallardo L
Summary: This study examined physical and technical demands and the influence of the team's level on elite goalkeepers' performance during six consecutive seasons in Spanish Professional Soccer League. The goalkeepers' performance data were obtained by analyzing a total of 3,874 matches using a multiple-camera computerized tracking system. The physical and technical match variables registered were: distance traveled; distance Sprinted and the number of sprints; total number of passes; successful passes; pass percentage; recovered balls; lost balls; ratio lost balls: recovered balls, and number of saves. The results showed that the number of saves made has shown a significant reduction (p < 0.001). When comparing between the teams' level, the goalkeepers of the worst classified teams showed a greater distance traveled by sprint (+3.72 m, IC95%: 1.00-6.44, ES: 0.41, p = 0.008). In conclusion, the results the influence of the team's level on the technical and physical parameters of the goalkeepers during the last six seasons


#7 Intra-seasonal variation of injury patterns among German Bundesliga soccer players
Reference: J Sci Med Sport. 2018 Dec 6. pii: S1440-2440(18)30449-3. doi: 10.1016/j.jsams.2018.12.001. [Epub ahead of print]
Authors: Leventer L, Eek F, Lames M
Summary: High fluctuations in injury-risk during the playing season in soccer have been reported. As seasons are structured in periods with homogenous loads and intensities, we investigated injury-risk over season periods, contrarily to previous studies adopting a month-based approach. Incidence-rate ratios (IRRs) for match and training injuries were compared across six consecutive seasons of German Bundesliga, divided into six periods each: Pre-season (PS), winter-break (WB), quarter 1-4: (Q1-Q4). Significant variations in injury-risk were observed for match and training injuries. IRRs in matches was 1.30 (95% CI: 1.11-1.53) times higher in Q3 and 1.53 (95% CI: 1.31-1.78) higher in Q4 compared to Q1. For training injuries, IRR peaked in Q1 and Q3 followed by a marked decrease in each subsequent quarter. Compared to Q4, IRR was 1.62 (95% CI: 1.40-1.86) times higher during Q3 and 1.78 (95% CI: 1.53-2.07) times higher in Q1. IRR was significantly higher in the competitive season compared to pre-season across match (IRR: 2.00, 95% CI: 1.30-3.00) and training (IRR: 1.27, 95% CI: 1.11-1.43) injuries. The increased match IRRs later during the season indicate that, in practice, coaches should consider putting even more emphasis on recovery in the last part of the season. Moreover, training injuries seem to indicate a carry-over effect. Further studies need to investigate how training during preparatory phases can be implemented in a way that prevents injuries during the competitive season.


#8 Changes in injury incidences and causes in Swiss amateur soccer between the years 2004 and 2015
Reference: Swiss Med Wkly. 2018 Dec 15;148:w14690. doi: smw.2018.14690. eCollection 2018 Dec 3.
Authors: Gebert A, Gerber M, Pühse U, Faude O, Stamm H, Lamprecht M
Summary: Injury prevention in amateur soccer has been promoted in recent years, but only a few studies have addressed long-term changes in injury incidence in amateur soccer. However, better knowledge of changes with respect to injury incidences and causes could make an important contribution to improving prevention strategies. The aim of this study was to investigate the long-term development of injury incidence in Swiss amateur soccer with respect to level of play, injury causes and injury characteristics. A representative sample of about 1000 Swiss amateur soccer coaches was interviewed by telephone in 2004, 2008 and 2015. They were asked to recall their last game and to report details on all injuries. For every injury, the coaches were asked to remember injury characteristics and causes. The same procedure was repeated for all games that took place during the previous 4 weeks. Additionally, all training injuries in the previous 4 weeks were recorded in detail. The incidence of game injuries decreased between the years 2004 and 2008 from 15.1 (95% confidence interval [CI] 14.2&ndash;16.0) to 13.3 (95% CI 12.4&ndash;14.2) injuries per 1000 hours, and increased between the years 2008 and 2015 to 16.5 (95% CI 15.5&ndash;17.4) injuries per 1000 hours. Between 2004 and 2015, the rate of contact injuries during games increased by 19.1%. The incidence of foul play injuries in games increased by 25.5% between 2008 and 2015. The rise in total training injury incidence between the years 2004 (2.4, 95% CI 2.2&ndash;2.7) and 2015 (2.9, 95% CI 2.6&ndash;3.1) was caused by a 22.2% higher rate of noncontact injuries. During the same period, game and training injury incidences increased across all amateur soccer leagues without exception, but these changes did not reach statistical significance. In 2015, the incidence of injuries leading to medical attention was higher than in 2004 (game 20.0%, training 37.5%). There is evidence that injury incidence in Swiss amateur soccer has increased in past years. &nbsp.


#9 The Effect of Block Versus Daily Undulating Periodization on Strength and Performance in Adolescent Football Players
Reference: Int J Sports Physiol Perform. 2018 Dec 20:1-25. doi: 10.1123/ijspp.2018-0609. [Epub ahead of print]
Authors: Gavanda S, Geisler S, Quittmann OJ, Schiffer T
Summary: Muscle mass, strength and power are important factors for performance. To improve these characteristics, periodized resistance training is used. However, there is no consensus regarding the most effective periodization model. Therefore the purpose of this study was to compare the effects of block (BLOCK) versus daily undulating periodization (DUP) on body composition, hypertrophy, strength, performance and power in adolescent American football players. Forty-seven subjects participated in this study (M±SD age = 17±0.8 years; strength training experience = 0.93±0.99 years). Pre- and post-measurements consisted of body mass (BM), fat mass (FMkg), body fat percentage (relFM), fat-free mass (FFM), muscle mass (MM) and muscle thickness of the M. vastus lateralis (VL), M. rectus femoris (RF) and M. triceps brachii (TB), one repetition maximum (1-RM) back squat (BS) and bench press (BP), countermovement jump (CMJ), estimated peak power from vertical jump performance (Wpeak), medicine ball put (MBP) and 40 yd sprint. Subjects were randomly assigned in either the BLOCK or DUP group prior to the 12 week intervention period consisting of 3 full-body sessions per week. Both groups displayed significantly higher BM (p<0.001), relFM (p=0.005), FFM (p<0.001), MM (p<0.001), RF (p<0.001), VL (p<0.001), TB (p<0.001), BS (p<0.001), BP (p<0.001), CMJ (p<0.001), Wpeak (p<0.001) and significant lower sprint times (p<0.001) following twelve weeks of resistance training with no difference between groups. Resistance training was effective to increase muscle mass, strength, power and performance in adolescent athletes. BLOCK and DUP affect anthropometric measures and physical performance equally.


#10 Transfer market activities and sportive performance in European first football leagues: A dynamic network approach
Reference: PLoS One. 2018 Dec 19;13(12):e0209362. doi: 10.1371/journal.pone.0209362. eCollection 2018.
Authors: Matesanz D, Holzmayer F, Torgler B, Schmidt SL, Ortega GJ
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209362&type=printable
Summary: Professional football is a globalized game in which players are the most valuable assets for clubs. In this study, we explore the evolution of the football players' transfer network among 21 European first leagues between the seasons 1996/1997 and 2015/2016. From a topological point of view, we show that this network achieved an upper limit expansion around season 2007/2008, thereafter becoming more connected and dense. Using a machine learning approach based on Self-Organizing Maps and Principal Component Analysis we confirm that European competitions, such as the UEFA Champions League or UEFA Europa League, are indeed a "money game" where the clubs with the highest transfer spending achieve better sportive performance. Some clubs' transfer market activities also affect domestic performance. We conclude from our findings that the relationship between transfer spending and domestic or international sportive performance might lead to substantial inequality between clubs and leagues, while potentially creating a virtuous (vicious) circle in which these variables reinforce (weaken) each other.

Tue

22

Jan

2019

Latest research in football - week 50 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Current Soccer Footwear, Its Role in Injuries and Potential for Improvement
Reference: Sports Med Int Open. 2018 May 25;2(2):E52-E61. doi: 10.1055/a-0608-4229. eCollection 2018 Apr.
Authors: Blanchard S, Palestri J, Guer JL, Behr M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6259463/pdf/10-1055-a-0608-4229.pdf
Summary: Soccer is the most popular sport in the world and generates great financial revenue. It is also a sport whose practice has evolved considerably in terms of intensity and commitment, and in which the intrinsic risk of injury (not directly related to an interaction with the environment) is particularly high. In this context, the cleated shoe as a major component of soccer equipment may play a key role in the overexposure to injury. Soccer shoe evolution is all the more challenging, because design and mechanical structure differ in many points compared to other modern shoes developed for sports such as running, tennis and basketball. This critical review aims to elucidate the characteristics of modern soccer footwear and their possible link to soccer-specific injuries, focusing on the following areas: (1) ergonomics, comfort and proprioception; (2) shoe mechanical characteristics; (3) field surfaces and shoe design.


#2 Does a bounding exercise program prevent hamstring injuries in adult male soccer players? - A cluster -RCT
Reference: Scand J Med Sci Sports. 2018 Dec 9. doi: 10.1111/sms.13353. [Epub ahead of print]
Authors: van de Hoef PAS, Brink MSM, Huisstede BMAB, van Smeden MM, de Vries NN, Goedhart EAE, Gouttebarge VV, Backx FJGF
Summary: Although the Nordic Hamstring Exercise (NHE) prevents hamstring injury in soccer players effectively, the annual incidence of these injuries still increases. This may be because of poor long-term compliance with the program. Furthermore, the timing and amplitude of gluteal and core muscle activation seem to play an important role in hamstring injury prevention, the NHE program was not designed to improve activation of these muscles. Therefore, we propose plyometric training as an alternative to reduce hamstring injuries soccer players. The purpose was to determine the preventive effect of the Bounding Exercise Program (BEP) on hamstring injury incidence and severity in adult male amateur soccer players. Thirty-two soccer teams competing in the first-class amateur league were cluster-randomized into the intervention or control group. Both groups were instructed to perform their regular training program, and the intervention group additionally performed BEP. Information about player characteristics was gathered at baseline and exposure, hamstring injuries and BEP compliance were weekly registered during one season (2016-2017). The data of 400 players were analyzed. In total, 57 players sustained 65 hamstring injuries. The injury incidence was 1.12/1000 hours in the intervention group and 1.39/1000 hours in the control group. There were no statistically significant differences in hamstring injury incidence (OR=0.89, 95% CI 0.46-1.75) or severity between the groups (p>0.48). In this large cluster-randomized controlled trial, no evidence was found for plyometric training in its current form to reduce hamstring injuries in amateur soccer players.


#3 Professional Soccer Players' Return to Play and Performance After Operative Repair of Achilles Tendon Rupture
Reference: Orthop J Sports Med. 2018 Nov 28;6(11):2325967118810772. doi: 10.1177/2325967118810772. eCollection 2018 Nov.
Authors: Trofa DP, Noback PC, Caldwell JE, Miller JC, Greisberg JK, Ahmad CS, Vosseller JT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280612/pdf/10.1177_2325967118810772.pdf
Summary: The majority of Achilles tendon ruptures are sports related; however, no investigation has examined the impact of surgical repair for complete ruptures on professional soccer players. The purpose was to examine the return to play, playing time, and performance of professional soccer players following Achilles tendon repair. Union of European Football Associations (UEFA) and Major League Soccer (MLS) athletes who sustained a primary complete Achilles tendon rupture and were treated surgically between 1988 and 2014 were identified via public injury reports. Demographic information and performance-related statistics for the identified athletes were recorded for the season before surgery and 2 seasons after surgery and were compared with information for matched controls. Statistical analyses were used to assess differences in recorded metrics. A total of 24 athletes with Achilles ruptures met inclusion criteria, 17 (70.8%) of whom were able to return to play. On average, players had 8.3 years of professional-level experience prior to sustaining an Achilles rupture. Among athletes who returned to play, no differences were found in the number of games played or started, minutes played, or goals scored 1 year postoperatively compared with the year prior to injury. However, 2 years postoperatively, these athletes played 28.3% (P = .028) fewer minutes compared with their preoperative season, despite starting and playing in an equivalent number of games. Matched controls had baseline playing time and performance statistics similar to those of players. However, controls played and started in significantly more games and played more minutes at 1 and 2 years compared with players (P < .05). No differences were found in goals scored at any time point. This is the first investigation examining the effect of an Achilles repair on the career of professional soccer players. This is a difficult injury that most commonly occurs in veteran players and prevents 29.2% of players from returning to play despite surgical management. Additionally, athletes able to return to play were found to play fewer minutes 2 years postoperatively compared with their baseline as well as playing less at 1 and 2 years postoperatively compared with uninjured matched controls. The reduction in playing time following an Achilles repair has significant implications for professional players and teams.


#4 Changes in Echocardiographic Parameters among Beninese Soccer Referees during the Division 1 Championship in 2016
Reference: J Sports Med (Hindawi Publ Corp). 2018 Nov 7;2018:6024574. doi: 10.1155/2018/6024574. eCollection 2018.
Authors: Coffi Q, Arnaud S, Polycarpe G, Hyacinthe A, Folly M, Basile N, Murielle H, Martin HD
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6247468/pdf/JSM2018-6024574.pdf
Summary: The goal of this study was to describe the echocardiographic parameters of soccer referees and to examine the changes in these parameters after a period of intensive physical exercise. We conducted a prospective study that included Beninese soccer referees. The study of the geometry and function of the left ventricle (LV) was made at the beginning and end of the national Division 1 championship, which was held during the course of 10 weeks. There were 37 referees included in this study; 20 at the national level (G1: 27.8 ± 6.6 years) and 17 at the international level (G2: 32.1 ± 6.4 years). Dimensions of the LV were normal for all the referees. At the beginning of the championship, 51.3% of the referees had a normal LV geometry, 37.8% had concentric remodelling, 2.7% had concentric hypertrophy, and 8.1% had eccentric hypertrophy. In the group of referees with normal LV geometry, a modification in concentric remodelling at the end of the championship was seen in 30% of the referees in G1, 33.3% of the referees in G2, and 31.6% of the whole sample. In the group of subjects who presented concentric LV remodelling, a modification in the normal geometry was observed in 37.5% of those in G1, in 0% of those in G2, and in 21.4% of the whole sample. The cases of LV hypertrophy showed no change regardless of the group considered. An LV ejection fraction of more than 50% and an E/E' ratio less than 8 were found in all referees. All the referees studied had normal cardiac morphology and function. The intensity of the physical load was insufficient to impact this morphology.


#5 In-season training load quantification of one-, two- and three-game week schedules in a top European professional soccer team
Reference: Physiol Behav. 2018 Dec 6. pii: S0031-9384(18)30585-7. doi: 10.1016/j.physbeh.2018.11.036. [Epub ahead of print]
Authors: Oliveira R, Brito J, Martins A, Mendes B, Calvete F, Carriço S, Ferraz R, Marques M
Summary: Top European soccer teams that play in UEFA competitions often participate in one, two- or three-games per week. Therefore, it is necessary to understand the variations in training load (TL) according to each team's competitive schedule. The aim of this study was to quantify internal and external TLs within five microcycles: M4 and M5 - one-game weeks; M1 and M3 - two-game weeks; M2 - three-game week). The sample consisted of thirteen elite soccer players. A global positioning system (GPS) was used to measure the total distance covered and distances of different exercise training zones (1-5), the session ratings of perceived exertion (s-RPE) scores and the amount of creatine kinase (CK) created during daily training sessions for the 2015-2016 in-season period. The data were analysed with respect to the number of days prior to a given match. The main results indicate that there was a significant difference in training intensity for zone 1 between M5 and M3 (4010.2 ± 103.5 and 4507.6 ± 133.0 m, respectively); a significant difference in training intensity for zone 3 between M4 and M2 (686.1 ± 42.8 and 801.2 ± 61.2 m, respectively); a significant difference in the duration of the training sessions and matches between M5 and M2 (69.2 ± 2.1 and 79.6 ± 2.3) and M1 and M2 (69.7 ± 1.0 and 79.6 ± 2.3); and finally, there was a significant difference in CK between M1 and M5 (325.5 ± 155.0 and 194.4 ± 48.9). Moreover, there was a significant decrease in TL in the last day prior to a match, for all microcycles and all variables. There was no significant difference with respect to s-RPE. This study provides the first report of daily external and internal TLs and weekly accumulated load (training sessions and match demands) during one, two, and three-game week schedules in a group of elite soccer players. Expected significant differences are found in daily and accumulated loads for within- and between-game schedules. A similar pattern is exhibited for one- and two-game week microcycles regarding the day before the match, which exhibits a decrease in all variables.


#6 Estimating fat-free mass in elite youth male soccer players: cross-validation of different field methods and development of prediction equation
Reference: J Sports Sci. 2018 Dec 11:1-8. doi: 10.1080/02640414.2018.1551045. [Epub ahead of print]
Authors: Munguía-Izquierdo D, Suárez-Arrones L, Di Salvo V, Paredes-Hernández V, Ara I, Mendez-Villanueva A
Summary: This study determined the most effective field method for quantifying fat-free mass (FFM) in elite youth male soccer players compared to dual X-ray absorptiometry (DXA) values and to develop prediction equations for FFM based on anthropometric variables. Forty-one male elite-standard youth soccer players, ages 16.2-18.0 years, undertook FFM assessments including bioelectrical impedance analysis, and different skinfold-based prediction equations. DXA provided a criterion measure of FFM. Correlation coefficients, bias, limits of agreement, and differences were used as validity measures, and regression analyses to develop soccer-specific prediction equations. Slaughter et al (1988), Durnin and Wormersley (1974), and Sarria et al (1998) equations showed the lowest biases, and no significant, standardized, and substantial differences against DXA. The new youth soccer-specific anthropometric equation explained 91% of the DXA-derived FFM variance using three circumferences, eight skinfolds, and one bone breadth. All field methods compared in this study may not be adequate for estimating FFM in elite youth male soccer players, except the equations of Slaughter et al (1988), Durnin and Wormersley (1974), and Sarria et al (1998). We recommend the use of the new soccer-specific equation proposed in this study as a valid alternative to DXA to quantify FFM among elite youth male players.


#7 Dynamic and Static Assessment of Single Leg Postural Control in Female Soccer Players
Reference: J Sport Rehabil. 2018 Dec 11:1-19. doi: 10.1123/jsr.2018-0072. [Epub ahead of print]
Authors: Meiners KM, Loudon JK
Summary: Various methods are available for assessment of static and dynamic postural stability. The purpose of this study was to investigate the relationship between dynamic postural stability as measured by the Star Excursion Balance Test (SEBT) and static postural sway assessment as measured by the Technobody™ Prokin in female soccer players. A secondary purpose was to determine side-to-side symmetry in this cohort. 18 female soccer players completed testing on the SEBT and TechnobodyTM Prokin balance device. Outcome measures were: anterior, posterior medial, and posterior lateral reaches from the SEBT and Center of Pressure (COP) in the X and Y axis and Standard Deviation of movement in the forward-backward and medial-lateral directions from the force plate on left and right legs. Bivariate correlations were determined between the 8 measures. Additionally, paired Wilcoxon Signed Ranks were performed to determine similarity between limb scores. All measures on both the SEBT and postural sway assessment were significantly correlated when comparing dominant to non-dominant lower extremities with exception of SD of movement in both X and Y axis. When correlating results of the SEBT with postural sway assessment, a significant correlation was found between SEBT right lower extremity posterior lateral reach (r=.567, p<.05) and summed SEBT (r=.486, p<.05) and the COP in the Y axis. A significant correlation was also found on the left lower extremity, with Standard Deviation of movement forward-backward and SEBT posterior medial reach (r=-.511, p<.05). Dynamic postural tests and static postural tests provide different information to the overall assessment of balance in the female soccer player. Relationship between variables differed based on the subject's lower extremity dominance.


#8 Validation study of the Functional Assessment Scale for Acute Hamstring injuries in Spanish professional soccer players
Reference: Clin Rehabil. 2018 Dec 10:269215518815540. doi: 10.1177/0269215518815540. [Epub ahead of print]
Authors: Hernández-Sanchez S, Korakakis V, Malliaropoulos N, Moreno-Perez V
Summary: The purpose of the study was to cross-culturally adapt and validate the Functional Assessment Scale for acute hamstring injury for professional Spanish-speaking soccer players. Clinical measurement study. Cross-cultural adaptation was conducted following international recommendations. Indicators of validity, reliability and responsiveness are provided. The Spanish version of the Functional Assessment Scale for acute hamstring injury scale was administered to 165 participants: 45 professional soccer players with acute hamstring muscle injury diagnosis, 40 healthy subjects, 40 individuals at-risk for a hamstring muscle injury and 40 patients with injuries of the lower limb other than hamstring muscle injury. The Functional Assessment Scale for acute hamstring injury were main outcome measures. Spanish version of the Quality of Life Short-Form 36 questionnaire (SF-36) and the Lower Limb Functional Index (LLFI) were used as the reference measures. Cronbach's alpha (internal consistency) for the Spanish version of the Functional Assessment Scale for acute hamstring injury scale was >0.8. The intraclass correlation coefficient using the two-way random model (ICC2,1) (test-retest) was 0.993 (95% confidence interval (CI): 0.991-0.995; P < 0.05). In the exploratory factor analysis, a one-factor solution explained 85% of the variance. Subjects with hamstring muscle injury scored significantly lower than the other groups in the Spanish version of the Functional Assessment Scale for acute hamstring injury scale ( P < 0.001). The Spanish version of the Functional Assessment Scale for acute hamstring injury scale score within the hamstring muscle injury group showed moderate and significant correlations with SF-36 physical components (Spearman's rs > 0.6; P < 0.001), and LLFI score at baseline ( rs = 0.42; P < 0.01). The standard error of measurement (SEM) and minimum detectable change threshold (MDC95%) were 2.6 and 7.2 points, respectively. The responsiveness indicators have an effect size of 3.62, and the standardized response mean is 3.24. The Spanish version of the Functional Assessment Scale for acute hamstring injury scale showed satisfactory psychometric properties. It can be considered a reliable and valid instrument to assess the functional impact of acute hamstring muscle injury in professional Spanish-speaking football players.


#9 Effective But Not Adhered to: How Can We Improve Adherence to Evidence-Based Hamstring Injury Prevention in Amateur Football?
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000710. [Epub ahead of print]
Authors: van der Horst N, Hoef SV, Otterloo PV, Klein M, Brink M, Backx F
Summary: The purpose was to investigate adherence to a Nordic hamstring exercise (NHE) program in a real-world context of male amateur football, and the perceptions of end users (players) and intervention deliverers (coaches and medical staff) about adherence to this proven effective program.
Dutch amateur football. Two hundred sixty-four players, 23 coaches, and 29 medical staff from Dutch amateur football teams that participated in a national randomized controlled trial 2 years earlier. Nordic hamstring exercise program were used as the independent variable. Main outcome measures were the Nordic hamstring exercise program adherence during 2014 and 2015. Intervention or control group allocation during the trial, transfers, and personal perception about adherence to the program were also examined. Of all players, 69% reported never, 16% sometimes, 6% frequently, 5% often, and 4% always performing exercises of the NHE program. Adherence to the NHE program was higher among players who had been in the NHE arm of the previous trial and among players who had not been transferred to another club compared with players who had been transferred. Key factors in stimulating players to adhere to the NHE program were knowledge of the NHE and personal motivation. Coaches and medical staff members also mentioned personal motivation and consensus with team staff as key factors to encourage NHE adherence. Among high-level male amateur football players, adherence to an evidence-based hamstring injury-prevention program was very low. It is essential to recognize factors that stimulate or limit adherence to injury-prevention programs for effective programs to actually lead to a reduction in hamstring injuries in a real-world context.


#10 Does Night-Training Load Affect Sleep Patterns and Nocturnal Cardiac Autonomic Activity in High-Level Female Soccer Players?
Reference: Int J Sports Physiol Perform. 2018 Dec 20:1-26. doi: 10.1123/ijspp.2018-0652. [Epub ahead of print]
Authors: Costa JA, Brito J, Nakamura FY, Oliveira EM, Costa OP, Rebelo AN
Summary: The purpose was to analyse whether exercise training conducted at night disturbs sleep and affects nocturnal cardiac autonomic control in high-level female athletes. Eighteen high-level female soccer players (mean±SD; age: 20.4±2.1 years) wore actigraphs and heart rate (HR) monitors during night-sleep throughout night-training days (n=8) and resting days (n=8), for 3 consecutive weeks. This was a longitudinal study that measured internal training load, sleep, nocturnal cardiac autonomic activity, and well-being ratings prior to training sessions. Training load varied across training days (e.g., training impulse range; mean±SD; ES [95% confidence interval]: 72.9±18.8 to 138.4±29.6 a.u.; F(4,62)=32.331; ηp2=0.673 [0.001-0.16], large effect; p<0.001). However, no differences in subjective well-being ratings were observed, although ES was large. Total sleep time (training days vs. resting days: 7:17±0:47 hours vs. 7:51±0:42 hours; ES=0.742 [0.59-0.92], p=0.005; moderate effect) and sleep onset time (00:58±0:19 vs. 00:44±0:16 hours; ES=0.802 [0.68-0.94], p=0.001; moderate effect) were negatively affected after night-training. In addition, small effects were detected for wake up time, time in bed, and sleep latency (p>0.05). No differences were detected in HR variability (HRV) during sleep (range of lnRMSSD: 4.3±0.4 to 4.5±0.4 ln[ms] vs. 4.6±0.3 to 4.5±0.4 ln[ms]; F(3,52)=2.148; p>0.05; ηp2=0.112 [0.01-0.25], medium effect), but the HR during sleep was significantly higher after training days (range of HR: 56±4 to 63±7 vs. 54±4 to 57±6 b.p.m; F(2,32) = 15.956; p<0.001 ηp2=0.484 [0.20-0.63], large effect). Overall, the results indicate that exercise training conducted at night may disturb sleep and affect HR, whereas limited effects can be expected in HRV assessed during sleep in high-level female soccer players.


#11 Modelling the Prediction of the Session Rate of Perceived Exertion in Soccer: Unravelling the Puzzle of Predictive Indicators
Reference: Int J Sports Physiol Perform. 2018 Dec 20:1-22. doi: 10.1123/ijspp.2018-0698. [Epub ahead of print]
Authors: Geurkink Y, Vandewiele G, Lievens M, de Turck F, Ongenae F, Matthys SPJ, Boone J, Bourgois JG
Summary: This study aimed to predict the session Rate of Perceived Exertion (sRPE) in soccer and determine the main predictive indicators of the sRPE. A total of 70 External Load Indicators (ELIs), Internal Load Indicators (ILIs), Individual Characteristics (ICs) and Supplementary Variables (SVs) were used to build a predictive model. The analysis using Gradient Boosting Machines showed a mean absolute error (MAE) of 0.67 ± 0.09 AU and a Root Mean Squared Error (RMSE) of 0.93 ± 0.16 AU. ELIs were found to be the strongest predictors of the sRPE, accounting for 61.5% of the total normalized importance (NI), with total distance as the strongest predictor. The included ILIs and ICs accounted only for respectively 1.0% and 4.5% of the total NI. Predictive accuracy improved when including SVs such as group-based sRPE-predictions (10.5% of NI), individual deviation variables (5.8% of NI) and individual player markers (17.0% of NI). The results showed that the sRPE can be predicted quite accurately, using only a relatively limited number of training observations. ELIs are the strongest predictors of the sRPE. It is however useful to include a broad range of variables, other than ELIs, because the accumulated importance of these variables account for a reasonable component of the total normalized importance. Applications resulting from predictive modelling of the sRPE can help the coaching staff to plan, monitor and evaluate both the external and internal training load.


#12 Data-Driven Visual Performance Analysis in Soccer: An Exploratory Prototype
Reference: Front Psychol. 2018 Dec 5;9:2416. doi: 10.3389/fpsyg.2018.02416. eCollection 2018.
Authors: Benito Santos A, Theron R, Losada A, Sampaio JE, Lago-Peñas C
Download link: https://www.frontiersin.org/articles/10.3389/fpsyg.2018.02416/full
Summary: In soccer, understanding of collective tactical behavior has become an integral part in sports analysis at elite levels. Evolution of technology allows collection of increasingly larger and more specific data sets related to sport activities in cost-effective and accessible manner. All this information is minutely scrutinized by thousands of analysts around the globe in search of answers that can in the long-term help increase the performance of individuals or teams in their respective competitions. As the volume of data increases in size, so does the complexity of the problem and the need for suitable tools that leverage the cognitive load involved in the investigation. It is proven that visualization and computer-vision techniques, correctly applied to the context of a problem, help data analysts focus on the relevant information at each stage of the process, and generally lead to a better understanding of the facts that lie behind the data. In the current study, we presented a software prototype capable of assisting researchers and performance analysts in their duty of studying group collective behavior in soccer games and trainings. We used geospatial data acquired from a professional match to demonstrate its capabilities in two different case studies. Furthermore, we successfully proved the efficiency of the different visualization techniques implemented in the prototype and demonstrated how visual analysis can effectively improve some of the basic tasks employed by sports experts on their daily work, complementing more traditional approaches.


#13 When Something Is at Stake: Differences in Soccer Performance in 11 vs. 11 During Official Matches and Training Games
Reference: J Strength Cond Res. 2019 Jan;33(1):167-173. doi: 10.1519/JSC.0000000000002936.
Authors: Olthof SBH, Frencken WGP, Lemmink KAPM
Summary: Training games are used to mimic the official match, but differ in playing duration and a consequence of winning or losing. Anxiety levels, crowd pressure, and the intention to win are examples of constraints present in the match, but absent or less prevalent in training. The aim is, therefore, to compare soccer performance in official matches with 11 vs. 11 training games. Six elite youth soccer teams played 5 official matches and 15 training games. Soccer performance, defined as a combination of game characteristics (game duration, transitions, and ball possession duration) and physical (distance covered, high-intensity distance, and sprints), technical (passing), and team tactical performance (inter-team and intra-team distances) and corresponding interaction patterns, was determined with video footage and positional data (local position measurement system). Soccer performance in official matches differed from similar training games, in a way that players covered more distance, sprinted more often, but game pace was lower and players made more mistakes. In addition, team width was smaller and length-per-width ratio larger and teams were tighter coupled in official matches. 11 vs. 11 training games can be used to mimic the match, in particular the team tactical performance. Coaches could increase physical and technical representativeness of training games by raising the stakes and increasing the consequence of winning or losing.


#14 The influence of short-term fixture congestion on position specific match running performance and external loading patterns in English professional soccer
Reference: J Sports Sci. 2018 Dec 18:1-9. doi: 10.1080/02640414.2018.1558563. [Epub ahead of print]
Authors: Jones RN, Greig M, Mawéné Y, Barrow J, Page RM
Summary: The aim of the current study was to investigate positional specific physical performance and external load responses to short term fixture congestion in English professional soccer. A total of 515 match observations were categorised as G1: the first game in a week with >4 days following a previous game, G2: the second game in a week played <4 days since G1, and G3: the third game in a week played with <4 days between each of the previous games. Global positioning system and accelerometer-based metrics were partitioned into fifteen-minute epochs. These data were then analysed using a linear mixed model to assess both the within and between game positional differences. Total, low-intensity (<4.0 m·s-1), medium-intensity (MID; 4.0-5.5 m·s-1), and sprint distance (>7.0 m·s-1) were significantly different across games. No between game positional differences were identified; however, within match position specific differences were observed for measures of MID and HID. No significant differences were evident for accelerometer derived metrics between games or across positions. The current data suggests that the use of fifteen minute within game epochs enables the detection of alterations in physical output during congested schedules. The observed within game positional differences has implications for player specific conditioning and squad rotation strategies.

Sun

06

Jan

2019

Latest research in football - week 49 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Football Compared with Usual Care in Men with Prostate Cancer (FC Prostate Community Trial): A Pragmatic Multicentre Randomized Controlled Trial
Reference: Sports Med. 2018 Dec 1. doi: 10.1007/s40279-018-1031-0. [Epub ahead of print]
Authors: Bjerre ED, Brasso K, Jørgensen AB, Petersen TH, Eriksen AR, Tolver A, Christensen JF, Poulsen MH, Madsen SS, Østergren PB, Borre M, Krustrup P, Johansen C, Rørth M, Midtgaard J
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-1031-0.pdf
Summary: Physical activity has been shown to mitigate the unwanted psychological and physiological side effects of prostate cancer treatments, but sustainable exercise possibilities are limited. Our objective was to examine whether football in a real-world setting (i.e., local football clubs) was safe and feasible in practice and could improve quality of life, mitigate decline in muscle mass and bone density, and increase fat mass in patients with prostate cancer. In this pragmatic, multicentre, parallel randomized controlled trial, men diagnosed with prostate cancer were recruited from five Danish urological departments. Men (N = 214) diagnosed with prostate cancer were randomly allocated, using random generated lists (block size 4-8) stratified for center and androgen-deprivation therapy status, to either 1 h of football twice weekly in a local football club or to usual care, which was a 15- to 30-min telephone session covering their options for physical activity or free-of-charge rehabilitation delivered as standard in Denmark. Allocation was concealed from the trial investigator performing the randomization, but-given the nature of the intervention-this was not possible for personnel and participants. Assessments were performed at baseline, 12 weeks, and 6 months. The primary outcome was mean change difference in prostate cancer-specific quality of life at 12 weeks. Secondary outcomes were body composition, 12-Item Short Form Health Survey (SF-12) physical and mental health, and safety-reported as fractures, falls, and serious adverse events. Attrition was 1 and 3% at 12 weeks, and 5% and 5% at 6 months for the usual care and football groups, respectively. Prostate cancer-specific quality of life was equal between groups at 12 weeks (mean difference + 1.9 points, 95% confidence interval [CI] -1.0-4.8; P = 0.20) and at 6 months (+ 0.5 points, 95% CI -2.8-3.8; P = 0.76). Fractures were equally distributed, with two fractures in the usual care group and one in the football group. Likewise, body composition outcomes were equal. Mental health improved after 6 months of football (mean difference + 2.7 points, 95% CI 0.8-4.6; P = 0.006). In this trial, community-based football was a feasible exercise strategy for men with prostate cancer. Football did not improve prostate cancer-specific quality of life but did improve mental health; the clinical significance of this is unclear.


#2 Faster physical performance recovery with cold water immersion is not related to lower muscle damage level in professional soccer players
Reference: J Therm Biol. 2018 Dec;78:184-191. doi: 10.1016/j.jtherbio.2018.10.001. Epub 2018 Oct 12.
Authors: Bouzid MA, Ghattassi K, Daab W, Zarzissi S, Bouchiba M, Masmoudi L, Chtourou H
Summary: The aim of the present study was to assess the effects of cold water immersion (CWI) after an intermittent test on the recovery kinetic of physical performance, muscle damage and perceived muscle soreness in professionals soccer players. In a randomized design, eight soccer players completed the Loughborough Intermittent Shuttle Test followed by 10 min of either CWI (10C°) or thermoneutral water immersion (TWI) (28C°). Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 m sprint: SP), muscle damage parameter (creatine kinase: CK) and perceived muscle soreness were assessed at baseline, 0 h, 24 h, 48 h and 72 h after the intermittent test. After the test, a decrease was observed in SJ and in CMJ at 0 h, 24 h, 48 h and 72 h with TWI (p < 0.05) and only at 0 h for SJ with CWI (p < 0.05). SP decreased at 24 h and 48 h after the test with TWI (p < 0.05) and only at 24 h with CWI (p < 0.05). MVC, CK activity and perceived muscle soreness increased in both condition after the test and returned to baseline levels 72 h after the test with TWI (p < 0.05) and at 48 h with CWI (p < 0.05). For the correlation between physical performance and muscle damage parameters in CWI session, the statistical analysis didn't reveal any significant link between CK and SJ, CMJ, MVC or SP values (p > 0.05). The results suggest that CWI immediately after an intermittent test reduces muscle damage and perceived muscle soreness, and accelerate recovery of physical performance in professional soccer players. However, the faster recovery of physical performance seems not be related to the lower level of muscle damage induced by CWI.


#3 Use of Individual Relative Thresholds to Assess Acceleration in Young Soccer Players According to Initial Speed
Reference: J Strength Cond Res. 2018 Nov 29. doi: 10.1519/JSC.0000000000002902. [Epub ahead of print]
Authors: Martínez-Cabrera FI, Núñez-Sánchez FJ, Losada J, Otero-Esquina C, Sánchez H, De Hoyo M
Summary: The aims of the current study were (a) to analyze the characteristics of acceleration efforts using individual relative thresholds according to the initial speed during official matches in elite young soccer players according to player position and (b) to compare the differences between absolute and relative thresholds in assessing high-intensity acceleration. Player acceleration profiles were assessed using an individual relative threshold based on their acceleration capacity at different initial speeds (standing, 6, 10.8, and 15 km·h), and the number of accelerations (>75% of the maximal acceleration) performed during soccer matches was divided into 3 categories attending to the initial speed. (S1 = 0-7 km·h; S2 = 7.1-14 km·h; and S3 = ≥14.1 km·h). Within-group analyses showed that the number of accelerations performed in each category was higher when the effort started from a static or walking position than at moderate- or high-intensity running (S1 > S2 > S3; very likely to almost certain). Between-group analyses revealed substantial differences between some playing positions according to initial speed. In S1 and S3, central defenders had the lowest number of accelerations (likely to almost certain), whereas midfielders had the greatest number of high-intensity accelerations in S1 and S2. There were also substantial differences between the other playing positions (possibly to almost certain). Regarding relative and absolute thresholds (>3 m·s), the results showed that absolute threshold overestimated the number of high-intensity accelerations compared with the individual relative threshold in S1 and underestimated the results in S2 and S3 (almost certain). The use of an individual relative threshold to measure acceleration demands allows to distinguish between the numbers of accelerations in function of the initial speed and playing positions. In addition, the absolute acceleration threshold could overestimate or underestimate the acceleration demands in young soccer players as a function of the initial speed. Then, the absolute acceleration thresholds should be taken with caution in the assessment of acceleration activities.


#4 Ingesting a 12% Carbohydrate-Electrolyte Beverage Before Each Half of a Soccer-Match Simulation Facilitates Retention of Passing Performance and Improves High-Intensity Running Capacity in Academy Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Dec 3:1-28. doi: 10.1123/ijsnem.2018-0214. [Epub ahead of print]
Authors: Rodriguez-Giustiniani P, Rollo I, Witard OC, Galloway SDR
Summary: This study investigated the influence of ingesting a 12% carbohydrate plus electrolyte (CHO-E) solution providing 60 g of carbohydrate before each half of a 90-min soccer match simulation (SMS) protocol on skill performance, sprint speed and high-intensity running capacity. Eighteen elite academy (age 18±2 y) soccer players ingested two 250 mL doses (pre-exercise and at half-time) of a 12% CHO-E solution or electrolyte placebo administered in a double-blind randomised cross-over design. During an indoor (artificial grass pitch) SMS, dribbling, passing and sprint performance were assessed, and blood was drawn for glucose and lactate analysis. High-intensity running capacity was assessed following the SMS. Dribbling speed/accuracy and sprint speed remained unchanged throughout the SMS. Conversely, passing accuracy for both dominant (mean % difference (95% CI): 9 (3-15)) and non-dominant (mean % difference (95% CI): 13 (6-20)) feet was better maintained during the SMS on CHO-E (p<0.05), with passing speed better maintained in the non-dominant foot (mean % difference (95% CI): 5.3 (0.7 to 9.9), p=0.032). High-intensity running capacity was greater in CHO-E vs. placebo (mean % difference (95% CI): 13 (6 to 20), p=0.010). Capillary blood glucose concentration was higher in CHO-E than placebo at half-time (CHO-E: 5.8±0.5 mM vs. placebo: 4.1±0.4 mM, p=0.001) and following the high-intensity running capacity test (CHO-E: 4.9±0.4 mM vs. placebo: 4.3±0.4 mM, p=0.001). Ingesting a 12% CHO-E solution before each half of a match can aid in the maintenance of soccer-specific skill performance, particularly on the non-dominant foot, and improves subsequent high-intensity running capacity.


#5 Ruptured Extensor Pollicis Longus Tendon After a Nondisplaced Distal Radius Fracture in a Young Adult Soccer Player
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000708. [Epub ahead of print]
Authors: Bogart R, Vidlock K
Summary: Forearm fractures of the distal radius are one of the most common fractures seen in the upper extremity, and they represent approximately 1/6 of fractures treated in the emergency department. Forearm fractures are associated with a rare but known complication of a delayed ruptured extensor pollicis longus (EPL) tendon. This sequela is more commonly seen in adults after a nondisplaced distal radius fracture, with much variability in the incidence ranging from 0.07% to 5%. By contrast, this complication in the pediatric population is almost exclusively seen after a displaced or unstable fracture necessitating surgical correction with open reduction and internal fixation.


#6 Postural Control Deficits After Repetitive Soccer Heading
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000709. [Epub ahead of print]
Authors: Caccese JB, Buckley TA, Tierney RT, Rose WC, Glutting JJ, Kaminski TW
Summary: The objective was to determine the acute effects of repetitive soccer heading on postural control. One hundred sixty participants, including youth (age = 13.0 ± 0.8 years), high school (age = 17.2 ± 1.0 years), and collegiate (age = 20.2 ± 1.3 years) male and female soccer players, participated in this study. Participants in the soccer heading group performed 12 soccer headers (initial velocity = 11.2 m/s). Postural control testing was performed both before (PRE) and immediately after (POST) the purposeful soccer headers. Control participants performed postural control testing PRE and POST a 15-minute wait period. During postural control testing, participants were asked to stand on the MobileMat (Tekscan Inc, Boston, Massachusetts) for two 2-minute intervals with their hands on their hips and their feet together with one eyes-open and one eyes-closed trial. Using the center-of-pressure data, 95% area, sway velocity, and ApEn were calculated. Multilevel linear models were used to analyze the effects of age, sex, group, condition, and concussion history simultaneously. Participants in the soccer heading group had significantly higher sway velocity POST than participants in the control group after controlling for age, sex, concussion history, condition, and PRE (t = -3.002; P = 0.003; 95% confidence interval, -0.482 to -0.100). There were no significant differences from PRE to POST for 95% area, M/L ApEn, and A/P ApEn. Repetitive soccer heading does not affect most postural control measures, even among youth athletes. However, sway velocity increased after heading relative to control participants independent of age, sex, and concussion history.


#7 A Match-Derived Relative Pitch Area Facilitates the Tactical Representativeness of Small-Sided Games for the Official Soccer Match
Reference: J Strength Cond Res. 2018 Dec 13. doi: 10.1519/JSC.0000000000002978. [Epub ahead of print]
Authors: Olthof SBH, Frencken WGP, Lemmink KAPM
Summary: Small-sided games (SSGs) are a promising training format in soccer to replicate (situations of) the official match across all age groups. Typically, SSGs are played on a smaller relative pitch area (RPA; i.e., <150 m) than the match (320 m RPA), which results in different tactical demands. To create a more precise replication of tactical match demands in SSGs with less than 11 players per team, a match-derived RPA (320 m) may be considered because this affords a similar playing area per player. In addition, subgroup analysis is necessary to deal with the different number of players in match and SSGs. Therefore, this study aims to investigate tactical demands of matches and various SSGs-with a different number of players and played on 320 m RPA-in talented youth soccer players. Twelve elite soccer teams in 4 age categories (under-13, under-15, under-17, and under-19) played official matches and 4 vs. 4 + goalkeepers (GKs), 6 vs. 6 + GKs, and 8 vs. 8 + GKs. Positional data were collected to calculate tactical variables (interpersonal distances, length, width, and surface areas) for all players and for 2- and 4-player subgroups. Corresponding tactical variability (coefficients of variation expressed as percentages) was determined for all players. Results demonstrated that in each age category, with an increase in number of players, team distances increased and tactical variability decreased. Subgroup analyses revealed similar team distances in matches and SSGs with the exception of larger interpersonal distances in 4 vs. 4 + GKs than the match in under-13, under-15, and under-17. Match-derived RPA in SSGs facilitates the tactical representativeness for the match. Soccer coaches can use such SSGs for an optimal tactical match preparation.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.


#8 A 9-months multidisciplinary rehabilitation protocol based on early post-operative mobilization following a chronic-degenerative patellar tendon rupture in a professional soccer player: a case report
Reference: Eur J Phys Rehabil Med. 2018 Dec 14. doi: 10.23736/S1973-9087.18.05479-5. [Epub ahead of print]
Authors: Vitale JA, Banfi G, Belli E, Negrini F, La Torre A
Summary: Isolated patellar tendon rupture (PTR) is the final stage of a long-standing tendon chronic degeneration. PTR requires immediate repair in order to avoid important muscle retraction and tendon fibrosis. The aim was to describe the effects of a rehabilitation protocol after chronic-degenerative PTR on subjective functional outcomes, knee range of motion (ROM), size, and strength in a professional football player. A 26-years-old football player who experienced RPT after a 3-year history of proximal patellar tendinopathy. After early surgical repair of the tendon, the athlete underwent a 9-months multidisciplinary rehabilitation program, based on early post-operative mobilization. Early knee mobilization and gradual controlled load from the second week determined a large increase in flexion ROM, muscular strength and trophy over the weeks by the athlete. Early surgical repair of PTR together with an early knee mobilization program demonstrated excellent results after a 9-months follow-up.


#9 Comparative Analysis of Load Profile between Small-Sided Games and Official Matches in Youth Soccer Players
Reference: Sports (Basel). 2018 Dec 12;6(4). pii: E173. doi: 10.3390/sports6040173.
Authors: Gómez-Carmona CD, Gamonales JM, Pino-Ortega J, Ibáñez SJ
Download link: https://www.mdpi.com/2075-4663/6/4/173/pdf
Summary: The purposes of the present study are: (a) to characterize the external (eTL) and internal load (iTL) of official matches and small-sided games (SSGs) in relation to their objective, (b) to compare demands between SSG, and (c) to analyze the SSG requirements in relation to official matches during a one-month competition period. Twenty under-18 national-level soccer players were recorded using WIMUTM inertial devices (RealTrack Systems, Almeria, Spain) during four official matches and 12 training sessions where four SSGs with different objectives were performed: (SSG1) keeping the ball; (SSG2) keeping the ball and progressing; (SSG3) keeping the ball, progressing and ending in mini-goals; and (SSG4) keeping the ball, progressing and ending in an official goal with a goalkeeper. Statistical analysis included Kruskall-Wallis' H and Mann-Whitney's U with Cohen's d effect size. The SSGs presented walking and jogging intensity movements (0.7⁻7 to 7⁻14 km/h), with a 5-to-8 %HIA (high intensity activity, >16 km/h), where low intensity accelerations, decelerations and impacts were predominant (1⁻2.5 m/s²; 5⁻7 G), and %HRMAX (maximum heart rate percentage) was between 70⁻90%. Only SSG4 presented similar demands to competition, finding differences between SSGs (p < 0.05; d = 1.40 - 0.36). In conclusion, the objective of the SSGs directly influenced the demands on the players in training sessions. For this reason, it is important to monitor demands for designing specific training sessions.


#10 Spatiotemporal and Kinetic Determinants of Sprint Acceleration Performance in Soccer Players
Reference: Sports (Basel). 2018 Dec 9;6(4). pii: E169. doi: 10.3390/sports6040169.
Authors: Murata M, Takai Y, Kanehisa H, Fukunaga T, Nagahara R
Dowload link: https://www.mdpi.com/2075-4663/6/4/169/pdf
Summary: We aimed to elucidate spatiotemporal and kinetic determinants of sprint acceleration performance in soccer players. Thirty-seven male soccer players performed 60-m sprints. The spatiotemporal variables and ground reaction impulses were calculated over a 50-m distance. When controlling the influence of stature and body mass, change in running speed was correlated with the step length at the 1st⁻4th step section (r = 0.695), step frequency from the 9th to 20th step sections (r = 0.428 to 0.484), braking impulse during the 17th⁻20th step section (r = 0.328), propulsive impulse from the 1st to 8th step sections (r = 0.738 and 0.379), net anteroposterior impulse for all step sections (r = 0.384 to 0.678), and vertical impulse from the 9th⁻12th step section and thereafter (r = -0.355 to -0.428). These results confirmed that an effective acceleration is probably accomplished by a greater step length originated in greater propulsive impulse during the initial acceleration phase (to the 8th step), a higher step frequency through smaller vertical impulse and smaller braking impulse during the middle and later acceleration phases (from the 9th step), as well as greater net anteroposterior impulse during the entire acceleration phase.


#11 Positional Differences in GPS Outputs and Perceived Exertion During Soccer Training Games and Competition
Reference: J Strength Cond Res. 2018 Nov;32(11):3222-3231. doi: 10.1519/JSC.0000000000002387.
Authors: Abbott W, Brickley G, Smeeton NJ
Summary: Soccer training games are popular training modalities, allowing technical, tactical, and physical aspects to be trained simultaneously. Small (SSGs), medium (MSGs), and large training games (LSGs) elicit differing physical demands. To date, no research has investigated physical and perceived demands of training games on soccer playing positions relative to competitive demands. In addition, previous research has referenced average competitive intensities, ignoring peak demands of competition. The current aim was to investigate the effect of training game formats on average and peak physical outputs produced by soccer playing positions. Physical and perceptual data from 22 competitive matches and 39 training game sessions were collected for 46 U23 professional players using 10-Hz global positioning system (GPS) and 100-Hz accelerometer devices (MinimaxX version 4.0; Catapult Innovations, Melbourne, Australia). Data analyzed included GPS-derived distance, speed, acceleration, deceleration, and rating of perceived exertion (RPE). Two-way between-subjects analyses of variance were used to compare average and peak GPS metrics, and RPE, between training games and competition for playing positions. Despite eliciting significantly higher average total distances compared with competition (p < 0.01), LSGs produced significantly lower peak total distance relative to the competition (p < 0.01). For very high-speed running and sprinting, LSGs elicited similar average intensities to competition; however, peak intensities were significantly lower than competition (p < 0.01). Medium training games and LSGs produced significantly higher average and peak moderate-intensity explosive distances than competition (p < 0.01). Results indicate the importance of analyzing relative to peak competitive demands, instead of focusing solely on average demands. The study demonstrates that specific game formats can overload the competitive demands of playing positions and provide an individualized training stimulus.


#12 Pre-season Fitness Level and Injury Rate in Professional Soccer - A Prospective Study
Reference: Sports Med Int Open. 2018 Aug 22;2(3):E84-E90. doi: 10.1055/a-0631-9346. eCollection 2018 Jun.
Authors: Eliakim E, Doron O, Meckel Y, Nemet D, Eliakim A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6225967/pdf/10-1055-a-0631-9346.pdf
Summary: The aim of the present study was to assess prospectively the effect of pre-season fitness on injury rate during the competitive season among professional soccer players. Thirty-one players participated in the study during two consecutive competitive seasons (2015-16 and 2016-17; a squad of 22 players in each season). During the 6-week pre-season training period (8 training sessions and a friendly match every week, 14-18 training hours/week) there was a significant improvement in VO 2 max, a significant increase in ideal and total sprint time and no change in vertical jump, flexibility and repeated sprint-test performance decrement. During the two consecutive seasons, 28 injuries were recorded. Ten injuries were classified as mild (missing 3-7 days of practice/match), 8 as moderate (missing 8-28 days) and 10 as severe (missing >28 days). The rate of match injuries was higher (9.4 per 1000 match hours) compared to practice injuries (4.7 per 1000 training hours). Most injuries were overuse injuries (72%) of the lower limbs (71%). Most of match injuries occurred during the last 15 min of each half. There were no differences in fitness characteristics in the beginning of pre-season training between injured and non-injured players. However, improvements in VO 2 max during the pre-season training period were significantly lower among injured players (0.9±5.5%) compared to non-injured players (10.4±6.5%, p<0.05). Our results emphasize the importance of pre-season training in professional soccer players not only for improvement in fitness but also for injury prevention during the following competitive season.

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Latest research in football - week 48 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Foot and Ankle Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0096.
Authors: Feria-Arias E, Boukhemis K, Kreulen C, Giza E
Download link: https://www.amjorthopedics.com/node/378448/pdf
Summary: The ankle is one of the most commonly injured joints in soccer and represents a significant cost to the healthcare system. The ligaments that stabilize the ankle joint determine its biomechanics-alterations of which result from various soccer-related injuries. Acute sprains are among the most common injury in soccer players and are generally treated conservatively, with emphasis placed on secondary prevention to reduce the risk for future sprains and progression to chronic ankle instability. Repetitive ankle injuries in soccer players may cause chronic ankle instability, which includes both mechanical ligamentous laxity and functional changes. Chronic ankle pathology often requires surgery to repair ligamentous damage and remove soft-tissue or osseous impingement. Proper initial treatment, rehabilitation, and secondary prevention of ankle injuries can limit the amount of time lost from play and avoid negative long-term sequelae (eg, osteochondral lesions, arthritis). On the other hand, high ankle sprains portend a poorer prognosis and a longer recovery. These injuries will typically require surgical stabilization. Impingement-like syndromes of the ankle can undergo an initial trial of conservative treatment; when this fails, however, soccer players respond favorably to arthroscopic debridement of the lesions causing impingement. Finally, other pathologies (eg, stress fractures) are highly encouraged to be treated with surgical stabilization in elite soccer players.


#2 Female Soccer Players With Anterior Cruciate Ligament Reconstruction Have a Higher Risk of New Knee Injuries and Quit Soccer to a Higher Degree Than Knee-Healthy Controls
Reference: Am J Sports Med. 2018 Nov 27:363546518808006. doi: 10.1177/0363546518808006. [Epub ahead of print]
Authors: Fältström A, Kvist J, Gauffin H, Hägglund M
Summary: Many patients with anterior cruciate ligament (ACL) reconstruction who return to sport suffer new ACL injuries or quit sports soon after returning. The purpose was to prospectively follow a cohort of female soccer players with primary unilateral ACL reconstruction and matched knee-healthy controls from the same soccer teams to compare (1) the rate of new traumatic and nontraumatic knee injuries and other injuries, (2) the proportion of players who quit soccer, and (3) player-reported activity level and satisfaction with activity level and knee function. A total of 117 active female soccer players (mean ± SD age, 19.9 ± 2.5 years) 18.9 ± 8.7 months after ACL reconstruction and 119 knee-healthy female soccer players (19.5 ± 2.5 years) matched from the same teams were prospectively followed for 2 years for new knee injuries, other injuries, soccer playing level, activity level according to the Tegner Activity Scale, and satisfaction with activity level and knee function. Players with ACL reconstruction had a higher rate of new ACL injuries (n = 29 vs 8; 19 vs 4 per 100 player years; rate ratio [RR], 4.82; 95% CI, 2.20-10.54; P < .001), other traumatic knee injuries (29 vs 16 per 100 player years; RR, 1.84; 95% CI, 1.16-2.93; P < .01), and nontraumatic knee injuries (33 vs 9 per 100 player years; RR, 3.62; 95% CI, 2.11-6.21; P < .001) as compared with controls. There was no difference in the rate of other (not knee) injuries (43 vs 48 per 100 player years; RR, 0.90; 95% CI, 0.65-1.23; P = .494). During the 2-year follow-up, 72 (62%) players with ACL reconstruction quit soccer, as opposed to 43 (36%) controls ( P = .001). The median Tegner Activity Scale score decreased in both groups ( P < .001) but more for the ACL-reconstructed group ( P < .015). Female soccer players with ACL reconstruction had nearly a 5-fold-higher rate of new ACL injuries and a 2- to 4-fold-higher rate of other new knee injuries, quit soccer to a higher degree, and reduced their activity level to a greater extent as compared with knee-healthy controls.


#3 There Is No Such Thing as an International Elite Under-9 Soccer Player
Reference: J Sports Sci Med. 2018 Nov 20;17(4):686-688. eCollection 2018 Dec.
Authors: Kirkland A, O'Sullivan M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243622/pdf/jssm-17-686.pdf


#4 Establishing the Reliability and Limits of Meaningful Change of Lower Limb Strength and Power Measures during Seated Leg Press in Elite Soccer Players
Reference: J Sports Sci Med. 2018 Nov 20;17(4):539-546. eCollection 2018 Dec.
Authors: Redden J, Stokes K, Williams S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243620/pdf/jssm-17-539.pdf
Summary: Measurement of lower limb strength, power and asymmetries of soccer players is important for monitoring physical development and injury risk. The aim of the present study was to establish the reliability and limits of meaningful change of single and double leg maximal strength, power and bilateral imbalance measures in elite soccer players using a pneumatic resistance based seated leg press. Thirteen participants undertook an incremental resistance leg press test on three separate testing days within a seven day period. Paired t-tests established no significant differences (p > 0.156) between consecutive tests, whilst 'good' reliability (intraclass correlation coefficient-ICC >0.762) and acceptable typical percentage errors (< 6.9%) were observed for maximal resistance, velocity and force pushed as well as average and peak power outputs. Imbalance variables accounting for left and right leg average power output across all repetitions were established as the most reliable imbalance variables, with 'good' reliability (ICC > 0.874) and absolute typical error values of 2.1%. Imbalance variables calculated using peak power output or average power output from the last 4 repetitions resulted in weaker reliability (ICC < 0.657) and significant differences between tests, and therefore were considered less suitable for applied use. Subsequently, to better inform the practitioner, limits of meaningful change were calculated for all strength, power and imbalance variables. The current study shows that lower limb strength, and power output variables and average imbalance measures of soccer players assessed through a seated leg press protocol show acceptable levels of reliability, and provides practitioners with limits of meaningful change around parameters to better evaluate test results.


#5 Motivation counteracts fatigue-induced performance decrements in soccer passing performance
Reference: J Sports Sci. 2018 Nov 24:1-8. doi: 10.1080/02640414.2018.1548919. [Epub ahead of print]
Authors: Barte JCM, Nieuwenhuys A, Geurts SAE, Kompier MAJ
Summary: Recent theories suggest that negative effects of fatigue on performance are determined by perception of effort and motivation rather than being directly caused by reaching physiological limits. In the current experiment, the influence of motivation on fatigue-induced decrements in soccer performance was experimentally investigated. Sixty amateur soccer players performed a validated soccer-passing test before and after a fatigue protocol. Results showed that players' motivation and performance decreased after the fatigue protocol for players in the control group. In contrast, players in the motivation group (i.e., with motivation experimentally induced after the fatigue protocol) were able to uphold their motivation and increase their performance. These results indicate that motivation plays a crucial role in performance under fatigue, as fatigue-induced decrements in soccer passing performance can be counteracted by high levels of motivation. Future research may explore the limits of this counteracting effect and extend findings to other relevant performance aspects.


#6 Dribbling speed along curved paths predicts attacking performance in match-realistic one vs. one soccer games
Reference: J Sports Sci. 2018 Nov 23:1-8. doi: 10.1080/02640414.2018.1544110. [Epub ahead of print]
Authors: Wilson RS, Smith NMA, Ramos SP, Giuliano Caetano F, Aparecido Rinaldo M, Santiago PRP, Cunha SA, Moura FA
Summary: This study assessed whether a new, closed-skill dribbling or sprinting task could predict attacking performance in soccer. Twenty-five male players were recruited from the Londrina Junior Team Football Academy in Brazil and asked to either dribble the ball or sprint through five custom circuits that varied in average curvature (0-1.37 radians.m-1). These measures were then validated using a realistic one vs. one competition in which each player acted as attacker or defender in turn (N = 1330 bouts). Sprinting (ICC = 0.96) and dribbling (ICC = 0.97) performances were highly repeatable for individual players. Average dribbling speed decreased non-linearly with increasing circuit curvature (F = 239.5; P < 0.001) from 5.19 ± 0.11 ms-1 on the straightest path to 2.13 ± 0.03 ms-1 on the curviest. Overall, dribbling but not sprinting performance predicted attacking success in the one vs. one competition, explaining more than 50% of the variation in attacking success alone (rp = 0.70; P < 0.001). In conclusion, our new closed-skill dribbling assessment is a valid and reliable protocol to predict a soccer player's success in attacking performance in one vs. one situation, and can be used to identify talented players.


#7 Career Termination of Portuguese Elite Football Players: Comparison between the Last Three Decades
Reference: Sports (Basel). 2018 Nov 28;6(4). pii: E155. doi: 10.3390/sports6040155.
Authors: Carapinheira A, Mendes P, Guedes Carvalho P, Torregrossa M, Travassos B
Download link: https://www.mdpi.com/2075-4663/6/4/155/pdf
Summary: The aim of this study was to explore the process of career termination of elite soccer players, comparing the quality and the resources to support career termination over the last three decades. To this end, was developed a questionnaire defined by four sections: (a) biographical data, (b) athletic career, (c) quality of career termination and (d) available resources at the moment of career termination. Ninety male former elite Portuguese soccer players participated in this study. The results highlighted a decrease in the length of athletic career as football players and an increase in the number of years as youth players over the last 30 years. The results also revealed that the quality of career termination was difficult. The analysis of resources for career termination revealed an increase in a high level of education over the years. Despite the evolution in the level athletes' education in the last three decades, the athletic career termination remained difficult and it was reported that they did not plan their career termination. In line with previous studies, the results highlight that the lack of plans for career termination is one of the most important factors that constrain the quality of career transition.


#8 Changes in Cortisol and Immunoglobulin a Concentrations in Referees during a Professional Football Match
Reference: J Sports Sci Med. 2018 Nov 20;17(4):689-690. eCollection 2018 Dec.
Authors: Kokaly M, Peñailillo L, Villagrán C, Mackay K, Jannas S, Deldicque L, Zbinden-Foncea H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243613/pdf/jssm-17-689.pdf


#9 Decline in Match Running Performance in Football is affected by an Increase in Game Interruptions
Reference: J Sports Sci Med. 2018 Nov 20;17(4):662-667. eCollection 2018 Dec.
Authors: Linke D, Link D, Weber H, Lames M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243615/pdf/jssm-17-662.pdf
Summary: This study quantified the contribution of game interruptions to the fatigue-related declines in match running performance over the course of a football match. Using a semi-automatic multiple camera system, the running activity of 792 individual German Bundesliga performances was divided into pre-defined 15-minute intervals and subsequently analysed under two prerequisites: with (effective playing time) and without (total playing time) consideration of game interruptions. Results showed a significant decline in effective playing time over the course of a match, from 66.3% of the total playing time in the first 15 minutes to 55.9% in the final 15 minutes of a match. Under consideration of the total playing time, match running performances decreased by 24.2% on average; considering the effective playing time, they decreased on average by only 10.2%. It can, therefore, be concluded that more than half (57.9%) of the commonly reported decline in match running performance cannot be assigned to physical fatigue, but rather to an increase in game interruptions as the game progresses. In conclusion, this study demonstrated for the first time that the decline in players' match running performance during football matches is substantially amplified by a proven increase in game interruptions, indicating that there may be a tendency among practitioners to overestimate fatigue-induced performance declines.


#10 Positional Differences in the Most Demanding Passages of Play in Football Competition
Reference: J Sports Sci Med. 2018 Nov 20;17(4):563-570. eCollection 2018 Dec.
Authors: Martín-García A, Casamichana D, Díaz AG, Cos F, Gabbett TJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243617/pdf/jssm-17-563.pdf
Summary: The aim of this investigation was to determine the position and duration specific activity of the most demanding passages of play in football players. Global positioning system data were collected from twenty-three football players across a competitive season. A total of 605 individual match files were analysed. Players were categorised based on positional groups; full-back (FB), central defender (CD), midfielder (MF), wide midfielders (WMF) and forwards (FW). The most demanding passage of a match play was analysed using a rolling average method, where maximal values were calculated for four different time durations (1', 3', 5' and 10') using distance (m·min-1), high metabolic load distance (HMLD) and average metabolic power (AMP) as variables of interest. Using distance as the criterion variable, MF and WMF positions covered greater distance, and fewer sprinting meters (>7.0 m·s-1, m·min-1). With HMLD as the criterion variable, the values for WMF and MF positions were higher than the CD and FW positions. The MF and WMF positions performed more high-intensity accelerations and decelerations when the criterion variable was AMP. These results provide an understanding of the most demanding passages of play to inform training practices for specific football playing positions.


#11 Orhtopedic injuries in mens’s professional soccer in brazil: Prospective comparison of two consecutive seasons 2017/2016
Reference: Acta Ortop Bras. 2018;26(5):338-341. doi: 10.1590/1413-785220182605194940.
Authors: de Moraes ER, Arliani GG, Lara PHS, da Silva EHR, Pagura JR, Cohen M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6220654/pdf/1809-4406-aob-26-05-0338.pdf
Summary: The purpose was to compare the incidence and characteristics of injuries sustained in two consecutive seasons of the São Paulo State Football Championship. Prospective study performed using an electronic form previously developed by the Medical Committee of the São Paulo State Football Federation, sent to the physicians responsible for the tournament's series A1 and A2 teams, after each round. 17.63 injuries sustained per 1000 hours of matches in the A1 series and 14.91 injuries sustained per 1000 hours of matches in the A2 series. Incidence of injuries per 1000 hours of matches decreased from 24.16 to 17.63 in the A1 series (p<0.037) and from 19.10 to 14.01 in the A2 series (p<0.064). External defenders suffered most injuries, while muscular injuries were most common and lower limbs, the most affected areas. Most injuries occurred between 30 and 45 minutes of the match and only 11.9% of the injuries required surgery. Prevalence and frequency of injuries decreased between seasons. Most injuries were sustained in the lower limbs; strains were the most common injuries, followed by strains and contusions; MRIs were the most frequently requested exams and most injuries were classified as moderate (8-28 days).


#12 Effects of Strength Training Program and Infrared Thermography in Soccer Athletes Injuries
Reference: Sports (Basel). 2018 Nov 19;6(4). pii: E148. doi: 10.3390/sports6040148.
Authors: Menezes P, Rhea MR, Herdy C, Simão R
Download link: https://www.mdpi.com/2075-4663/6/4/148/pdf
Summary: The purpose of this investigation was to examine the effects of a periodized strength training program and the use of infrared thermography (IRT) in injuries mapping in under 20-year-old (U-20) soccer players. In this study, 26 professional soccer players participated in strength training (ST) twice a week and were tested with IRT consistently across the 1-year. Strength, vertical jump, heat differences and injuries were tracked and analyzed. Results: 69 injuries occurred during 12 months of tracking; most identified injuries were: contusions, sprains, strains to the thigh (n = 16), ankle (n = 15) and knee (n = 12). Differences (>7 °C) in IRT patterns were noted among injured and non-injured athletes. Significant improvements in strength (p < 0.005) were found for vertical jump, bench press, front lat pull down, shoulder press, leg press, leg curl and squat. Number of injuries decreased from 23 (33.3%) to 14 (20.3%) when early year rates were compared to late year (p < 0.005). Combined ST and IRT represent useful strategies for reducing injuries among U-20 soccer players.


#13 Can professional football clubs deliver a weight management programme for women: a feasibility study
Reference: BMC Public Health. 2018 Dec 3;18(1):1330. doi: 10.1186/s12889-018-6255-2.
Authors: Bunn C, Donnachie C, Wyke S, Hunt K, Brennan G, Lennox J, Maclean A, Gray CM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6276211/pdf/12889_2018_Article_6255.pdf
Summary: Levels of obesity remain high in the UK. The Football Fans in Training (FFIT) randomised controlled trial (RCT) demonstrated that a 12-week, gender-sensitised weight management, physical activity and healthy eating group programme delivered through professional football clubs helped men aged 35-65 years with BMI at least 28 kg/m2 lose a clinically-significant amount of weight. We aimed to test the feasibility of a minimally-adapted FFIT programme for delivery to women by assessing recruitment and completion rates; determining if the programme content and delivery required further refinement; and evaluating the potential of FFIT for Women to deliver improvements in weight and other clinical, behavioural and psychological outcomes. A feasibility study of the FFIT for Women programme including before-and-after measurements of clinical (weight, waist, body mass index [BMI], blood pressure) behavioural (self-reported physical activity, food and alcohol intake) and psychological (self-esteem, positive and negative affect, physical and mental HRQoL) outcomes at five professional football clubs. Post-programme focus groups assessed acceptability of the programme format, content and style of delivery for women. Recruitment across the five clubs resulted in 123 women aged 35-65 years with BMI at least 28 kg/m2 taking part in the study. The mean weight (95.3 kg) and BMI (36.6 kg/m2) of the cohort were both suggestive of high risk of future disease. Of 123 women who started the programme, 94 (76%) completed it; 72 (58.5%) returned for 12-week follow-up measurements. Participants compared FFIT for Women favourably to commercial weight loss programmes and emphasised the importance of the programme's physical activity content. They also spoke positively about group dynamics, suggested that the approach to food was less restrictive than in other weight loss approaches, and broadly enjoyed the football setting. Mean weight loss was 2.87 kg (95% CI 2.09, 3.65, p ≤ 0.001). Mean waist reduction was 3.84 cm (2.92, 4.77, p ≤ 0.001). In this evaluation, FFIT for Women was feasible, acceptable and demonstrated potential as a weight loss programme. Our findings suggest the programme has the potential to produce outcomes that are on a par with existing commercial and state-funded offerings.

Sat

05

Jan

2019

Latest research in football - week 47 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 High-Intensity Demands of 6-a-Side Small-Sided Games and 11-a-Side Matches in Youth Soccer Players
Reference: Pediatr Exerc Sci. 2018 Nov 30:1-6. doi: 10.1123/pes.2018-0122. [Epub ahead of print]
Authors: Goto H, King JA
Summary: The purposes of the present study were to examine high-intensity running distance during 6-a-side small-sided games (SSGs) and 11-a-side matches (11M) in youth soccer players using speed and metabolic power approaches and the magnitude of difference between the high-intensity running distance calculated with the 2 approaches. A total of 11 outfield players (age = 16.3 [0.6] y) performed SSGs with 3 pitch sizes (small SSG [SSGS], medium SSG, and large SSG [SSGL]) and 11M. A Global Positioning System (15 Hz) was employed to calculate total distance covered, distance covered at a speed ≥4.3 m·s-1 (TS), and metabolic power of ≥20 W·kg-1 (TP). The total distance covered increased from SSGS through to SSGL (P < .001) and was greater during 11M and SSGL compared with other SSGs (P < .01). TS and TP increased from SSGS (TS vs TP = 98 [55] vs 547 [181] m) through to SSGL (538 [167] vs 1050 [234] m; P < .001). TS and TP during 11M (370 [122] vs 869 [233] m) was greater than SSGS (P < .001 for both) and less than SSGL (P < .05 for both). The magnitude of difference between TS and TP (as a percentage) was lower with an increase in pitch size during SSGs and was greater in SSGS (615% [404%]; P < .001), medium SSG (195% [76%]; P < .05), and smaller in SSGL (102% [33%]; P < .01) compared with 11M (145% [53%]). SSGs can replicate the high-intensity demands of 11M and the speed approach underestimates the high-intensity demands of SSGs and 11M compared with the metabolic power approach.


#2 Injury prevalence and risk factors in a Greek team's professional football (soccer) players: a three consecutive seasons survey
Reference: Res Sports Med. 2018 Nov 30:1-13. doi: 10.1080/15438627.2018.1553779. [Epub ahead of print]
Authors: Smpokos E, Mourikis C, Theos C, Linardakis M
Summary: This study investigated the prevalence and risk factors of injuries on a cohort of 123 Greek team's professional football players during three consecutive seasons, 2015/16-to-2017/18. Injuries were assessed and regression analysis was used to evaluate the potential risk factors. Three-quarters of the players were recorded as injured with 2.3 injuries/injured player, and the injury incidence was 55 injuries/1,000 match-playing-exposure-hours. The mean rehabilitation days were 29.3/injured player (95%CI 22.4-36.8) and 13.0/injury (95%CI 8.6-17.4). The majority of injured players has been found to have moderate-to-major/severe injuries and most of the injuries were traumatic than overuse (p < 0.05). The number of injuries were related to the recurrence of injury (beta = 0.646, p < 0.001) and the rehabilitations days (beta = 0.271, p < 0.001). High prevalence of injuries was found as the recurrence of injury and rehabilitation days were their main predictive risk factors. In order to reduce the risk of injuries, continuous effort is required in the rehabilitation of players.


#3 ACL injury incidence, severity and patterns in professional male soccer players in a Middle Eastern league
Reference: BMJ Open Sport Exerc Med. 2018 Oct 23;4(1):e000461. doi: 10.1136/bmjsem-2018-000461. eCollection 2018.
Authors: Rekik RN, Tabben M, Eirale C, Landreau P, Bouras R, Wilson MG, Gillogly S, Bahr R, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6241976/pdf/bmjsem-2018-000461.pdf
Summary: The purpose was to ascertain ACL injury incidence, severity (injury burden) and patterns (contact/non-contact and reinjuries) in a professional male football league in the Middle East over five consecutive seasons. Prospective epidemiological study reporting ACL injuries in professional male soccer players in the Qatar Stars League, with complete matches/training exposure over five seasons (2013-2014 to 2017-2018), corresponding to 2243 player seasons and 729 team months. 37 complete ACL ruptures occurred in 37 players during 486 951  hours of player exposure. The overall ACL injury rate was 0.076 injuries/1000  hours of exposure (season range 0.045-0.098). Injury incidence during matches and training was 0.41 and 0.04 injuries/1000  hours of exposure, respectively. Match injury incidence was greater than that of training (OR 11.8, 95%  CI 6.21 to 23.23, p<0.001). Average injury-related time-loss following ACL injury was 225 days±65 (range 116-360). Overall injury burden was 16.3 days lost/1000  hours of exposure. The overall ACL injury rate in professional male soccer players competing in the Middle East was 0.076 injuries/1000  hours of exposure, match injury incidence was greater than training, while the average ACL time-loss was 225 days.


#4 Normative Data of the Wingate Anaerobic Test in 1 Year Age Groups of Male Soccer Players
Reference: Front Physiol. 2018 Nov 15;9:1619. doi: 10.3389/fphys.2018.01619. eCollection 2018.
Authors: Nikolaidis PT, Matos B, Clemente FM, Bezerra P, Camões M, Rosemann T, Knechtle B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6249309/pdf/fphys-09-01619.pdf
Summary: The Wingate anaerobic test (WAnT) has been used extensively to evaluate performance in soccer, however, a comprehensive sport-specific normative database has not been available so far. Therefore, the main aim of the present study was to develop norms of the main indices of the WAnT with regards to age in soccer. A secondary aim was to examine the relationship of WAnT with two common field tests, 20 m sprint and vertical jump, and study the variation of this relationship by age and playing position. Hundred and ninety five male soccer players (age 18.1 ± 4.9 years) performed the WAnT, and a sub-sample of 190 soccer players (age 19.4 ± 5.1 years) performed 20 m sprint, squat (SJ) and countermovement jump (CMJ). Age was related very largely with peak power (R 2 = 0.57) and mean power of the WAnT (R 2 = 0.60) when they were expressed in W, and largely (R 2 = 0.41 and R2 = 0.33, respectively) when they were expressed in W.kg-1, whereas it did not relate with fatigue index. After being adjusted for age, a relationship of SJ (B = 3.91, 90% CI: 2.49, 5.32; R 2 = 0.26), CMJ (B = 3.59, 90% CI: 2.22, 4.95; R 2 = 0.24) and 20 m sprint (B = -0.06, 90% CI: -0.10; -0.01; R 2 = 0.19) with peak power of the WanT was observed. In summary, Ppeak and Pmean were related very largely to age, especially during adolescence, and percentile norms of these indices were developed for 1-year age groups from 11 to 21 years old and for a single adult age group (22-39 years old). These findings on the largest dataset of soccer players ever studied would be expected to offer a practical tool to the members of the sports medicine team (e.g., exercise physiologists, fitness trainers, and coaches) working with them.


#5 Sprint Mechanical Properties of Female and Different Aged Male Top-Level German Soccer Players
Reference: Sports (Basel). 2018 Nov 28;6(4). pii: E161. doi: 10.3390/sports6040161.
Authors: Baumgart C, Freiwald J, Hoppe MW
Download link: https://www.mdpi.com/2075-4663/6/4/161/pdf
Summary: This study compared the sprint mechanical properties of female and different aged male top-level soccer players. A total of 14 adult females (FEM) and 115 different aged male field players, competing at German top levels, participated in this study. The males belonged to teams of under 12, 13, 14, 15, 17, 19, and 23 years (U 12⁻23) and professionals (PRO). All players were tested for a 30 m linear sprint. From timing gate derived sprint times, force-velocity and power-velocity relationships, as well as theoretical maximum running velocity, force, and power data were computed by an inverse dynamic approach applied to the center of mass. The approach was optimized for taking the starting time into account, which is a progress in the present research field, when aiming to compute sprint mechanical properties by different methodological approaches under field conditions. Sprint mechanical properties of FEM were lower than those of PRO. Compared to other age groups, sprint mechanical properties of FEM were similar to those of U 14 and U 15. An increase in sprint mechanical properties was found from U 12 to U 17. The study shows that sprint mechanical properties differ according to gender and age in top-level soccer players.


#6 Combination of Agility and Plyometric Training Provides Similar Training Benefits as Combined Balance and Plyometric Training in Young Soccer Players
Reference: Front Physiol. 2018 Nov 13;9:1611. doi: 10.3389/fphys.2018.01611. eCollection 2018.
Authors: Makhlouf I, Chaouachi A, Chaouachi M, Ben Othman A, Granacher U, Behm DG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243212/pdf/fphys-09-01611.pdf
Summary: Studies that combined balance and resistance training induced larger performance improvements compared with single mode training. Agility exercises contain more dynamic and sport-specific movements compared with balance training. Thus, the purpose of this study was to contrast the effects of combined balance and plyometric training with combined agility and plyometric training and an active control on physical fitness in youth. Fifty-seven male soccer players aged 10-12 years participated in an 8-week training program (2 × week). They were randomly assigned to a balance-plyometric (BPT: n = 21), agility-plyometric (APT: n = 20) or control group (n = 16). Measures included proxies of muscle power [countermovement jump (CMJ), triple-hop-test (THT)], muscle strength [reactive strength index (RSI), maximum voluntary isometric contraction (MVIC) of handgrip, back extensors, knee extensors], agility [4-m × 9-m shuttle run, Illinois change of direction test (ICODT) with and without the ball], balance (Standing Stork, Y-Balance), and speed (10-30 m sprints). Significant time × group interactions were found for CMJ, hand grip MVIC force, ICODT without a ball, agility (4 m × 9 m), standing stork balance, Y-balance, 10 and 30-m sprint. The APT pre- to post-test measures displayed large ES improvements for hand grip MVIC force, ICODT without a ball, agility test, CMJ, standing stork balance test, Y-balance test but only moderate ES improvements with the 10 and 30 m sprints. The BPT group showed small (30 m sprint), moderate (hand grip MVIC, ICODTwithout a ball) and large ES [agility (4 m × 9 m) test, CMJ, standing stork balance test, Y-balance] improvements, respectively. In conclusion, both training groups provided significant improvements in all measures. It is recommended that youth incorporate balance exercises into their training and progress to agility with their strength and power training.


#7 Use of Musculoskeletal Ultrasound and Regenerative Therapies in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0093.
Authors: Centurion AJ, Youmans H, Zeini IM
Download link: https://www.amjorthopedics.com/article/use-musculoskeletal-ultrasound-and-regenerative-therapies-soccer-1
Summary: Improvements in ultrasound technology have increased the popularity and use of ultrasound as a diagnostic and therapeutic modality for many soccer-related musculoskeletal (MSK) injuries. As a dynamic imaging modality, ultrasound offers increased accuracy and efficacy with minimally invasive procedures, such as guided injections, percutaneous tenotomy, and regenerative therapies, in the clinical setting. Emerging evidence indicates that regenerative therapies, such as platelet-rich-plasma (PRP), mesenchymal stem cells, and amniotic products, are a promising treatment for many MSK injuries and are gaining popularity among professional athletes. PRP is a safe treatment for a number of MSK conditions and has been included in the standard of care. However, conflicting evidence on return-to-play timeframes and efficacy in certain MSK conditions have led to inconsistent recommendations on indications for use, dose, and timing of treatment. Mesenchymal stem cell therapy, while promising, lacks high-level evidence of efficacy despite its increasing use among athletes. Currently, no data are available regarding the outcome of the use of amniotic products for the treatment of injuries in athletes. Furthermore, preparation of many regenerative therapies eclipses the concept of minimal manipulation and is subject to US Food and Drug Administration phase I to III trials. High-level research on regenerative medicine therapies should be continuously conducted to establish their clinical efficacy and safety data.


#8 Upper Extremity Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0091.
Authors: Marom N, Williams RJ 3rd
Download link: https://www.amjorthopedics.com/article/upper-extremity-injuries-soccer
Summary: Upper limb injuries in soccer represent only a marginal portion of injuries, however this is mainly true for outfield players. Goalkeepers are reported to have up to 5 times more upper extremity injuries, many of them requiring substantial time-loss for treatment and rehabilitation. The most common upper extremity injury locations are the shoulder/clavicle followed by the hand/finger/thumb, elbow, wrist, forearm, and upper arm. The mechanism of injury, presentation, physical examination, and imaging features all play a significant role in reaching the correct diagnosis. Taking to consideration the position the player plays and his demands will also enable tailoring the optimal treatment plan that allows timely and safe return to play. This article discusses common upper extremity injuries observed in soccer players, focusing on proper diagnosis and optimal management.


#9 The Three H's: Head, Heart, and Heat Considerations in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0087.
Authors: Whipple MT, Baggish AL, Pieroth EM, Chiampas GT
Download link: https://www.amjorthopedics.com/article/three-hs-head-heart-and-heat-considerations-soccer
Summary: Soccer requires significant physical conditioning and endurance, as well as the physicality required for contact play. In order to keep athletes safe, it is important that coaches, medical staff, and the players themselves are educated on the most common dangers to their health that they may encounter on a soccer pitch. This article aims to review the current literature and recommendations on concussion, cardiovascular considerations, and heat-related illness as they relate to competitive soccer, with a goal of educating all those who help to keep athletes healthy and competing to their full potential.


#10 The Effect of Playing Position on Injury Risk in Male Soccer Players: Systematic Review of the Literature and Risk Considerations for Each Playing Position
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0092.
Authors: Della Villa F, Mandelbaum BR, Lemak LJ
Download link: https://www.amjorthopedics.com/node/371449/pdf
Summary: Soccer (football) is a complex contact sport with a substantial risk of injury. As injury surveillance is the first step of the injury prevention paradigm, soccer epidemiology is well reported in the existing literature, but less is known about the actual role of player position on the general injury risk. The goal of this study is to present the existing evidence regarding the influence of player's position on general injury risk in male soccer. A systematic review of the Medline database was carried out. Only English written studies on male soccer and citing playing position as a possible determinant of injury risk were included. One hundred and two full texts were evaluated for eligibility, and 11 studies were selected for the qualitative synthesis. Of the 11 studies included in the systematic review, 5 didn't find any significant correlation with between player's position and general injury risk, while the remaining 6 studies found player's position to be correlated with injury risk, with mixed findings depending on each study. The most consistent finding was a tendency for goalkeepers (GKs) to sustain less injuries compared to outfield players. When considering only the studies reporting just the match injury risk, forwards seemed to be at higher risk, even if there wasn't a complete agreement. Few studies have evaluated a possible effect of playing position on general injury risk in male soccer. There is no agreement if weather or not different playing positions are associated to a higher injury risk. GKs seem to be at lower risk of injury when compared to outfield players.


#11 Soccer or Football Medicine? Global Sports Medicine for a Global Game
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0089.
Authors: Osbahr DC
Download link: https://www.amjorthopedics.com/node/366226/pdf


#12 Knee Injuries in Elite Level Soccer Players
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0088.
Authors: Roth TS, Osbahr DC
Download link: https://www.amjorthopedics.com/node/365357/pdf
Summary: As one of the most popular sports in the world, soccer injury rates involving the knee continue to rise. An alarming trend of knee injuries, including increased anterior cruciate ligament ruptures, underscores the need to review our current understanding of these injuries in soccer players. This article includes a critical review of the epidemiology of knee injuries in soccer, anterior cruciate ligament and other ligamentous injuries, cartilage and meniscal injury, post-traumatic osteoarthritis, as well as current prevention initiatives.


#13 Hip and Core Muscle Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0094.
Authors: Sherman B, Chahla J, Hutchinson W, Gerhardt M
Download link: https://www.amjorthopedics.com/node/371702/pdf
Summary: Soccer is the most popular sport in the world and has the fourth highest number of sports injuries. Hip and groin injuries account for 14% of soccer injuries and can be difficult to recognize and treat as they often require a high level of suspicion and advanced imaging. Groin pain can be separated into 3 categories: (1) defined clinical entities for groin pain (adductor-related, iliopsoas-related, inguinal-related [sports hernias/athletic pubalgia], and pubic-related groin pain), (2) hip-related groin pain (hip morphologic abnormalities, labral tears, and chondral injuries), and (3) other causes of groin pain. Conservative approaches are typically the first line of treatment, but operative intervention has been reported to result in higher rates of return to sport in athletes with hip-related and inguinal-related groin pain injuries. In patients with concurrent hip-related and inguinal-related groin pain, the failure to recognize the relationship and treat both conditions may result in lower rates of return to sport. Preseason screening programs can identify high-risk athletes, who may benefit from a targeted prevention program. Further study on exercise therapy, early surgical intervention, and potential biologic intervention are needed to determine the most effective methods of preventing groin injuries in athletes.

Sat

05

Jan

2019

Latest research in football - week 46 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effect of a Habitual Late-Evening Physical Task on Sleep Quality in Neither-Type Soccer Players
Reference: Front Physiol. 2018 Nov 6;9:1582. doi: 10.3389/fphys.2018.01582. eCollection 2018.
Authors: Vitale JA, Banfi G, La Torre A, Bonato M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6232308/pdf/fphys-09-01582.pdf
Summary: The aim of this study was to investigate objective and subjective sleep quality, daytime tiredness and sleepiness in response to a late-evening high intensity interval training (HIIT) session in neither-type soccer players that habitually trained late in the day. This is the first study that considered both athletes' chronotype and habitual training time as crucial factors when assessing sleep quality in relation to an evening physical task. In this longitudinal, prospective, observational study, 14 Italian soccer players were recruited (mean age: 26.1 ± 4.5 years; height: 1.81 ± 0.06 m; weight: 78.9 ± 6.1 kg) and performed an extra-routine 4 × 4-min HIIT session at 09:00 p.m. Players used to train always between 09:00 and 11:00 p.m during the competitive season. All subjects wore an actigraph to evaluate their objective sleep parameters and a sleep diary was used to record subjective values of sleep quality, daytime tiredness, and daytime sleepiness. All data were analyzed as: the mean of the two nights before (PRE), the night after (POST 1), and the mean of the two nights after (POST 2) the extra-routine HIIT session. The subjects' chronotype was assessed by the morningness-eveningness questionnaire (MEQ). All players were classified as N-types (mean MEQ score: 49.4 ± 3.7). None of the actigraph parameters nor the subjective values of sleep quality, tiredness, and sleepiness showed significant changes in PRE, POST 1, and POST 2. The results of our study added more information regarding sleep quality outcomes in response to a late-evening HIIT session. Athletic trainers and medical staff should always control for chronotype and habitual training time when assessing variations to sleep quality in athletes.


#2 Match outcome and running performance in different intensity ranges among elite soccer players
Reference: Biol Sport. 2018 Jun;35(2):197-203. doi: 10.5114/biolsport.2018.74196. Epub 2018 Mar 31.
Authors: Chmura P, Konefał M, Chmura J, Kowalczuk E, Zając T, Rokita A, Andrzejewski M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234309/pdf/JBS-35-74196.pdf
Summary: The monitoring of players' work-rate profiles during competition is now feasible through computer-aided motion analysis. The aim of the present study was to examine how various playing positions and match outcomes (i.e. won, drawn, lost) affect the total distance, and the distances covered at different intensities, by soccer players in Germany's Bundesliga. Match performance data were collected for 556 soccer players competing in the Bundesliga during the 2014/15, 2015/16 and 2016/17 domestic seasons. A total of 13 039 individual match observations were made of outfield players (goalkeepers excluded). The analysis was carried out using an IMPIRE AG motion analysis system, with records of all players' movements in all the 918 matches. The recorded variables included total distance covered [km] and distance covered at intensities in the ranges below 11 km/h, 11-14 km/h, 14-17 km/h, 17-21 km/h, 21-24 km/h, and above 24 km/h. In won matches, as opposed to drawn and lost matches, the wide midfielders and forwards ran a significantly longer distance, primarily covered at intensities of 21-23.99 and above 24 km/h (p ≤ 0.05). The analysis of full-backs, central defenders and central midfielders in won matches - as opposed to drawn and lost matches - in turn reveals that players ran a significantly shorter distance, most likely to be covered at intensities of 17-20.99 and 21-23.99 km/h (p ≤ 0.05). The results of the present study emphasise the importance of match outcome and playing positions during the assessment of physical aspects of soccer performance.


#3 The "FIFA 11+" injury prevention program improves body stability in child (10 year old) soccer players
Reference: Biol Sport. 2018 Jun;35(2):153-158. doi: 10.5114/biolsport.2018.71604. Epub 2017 Nov 23.
Authors: Gatterer H, Lorenzi D, Ruedl G, Burtscher M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234308/pdf/JBS-35-71604.pdf
Summary: The suitability of the FIFA 11+ prevention programme to improve selected performance outcomes in children aged < 14 years has not been established yet. This study aimed to investigate the effects of the FIFA 11+ programme on jump ability and stability in 10-year-old child soccer players. Sixteen young soccer players (aged 10 years) were randomly assigned to a conventional or a FIFA 11+ warm-up group. During a 5-week training period with 2 sessions per week the FIFA 11+ group warmed up with the 11+ programme, whereas the control group subjects performed their usual warm-up programme (e.g. running exercises with dribbling and/or passing techniques included). After the warm-up, both groups performed the same training exercises during each session. Before and after the training period, standing long jump performance and body stability (S3 Check, unstable uniaxial platform) were assessed. Significant improvements in the stability index were found in both groups (5.6±1.1 to 3.5±1.0 and 5.5±0.8 to 4.0±1.5 for the FIFA 11+ and the control group, respectively, p<0.001, partial η²=0.886 for the training effect of the analysis of variance) with likely (qualitative inference analysis) greater improvements in the FIFA 11+ group compared to the control group (p=0.078, partial η²=0.205 for the training x group interaction effect of the analysis of variance). Training had no effect on standing long jump performance (p>0.05). Data indicate that in 10-year-old soccer players the FIFA 11+ programme may have the potential to improve stability. Thus, the FIFA 11+ programme might contribute to injury prevention and possibly to better soccer performance as well. This might especially apply if the programme is performed over a longer period and/or with more weekly training sessions. Based on the present results the inclusion of such a programme within the training practice of the child soccer player can be recommended.


#4 Physiological responses, fatigue and perception of female soccer players in small-sided games with different pitch size and sport surfaces
Reference: Biol Sport. 2018 Sep;35(3):291-299. doi: 10.5114/biolsport.2018.77829. Epub 2018 Aug 27.
Authors: López-Fernández J, Sánchez-Sánchez J, Rodríguez-Cañamero S, Ubago-Guisado E, Colino E, Gallardo L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224843/pdf/JBS-35-77829.pdf
Summary: The aim of this research was to evaluate the influence of game surface and pitch size on the physiological responses, jump performance and perceptions of sub-elite female soccer players playing four-a-side games. Sixteen sub-elite female soccer players were divided into four groups of four players each. Three small-sided games (SSGs; pitch size: 400 m2, 600 m2 and 800 m2) were played on three surfaces (dirt [DT], artificial turf [AT] and natural grass [NG]). Players' heart rate (HR) was monitored during each game. Before and after each SSG, participants performed two counter-movement jumps (CMJs) and answered a questionnaire based on visual analogue scales (VASs) to indicate their perception of the effort required on each surface. DT obtained lower outputs for most variables. In the SSG 600 mean HR was higher on NG than AT (+3.31 %HRmax; p = 0.029), but players' overall satisfaction with both surfaces was similar (p>0.05). The SSG 400 received the lowest ratings for most variables, whereas the SSG 600 resulted in higher mean HR than SSG 800 [NG (+9.14 b.p.m.; p = 0.001); AT (+7.32 b.p.m.; p = 0.014)]. No surface differences in CMJ performance were found. In conclusion, a higher internal load can be achieved on NG, whereas DT is not recommended for playing soccer. Moreover, the internal load on players in SSGs can be controlled by manipulating pitch size, but over-large pitches may entail a reduction in the physiological profile of female soccer players.


#5 Effects of preconditioning hamstring resistance exercises on repeated sprinting-induced muscle damage in female soccer players
Reference: Biol Sport. 2018 Sep;35(3):269-275. doi: 10.5114/biolsport.2018.77827. Epub 2018 Aug 27.
Authors: Chen CH, Chen YS, Wang YT, Tseng WC, Ye X.
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224846/pdf/JBS-35-77827.pdf
Summary: The purpose was to examine whether adding preconditioning hamstring resistance exercises to a regular warm-up prior to a repeated sprinting exercise provides protection against the sprinting-induced muscle damage. Ten female soccer players (mean ± SD age: 21.3 ± 4.5yrs; height: 171.34 ± 8.29 cm; weight: 68.53 ± 11.27 kg) participated in this study. After the familiarization visit, the subjects completed three separate randomly sequenced experimental visits, during which three different warm-up interventions were performed before the muscle-damaging protocol (12 sets of 30-m maximal repeated sprints): 1. Regular running and static stretching (Control); 2. Control with hyperextensions (HE); 3. Control with single leg Romanian deadlift (SLRD). Before (Pre), immediately (Post0), 24 hours (24hr), and 48 hours after (48hr) the sprints, hamstring muscle thickness, muscle stiffness, knee flexion eccentric peak torque, knee extension concentric peak torque, and functional hamstring to quadriceps ratios were measured. Repeated sprints have induced muscle damage (e.g., an average of 42% knee flexion eccentric strength reduction) in all three conditions. After the SLRD, hamstring muscle thickness decreased from 24hr to 48hr (p < 0.001). Additionally, muscle stiffness and eccentric strength for the SLRD showed no difference from baseline at 24hr and 48hr, respectively. When compared with the SLRD at 48hr, the muscle stiffness and the eccentric strength were greater and lower, respectively, in other protocols. The SLRD protocol had protective effect on sprinting-induced muscle damage markers than other protocols. Athletes whose competitions/training are densely scheduled may take advantage of this strategy to facilitate muscle recovery.


#6 Effect of the 11+ injury prevention programme on fundamental movement patterns in soccer players
Reference: Biol Sport. 2018 Sep;35(3):229-236. doi: 10.5114/biolsport.2018.74636. Epub 2018 Apr 1.
Authors: Rey E, Padrón-Cabo A, Penedo-Jamardo E, González-Víllora S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224851/pdf/JBS-35-74636.pdf
Summary: No studies have assessed whether changes in an individual's fundamental movement patterns can be achieved with the 11+ prevention programme in soccer players. The aim of this study was to assess the effect of the 11+ compared with a standard warm-up on fundamental movement patterns using the Functional Movement Screen (FMS) in amateur male soccer players. Twenty-three male soccer players (age: 24.7±.3.8 years; height: 1.77±0.58 m; body mass: 73.9±6.2 kg) were randomly assigned to the 11+ (n= 12) or control (n= 11) group. The intervention programme had to be carried out 3 times a week over 6 weeks. The 11+ warm-up lasted ~25 minutes and was conducted before starting regular practice, replacing the team's standard warm-up. The control group warmed up with standard jogging, ball exercises, and active stretching to match the duration of the 11+. Within-group analysis revealed significant improvements in the FMS total score in the 11+ (+10.51%; d= 0.83) and control group (+7.99%; d= 0.68) from pre-test to post-test. In the between-group analysis, there were no significant differences between groups. At the post-test a significantly greater number of players in the 11+ group exhibited a score that improved to above the injury threshold (≤14) (p= 0.046). This study suggests that regular implementation of the 11+ injury prevention programme may not produce additional improvements in fundamental movement patterns other than those produced by a standard warm-up.


#7 Are tibial angles measured with inertial sensors useful surrogates for frontal plane projection angles measured using 2-dimensional video analysis during single leg squat tasks? A reliability and agreement study in elite football (soccer) players
Reference:  J Electromyogr Kinesiol. 2018 Nov 10;44:21-30. doi: 10.1016/j.jelekin.2018.11.005. [Epub ahead of print]
Authors: Hughes T, Jones RK, Starbuck C, Picot J, Sergeant JC, Callaghan MJ
Download link: https://reader.elsevier.com/reader/sd/pii/S1050641118303419?token=E1B0B5B18BD00B5331DDA5375C0DF58DA9AE8FE7C4A0F44DCC209E6B906A0DE3B9EB9779AA1722C2D3EB313DB6B74A08
Summary: During single leg squats (SLS), tibial angle (TA) quantification using inertial measurement units (IMU) may offer a practical alternative to frontal plane projection angle (FPPA) measurement using 2-dimensional (2D) video analysis. This study determined: (i) the reliability of IMUs and 2D video analysis for TA measurement, and 2D video analysis for FPPA measurement; (ii) the agreement between IMU TA and both 2D video TA and FPPA measurements during single leg squats in elite footballers. 18 players were tested on consecutive days. Absolute TA (ATA) and relative TA (RTA) were measured with IMUs. ATA and FPPA were measured concurrently using 2D video analysis. Within-session reliability for all measurements varied across days (intraclass correlation coefficient (ICC) range = 0.27-0.83, standard error of measurement (SEM) range = 2.12-6.23°, minimal detectable change (MDC) range = 5.87-17.26°). Between-sessions, ATA reliability was good for both systems (ICCs = 0.70-0.74, SEMs = 1.64-7.53°, MDCs = 4.55-7.01°), while IMU RTA and 2D FPPA reliability ranged from poor to good (ICCs = 0.39-0.72, SEMs = 2.60-5.99°, MDCs = 7.20-16.61°). All limits of agreement exceeded a 5° acceptability threshold. Both systems were reliable for between-session ATA, although agreement was poor. IMU RTA and 2D video FPPA reliability was variable. For SLS assessment, IMU derived TAs are not useful surrogates for 2D video FPPA measures in this population.


#8 Exploring how playing football with different age groups affects tactical behaviour and physical performance
Reference: Biol Sport. 2018 Jun;35(2):145-153. doi: 10.5114/biolsport.2018.71603. Epub 2017 Nov 23.
Authors: Figueira B, Gonçalves B, Masiulis N, Sampaio J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234305/pdf/JBS-35-71603.pdf
Summary: The study aimed to compare footballers' performances when playing with teammates and opponents from the same age group with performances when playing with teammates and opponents of different age groups. Three football matches were played: i) under-15 (U15) players played with each other; ii) under-17 (U17) players played with each other; and iii) players under the age of 15 and 17 played with each other in two equivalent mixed age teams. The players' physical performance was measured using the distances covered at different speed categories and tactical behaviour was assessed using several positioning-derived variables. The results showed that, when playing in the mixed age condition, the U15 players increased the distance covered in sprinting intensity (18.1%; ±21.1%) and the U17 players increased the distance covered in jogging zones (6.8%; ±6.5%). The intra-team movement synchronization in longitudinal and lateral displacements was higher when U15 players confronted peers of the same age, in the first half (-13.4%; ±2.0%, -20.3%; ±5.7% respectively), and when U17 players confronting the mixed group, in both halves (-16.9%; ±2.5%, 9.8%; ±4.0% and 7.9%; ±5.7%, 10.6% ±4.4%, respectively). The differences between age groups and the mixed condition may be connected with the level of players' tactical expertise and adaptive positioning according to the dynamic environmental information. In general, these results suggest that mixing the age groups may be useful to promote a wider range of training session stimuli in these young football players.


#9 Elite football teams that do not have a winter break lose on average 303 player-days more per season to injuries than those teams that do: a comparison among 35 professional European teams
Reference: Br J Sports Med. 2018 Nov 15. pii: bjsports-2018-099506. doi: 10.1136/bjsports-2018-099506. [Epub ahead of print]
Authors: Ekstrand J, Spreco A, Davison M
Summary: The purpose was to compare injury rates among professional men's football teams that have a winter break in their league season schedule with corresponding rates in teams that do not. 56 football teams from 15 European countries were prospectively followed for seven seasons (2010/2011-2016/2017)-a total of 155 team-seasons. Individual training, match exposure and time-loss injuries were registered. Four different injury rates were analysed over four periods within the season, and linear regression was performed on team-level data to analyse the effect of winter break on each of the injury rates. Crude analyses and analyses adjusted for climatic region were performed. 9660 injuries were reported during 1 447 011 exposure hours. English teams had no winter break scheduled in the season calendar: the other European teams had a mean winter break scheduled for 10.0 days. Teams without a winter break lost on average 303 days more per season due to injuries than teams with a winter break during the whole season (p<0.001). The results were similar across the three periods August-December (p=0.013), January-March (p<0.001) and April-May (p=0.050). Teams without a winter break also had a higher incidence of severe injuries than teams with a winter break during the whole season (2.1 severe injuries more per season for teams without a winter break, p=0.002), as well as during the period January-March (p=0.003). A winter break was not associated with higher team training attendance or team match availability. Climatic region was also associated with injury rates. The absence of a scheduled winter break was associated with a higher injury burden, both before and during the two periods following the time that many European teams take a winter break. Teams without a winter break (English clubs) had a higher incidence of severe injuries following the time of the year that other teams (other European clubs) had their scheduled break.


#10 Cardiovascular incidents in male professional football players with negative preparticipation cardiac screening results: an 8-year follow-up
Reference: Br J Sports Med. 2018 Nov 15. pii: bjsports-2018-099845. doi: 10.1136/bjsports-2018-099845. [Epub ahead of print]
Authors: Berge HM, Andersen TE, Bahr R
Summary: Preparticipation cardiac screening of athletes aims to detect cardiovascular disease at an early stage to prevent sudden cardiac arrests and deaths. Few studies have described the cardiovascular outcomes in athletes classified as negative on screening.  The purpose was to identify cardiovascular incidents in a cohort of male professional football players who were cleared to play after a negative screening result. This is a retrospective 8-year follow-up study of 595 professional male football players in Norway who underwent preparticipation cardiac screening by experienced cardiologists, including electrocardiography (ECG) and echocardiography, in 2008. We performed a media search to identify sudden cardiovascular incidents between January 2008 and February 2016. Incidents were cross-checked with medical records. Six of the 595 players (1%), all classified as negative on cardiac screening, experienced severe cardiovascular incidents during follow-up. Retrospective review revealed abnormal ECG findings in one case, not recognised at the time of screening. Three players suffered a sudden cardiac arrest (all resuscitated successfully), one a myocardial infarction, one a transient ischaemic attack and one atrial flutter. Three of the players ignored chest pain, paresis, dyspnoea or near-syncope, two completed a match with symptoms before seeking medical assistance, one player's symptoms were misinterpreted and received inappropriate treatment initially, and two players were discharged from hospital without proper follow-up, despite having serious cardiovascular symptoms. A comprehensive preparticipation cardiac screening did not identify a subset of 6 of 595 players who experienced subsequent cardiovascular incidents as being at risk. It is important to remind athletes that a normal cardiac screening exam does not protect against all cardiac diseases. Timely reporting of symptoms is essential.

Tue

01

Jan

2019

Latest research in football - week 45 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 The Within-Subject Correlation Between Salivary IgA and Measures of Training Load in Elite Football Players
Reference: Int J Sports Physiol Perform. 2018 Nov 14:1-11. doi: 10.1123/ijspp.2018-0455. [Epub ahead of print]
Authors: Figueiredo P, Nassis GP, Brito J
Summary: The purpose was to quantify the association between salivary secretory immunoglobulin A (sIgA) and training load in elite football players. Data were obtained in four consecutive days during the preparation camp for the Rio 2016 Olympic Games. Saliva samples of 18 elite male football players were collected prior to breakfast. The session rating of perceived exertion (s-RPE) and external training load metrics from GPS were recorded. Within-subject correlation coefficients between training load and sIgA concentration, and magnitude of relationships were calculated. sIgA presented moderate to large negative correlations with s-RPE (r=-0.39), total distance covered (r=-0.55), accelerations (r=-0.52) and decelerations (r=-0.48). Trivial to small associations were detected between sIgA and distance covered per minute (r=0.01), high-speed distance (r=-0.23) and number of sprints (r=-0.18). sIgA displayed a likely moderate decrease from day 1 to day 2 (d=-0.7) but increased on day 3 (d=0.6). The training load variables had moderate to very large rises from day 1 to day 2 (d=0.7 to 3.2), but lowered from day 2 to day 3 (d=-5.0 to -0.4), except for distance per minute (d=0.8) and sprints (unclear). On day 3, all training load variables had small to large increments compared with day 1 (d=0.4 to1.5), with exception of accelerations (d=-0.8) and decelerations (unclear). In elite football sIgA might be more responsive to training volume rather than intensity. External load such as GPS-derived variables presented stronger association with sIgA compared with s-RPE. Salivary IgA can be used as an additional objective tool in monitoring football players.


#2 The Influence of Hamstring Muscle Peak Torque and Rate Of Torque Development for Sprinting Performance in Football Players: A Cross-Sectional Study
Reference: Int J Sports Physiol Perform. 2018 Nov 14:1-27. doi: 10.1123/ijspp.2018-0464. [Epub ahead of print]
Authors: Ishøi L, Aagaard P, Nielsen MF, Thornton KB, Krommes KK, Hölmich P, Thorborg K
Summary: This cross-sectional study aimed to investigate the association between hamstring muscle peak torque and rapid force capacity (rate of torque development: RTD) versus sprint performance in elite youth football players. Thirty elite academy youth football players (16.75 ± 1.1 years, 176.9 ± 6.7 cm, 67.1 ± 6.9 kg) were included. Isometric peak torque (Nm/kg) and early (0-100 ms) and late (0-200 ms) phase RTD (RTD100, RTD200) (Nm/s/kg) of the hamstring muscles were obtained as independent predictor variables. Sprint performance was assessed during a 30-m sprint trial. Mechanical sprint variables (maximal horizontal force production (FH0) (N/kg); maximal theoretical velocity (V0) (m/s); maximal horizontal power output (Pmax) (W/kg)) and sprint split times (0-5 m; 0-15 m; 0-30 m; 15-30 m) (s) were derived as dependent variables. Subsequently, linear regression analysis was conducted for each pair of dependent and independent variables. Positive associations were observed between hamstring RTD100 and FH0 (r2=0.241, p=0.006) and Pmax (r2=0.227, p=0.008). Furthermore, negative associations were observed between hamstring RTD100 and 0-5 m (r2=0.206, p=0.012), 0-15 m (r2=0.217, p=0.009) and 0-30 m sprint time (r2=0.169, p=0.024). No other associations were observed. The present data indicate that early-phase (0-100 ms) rapid force capacity of the hamstring muscles plays an important role for the acceleration capacity in elite youth football players. In contrast, no associations were observed between hamstring muscle function and maximal sprint velocity. This indicates that strength training focusing on improving early-phase hamstring rate of force development may contribute to enhance sprint acceleration performance in this athlete population.


#3 Circulation, Cell-free DNA for Monitoring Player Load in Professional Football
Reference: Int J Sports Physiol Perform. 2018 Nov 14:1-27. doi: 10.1123/ijspp.2018-0756. [Epub ahead of print]
Authors: Haller N, Ehlert T, Schmidt S, Ochmann D, Sterzing B, Grus F, Simon P
Authors: Player monitoring in elite sports settings is becoming increasingly important. Beside questionnaire based methods, biomarkers, such as circulating, cell-free DNA (cfDNA) are sug-gested for load monitoring. cfDNA concentrations were shown to increase dependent on total distance covered in football and was associated with overtraining in weightlifters. Thus, the objective of this study was to examine whether cfDNA is feasible as a monitoring tool in elite football players. We collected capillary blood samples from 22 male elite football players over 4 months of a regular season. Sampling was conducted the day before, one day after or several days after regular season games and/or training. In addition, each player filled in a Visual-Analogue-Scale questionnaire (VAS) including the items "general perceived exer-tion", "muscular fatigue" and "mental fatigue". Performance during training and games was tracked by the Catapult system (training) and with the OPTA system (games), respectively. cfDNA values were significantly elevated in players the day after regular season games (1.4-fold; p=0.0004) in line with the scores of the VAS. Both parameters showed sig-nificantly higher values during midweek game weeks. While cfDNA concentrations correlated with training data, the VAS was correlated with the tracking of the season games. However, cfDNA and VAS did not correlate with each other. Here we show that cfDNA concentrations at rest and VAS scores are influenced by previous load in professional football players. Future studies will reveal whether cfDNA might serve as a practically applicable marker for player load in football players.


#4 Towards the use of multidimensional performance indicators in football small-sided games: the effects of pitch orientation
Reference: J Sports Sci. 2018 Nov 14:1-8. doi: 10.1080/02640414.2018.1543834. [Epub ahead of print]
Authors: Folgado H, Bravo J, Pereira P, Sampaio J
Summary: This study aimed to compare youth football players' performance during two small-sided games with different pitch orientation: i) 40x30m and ii) 30x40m formats. Twenty under-15 players (age = 14.1 ± 0.5 years) participated in nine GK+4vs4+GK situations in each format, with the duration of six minutes each. Positional data were collected using individual GPS units, and computed for tactical and physical performance indicators. The SSG were video recorded, using notational analysis for collecting technical indicators. A novel method that incorporates time dependent notational information with spatiotemporal data was used to compute multidimensional parameters. Standardised effect sizes and non-clinical magnitude-based inferences were used to compare formats. Results showed that players covered more distance at higher intensities, presented more passes and dribbles and were more synchronised in the longitudinal axis while playing in the 40x30m pitch. In the 30x40m pitch, results showed a lower distance between team centroids, higher number of shots, more lateral passes and a wider team positioning. Multidimensional indicators, as players position and distance to the closest defender while shooting, revealed a more constant distance between attacker and defender in the 40x30m pitch. These results highlight the importance of integrating information from different indicators for a contextually valid information.


#5 Analysis of the PPARD Gene Expression Level Changes in Football Players in Response to the Training Cycle
Reference: Balkan J Med Genet. 2018 Oct 29;21(1):19-25. doi: 10.2478/bjmg-2018-0008. eCollection 2018 Jun.
Authors: Domańska-Senderowska D, Snochowska A, Szmigielska P, Jastrzębski Z, Jegier A, Kiszałkiewicz J, Dróbka K, Jastrzębska J, Pastuszak-Lewandoska D, Cięszczyk P, Maciejewska-Skrendo A, Zmijewski P, Brzeziańska-Lasota E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231314/pdf/bjmg-21-019.pdf
Summary: The PPARD gene codes protein that belongs to the peroxisome proliferator-activated receptor (PPAR) family engaged in a variety of biological processes, including lipid metabolism in muscle cells. In this study, we assess the relationship between PPARD gene expression lipid metabolism parameters and the variation of the PPARD gene expression before (T1) and after 12 hours of training (T2) sessions in a group of football players. Peripheral blood lymphocytes were obtained from 22 football players (17.5±0.7 years, 178±0.7 cm, 68.05±9.18 kg). The PPARD gene expression, analyzed by quantitative polymerase chain reaction (qPCR), was significantly higher after T2 (p = 0.0006). Moreover, at the end of the training cycle, there was a significant decrease in relative fat tissue (FAT) (%) (p = 0.01) and absolute FAT (kg) (p = 0.01). A negative correlation was observed between absolute FAT (kg) and PPARD gene expression level in T2 (p = 0.03). The levels of cholesterol and triglyceride (TG) fractions were not significantly different (p >0.05) before and after training. No significant relationship between PPARD expression and cholesterol or TG levels was found. We found that physical training affects PPARD expression. Moreover, the negative correlation between PPARD expression and absolute FAT (kg) level may be indicative of the contribution of PPARD in metabolic adaptation to increased lipid uptake that can be used to control the body composition of athletes.


#5 Tattoos among elite football players during the 2018 FIFA World Cup Russia
Reference: J Eur Acad Dermatol Venereol. 2018 Nov 13. doi: 10.1111/jdv.15338. [Epub ahead of print]
Authors: Kluger N, Samimi M
Download link: J Eur Acad Dermatol Venereol. 2018 Nov 13. doi: 10.1111/jdv.15338. [Epub ahead of print]
Summary: Currently 10 to 30% of the general population has tattoos. Professional athletes harbor visible tattoos during sports events and advertisement. Motivations for tattoos may include body embellishment, expression of personal values or group affiliation. Tattoos may bolster ego, be the expression of physical strength and of traits of aggression and rebelliousness. We wondered whether being tattooed reflects players' performance and discipline. We investigated this hypothesis among elite football players during the 2018 FIFA World Cup.


#6 High incidence of hip and knee arthroplasty in former professional, male football players
Reference: J Sports Med Phys Fitness. 2018 Nov 8. doi: 10.23736/S0022-4707.18.08962-4. [Epub ahead of print]
Authors: Volpi P, Quaglia A, Carimati G, Petrillo S, Bisciotti GN
Summary: The purpose of this study was to estimate the incidence of hip and knee arthroplasty in Italian male professional football (soccer) players who have played for a minimum 10 years in the Italian major football leagues. The study group was formed by 104 male professional football players who were interviewed to evaluate the incidence of hip and knee arthroplasty. The data were collected through a questionnaire and the results collected were compared with a control group of 100 volunteers matched for age, weight and height, who did not present orthopaedic diseases but had never practiced sport. In the study group, 26 subjects (25 %) underwent hip and knee arthroplasty at an average mean age of 62.1 + 6 years. The frequency of arthroplasty was: 13.5% for the hip, 5.8% for the knee and 5.8% for both hip and knee. In the control group, the incidence of arthroplasty was 1% for the knee and no subjects presented hip arthroplasty. Italian male, former professional football players present a higher than normal incidence of hip and knee arthroplasty. Further studies are necessary to understand the pathological pathways underlying the ethiology of hip and knee osteoarthritis in male populations of former professional football players in order to develop effective preventive programmes to reduce the percentage of arthroplasties.


#7 Stepovers and Signal Detection: Response Sensitivity and Bias in the Differentiation of Genuine and Deceptive Football Actions
Reference: Front Psychol. 2018 Oct 29;9:2043. doi: 10.3389/fpsyg.2018.02043. eCollection 2018.
Authors: Jackson RC, Barton H, Ashford KJ, Abernethy B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6215843/pdf/fpsyg-09-02043.pdf
Summary: The ability to differentiate genuine and deceptive actions was examined using a combination of spatial and temporal occlusion to examine sensitivity to lower body, upper body, and full body sources of visual information. High-skilled and low-skilled association football players judged whether a player genuinely intended to take the ball to the participant's left or right or intended to step over the ball then take it in the other direction. Signal detection analysis was used to calculate measures of sensitivity (d') in differentiating genuine and deceptive actions and bias (c) toward judging an action to be genuine or deceptive. Analysis revealed that high-skilled players had higher sensitivity than low-skilled players and this was consistent across all spatial occlusion conditions. Low-skilled players were more biased toward judging actions to be genuine. Receiver Operating Characteristic (ROC) curves revealed that accuracy on deceptive trials in the lower body and full body conditions most accurately classified participants as high-skilled or low-skilled. The results highlight the value of using signal detection analysis in studies of deceptive actions. They suggest that information from the lower body or upper body was sufficient for differentiating genuine and deceptive actions and that global information concurrently derived from these sources was not necessary to support the expert advantage.


#8 Effectiveness of Field-Based Resistance Training Protocols on Hip Muscle Strength Among Young Elite Football Players
Reference: Clin J Sport Med. 2018 Oct 29. doi: 10.1097/JSM.0000000000000649. [Epub ahead of print]
Authors: Kohavi B, Beato M, Laver L, Freitas TT, Chung LH, Dello Iacono A
Summary: The objective of this study was to examine the effects of an 8-week progressive resistance training program on hip joint muscles' strength measures, using the Copenhagen adduction (CA) and the sliding hip (SH) exercises. Forty-two young male football athletes (age 17.5 ± 1.1 years; height 178.3 ± 3.2 cm; body mass 66.1 ± 8.6 kg) allocated to a CA, SH, and matched control (C) group participated in this study. Maximal eccentric strength test for the hip adductor (EHAD) and maximal eccentric strength test for the hip abductor (EHAB) muscles, and the relative EHAD/EHAB ratio assessed through a break test in the side-lying position. No significant differences between groups were found at baseline for any of the assessed variables (all P > 0.053). The CA group had a significant strength increase in the right and left leg (d = 2.11, d = 1.9, respectively). The SH group also had a significant strength increase in the right and left leg (d = 1.68 and d = 1.67, respectively). The CA group presented EHAD/EHAB improvements in the right and left leg (d = 0.84 and d = 1.14, respectively). The SH group also presented EHAD/EHAB improvements in the right and left leg (d = 1.34 and d = 1.44, respectively). Both exercises' protocols were effective in inducing significant increases on EHAD, EHAB, and EHAD/EHAB ratio when compared with the control group. Practitioners should be aware of the training effectiveness of both protocols.


#9 Recommendations for hamstring injury prevention in elite football: translating research into practice
Reference: Br J Sports Med. 2018 Nov 9. pii: bjsports-2018-099616. doi: 10.1136/bjsports-2018-099616. [Epub ahead of print]
Authors: Buckthorpe M, Wright S, Bruce-Low S, Nanni G, Sturdy T, Gross AS, Bowen L, Styles B, Della Villa S, Davison M, Gimpel M
Download link: https://bjsm.bmj.com/content/bjsports/early/2018/11/09/bjsports-2018-099616.full.pdf

Tue

01

Jan

2019

Latest research in football - week 44 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Variation in the Correlation Between Heart Rate and Session Rating of Perceived Exertion-Based Estimations of Internal Training Load in Youth Soccer Players
Reference: Pediatr Exerc Sci. 2018 Oct 28:1-8. doi: 10.1123/pes.2018-0033. [Epub ahead of print]
Authors: Vahia D, Kelly A, Knapman H, Williams CA
Summary: When exposed to the same external load, players receive different internal loads, resulting in varied adaptations in fitness. In adult soccer, internal training load is measured using heart rate (HR) and session rating of perceived exertion (sRPE) scales, but these have been underutilized in youth soccer. This study investigated the in-season variation in correlation between HR and sRPE estimations of training load for adolescent soccer players. Fifteen male professional adolescent players were monitored for 7 months. Within-participant correlations and Bland-Altman agreement plots for HR and sRPE were calculated for each month to analyze variation over the season and for individual players to analyze the validity of the scale. The monthly correlations ranged from r = .60 to r = .73 (P < .05) and the overall correlation was r = .64 (95% confidence interval, .60-.68; P < .001). Bland-Altman plots showed an agreement of methods. Results showed consistently large correlations for all months. sRPE is a consistent method of measure of internal training load for the entire season for youth soccer players. Validity analysis found no bias in sRPE measurements when compared with HR for all players in the study.


#2 Mental Fatigue in Football: Is it Time to Shift the Goalposts? An Evaluation of the Current Methodology
Reference: Sports Med. 2018 Nov 2. doi: 10.1007/s40279-018-1016-z. [Epub ahead of print]
Authors: Thompson CJ, Fransen J, Skorski S, Smith MR, Meyer T, Barrett S, Coutts AJ
Summary: Research in football for a long time has focused on the physical nature of fatigue as opposed to its mental aspects. However, since 2016, six original articles have investigated the effects of induced mental fatigue in football on isolated physical, skill and decision-making performance tests, along with physical, technical and tactical performance outcomes in small-sided games. Whilst these studies have overall shown a negative impact of mental fatigue on task performance, this current opinion aims to critically examine the methodological approach to this problem, most notably the lack of ecological validity when inducing mental fatigue and the present approach to measuring mental fatigue using visual analogue scales (VAS). It is suggested that future research on mental fatigue in football may benefit from the use of surveys/interviews to understand the true cognitive demands of elite football players. Additionally, future research should aim to reduce the reliance on using VAS to measure mental fatigue as results from this tool may be confounded by several response biases. In conclusion, this article highlights the need for mentally fatiguing tasks that adequately represent football-associated mental fatigue and assessments of mental fatigue that minimise the confounding effect of response bias.


#3 A systematic review on small-sided games in football players: Acute and chronic adaptations
Reference: J Sports Sci. 2018 Oct 29:1-29. doi: 10.1080/02640414.2018.1535821. [Epub ahead of print]
Authors: Bujalance-Moreno P, Latorre-Román PÁ, García-Pinillos F
Summary: Small-sided games (SSG) are played on a small pitch, often using modified rules and involving a smaller number of players. This article aimed to critically analyse the literature to determine how small-sided games affect the performance of football players in the short- and long term. Electronic databases were searched for literature dating from January 2000 to July 2018. The methodological quality of the studies was evaluated using the modified Downs and Black Quality Index (cross-sectional studies) and the Physiotherapy Evidence Database (PEDro) scale (intervention studies). Fifty-three studies, 44 cross-sectional and 9 intervention studies, met the inclusionary criteria for review. Most of the cross-sectional studies focused on describing the differences between SSG protocols, whereas 4 studies focused on making a comparison between "interval" and "continuous" SSG training regimes. On the other hand, intervention studies focused on making a comparison between SSG-based protocols and high-intensity intermittent training (HIIT)-based running protocols, in addition to determine the effect of a SSG-based training programme alone. SSG-based football plans (2 to 4 SSG sessions per week) show athletic performance improvements in football players by improving sprint, repeated sprint ability (RSA) and change of direction (COD) along with muscular and physiological adaptation.


#4 Player Tracking Data Analytics as a Tool for Physical Performance Management in Football: A Case Study from Chelsea Football Club Academy
Reference: Sports (Basel). 2018 Oct 26;6(4). pii: E130. doi: 10.3390/sports6040130.
Authors: De Silva V, Caine M, Skinner J, Dogan S, Kondoz A, Peter T, Axtell E, Birnie M, Smith B
Summary: Global positioning system (GPS) based player movement tracking data are widely used by professional football (soccer) clubs and academies to provide insight into activity demands during training and competitive matches. However, the use of movement tracking data to inform the design of training programmes is still an open research question. The objective of this study is to analyse player tracking data to understand activity level differences between training and match sessions, with respect to different playing positions. This study analyses the per-session summary of historical movement data collected through GPS tracking to profile high-speed running activity as well as distance covered during training sessions as a whole and competitive matches. We utilise 20,913 data points collected from 53 football players aged between 18 and 23 at an elite football academy across four full seasons (2014⁻2018). Through ANOVA analysis and probability distribution analysis, we compare the activity demands, measured by the number of high-speed runs, the amount of high-speed distance, and distance covered by players in key playing positions, such as Central Midfielders, Full Backs, and Centre Forwards. While there are significant positional differences in physical activity demands during competitive matches, the physical activity levels during training sessions do not show positional variations. In matches, the Centre Forwards face the highest demand for High Speed Runs (HSRs), compared to Central Midfielders and Full Backs. However, on average the Central Midfielders tend to cover more distance than Centre Forwards and Full Backs. An increase in high-speed work demand in matches and training over the past four seasons, also shown by a gradual change in the extreme values of high-speed running activity, was also found. This large-scale, longitudinal study makes an important contribution to the literature, providing novel insights from an elite performance environment about the relationship between player activity levels during training and match play, and how these vary by playing position.


#5 Fitness effects of one year soccer training of 8-10 and 10-12 years old school children
Reference: J Sports Med Phys Fitness. 2018 Oct 31. doi: 10.23736/S0022-4707.18.08612-7. [Epub ahead of print]
Authors: Michailidis Y, Metaxas TI, Stefanidis P, Christoulas K
Summary: The purpose of the study was to investigate the effect of one year soccer training on physical fitness performance, of U10 and U12 youth levels. 28, 10-year-old and 28, 12-year-old children participated in the study. In the U12 group, 19 children participated only in the physical fitness sessions at school (control group - CG) and 9 children in four extra soccer trainings (Soccer group - SG). In the U10 group, 11 children participated only in the physical fitness sessions at school (control group - CG) and 17 children in four extra soccer trainings (Soccer group - SG). Height, body weight, body fat, standing long jump, 30 m sprint, sit and reach test, abdominal test and Yo-Yo IE1 tests were performed at the beginning and at the end of the season. School physical education programs and soccer training cannot affect anthropometric characteristics like body fat and body mass index. Soccer groups improve their performances at all fitness tests (p<0.05). The U10 control group didn't increase its performance in abdominal test and the U12 level control group didn't improve in the abdominal test nor Yo-Yo IE1 test. Soccer groups in all ages indicated greater improvements than control groups (p<0.05). In conclusion soccer training four times per week can improve the physical fitness of U10 and U12 children's.


#6 Prevalence of vitamin D deficiency amongst soccer athletes and effects of 8 weeks supplementation
Reference: J Sports Med Phys Fitness. 2018 Oct 31. doi: 10.23736/S0022-4707.18.08551-1. [Epub ahead of print]
Authors: Teixeira P, Santos AC, Casalta-Lopes J, Almeida M, Loureiro J, Ermida V, Caldas J, Fontes-Ribeiro C
Summary: High prevalence of vitamin D deficiency is well known around the world in risk populations. Although less is known about the athletic population, some studies report vitamin D deficiency amongst athletic population and adequate vitamin D levels are crucial for athletic population as it can prevent injuries such as stress fractures and might even have ergogenic effects for example on muscle function. The main objectives were to evaluate the basal serum levels of 25(OH)D and calcium in professional soccer athletes on the latitude 40 ̊N, to evaluate the effects in 25(OH)D and calcium serum levels following supplementation of 1667 IU/day of cholecalciferol during a period of 8 weeks and evaluate eventual toxicity arising from it. 28 professional athletes were evaluated according to the skin type. Basal serum levels of 25(OH)D and calcium were evaluated during winter months. Athletes were then supplemented with cholecalciferol 25.000 IU every two weeks. Serum levels of 25(OH)D and calcium were evaluated after supplementation. 25(OH)D initially ranged between 9.9 ng/mL and 32.9 ng/mL with a median of 19.2 IQR 7.24 ng/mL. A statistically significant inverse correlation exists between vitamin D deficiency and the Fitzpatrick scale (ρ= - 0,555 p=0.003). After 8 weeks, 25(OH)D ranged between 10.6 ng/mL and 43.4 ng/mL with a median of 33.2 ng/mL IQR 6.1 ng/mL. We verified a statistically significant increase of serum 25(OH) D levels (11.74 ± 5.988; IC95% [9,02; 14,47]; p<0,001. In addition, there was a statistically significant reduction of calcium: -0,36 ± 0,457; IC95% [- 0,57; -0,15]; p=0,002. Professional athletes have a high prevalence of vitamin D. Supplementation with cholecalciferol in winter months during 8 weeks is safe and effective in raising 25(OH)D serum levels. However, it may not be sufficient for athletes to reach adequate vitamin D levels.


#7 Changes in Transcranial Sonographic Measurement of the Optic Nerve Sheath Diameter in Non-concussed Collegiate Soccer Players Across a Single Season
Reference: Cureus. 2018 Aug 3;10(8):e3090. doi: 10.7759/cureus.3090.
Authors: Sadrameli SS, Wong MS, Kabir R, Wiese JR, Podell K, Volpi JJ, Gadhia RR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207277/pdf/cureus-0010-00000003090.pdf
Summary: Introduction Bedside ultrasound measurement of the optic nerve sheath diameter (ONSD) is emerging as a non-invasive technique to evaluate and predict raised intracranial pressure (ICP) in both children and adults. The prognostic value of increased ONSD on brain computed tomography (CT) scan has previously been correlated with increased intensive care unit (ICU) mortality in patients with severe traumatic brain injury (TBI). Previous studies have also evaluated the association between high-contact sports, such as soccer, and TBI; however, the related changes in ONSD are still unknown. The aim of this study was to evaluate for the natural evolution of changes in ONSD in athletes who participate in high-contact sports. Methods In this prospective observational study, volunteers from a collegiate women's soccer team underwent the measurement of ONSD with transcranial Doppler (TCD). ONSDs were measured during the initial visit during the pre-season period and again at the three-month follow-up. A single experienced neuro-sonographer performed all measurements to eliminate any operator bias. Results Twenty-four female college soccer players between the ages of 18 and 23 were included in this analysis. Mean ONSD during the initial pre-season clinic visit and the three-month follow-up were 4.14±0.6 mm and 5.02±0.72 mm, respectively (P < 0.0001). A two-tailed t-test analysis was performed, which resulted in a t-value of 4.76 and P < 0.00001. The average ONSD measured during the post-season follow-up showed a 21.3% increase compared to the baseline. Conclusion The evaluation of high-contact sports athletes is limited due to the lack of objective radiologic and diagnostic tools. Moreover, in an athlete suffering a concussion, return-to-play decisions are heavily dependent on the symptoms reported by the athletes. In our analysis of collegiate women's soccer players, active participation in soccer competitions and practice may be associated with an increase in ONSD, independent of concussions. Further studies are underway to evaluate the clinical significance of these findings as well as possible correlations between concussions and changes in ONSD.


#8 Changes in Sport Nutrition Knowledge, Attitudes/Beliefs and Behaviors Following a Two-Year Sport Nutrition Education and Life-Skills Intervention among High School Soccer Players
Reference: Nutrients. 2018 Nov 2;10(11). pii: E1636. doi: 10.3390/nu10111636.
Authors: Patton-Lopez MM, Manore MM, Branscum A, Meng Y, Wong SS
Download link: https://www.mdpi.com/2072-6643/10/11/1636/pdf
Summary: The purpose of this study was to examine the impact of a sport nutrition education and life-skills intervention on sport nutrition knowledge (SNK), attitudes/beliefs and dietary behaviors relevant to sport nutrition among high school (HS) soccer players. Three assessments were done over the 2-year intervention (baseline = time 1, end year 1 = time 2, end year 2 = time 3). Participants (n = 217; females = 64%; Latino = 47.5%; 14.9 ± 0.9-year; 46.5% National School Breakfast/Lunch Program) were assigned to an intervention group (IG, n = 153; 9 schools) or comparison group (CG, n = 64; 4 schools) based on geographical location. Differences over time were examined based on group, sex, socioeconomic status (SES) and race/ethnicity. The IG increased SNK scores by ~10% (time 1 = 51.6%; time 3 = 60.9%; p ≤ 0.001), with the greatest change in the female IG vs. CG and no differences in male IG vs. CG. Daily breakfast consumption was 53.7% in both groups. IG players were 3 times more likely (95%CI = 2.59, 7.77) to report trying to eat for performance (IG = 48.7% vs. CG = 30.2%). By time 3, IG players were less likely to report that 'diet met nutritional requirements' (31.6%) compared to CG (47.6%). For IG, the consumption of lunch (≥5-days/week) did not change (92.2⁻93.4%), but declined in the CG (90.6%) (p = 0.04). No other differences by sub-population (race/ethnicity, SES) were observed. Our findings indicate that HS athletes are motivated to learn and improve diet behaviors, and benefit from team-based nutrition interventions. Future interventions should consider delivery of curriculum/experiential learning during a defined training period, with messages reinforced with supports at home, school and athletic settings.


#9 Effects of the pitch configuration design on players' physical performance and movement behaviour during soccer small-sided games
Reference: Res Sports Med. 2018 Nov 5:1-16. doi: 10.1080/15438627.2018.1544133. [Epub ahead of print]
Authors: Coutinho D, Gonçalves B, Santos S, Travassos B, Wong DP, Sampaio J
Summary: This study aimed to identify the effects of different pitch configurations on youth players positional and physical performances. Forty players participated in a Gk + 5vs5 + Gk small-sided game under four conditions: regular condition (regular), pitch with the direction of competitive matches; sided condition (sided), goals were changed to width; different pitch orientation (≠orientation), performed in side-to-side line compared to competitive matches; dynamic pitch (dynamic), boundaries were randomly changed every minute by: regular pitch; decrease 6 m width; diamond shape. The following variables were considered: players' effective playing space, distance between teammates' dyads time spent synchronized, average speed and a ratio between the distance covered at different intensities and distance covered while recovering. Overall, players exhibited better performances in pitches that are more representative of the environmental information seen during competitive matches (regular and ≠orientation). However, coaches may also use different boundary conditions to promote the players' ability to adapt to different context information.


#10 Chronic Ingestion of Sodium and Potassium Bicarbonate, with Potassium, Magnesium and Calcium Citrate Improves Anaerobic Performance in Elite Soccer Players
Reference: Nutrients. 2018 Nov 1;10(11). pii: E1610. doi: 10.3390/nu10111610.
Authors: Chycki J, Golas A, Halz M, Maszczyk A, Toborek M, Zajac A
Download link: https://www.mdpi.com/2072-6643/10/11/1610/pdf
Summary: Anaerobic power and anaerobic capacity significantly influence performance in many sport disciplines. These include prolonged sprints in athletics, swimming, or cycling, and other high intensity intermittent sports, such as soccer or basketball. Considering the association of exercise-induced acidosis and fatigue, the ingestion of potential buffering agents such as sodium bicarbonate, has been suggested to attenuate metabolic acidosis and improve anaerobic performance. Since elite soccer players cover from 200 to 350 m while sprinting, performing 40⁻60 all out sprints during a game, it seems that repeated sprint ability in soccer players is among the key components of success. In our experiment, we evaluated the effectiveness of chronic supplementation with sodium and potassium bicarbonate, fortified with minerals, on speed and speed endurance in elite soccer players. Twenty-six soccer players participated in the study. The subjects were randomly divided into two groups. The experimental group was supplemented with sodium bi-carbonate and potassium di-carbonate fortified with minerals, while the control group received a placebo. The athletes were tested at baseline and after nine days of supplementation. Anaerobic performance was evaluated by the Repeated Anaerobic Sprint Test (RAST) protocol which involved 6 × 30 m max sprints, separated by 10 s of active recovery. Resting, post ingestion and post exercise concentrations of HCO₃- and blood pH were measured as well as lactate concentration. The current investigation demonstrated a significant increase in RAST performance of elite soccer players supplemented with sodium and potassium bicarbonate along with calcium phosphate, potassium citrate, and magnesium citrate ingested twice a day over a nine-day training period. The improvements in anaerobic performance were caused by increased resting blood pH and bicarbonate levels.


#11 Epidemiology of injury in English Professional Football players: A cohort study
Reference: Phys Ther Sport. 2018 Oct 29;35:18-22. doi: 10.1016/j.ptsp.2018.10.011. [Epub ahead of print]
Authors: Jones A, Jones G, Greig N, Bower P, Brown J, Hind K, Francis P
Summary: The purpose was to estimate the current incidence and location of injury in English professional football. Professional football players (243 players from 10 squads (24.3 ± 4.21 per squad)) competing in the English Football League and National Conference took part in this study. Injury incidence, training and match exposure were collected in accordance with the international consensus statement on football injury epidemiology. 473 injuries were reported. The estimated incidence of injury was, 9.11 injuries/1000 h of football related activity. There was a higher incidence of injury during match play (24.29/1000 h) compared to training (6.84/1000 h). The thigh was the most common site of injury (31.7%), muscle strains accounted for 41.2% of all injuries. The hamstrings were the most frequently strained muscle group, accounting for 39.5% of all muscle strains and 16.3% of all injuries. Moderate severity injuries (8-28 days) were the most common (44.2%). Incidence of injury has increased over the last 16 years with muscle strains remaining the most prevalent injury. The hamstrings remain the most commonly injured muscle group.


#12 Evidence for a Role of ACTN3 R577X Polymorphism in Football Player's Career Progression
Reference: Int J Sports Med. 2018 Nov 6. doi: 10.1055/a-0753-4973. [Epub ahead of print]
Authors: Coelho DB, Pimenta EM, Rosse IC, de Castro BM, Becker LK, de Oliveira EC, Carvalho MRS, Garcia ES
Summary: The aim was to investigate a possible role of the ACTN3 R577X polymorphism in a Brazilian football player's career progression. 2 questions were formulated: 1. Does ACTN3 polymorphism affect the probability of an individual being a professional football player? 2. Does this polymorphism affect the progression of the athlete throughout his career? The study included 353 players from first division Brazilian football clubs in the following categories: under-14 (U-14), U-15, U-17, U-20, and professional (PRO). The control group (CON) was composed of 100 healthy non-athletes. The chi-squared test was used to assess differences between the allele and genotype frequencies. Comparing football categories, the XX genotype was less frequent among professional players than in the U-20 (p<0.05) or the U-15 category (p<0.05). The RX genotype also presented more frequently in the PRO category than the U-14 category (p<0.05). Moreover, a trend towards a higher frequency of the RX genotype and a lower frequency of the XX genotype was observed in the professional category compared to U-20. These results suggest that the genotype in the ACTN3 polymorphism affects the probability of a football player progressing throughout his career and becoming professional, meaning that playing football selects against the ACTN3 XX genotype.


#13 MRI characteristics of adductor longus lesions in professional football players and prognostic factors for return to play
Reference: Eur J Radiol. 2018 Nov;108:52-58. doi: 10.1016/j.ejrad.2018.09.018. Epub 2018 Sep 17.
Authors: Pezzotta G, Pecorelli A, Querques G, Biancardi S, Morzenti C, Sironi S
Summary: The purpose was to correctly define through Magnetic Resonance Imaging (MRI), diagnosis, staging and prognosis of the adductor longus (AL) acute lesions and to identify a correlation between Return to Play (RTP) and sport-related injury predisposing conditions and complications. Twenty professional football players with acute groin pain and clinical suspicion of AL injury subsequent to sport's activity were evaluated. MRI examinations were performed by one and reviewed by other two radiologists with more than 10 years of experience. Lesions were stratified according to both Munich consensus statement and British Athletics Muscle Injury Classification (BAMIC). Patients were monitored until clinical recovery occurred. According to the Munich consensus statement, 75% of lesions were defined as type 3 and 25%as type 4; while according to the BAMIC, 45% were considered as Grade 1, 20% as Grade 2, 10% as Grade 3, and 25% as Grade 4. RTP was 1-2 weeks for minor lesions (45%), 4-6 weeks for moderate lesions (30%), and more than 6 weeks for complete lesions (25%). Both BAMIC and Munich consensus significantly correlated with RTP (R = 0.958 and 0.974, respectively). The extent of gap was the only independent prognosticator of RTP always present in all three different models of multivariate analysis (p < 0.006, p < 0.002, and p < 0.001, respectively). MRI represents the gold standard imaging technique for the evaluation of AL due to its ability not only to recognize but also to classify acute lesions and define patient's prognosis. MRI is also useful to detect potential predisposing conditions and complications, which may correlate with RTP.

Sat

29

Dec

2018

Latest research in football - week 43 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Bone mineral density in lifelong trained male football players compared with young and elderly untrained men
Reference: J Sport Health Sci. 2018 Apr;7(2):159-168. doi: 10.1016/j.jshs.2017.09.009. Epub 2017 Sep 20.
Authors: Hagman M, Helge EW, Hornstrup T, Fristrup B, Nielsen JJ, Jørgensen NR, Andersen JL, Helge JW, Krustrup P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180542/pdf/main.pdf
Summary: The purpose of the present controlled cross-sectional study was to investigate proximal femur and whole-body bone mineral density (BMD), as well as bone turnover profile, in lifelong trained elderly male football players and young elite football players compared with untrained age-matched men. One hundred and forty healthy, non-smoking men participated in the study, including lifelong trained football players (FTE, n = 35) aged 65-80 years, elite football players (FTY, n = 35) aged 18-30 years, as well as untrained age-matched elderly (UE, n = 35) and young (UY, n = 35) men. All participants underwent a regional dual-energy X-ray Absorptiometry (DXA) scan of the proximal femur and a whole-body DXA scan to determine BMD. From a resting blood sample, the bone turnover markers (BTMs) osteocalcin, carboxy-terminal type-1 collagen crosslinks (CTX-1), procollagen type-1 amino-terminal propeptide (P1NP), and sclerostin were measured. FTE had 7.3%-12.9% higher (p < 0.05) BMD of the femoral neck, wards, shaft, and total proximal femur in both legs compared to UE, and 9.3%-9.7% higher (p < 0.05) BMD in femoral trochanter in both legs compared to UY. FTY had 24.3%-37.4% higher (p < 0.001) BMD in all femoral regions and total proximal femur in both legs compared to UY. The whole-body DXA scan confirmed these results, with FTE showing similar whole-body BMD and 7.9% higher (p < 0.05) leg BMD compared to UY, and with FTY having 9.6% higher (p < 0.001) whole-body BMD and 18.2% higher (p < 0.001) leg BMD compared to UY. The plasma concentration of osteocalcin, CTX-1, and P1NP were 29%, 53%, and 52% higher (p < 0.01), respectively, in FTY compared to UY. BMD of the proximal femur and whole-body BMD are markedly higher in lifelong trained male football players aged 65-80 years and young elite football players aged 18-30 years compared to age-matched untrained men. Elderly football players even show higher BMD in femoral trochanter and leg BMD than untrained young despite an age difference of 47 years.

 


#2 A rare case of non-contact salter harris type 2 fracture of distal femur during a football match
Reference: Med J Malaysia. 2018 Oct;73(5):342-343.
Authors: Razzi M, Nordin A
Download link: http://www.e-mjm.org/2018/v73n5/distal-femoral-physeal-fractures.pdf
Summary: Distal femoral physeal fractures in adolescents are often due to high velocity injuries. We present an unusual case of a non-contact distal femoral physeal fracture that occurred during a football match. A torsional force had been directed at the fracture site occurring at the growth plate causing a transverse fracture rather than a spiral fracture. It is important to be aware that such fractures can occur despite little or no evidence of contact. These type of injuries should also be treated as an emergency to reduce the risk of further complications.


#3 Using Network Science to Analyse Football Passing Networks: Dynamics, Space, Time, and the Multilayer Nature of the Game
Reference: Front Psychol. 2018 Oct 8;9:1900. doi: 10.3389/fpsyg.2018.01900. eCollection 2018.
Authors: Buldú JM, Busquets J, Martínez JH, Herrera-Diestra JL, Echegoyen I, Galeano J, Luque J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6186964/pdf/fpsyg-09-01900.pdf


#4 Multilevel modelling of longitudinal changes in isokinetic knee extensor and flexor strength in adolescent soccer players
Reference: Ann Hum Biol. 2018 Oct 31:1-4. doi: 10.1080/03014460.2018.1521470. [Epub ahead of print]
Authors: Duarte JP, Valente-Dos-Santos J, Costa D, Coelho-E-Silva MJ, Deprez D, Philippaerts R, Lenoir M, Vaeyens R, Malina RM
Summary: The purpose of the study was to model the longitudinal development of knee extension (KE) and flexion (KF) strength in adolescent soccer players. A mixed-longitudinal sample composed of 67 soccer players aged 11.0-13.9 years at baseline was followed on three-to-five occasions over 5 years. Stature, body mass and several skinfold thicknesses were measured. Fat mass was estimated from skinfolds and fat-free mass (FFM) derived. Skeletal age was estimated with the TW2-RUS protocol. An isokinetic dynamometer was used to obtain peak torque of KE and KF from concentric assessments at an angular velocity of 180°/s. Multilevel random effects regression analyses were performed. Among youth soccer players aged 11-16 years, isokinetic strength of the knee muscle groups was reasonably predicted from chronological age (CA), stature and FFM: KE = -66.170 + 5.353 × (CA) + 0.594 × (CA2) + 0.552 × (stature) + 1.414 × (FFM), and KF = -9.356 + 2.708 × (CA) + 1.552 × (FFM). In conclusion, CA per se accounted for annual increments of 5.4 Nm in KE and 2.7 Nm in KF.


#5 Artificial neural networks and player recruitment in professional soccer
Reference: PLoS One. 2018 Oct 31;13(10):e0205818. doi: 10.1371/journal.pone.0205818. eCollection 2018.
Authors: Barron D, Ball G, Robins M, Sunderland C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205818&type=printable
Summary: The aim was to objectively identify key performance indicators in professional soccer that influence outfield players' league status using an artificial neural network. Mean technical performance data were collected from 966 outfield players' (mean SD; age: 25 ± 4 yr, 1.81 ±) 90-minute performances in the English Football League. ProZone's MatchViewer system and online databases were used to collect data on 347 indicators assessing the total number, accuracy and consistency of passes, tackles, possessions regained, clearances and shots. Players were assigned to one of three categories based on where they went on to complete most of their match time in the following season: group 0 (n = 209 players) went on to play in a lower soccer league, group 1 (n = 637 players) remained in the Football League Championship, and group 2 (n = 120 players) consisted of players who moved up to the English Premier League. The models created correctly predicted between 61.5% and 78.8% of the players' league status. The model with the highest average test performance was for group 0 v 2 (U21 international caps, international caps, median tackles, percentage of first time passes unsuccessful upper quartile, maximum dribbles and possessions gained minimum) which correctly predicted 78.8% of the players' league status with a test error of 8.3%. To date, there has not been a published example of an objective method of predicting career trajectory in soccer. This is a significant development as it highlights the potential for machine learning to be used in the scouting and recruitment process in a professional soccer environment.


#6 Oculomotor dynamics in skilled soccer players: The effects of sport expertise and strenuous physical effort
Reference: Eur J Sport Sci. 2018 Oct 31:1-9. doi: 10.1080/17461391.2018.1538391. [Epub ahead of print]
Authors: Zwierko T, Jedziniak W, Florkiewicz B, Stępiński M, Buryta R, Kostrzewa-Nowak D, Nowak R, Popowczak M, Woźniak J
Summary: The ability to quickly locate objects within the visual field has a significant influence on athletic performance. Saccades are conjugate eye movements responsible for the rapid shift that brings a new part of the visual field into foveal vision. The aim of this study was to investigate the effects of sport expertise and intense physical effort on saccade dynamics during a free-viewing visual search task in skilled soccer players. Two groups of male subjects participated in this study: 18 soccer players and 18 non-athletes as the control group. Two sessions of visual search tasks without a sport-specific design were employed. Eye movements during the visual search tasks were recorded binocularly. Between pre- and post-test sessions, athletes performed a maximal incremental treadmill test. Cardiorespiratory parameters were measured continuously. Capillary lactate samples were collected. Pre-test findings indicated that athletes, in comparison to non-athletes, achieve higher values of the following characteristics of saccades (1) average acceleration, (2) acceleration peak, (3) deceleration peak, and (4) average velocity. An increase in post-test saccade duration and a decrease in post-test saccade velocity was observed in athletes due to the strenuous physical effort in relation to the pre-test state. Athletes may transfer high saccadic function efficiency to non-specific visual stimuli. The findings partially confirm that physical exertion can reduce oculomotor efficiency in athletes.


#7 Accumulation of high magnitude acceleration events predicts cerebrovascular reactivity changes in female high school soccer athletes
Reference: Brain Imaging Behav. 2018 Oct 30. doi: 10.1007/s11682-018-9983-0. [Epub ahead of print]
Authors: Svaldi DO, Joshi C, McCuen EC, Music JP, Hannemann R, Leverenz LJ, Nauman EA, Talavage TM
Summary: Mitigating the effects of repetitive exposure to head trauma has become a major concern for the general population, given the growing body of evidence that even asymptomatic exposure to head accelerations is linked with increased risk for negative life outcomes and that risk increases as exposure is prolonged over many years. Among women's sports, soccer currently exhibits the highest growth in participation and reports the largest number of mild traumatic brain injuries annually, making female soccer athletes a relevant population in assessing the effects of repetitive exposure to head trauma. Cerebrovascular biomarkers may be useful in assessing the effects of repetitive head trauma, as these are thought to contribute directly to neurocognitive symptoms associated with mild traumatic brain injury. Here we use fMRI paired with a hypercapnic breath hold task along with monitoring of head acceleration events, to assess the relationship between cerebrovascular brain changes and exposure to repetitive head trauma over a season of play in female high school soccer athletes. We identified longitudinal changes in cerebrovascular reactivity that were significantly associated with prolonged accumulation to high magnitude (> 75th percentile) head acceleration events. Findings argue for active monitoring of athletes during periods of exposure to head acceleration events, illustrate the importance of collecting baseline (i.e., pre-exposure) measurements, and suggest modeling as a means of guiding policy to mitigate the effects of repetitive head trauma.


#8 Are oral health and fixed orthodontic appliances associated with sports injuries and postural stability in elite junior male soccer players?
Reference: BMC Sports Sci Med Rehabil. 2018 Oct 20;10:16. doi: 10.1186/s13102-018-0105-5. eCollection 2018.
Authors: Solleveld H, Flutter J, Goedhart A, VandenBossche L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6196014/pdf/13102_2018_Article_105.pdf
Summary: Dental caries and periodontitis are associated with elevated levels of pro-inflammatory cytokines which may trigger muscle fatigue during exercise, a strong risk factor for sports injuries. Fixed orthodontic appliances (FOA) may cause poor oral health and may disturb proprioceptive inputs of the stomatognathic system. This study aims to explore associations of poor oral health and of use of a FOA with injury frequency and postural stability. One hundred eighty seven Belgian elite junior male soccer players, aged 12-17 years, completed a self-report questionnaire asking about injuries in the past year, oral health problems, use of a FOA, demographics and sports data, and stood in unipedal stance with eyes closed on a force plate to assess postural stability. Ordinal logistic regression with number of injuries in the past year as ordinal dependent variable and dental caries and/or gum problems, age and player position as covariates, showed that participants who reported dental caries and/or gum problems and never had had a FOA reported significant more injuries in the past year compared to the reference group of participants who reported no oral health problems and never had had a FOA (adjusted OR = 2.45; 95% CI, 1.19-5.05; p = 0.015). A 2 (temporomandibular joint problems) × 2 (FOA) × 2 (age) ANOVA with postural stabilities as dependent variables, showed a significant FOA x age interaction for the non-dominant (standing) leg. Post-hoc t-tests showed a significant better postural stability for the non-dominant leg (and a trend for the dominant leg) for the older compared with the younger participants in the non-FOA group (p = .002, ES = 0.61), while no age differences were found in the FOA-group. These results indicate that poor oral health may be an injury risk factor and that a FOA may hinder the development of body postural stability.


#9 Physical and technical differences between domestic and foreign soccer players according to playing positions in the China Super League
Reference: Res Sports Med. 2018 Oct 30:1-12. doi: 10.1080/15438627.2018.1540005. [Epub ahead of print]
Authors: Gai Y, Leicht AS, Lago C, Gómez MÁ
Summary: Physical demands and technical skills of different playing positions within soccer match-play have been rarely studied in competitions from Asia that have unique restrictions that limit the number of foreign players per team. Therefore, the aims of this study were to identify the technical and physical differences between domestic and foreign soccer players according to playing-positions in the China Super League (CSL); and to classify domestic and foreign players (best/worst) based on their match performance characteristics. Data were provided by Amisco Sports Analysis Services (n = 3468 observations). Discriminant and ANOVA analyses showed important differences between domestic and foreign players in the CSL in terms of physical and technical performance indicators for various playing positions. The unique match performance profiles of domestic and foreign players within the CSL highlighted important features for coaches and managers to improve the recruitment process within a league that implements a restrictive foreign player policy.


#10 The First Decade of Web-Based Sports Injury Surveillance: Descriptive Epidemiology of Injuries in US High School Boys' Soccer (2005-2006 Through 2013-2014) and National Collegiate Athletic Association Men's Soccer (2004-2005 Through 2013-2014)
Reference: J Athl Train. 2018 Sep;53(9):893-905. doi: 10.4085/1062-6050-166-17.
Authors: Kerr ZY, Putukian M, Chang CJ, DiStefano LJ, Currie DW, Pierpoint LA, Knowles SB, Wasserman EB, Dompier TP, Comstock RD, Marshall SW
Summary: The advent of Web-based sports injury surveillance via programs such as the High School Reporting Information Online system and the National Collegiate Athletic Association Injury Surveillance Program has aided the acquisition of boys' and men's soccer injury data. The purpose was to describe the epidemiology of injuries sustained in high school boys' soccer in the 2005-2006 through 2013-2014 academic years and collegiate men's soccer in the 2004-2005 through 2013-2014 academic years using Web-based sports injury surveillance. Online injury surveillance from soccer teams of high school boys (annual average = 100) and collegiate men (annual average = 41) were utilized. Boys' or men's soccer players who participated in practices and competitions during the 2005-2006 through 2013-2014 academic years in high school and the 2004-2005 through 2013-2014 academic years in college, respectively. Athletic trainers collected time-loss (≥24 hours) injury and exposure data. Injury rates per 1000 athlete-exposures (AEs), injury rate ratios (IRRs) with 95% confidence intervals (CIs), and injury proportions by body site and diagnosis were calculated as main outcome measures. High School Reporting Information Online documented 2912 time-loss injuries during 1 592 238 AEs; the National Collegiate Athletic Association Injury Surveillance Program documented 4765 time-loss injuries during 686 918 AEs. The injury rate was higher in college than in high school (6.94 versus 1.83/1000 AEs; IRR = 3.79; 95% CI = 3.62, 3.97). Injury rates increased with smaller school size for high schools and were higher in Division I than in Divisions II and III. The injury rate was higher during competitions than during practices in both high school (IRR = 3.55; 95% CI = 3.30, 3.83) and college (IRR = 3.45; 95% CI = 3.26, 3.65). Most injuries were to the lower extremity. However, concussion was a common injury, particularly in collegiate goalkeepers and at all positions for high school players. Concussions accounted for more than one-fifth of injuries in high school games. Injury-prevention interventions should be tailored to reflect variations in the incidence and type of injury by level of competition, event type, and position.

Sun

23

Dec

2018

Latest research in footbal - week 42 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Muscle Damage-Based Recovery Strategies Can Be Supported by Predictive Capacity of Specific Global Positioning System Accelerometry Parameters Immediately a Post-Soccer Match-Load
Reference: J Strength Cond Res. 2018 Oct 22. doi: 10.1519/JSC.0000000000002922. [Epub ahead of print]
Authors: da Silva CD, Machado G, Fernandes AA, Teoldo I, Pimenta EM, Marins JCB, Garcia ES
Summary: Soccer match-load can be linked to recovery kinetic markers. However, match variability hinders the magnitude of relationship between parameters of interest. Therefore, we examined the correlation between 21 global positioning system accelerometry (GPS-A) parameters and changes in serum creatine kinase (CK) concentrations, muscle soreness (MS), and perceptive recovery quality (PRQ) assessed at baseline (1 h before) and post (0 minute, 2, 4, and 24 hours) a standardized 90-minute match-simulation in 12 university players. Global positioning system accelerometry (15 Hz) data were tested as manufacturer and configurable thresholds. Four GPS-A parameters showed moderate to very large correlations with CK changes at all time points (average speed [avgSP, r = 0.75 to r = 0.84]; running symmetry foot strikes [RSfst, r = 0.53-0.63]; running series [RunS, r = 0.53-0.61]; and acceleration distance [AccD ≥ 1.5 m·s; r = 0.46-0.61]). Sprint count (≥2 m·s), AccD (≥2.5 m·s) and speed exertion (SpEx) had a moderate to large correlation (r = 0.46-0.56) with CK changes from 2 to 24 hours. Changes in MS at 0 minute had large correlation with avgSP (r = 0.53) and moderate with deceleration distance (≥-2 and ≥-3 m·s; r = 0.47, r = 0.48, respectively). The PRQ changes had moderate inverse correlation with avgSP at 0 minute (r = -0.39) and SpEx at 2 h (r = -0.69). Our results suggest that during a simulated soccer protocol with a standard workload, only the avgSP has practical application for predicting CK changes over 24 hours, allowing for a decision-making toward a postgame recovery based on previously known CK cutoff points. Global positioning system accelerometry parameters and subjective variables did not demonstrate relevant correlation.


#2 Influence of Night Soccer Matches on Sleep in Elite Players
Reference: J Strength Cond Res. 2018 Oct 22. doi: 10.1519/JSC.0000000000002906. [Epub ahead of print]
Authors: Nédélec M, Dawson B, Dupont G
Summary: This study examined the impact of night matches on the sleep/wake behavior of elite soccer players participating in the UEFA Champions League and French Ligue 1. A mixed method approach was used, combining objective sleep assessment with wrist activity monitors, and a survey to ascertain the sleep complaints after night matches (kick off after 18:00 hours). Most players (90%) indicated worse sleep in the nights after evening matches than after training days. Objective time in bed (-01:39 hours; effect size [ES] = 1.7; p < 0.001) and total sleep time (-01:32 hours; ES = 1.4; p < 0.001) were both lower after night matches than after training days. Night matches had a marked influence on sleep quantity later that night, both objectively and subjectively. The survey revealed that players may not have appropriate methods for better managing their sleep after night matches. It is yet to be determined whether players may benefit from individualized sleep interventions in these circumstances.


#3 Movement Economy in Soccer: Current Data and Limitations
Reference: Sports (Basel). 2018 Oct 23;6(4). pii: E124. doi: 10.3390/sports6040124.
Authors: Dolci F, Hart NH, Kilding A, Chivers P, Piggott B, Spiteri T
Summary: Soccer is an intermittent team-sport, where performance is determined by a myriad of psychological, technical, tactical, and physical factors. Among the physical factors, endurance appears to play a key role into counteracting the fatigue-related reduction in running performance observed during soccer matches. One physiological determinant of endurance is movement economy, which represents the aerobic energy cost to exercise at a given submaximal velocity. While the role of movement economy has been extensively examined in endurance athletes, it has received little attention in soccer players, but may be an important factor, given the prolonged demands of match play. For this reason, the current review discusses the nature, impact, and trainability of movement economy specific to soccer players. A summary of current knowledge and limitations of movement economy in soccer is provided, with an insight into future research directions, to make this important parameter more valuable when assessing and training soccer players' running performance.

#4 Seasonal Changes in the Physical Performance of Elite Youth Female Soccer Players
Reference: J Strength Cond Res. 2018 Oct 24. doi: 10.1519/JSC.0000000000002943. [Epub ahead of print]
Authors: Emmonds S, Sawczuk T, Scantlebury S, Till K, Jones B
Author information
Summary: This study investigated the seasonal change in physical performance of 113 (Under 10: U10 [n = 20], U12 [n = 30], U14 [n = 31], and U16 [n = 32]) elite youth female soccer players. Players completed testing pre-, mid-, and post-season, including speed (10- and 30-m sprint), change of direction (CoD; 505 test), power (countermovement jump [CMJ]), strength (isometric midthigh pull), and aerobic capacity (Yo-Yo intermittent recovery test level 1 [YYIRL1]). A general linear model was used to evaluate the change in physical characteristics and the influence of covariates (baseline performance; change in maturity status) on each characteristic across the season. U10's speed and CoD performance decreased from pre-post season, whereas relative strength likely improved. U12's relative strength very likely improved; however, 10-m sprint performance decreased. Relative strength likely decreased, whereas 30-m sprint and CoD time very likely improved in U14's. U16's likely improved relative strength, CMJ, and 10-m sprint, and very likely improved 30-m sprint and CoD from pre-post season. U12-U16's improved YYIRL1 performance pre-post season. Strength and conditioning coaches working with U10-U12 players should look to develop speed, lower-body power, and CoD ability as part of structured strength and conditioning sessions as well as within warm-ups before pitch-based sessions. With U14-U16 players' manipulation of small-sided games combined with short-duration high-intensity running drills may provide an efficient training stimulus to develop the aerobic system while concurrently developing technical/tactical skills. Findings of this study provide a basis for the implementation of strategies to enhance the long-term athletic development of youth female soccer players.


#5 The influence of different exercise intensities on kicking accuracy and velocity in soccer players
Reference: J Sport Health Sci. 2017 Dec;6(4):462-467. doi: 10.1016/j.jshs.2015.10.001. Epub 2015 Oct 20.
Authors: Ferraz R, van den Tillar R, Marques MC
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6189251/pdf/main.pdf
Summary: The aim of this study was to investigate the influence of different exercise intensities induced by a soccer specific protocol on kicking performance in soccer players. Twelve semi-professional male soccer players participated in this study and performed maximal instep kicks before and after the implementation of an exercise protocol to determine the influence of different intensities upon kicking ball velocity and the target-hitting accuracy. Analysis of variance designs with repeated measures showed that maximal ball velocity was affected only after the most intense circuit (F(6, 66) = 2.3; p = 0.041; η 2 = 0.18), while accuracy was not affected in the protocol (F(6, 66) = 0.19; p = 0.98; η 2 = 0.02). Low and moderate intensities did not affect accuracy or kicking ball velocity. These findings suggest that kicking ball velocity is influenced by high-exercise intensities. Low and moderate exercise intensities do not affect the performance of the kick, and intensity does not influence accuracy. Otherwise, it is possible that other mechanisms (not only physiological) may influence players during the exercise.


#6 Effects of soccer training on health-related physical fitness measures in male adolescents
Reference: J Sport Health Sci. 2018 Apr;7(2):169-175. doi: 10.1016/j.jshs.2017.10.009. Epub 2018 Jan 3.
Authors: Hammami A, Randers MB, Kasmi S, Razgallah M, Tabka Z, Chamari K, Bouhlel E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180556/pdf/main.pdf
Summary: The aims of this study were to (1) investigate the health-related physical fitness profile of untrained adolescent boys in comparison to adolescent soccer players, (2) determine the intensity and enjoyment of 6 v 6 and 4 v 4 small-sided games, and (3) evaluate the health-related effects of a short-period of soccer training in the untrained group. Forty-one adolescent boys (untrained, n = 24: age = 15.9 ± 0.6 years; trained, n = 17: age = 15.7 ± 0.7 years) were recruited. For Purpose 1, the players (n = 17) and the untrained (n = 24) boys were tested for speed, jumping power, postural balance, flexibility, and aerobic capacity. After baseline testing, Purposes 2 and 3 were addressed by randomly assigning the untrained boys to either a soccer-training group (small-sided games, 2 sessions per week for 8 weeks) or to a control group, followed by identical retesting. At baseline, physical fitness was higher (p < 0.001) in trained players than in untrained for aerobic fitness, sprinting, jumping power, and postural balance. Small-sided games using 6 v 6 or 4 v 4 elicited similar heart rate (HR) (mean:  ~ 85% peak heart rate, HRpeak), rate of perceived exertion, and enjoyment responses. Over 8 weeks, the between-group analysis revealed that soccer training had a large beneficial effect on postural balance (45%) when compared with control group with unclear effects on other fitness parameters. Adolescent soccer players had markedly higher physical fitness compared with untrained adolescents. Small-sided soccer games practiced by untrained adolescents elicited high exercise intensity. While 8 weeks of twice-weekly soccer training sessions induced significant improvement in postural balance, the short duration of the study was not sufficient to result in between-group differences in sprint and jump performance or aerobic fitness.


#7 Injuries in Spanish female soccer players
Reference: J Sport Health Sci. 2018 Apr;7(2):183-190. doi: 10.1016/j.jshs.2016.09.002. Epub 2016 Sep 21.
Authors: Del Coso J, Herrero H, Salinero JJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180559/pdf/main.pdf
Summary: Epidemiologic research to learn the incidence, type, location, and severity of female soccer injuries and the risk factors for sustaining a sport injury is the first step in developing preventive policies. The aim of this study was to analyze the incidence of injuries in the population of female soccer players in Spain. The injuries incurred by 25,397 female soccer players were registered by the medical staff of the Spanish Football Federation during 1 season. A standardized medical questionnaire was used to classify the injury according to type, severity, location, and injury mechanism. A total of 2108 injuries was reported with an incidence of 0.083 injuries per player per season. Most injuries were in the lower limbs (74.0%), mainly affecting knee (30.4%) and ankle joints (17.9%). The proportion of injuries derived from contact with another player was higher during matches (33.7%) than during training (11.4%; p < 0.001). Noncontact injuries were classified as severe more frequently than were contact injuries (51.0% vs. 42.6%; p < 0.001). A higher incidence of injury was found in adult soccer players (≥18 years) vs. their counterparts younger than18 years (0.094 vs. 0.072 injuries per player per year, respectively; p < 0.001). There were no differences between age groups in any other injury variable (e.g., type, mechanism, location, or severity; p > 0.05). Most female soccer injuries were located at the knee and ankle; the injury mechanism determined the playing time lost; and the player's age did not affect injury characteristics.


#8 Training load and schedule are important determinants of sleep behaviours in youth-soccer players
Reference: Eur J Sport Sci. 2018 Oct 24:1-9. doi: 10.1080/17461391.2018.1536171. [Epub ahead of print]
Authors: Whitworth-Turner CM, Di Michele R, Muir I, Gregson W, Drust B
Summary: The current study examined how sleep may be influenced by the scheduling of training and match load within 10 youth-soccer players. Sleep was measured over a 14-day in-season period using a commercially available wireless sleep monitor. Each collected sleep variable; lights out, sleep latency, total sleep time wake after sleep onset and final awakening, was compared for the specific day within the training schedule (e.g. match day [MD], day after match [MD + 1]) and to training/match load (high-speed distance (>5.5 m/s) [HSD] and rating of perceived exertion. The data were analysed using mixed models and effect sizes, to describe the magnitude of effects that training schedule and training load may have on sleep. A reduction of sleep duration was observed on the day after the match (MD + 1) in relation to the training days preceding the match (MD-2: -65 min, ES: 0.89 ± 0.79; MD-1 -61 min, ES: 0.82 ± 0.64) and reduction on match day (+45 min; ES: 1.91 ± 1.69). This may suggest youth-soccer players actively change their sleep scheduling behaviours in relation to the imposed soccer schedule. Increased high-speed running (for every 100 m) showed a small increase to total sleep time (+9 min; ES: 0.48 ± 0.31). This may suggest that increases in training load may be associated with small increases in sleep quantity. Such observations may highlight that the type of day and the associated load within the training microcycle may have important consequences for sleep within youth-soccer players.


#9 The acute effects of plyometric and sled towing stimuli with and without caffeine ingestion on vertical jump performance in professional soccer players
Reference: J Int Soc Sports Nutr. 2018 Oct 22;15(1):51. doi: 10.1186/s12970-018-0258-3.
Authors: Guerra MA Jr, Caldas LC, De Souza HL, Vitzel KF, Cholewa JM, Duncan MJ, Guimarães-Ferreira L
Download link: https://jissn.biomedcentral.com/track/pdf/10.1186/s12970-018-0258-3
Summary: Post-activation potentiation (PAP) is the phenomenon by which muscular performance is enhanced in response to a conditioning stimulus. PAP has typically been evidenced via improved counter movement jump (CMJ) performance. This study examined the effects of PAP, with and without prior caffeine ingestion, on CMJ performance. Twelve male professional soccer players (23 ± 5 years) performed two trials of plyometric exercises and sled towing 60 min after placebo or caffeine ingestion (5 mg.kg- 1) in a randomized, counterbalanced and double-blinded design. CMJ performance was assessed at baseline and 1, 3 and 5 min after the conditioning stimulus (T1, T3 and T5, respectively). Two way ANOVA main effects indicated a significant difference in jump height after the PAP protocol (F[3, 11] = 14.99, P < 0.001, partial η2 = 0.577). Analysis also indicated a significant difference in CMJ performance across conditions, with caffeine eliciting a greater response (F[1, 11] = 10.12, P = 0.009, partial η2 = 0.479). CMJ height was increased at T1, T3 and T5 in caffeine condition (5.07%, 5.75% and 5.40%, respectively; P < 0.01) compared to baseline. In the placebo condition, jump performance was increased at T3 (4.94%; P < 0.01) only. Jump height was higher in caffeine condition on T1, T3 and T5 (P < 0.05) but not on baseline (P > 0.05) compared to placebo. The results of this study suggest that acute plyometric and sled towing stimuli enhances jump performance and that this potentiation is augmented by caffeine ingestion in male soccer players.


#10 5-Hydroxymethylfurfural and Alpha-Ketoglutaric Acid as an Ergogenic Aid During Intensified Soccer Training: A Placebo Controlled Randomized Study
Reference: J Diet Suppl. 2018 Oct 22:1-12. doi: 10.1080/19390211.2018.1494662. [Epub ahead of print]
Authors: Gatterer H, Böcksteiner T, Müller A, Simi H, Krasser C, Djukic R, Schroth R, Wallner D
Summary: Intensified training may lead to fatigue or even a state of overreaching with temporary reductions in performance. Any aid helping to prevent these consequences and to better tolerate such a training regime would be of great importance. 5-hydroxymethylfurfural (5-HMF) and α-ketoglutaric acid (α-KG) supplementation has been suggested to support favorable training outcomes but its effectiveness to facilitate adaptations during an intensified training period has never been investigated. During an in-season competition break (2 weeks), seventeen young outfield soccer players (age:14.7 ± 0.4 yr) performed a 9-day lasting shock microcyle including 5-7 repeated sprint exercise sessions in addition to the regular training (∼6 sessions/wk) and match (1-2 matches/wk) schedule. Before the training period a treadmill test to exhaustion, a YOYO intermittent recovery level 2 (YYIR2) and a repeated sprint ability (RSA) test were performed. The treadmill test was repeated 3 days after the shock microcycle whereas the YYIR2 and the RSA test on day 10 after the training. Magnitude based inference analysis showed likely positive effects of the 5-HMF/α-KG compared to the control group for changes in the maximal running velocity (+0.3 ± 0.7 vs. -0.3 ± 0.8 km/h) and running velocity at lactate turn-point 1 (+0.2 ± 0.4 vs. -0.2 ± 0.6) and lactate turn-point 2 (+0.4 ± 0.4 vs. -0.2 ± 0.6 km/h, for the 5-HMF/α-KG and placebo group, respectively). Training improved YYIR2 performance (+180 ± 67 vs. +200 ± 168m) and RSA (mean time: -0.1 ± 0.1 vs. -0.1 ± 0.1s, for the 5-HMF/α-KG and placebo group, respectively) in both groups and to the same extent. In conclusion, an in-season shock microcyle including repeated sprint training improves YYIR2 performance and RSA in youth soccer players. Supplementation with 5-HMF/α-KG did not modify training adaptations but led to likely positive exercise performance responses shortly after the intensified training regime.


#11 The association between physical performance and match-play activities of field and assistants soccer referees
Reference: Res Sports Med. 2018 Oct 20:1-15. doi: 10.1080/15438627.2018.1534117. [Epub ahead of print]
Authors: Castillo D, Cámara J, Lozano D, Berzosa C, Yanci J
Author information
Summary: The aims of this study were to compare the external and internal match responses and fitness performance of national field referees (FRs) and assistant referees (ARs), and to examine the relationships between these fitness measures and physical and physiological responses during match play. Forty-four national soccer match officials (e.g. FRs and ARs) participated in this study. The distance covered and the VO2max in Yo-Yo Intermittent recovery test (YYIR1) and the 30 m sprint test correlated with high speed and high intensity activities during match play in FRs (r = -0.48-0.63, moderate to large, very likely to most likely, p < 0.05). In addition, YYIR1 performance was related to high accelerations (r = 0.41, moderate, likely, p < 0.05) and high decelerations (r = 0.44, moderate, very likely, p < 0.05) for FRs. Better sprint and cardiovascular fitness could be relevant to the performance of FRs during match play.


#12 Analyzing the Components of Emotional Competence of Football Coaches: A Qualitative Study from the Coaches' Perspective
Reference: Sports (Basel). 2018 Oct 23;6(4). pii: E123. doi: 10.3390/sports6040123.
Authors: Lee H, Wäsche H, Jekauc D
Summary: Emotional Competence (EC) is regarded as a fundamental skill for sports coaches. However, the applications of EC in football coaching are not well understood. This study analyzed the specific emotional processes football coaches experience. We interviewed 18 football coaches and analyzed the interview transcripts by using a systematic analysis process based on Grounded Theory principles. We derived a model from this analysis that comprises a four-phase process: emotional triggers, emotional experiences, emotion regulation strategies, and emotional consequences. In this model, we identified four categories which act as triggers of emotions in football coaches. These emotions can be positive or negative and are manifested at three levels. However, the coaches vary in their capability to perceive emotions. Our model also shows that coaches' emotion regulation strategies influence the effect of emotional experiences. Experienced emotions promote consequences with psychological and social implications for coaches and may influence their perception of future situations. In short, the process seems to be circular. This finding suggests that the ability to deal with emotions is an important aspect for football coaches.


#13 Modelling home advantage for individual teams in UEFA Champions League football
Reference: J Sport Health Sci. 2017 Sep;6(3):321-326. doi: 10.1016/j.jshs.2015.12.008. Epub 2015 Dec 24.
Authors: Goumas C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6189255/pdf/main.pdf
Summary: Home advantage (HA) is well documented in a wide range of team sports including association football (soccer). Although much attention has been paid to differences in the overall magnitude of HA between football competitions and across time, few studies have investigated HA at the team level. A novel method of estimating HA for individual teams, based solely on home performance, was used to compare HA between the highest performing teams and countries in the Union of European Football Associations (UEFA) Champions League over a 10-year period (2003/2004 to 2012/2013). Away disadvantage (AD) was also estimated based on each team's performance away from home. Poisson regression analysis was used to estimate covariate adjusted HA and AD in terms of the percentage of goals scored at home (HA) and conceded away from home (AD). When controlling for differences in team ability, HA did not vary significantly between the 13 selected teams. There was evidence (p < 0.1), however, of between-team variation in AD, ranging from 45% (away advantage) to 68% (away disadvantage). When teams were grouped into the 11 selected countries, both HA and AD varied significantly (p < 0.02) between countries: HA ranged from 52% for Turkish teams to 70% for English teams, while AD ranged from 52% (France) to 67% (Turkey). Differences in style of play and tactical approaches to home and away matches may explain some of the variation in HA and AD between teams from different countries.

Thu

20

Dec

2018

Latest research in football - week 41 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Skeletal maturity and oxygen uptake in youth soccer controlling for concurrent size descriptors
Reference: PLoS One. 2018 Oct 18;13(10):e0205976. doi: 10.1371/journal.pone.0205976. eCollection 2018.
Authors: Teixeira AS, Guglielmo LGA, Fernandes-da-Silva J, Konarski JM, Costa D, Duarte JP, Conde J, Valente-Dos-Santos J, Coelho-E-Silva MJ, Malina RM
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205976&type=printable
Summary: Interrelationships among skeletal maturity status, body size, ventilator thresholds (VT) and peak oxygen uptake (VO2peak) were considered in 47 adolescent male soccer players aged 12.5-15.4 years. Body mass, stature, and the triceps and subscapular skinfolds were measured. The latter were used to estimate fat mass and fat-free mass. Skeletal age was assessed with the Fels method. VO2peak and VO2 at the first (VT1) and second (VT2) ventilatory thresholds were determined during an incremental maximal exercise test on a motorized treadmill. Ratio standards and allometric models were used in the analysis. Scaling exponents suggested linearity for all combinations between size descriptors and physiological variables, except between log-transformed values of VT1 and body mass (mL·kg-0.801·min, 95%CI: 0.649 to 0.952). Early maturing players attained greater values than players classified as "on-time" in skeletal maturity for the three ventilatory parameters expressed in absolute terms (d ranged from 0.65 to 0.71). The differences were attenuated after normalizing for mass descriptors using ratio standards and scaled variables (d ranged from 0.00 to 0.31). The results suggested significant variability between maturity groups when moving from VT1 to maximal metabolic conditions expressed by unit of stature (VT1: t = -2.413, p = 0.02, d = 0.60; VT2: t = -2.488, p = 0.02, d = 0.65; VO2peak: t = -2.475, p = 0.02, d = 0.65). Skeletal maturity status and associated variation in overall body size affects VT1, VT2 and VO2peak. The observed scaling of ventilatory outputs for body size may be related to the better running economy and smaller body size of average maturing athletes.


#2 Life skills development and enjoyment in youth soccer: The importance of parental behaviours
Reference: J Sports Sci. 2018 Oct 17:1-7. doi: 10.1080/02640414.2018.1530580. [Epub ahead of print]
Authors: Mossman GJ, Cronin LD
Summary: This study investigated the relationships between parental behaviours and players' life skills development and enjoyment within youth soccer. In total, 317 players (Mage = 12.83, SD = 1.70, age range = 10-16 years) completed a survey assessing parental behaviours (praise and understanding, directive behaviour, and pressure), perceived life skills development (teamwork, goal setting, time management, emotional skills, interpersonal communication, social skills, leadership, and problem solving and decision making), and enjoyment of soccer. Multiple regression analyses found that praise and understanding was the key contributor to the outcome variables, making the largest unique contribution to teamwork, goal setting, leadership, and total life skills. Directive behaviour made the largest unique contribution to emotional skills, and problem solving and decision making; whereas pressure made the largest unique contribution to participants' time management and social skills. In practice, the results suggest that parents should display praise and understanding behaviours, which were the main contributor to players' development of life skills within soccer.


#3 In-season eccentric-overload training in elite soccer players: Effects on body composition, strength and sprint performance
Reference: PLoS One. 2018 Oct 16;13(10):e0205332. doi: 10.1371/journal.pone.0205332. eCollection 2018.
Authors: Suarez-Arrones L, Saez de Villarreal E, Núñez FJ, Di Salvo V, Petri C, Buccolini A, Maldonado RA, Torreno N, Mendez-Villanueva A
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205332&type=printable
Summary: The aim of this study was to describe the changes in body composition, strength and sprint performance in response to an entire competitive season of football training supplemented with 2 inertial eccentric-overload training sessions a week in young male professional soccer players. Whole body and regional composition (assessed using dual-energy X-ray absorptiometry), power output in half-squat and 40-m sprinting performance were evaluated in fourteen players. The eccentric-overload training consisted of training sessions a week of 1-2 sets of 10 exercises of upper-body and core (Day 1) and lower-body (Day 2), during the entire competitive season (27 weeks). Whole body fat mass decreased (-6.3 ± 3.6%, ES = -0.99 ± 0.54) substantially while lean mass increased (2.5 ± 0.8%, ES = 0.25 ± 0.09), with some regional differences. There was a substantial increase in half-squat power output (from 3% to 14%, ES from 0.45 to 1.73) and sprint performance (from 1.1% to 1.8%, ES from -0.33 to -0.44), however performance changes were not correlated with changes in body composition. A combined soccer and eccentric-overload training program was able to promote positive changes in body composition and physical factors relevant to both on-field performance and injury prevention in elite soccer players.


#4 Effects of Prolonging Eccentric Phase Duration in Parallel Back-Squat Training to Momentary Failure on Muscle Cross-Sectional Area, Squat One Repetition Maximum, and Performance Tests in University Soccer Players
Reference: J Strength Cond Res. 2018 Oct 12. doi: 10.1519/JSC.0000000000002838. [Epub ahead of print]
Authors: Shibata K, Takizawa K, Nosaka K, Mizuno M
Summary: This study aimed to compare 2 squat training programs repeated until momentary failure with different eccentric phase duration (2 seconds vs. 4 seconds) on the changes in muscle cross-sectional area, squat 1 repetition maximum (1RM), squat jump (SJ), and countermovement jump (CMJ) height, agility (T-test), and Yo-Yo intermittent recovery test (YY-IR2). Male university soccer players (19.9 ± 0.9 years, 172.2 ± 3.8 cm, 66.1 ± 6.6 kg) were randomly assigned to one of the 2 groups; CON for 2 seconds and ECC for 4 seconds (C2/E4, n = 11) or CON for 2 seconds and ECC for 2 seconds (C2/E2, n = 11). They performed parallel back-squat exercises twice a week for 6 weeks using 75% 1RM weight to momentary failure in each set for 3 sets with each protocol. Outcome measurements were taken before (Pre) and after 3 (Mid; 1RM, SJ, and CMJ only), and at 6 weeks (Post). One repetition maximum increased more (p < 0.05) for C2/E2 (Pre: 95.9 ± 12.2 kg, Mid: 108.2 ± 15.4 kg, Post: 113.6 ± 14.8 kg) than C2/E4 (95.5 ± 12.9 kg, 102.7 ± 15.6 kg, 105.5 ± 14.9 kg, respectively). Cross-sectional area (50% of the thigh length: 3.5 ± 2.8%), SJ (6.7 ± 8.9%) and CMJ height (6.3 ± 8.6%) increased similarly between C2/E2 and C2/E4, but no significant changes in T-test or YY-IR2 were evident in either group. These results suggest that increasing the ECC phase duration during squat exercises does not produce greater training effects when compared with a shorter ECC phase-duration program with momentary failure.


#5 Altered brain microstructure in association with repetitive subconcussive head impacts and the potential protective effect of jugular vein compression: a longitudinal study of female soccer athletes
Reference: Br J Sports Med. 2018 Oct 15. pii: bjsports-2018-099571. doi: 10.1136/bjsports-2018-099571. [Epub ahead of print]
Authors: Myer GD, Barber Foss K, Thomas S, Galloway R, DiCesare CA, Dudley J, Gadd B, Leach J, Smith D, Gubanich P, Meehan WP 3rd, Altaye M, Lavin P, Yuan W
Summary:  The purpose was to (1) quantify white matter (WM) alterations in female high school athletes during a soccer season and characterise the potential for normalisation during the off-season rest period, (2) determine the association between WM alterations and exposure to repetitive subconcussive head impacts, and (3) evaluate the efficacy of a jugular vein compression collar to prevent WM alterations associated with head impact exposure. Diffusion tensor imaging (DTI) data were prospectively collected from high school female soccer participants (14-18 years) at up to three time points over 9 months. Head impacts were monitored using accelerometers during all practices and games. Participants were assigned to a collar (n=24) or non-collar group (n=22). The Tract-Based Spatial Statistics approach was used in the analysis of within-group longitudinal change and between-group comparisons. DTI analyses revealed significant pre-season to post-season WM changes in the non-collar group in mean diffusivity (2.83%±2.46%), axial diffusivity (2.58%±2.34%) and radial diffusivity (3.52%±2.60%), but there was no significant change in the collar group despite similar head impact exposure. Significant correlation was found between head impact exposure and pre-season to post-season DTI changes in the non-collar group. WM changes in the non-collar group partially resolved at 3 months off-season follow-up. Microstructural changes in WM occurred during a season of female high school soccer among athletes who did not wear the collar device. In comparison, there were no changes in players who wore the collar, suggesting a potential prophylactic effect of the collar device in preventing changes associated with repetitive head impacts. In those without collar use, the microstructural changes showed a reversal towards normal over time in the off-season follow-up period.


#6 Hip and Groin Injuries Among Collegiate Male Soccer Players: The 10-Year Epidemiology, Incidence, and Prevention
Reference: Orthopedics. 2018 Oct 15:1-6. doi: 10.3928/01477447-20181010-01. [Epub ahead of print]
Authors: Tummala SV, Chhabra A, Makovicka JL, Patel KA, Hartigan DE
Summary: The physical and demanding style of play in soccer places these athletes at an elevated risk for hip and groin injuries. Several studies have examined hip and groin injuries in professional and youth soccer in European countries, but few have involved American counterparts. Hip injury data were analyzed retrospectively from the National Collegiate Athletic Association Injury Surveillance Program for the 2004 to 2014 academic years for collegiate men's soccer. This study found that hip and groin injuries among collegiate male soccer players were most often new injuries (87.8%; n=527) that were noncontact in nature (77.3%; n=464) and resulted in time loss of less than 7 days (67.5%; n=405). Hip injuries were significantly more likely during the pre-season (5.72 per 1000 athlete exposures) relative to in-season (injury proportion ratio, 1.64; 95% confidence interval, 1.39-1.94) and post-season (injury proportion ratio, 1.69; 95% confidence interval, 1.18-2.41). Further, they were more likely in competition relative to practice (injury proportion ratio, 2.33; 95% confidence interval, 1.98-2.74). The most common injuries were adductor strains (46.5%; n=279) followed by hip flexor strains (27.3%; n=164) and hip contusions (10.8%; n=65). Among these injuries, adductor (73.1%; n=204) and hip flexor (59.8%; n=98) strains were more commonly noncontact related and occurred in practice, whereas hip contusions were due to contact and during competition. The study of the complex and lingering nature of hip and groin injuries in soccer players is critical because these injuries not only are prevalent but also have multifactorial risks associated with coexisting pathologies that make them difficult to prevent and treat effectively.


#7 Psychological talent predictors in youth soccer: A systematic review of the prognostic relevance of psychomotor, perceptual-cognitive and personality-related factors
Reference: PLoS One. 2018 Oct 15;13(10):e0205337. doi: 10.1371/journal.pone.0205337. eCollection 2018.
Authors: Murr D, Feichtinger P, Larkin P, O'Connor D, Höner O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6188900/pdf/pone.0205337.pdf
Summary: Within the multidimensional nature of soccer talent, recently there has been an increasing interest in psychological characteristics. The aim of this present research was to systematically review the predictive value of psychological talent predictors and provide better comprehension of the researchers' methodological approaches and the empirical evidence for individual factors (i.e., psychomotor, perceptual-cognitive and personality-related). Results highlighted heterogeneous study designs (e.g., participants, measurement methods, statistical analyses) which may limit the comparability of studies' findings. Analyzing the number of included studies, psychomotor (n = 10) and personality-related factors (n = 8) received more consideration within the literature than perceptual-cognitive factors (n = 4). In regard to empirical evidence, dribbling (0.47 ≤ d ≤ 1.24), ball control (0.57 ≤ d ≤ 1.28) and decision-making (d = 0.81) demonstrated good predictive values as well as the achievement motives hope for success (0.27 ≤ d ≤ 0.74) and fear of failure (0.21 ≤ d ≤ 0.30). In conclusion, there is growing acceptance of the need for more complex statistical analyses to predict future superior performance based on measures of current talent. New research addresses the necessity for large-scale studies that employ multidisciplinary test batteries to assess youth athletes at different age groups prospectively.


#8 Not Every Pass Can Be an Assist: A Data-Driven Model to Measure Pass Effectiveness in Professional Soccer Matches
Reference: Big Data. 2018 Sep 21. doi: 10.1089/big.2018.0067. [Epub ahead of print]
Authors: Goes FR, Kempe M, Meerhoff LA, Lemmink KAPM
Summary: In professional soccer, nowadays almost every team employs tracking technology to monitor performance during trainings and matches. Over the recent years, there has been a rapid increase in both the quality and quantity of data collected in soccer resulting in large amounts of data collected by teams every single day. The sheer amount of available data provides opportunities as well as challenges to both science and practice. Traditional experimental and statistical methods used in sport science do not seem fully capable to exploit the possibilities of the large amounts of data in modern soccer. As a result, tracking data are mainly used to monitor player loading and physical performance. However, an interesting opportunity exists at the intersection of data science and sport science. By means of tracking data, we could gain valuable insights in the how and why of tactical performance during a soccer match. One of the most interesting and most frequently occurring elements of tactical performance is the pass. Every team has around 500 passing interactions during a single game. Yet, we mainly judge the quality and effectiveness of a pass by means of observational analysis, and whether the pass reaches a teammate. In this article, we present a new approach to quantify pass effectiveness by means of tracking data. We introduce two new measures that quantify the effectiveness of a pass by means of how well a pass disrupts the opposing defense. We demonstrate that our measures are sensitive and valid in the differentiation between effective and less effective passes, as well as between the effective and less effective players. Furthermore, we use this method to study the characteristics of the most effective passes in our data set. The presented approach is the first quantitative model to measure pass effectiveness based on tracking data that are not linked directly to goal-scoring opportunities. As a result, this is the first model that does not overvalue forward passes. Therefore, our model can be used to study the complex dynamics of build-up and space creation in soccer.


#9 Basal Mild Dehydration Increase Salivary Cortisol After a Friendly Match in Young Elite Soccer Players
Reference: Front Physiol. 2018 Sep 26;9:1347. doi: 10.3389/fphys.2018.01347. eCollection 2018.
Authors: Castro-Sepulveda M, Ramirez-Campillo R, Abad-Colil F, Monje C, Peñailillo L, Cancino J, Zbinden-Foncea H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168646/pdf/fphys-09-01347.pdf
Summary: A soccer match induce changes in physiological stress biomarkers as testosterone (T), cortisol (C), and testosterone:cortisol (T:C) ration. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to soccer match. The role of hydration status before the match in this biomarkers has not yet been reported. The aim of this study was to compare the salivary T, C, and the T:C ratio responses after two friendly matches in well-hydrated and mild-dehydrated (MD) elite young male soccer player. Seventeen players (age, 16.8 ± 0.4 years; VO2max 57.2 ± 3.6 ml/kg-1/min-1) were divided into two teams. Before the matches the athletes were assessed for hydration level by the urine specific gravity method and divided for the analysis into well-hydrated (WH; n = 9; USG < 1.010 g/mL-1) and mild-dehydrated (MD; n = 8; USG 1.010 to 1.020 g/mL-1) groups. Hormones were collected before and after each match by saliva samples. The mean (HRmean) and maximal (HRmax) heart rate were measured throughout the matches. A two-way ANOVA was used to compare T, C, and T:C between and within groups. Similar HRmean (WH, 83.1 ± 4.7%; MD, 87.0 ± 4.1; p = 0.12) and HRmax (WH, 93.2 ± 4.4%; MD, 94.7 ± 3.7%; p = 0.52) were found for both groups during the matches. No differences were found before the matches in the T (p = 0.38), C (p = 66), nor T:C (p = 0.38) between groups. No changes within groups were found after matches in neither group for T (WH, p = 0.20; MD, p = 0.36), and T:C (WH, p = 0.94; MD, p = 0.63). Regarding the C, only the MD group showed increases (28%) after the matches (MD, p = 0.03; WH, p = 0.13). In conclusion MD group exacerbate the C response to friendly matches in elite young male soccer players, suggesting that dehydration before match may be an added stress to be considered.


#10 Can compression stockings reduce the degree of soccer match-induced fatigue in females?
Reference: Res Sports Med. 2018 Oct 14:1-14. doi: 10.1080/15438627.2018.1527335. [Epub ahead of print]
Authors: Pavin LN, Leicht AS, Gimenes SV, da Silva BVC, Simim MAM, Marocolo M, da Mota GR
Summary: Soccer-induced fatigue and performance are different between the sexes. The effect of compression stockings (CS) use on fatigue during the soccer match in females is unknown. Thus, we evaluated the impact of CS use during a female soccer match on match-induced fatigue. Twenty soccer players were randomly allocated to two groups (n = 10 for each group): CS and Control (regular socks), and equally distributed within two teams. At rest (baseline 48-h before the match) and immediately post-match, we assessed agility T-test, standing heel-rise test and YoYo Intermittent Endurance Test level 2 (YoYoIE2) performance. Effort during the match (heart rate and rating of perceived exertion) was similar (p > 0.05) between groups. The YoYoIE2 performance was decreased post-match (p < 0.05) equally for both groups. Otherwise, the CS group exhibited a greater post-match performance (p < 0.05) for the agility T-test and heel-rise test (large effect sizes). Therefore, we conclude that the use of CS during an amateur female soccer match resulted in less match-induced fatigue.


#11 Acute and chronic effects of soccer game on the retinal vessel diameters in middle-aged adults
Reference: J Sports Med Phys Fitness. 2018 Oct 10. doi: 10.23736/S0022-4707.18.09164-8. [Epub ahead of print]
Authors: Solianik R, Streckis V, Imbrasiene D, Paunksnis A
Summary: Although changes in retinal vessel diameter is a new biomarker for the evaluation of cardiovascular risk factors, limited information is available regarding the effects of endurance exercises on retinal microcirculation. Thus, we aimed to evaluate both chronic and acute effects of soccer game on the diameters of retinal vessels in middle-aged players. Retinal vessel diameters were measured in 12 middle-aged amateur players (44.4 ± 7.0 years of age) with more than four years of soccer playing experience and 12 age matched sedentary adults (49.7 ± 7.1 years of age). In soccer players, diameters were also measured immediately after the soccer game. Cardiovascular risk profiles (anthropometry and body composition and blood pressure (BP)) and physical activity levels were also measured. Soccer players had wider retinal vessels than controls (P<0.05), resulting in greater arteriolar-to-venular diameter ratio (AVR) (P<0.05). Greater sports-related physical activity, lower body mass index (BMI) and fat mass were observed for soccer players compared to the controls (P<0.05), whereas BP did not differ. Physical activity level correlated positively with temporal retinal arteriolar (TRA) diameter and with AVR (P<0.05), whereas TRA diameter correlated negatively with BMI and fat mass (P<0.05). A significant correlation between temporal retinal venule (TRV) diameter and TRA diameter (P<0.05) was observed. The acute soccer game increased BP (P<0.05) and induced TRV dilatation (P<0.05). In middle-aged amateur soccer players, improvement of the retinal microcirculation was observed. Cardiovascular risk factors and physical inactivity were associated with adverse retinal microvascular alterations. In terms of acute effects, soccer play causes venular, but not arteriolar dilatation for middle-aged adults.


#12 Modulation of macrophage polarization by level-1 Yo-Yo intermittent recovery test in young football players
Reference: Medicine (Baltimore). 2018 Oct;97(42):e12739. doi: 10.1097/MD.0000000000012739.
Authors: Chiu CJ, Chi CW, Hsieh HR, Huang YC, Wu HJ, Chen YJ
Download link: https://pdfs.journals.lww.com/md-journal/2018/10190/Modulation_of_macrophage_polarization_by_level_1.21.pdf?token=method|ExpireAbsolute;source|Journals;ttl|1540669179803;payload|mY8D3u1TCCsNvP5E421JYK6N6XICDamxByyYpaNzk7FKjTaa1Yz22MivkHZqjGP4kdS2v0J76WGAnHACH69s21Csk0OpQi3YbjEMdSoz2UhVybFqQxA7lKwSUlA502zQZr96TQRwhVlocEp/sJ586aVbcBFlltKNKo+tbuMfL73hiPqJliudqs17cHeLcLbV/CqjlP3IO0jGHlHQtJWcICDdAyGJMnpi6RlbEJaRheGeh5z5uvqz3FLHgPKVXJzddFRrD2hcIwdDP9eSnSkfs8tQHGPCNVqu4yfd7VFcCxs=;hash|S8jVxvqAc5VVdXOn9m+AOA==
Summary: The aim of this study was to examine the effect of the level-1 Yo-Yo intermittent recovery test (YYIRT1) on polarization of macrophages in young football players.Fourteen male football players (19.9 ± 1.4 years old) were enrolled in this study. YYIRT1 was performed with 20-meter shuttle runs at increasing speeds and 10-second active recovery in a 5-meter distance between runs till exhaustion. Fasting blood samples were collected before and immediately after YYIRT1. Analysis for macrophage polarization by flow cytometry, reactive oxygen species (ROS) by flow cytometry, biochemical parameters by chemical reactions, and serum cytokines by ELISA were performed. The rating of perceived exertion (RPE) and cardiovascular parameters were recorded.The time to exhaustion was 714.1 ± 114.4 seconds. The oxygen uptake ((Equation is included in full-text article.)) was 48.7 ± 5.6 mL/min/kg, RPE scale was 19 ± 1, resting heart rate and maximal heart rate were 64.9 ± 8.8 beat/min and 181.9 ± 9.3 beat/min, respectively, indicating a high level of cardiopulmonary fitness. The expression of macrophage-specific CD14 and M1 marker HLA-ABC, but not M2 marker CD206, was down-regulated after YYIRT1. The intracellular ROS levels in macrophages had no significant change. In biochemical profile, the serum levels of lactic dehydrogenase (LDH), a marker of muscle damage, increased after YYIRT1 whereas no significant alteration was noted in creatine phosphokinase (CPK), blood urine nitrogen, creatinine, aspartate transaminase (AST), alanine transaminase (ALT), and C-reactive protein. The serum levels of interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF)-α had no significant change.The YYIRT1 may induce muscle damage accompanied by modulation of macrophage polarization toward suppression of M1 phenotype in young football players.


#13 Cam morphology in young male football players mostly develops before proximal femoral growth plate closure: a prospective study with 5-year follow-up
Reference: Br J Sports Med. 2018 Oct 15. pii: bjsports-2018-099328. doi: 10.1136/bjsports-2018-099328. [Epub ahead of print]
Authors: van Klij P, Heijboer MP, Ginai AZ, Verhaar JAN, Waarsing JH, Agricola R
Summary: Cam morphology is not completely understood. The aim of this study was threefold: (1) to investigate if cam morphology development is associated with growth plate status; (2) to examine whether cam morphology continues to develop after growth plate closure; and (3) to qualitatively describe cam morphology development over 5-year follow-up. Academy male football players (n=49) participated in this prospective 5-year follow-up study (baseline 12-19 years old). Anteroposterior and frog-leg lateral views were obtained at baseline (142 hips), 2.5-year (126 hips) and 5-year follow-up (98 hips). Cam morphology on these time points was defined as: (A) visual scores of the anterior head-neck junction, classified as: (1) normal, (2) flattening, and (3) prominence; and (B) alpha angle ≥60°.Proximal femoral growth plates were classified as open or closed. Cam morphology development was defined as every increase in visual score and/or increase in alpha angle from <60° to ≥60°, between two time points. This resulted in 224 measurements for cam morphology development analysis. Cam morphology development was significantly associated with open growth plates based on visual score (OR: 10.03, 95% CI 3.49 to 28.84, p<0.001) and alpha angle (OR: 2.85, 95% CI 1.18 to 6.88, p=0.020). With both definitions combined, cam developed in 104 of 142 hips during follow-up. Of these 104 hips, cam developed in 86 hips (82.7%) with open growth plate and in 18 hips (17.3%) with a closed growth plate. Cam morphology developed from 12 to 13 years of age until growth plate closure around 18 years. Cam morphology of the hip is more likely to develop with an open growth plate.


#14 The Effect of Blurred Perceptual Training on the Decision Making of Skilled Football Referees
Reference: Front Psychol. 2018 Sep 27;9:1803. doi: 10.3389/fpsyg.2018.01803. eCollection 2018.
Authors: van Biemen T, Koedijker J, Renden PG, Mann DL
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170623/pdf/fpsyg-09-01803.pdf
Summary: When judging ambiguous foul situations in football (soccer), referees must attune to the kinematic characteristics inherent in genuine fouls to ensure that they can (i) recognize when a foul has taken place, and (ii) discriminate the presence of deceptive intent on the part of the tackled player. The aim of this study was to determine whether perceptual training that removes superficial visual information would improve the decision-making performance of football referees. Two groups of skilled referees judged ambiguous foul situations on video before and after a training intervention that involved adjudicating foul situations. During the training phase, participants in a blurred-footage training group watched digitally altered, blurred videos that removed superficial visual information, whilst participants in a normal-footage control group viewed the same videos without blur (i.e., with the superficial information present). We hypothesized that blurred-training would train referees to ignore superficial visual information and instead focus on the basic kinematic movements that would better reveal the true nature of the inter-personal interaction. Consistent with this idea, training with blurred footage resulted in a positive change in response accuracy from pre to post-test when compared with normal-footage training. This improvement could not be explained on the basis of changes in response time or bias, but instead reflected a change in the sensitivity to genuine fouls. These findings provide a promising indication of the potential efficacy of blurred-footage training for referees to attune to the kinematic information that characterizes a foul. Blurred training might offer an innovative means of enhancing the decision-making performance of football referees via perceptual training.

Sun

04

Nov

2018

Latest research in football - week 40 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Cardio-respiratory values during recovery from exercise in soccer Spanish leagues
Reference: Physiol Meas. 2018 Oct 11;39(10):105003. doi: 10.1088/1361-6579/aae0e8.
Authors: Ramos-Álvarez JJ, Maffulli N, Bragazzi NL, Ardigò LP, Jiménez-Herranz E, Naranjo-Ortiz C, Padulo J, Calderón Montero FJ
Download link: http://iopscience.iop.org/article/10.1088/1361-6579/aae0e8/pdf
Summary: In this cross-sectional study, we compared Spanish division one (n  =  114) and division two (n  =  80) soccer players in terms of their cardio-respiratory response during recovery following a maximum laboratory effort test. Following the maximum laboratory effort protocol, we measured oxygen consumption ([Formula: see text]), heart rate (HR), and ventilation ([Formula: see text]) during recovery. Over the first 60 s of recovery, no significant differences were seen in either [Formula: see text] (28.7 versus 28.3 ml/kg/m, in division one and two players, respectively), HR, or [Formula: see text] (p  >  0.05). After 90 s, however, significant differences appeared between the players of the two divisions (p  <  0.01), although not among playing positions. Significant differences in [Formula: see text] (21.1 versus 26.0 ml/kg/m, in division one and two players, respectively) and HR were still apparent at 180 s into the recovery period. The change in professional soccer players' cardio-respiratory values over the recovery period following maximum effort are independent of the position played, but are associated with the division in which a player competes. Second division players show significantly higher [Formula: see text] and HR values than first division players at 180 s into the recovery period. These differences might influence performance in soccer and in other athletes whose sports require intermittent bouts of maximum effort and consequently times to repeat high-intensity efforts as short as possible.


#2 Lower limb injury prevention programs in youth soccer: a survey of coach knowledge, usage, and barriers
Reference: J Exp Orthop. 2018 Oct 11;5(1):43. doi: 10.1186/s40634-018-0160-6.
Authors: Mawson R, Creech MJ, Peterson DC, Farrokhyar F, Ayeni OR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6179968/pdf/40634_2018_Article_160.pdf
Summary: Participation in youth soccer carries a significant risk of injury, most commonly non-contact injuries of the lower extremity. A growing body of research supports the use of neuromuscular interventions by teams to prevent such injuries, yet the uptake of these recommendations by soccer teams remains largely unexplored. The purposes of the study were to determine (1) the level of awareness by youth coaches of injury prevention programs and their efficacy; (2) the number of youth coaches that use these interventions; and (3) barriers and potential facilitators to implementing a sustainable injury prevention program. Four hundred eighteen coaches of male and female youth soccer teams were emailed an online blinded survey. This survey consisted of 26 questions covering coaches' demographics, level of training, experience with injuries among players, and use of injury prevention programs. Question development was guided by the RE-AIM Sports Setting Matrix in combination with findings from the literature review and expert experience from orthopaedic surgeons specializing in sport medicine. Of the 418 coaches contacted, 101 responded. Only 29.8% of respondents used an injury prevention program in the prior soccer season. Coaches that had completed one or more coaching courses were more likely to use an intervention. Of those that did not already use an intervention, coaches agreed or strongly agreed that they would consider using one if it could be used in place of the warm up and take no more than 20 min (74.0%), if they could access information about the exercises (84.0%), and if the exercises could be properly demonstrated (84.0%). Additionally, 84% of coaches that did not already use an intervention agreed or strongly agreed that knowing that interventions may reduce a player's risk of injury by 45% would affect whether they would use one. This study suggests that the current use and awareness of injury prevention programs is limited by a lack of communication and education between sporting associations and coaches, as well as perceived time constraints. The results also suggest that improving coaching education of injury prevention could increase the frequency of intervention use.


#3 Low Doses of Caffeine: Enhancement of Physical Performance in Elite Adolescent Male Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Oct 9:1-21. doi: 10.1123/ijspp.2018-0536. [Epub ahead of print]
Authors: Ellis M, Noon M, Myers T, Clarke N
Summary: Large doses of ~6 mg·kg-1 body mass have improved performance during intermittent running, jumping, and agility protocols. However, there are sparse data on low doses of caffeine, especially in elite adolescent soccer players. Fifteen elite youth soccer players (177.3±4.8 cm, 66.9±7.9 kg and 16±1 y) participated in the study, consuming 1, 2, or 3 mg·kg-1 caffeine in a gelatin capsule or a 2-mg·kg-1 placebo in a single-blind, randomized, crossover study design. Testing consisted of a 20-m sprint, arrowhead agility (change of direction [CoD] right or left), countermovement jump (CMJ), and Yo-Yo Intermittent Recovery Test Level-1 (Yo-Yo IR1). Post-exercise CMJ performance was assessed as participants exited the Yo-Yo IR1. Data were analyzed using a Bayesian multilevel regression model to provide explained variance and probabilities of improvement (p=%). 3 mg·kg-1 caffeine presented the highest probabilities of change compared with placebo across a range of tests (mean ± SD, p= %). Times for 20-m sprint were 3.15±0.10s vs 3.18±0.09s (p=73%), CoD-R times were 8.43±0.24s vs 8.55±0.25s (p=99%), CoD-L times were 8.44±0.22s vs 8.52±0.18s (p=85%), Yo-Yo IR1 distance was 2440±531m vs 2308±540m (p=15%), and preexercise CMJ height was 41.6±7.2cm vs 38±8.5cm (p=96%). Postexercise CMJ was higher with 3 mg·kg-1 than with placebo (42.3±8cm vs 36.6±8cm [p=100%]). Doses of 1 or 2 mg·kg-1 caffeine also demonstrated the ability to enhance performance but were task dependent. Low doses of caffeine improve performance but are dose and task dependent. A dose of 3 mg·kg-1 caffeine improved performance across the majority of tests with potential to further improve postexercise CMJ height.


#4 The efficacy of lower limb screening tests in predicting PlayerLoad within a professional soccer academy
Reference: J Sport Rehabil. 2018 Oct 9:1-20. doi: 10.1123/jsr.2018-0175. [Epub ahead of print]
Authors: Bowen C, Weaver K, Relph N, Greig M
Summary: Training exposure has been associated with injury epidemiology in elite youth soccer, where lower limb musculoskeletal screening is commonly used to highlight injury risk. However, there has been little consideration of the relationship between lower limb screening and the loading response to soccer activities. The purpose was to quantify the efficacy of using screening tests to predict the loading elicited in soccer-specific activities, and to develop a hierarchical ordering of musculoskeletal screening tests to identify test redundancy and inform practice. 21 elite male soccer players aged 15.7 ± 0.9 years participated in this study. Players completed a battery of five screening tests (knee to wall, hip internal rotation, adductor squeeze, single leg hop, anterior reach), and a 25min standardised soccer session with a GPS unit placed at C7 to collect multi-planar PlayerLoad data. Baseline data on each screening test, along with uni-axial PlayerLoad in the medio-lateral, anterio-posterior and vertical planes were utilized as outcome measures. Stepwise hierarchical modelling of the screening tests revealed that dominant leg knee to wall distance was the most prevalent and powerful predictor of multi-planar PlayerLoad, accounting for up to 42% of variation in uni-axial loading. The adductor squeeze test was the least powerful predictor of PlayerLoad. Of note, one player who incurred a knee injury within three weeks of testing had shown a 20% reduction in knee to wall distance compared with peers, and elicited 23% greater PlayerLoad, supporting the hierarchical model. There was some evidence of redundancy in the screening battery, with implications for clinical choice. Hierarchical ordering and a concurrent case study highlight dominant leg knee to wall distance as the primary predictor of multi-axial loading in soccer. This has implications for the design and interpretation of screening data in elite youth soccer.


#5 Differences in Sprint Mechanical Force-Velocity Profile Between Trained Soccer and Futsal Players
Reference: Int J Sports Physiol Perform. 2018 Oct 9:1-21. doi: 10.1123/ijspp.2018-0402. [Epub ahead of print]
Authors: Jiménez-Reyes P, García-Ramos A, Cuadrado-Peñafiel V, Párraga-Montilla JA, Morcillo-Losa JA, Samozino P, Morin JB
Summary: This study aimed to compare the sprint mechanical force-velocity (F-V) profile between soccer and futsal players. A secondary aim was, within each sport, to study the differences in sprint mechanical F-V profile between sexes and players of different levels. 102 soccer players (63 men) and 77 futsal players (49 men) that were competing from the elite to amateur levels in the Spanish league participated in this investigation. The testing procedure consisted of 3 unloaded maximal 40-m sprints. The velocity-time data recorded by a radar device was used to calculate the variables of the sprint acceleration F-V profile (maximal theoretical force [F0], maximal theoretical velocity [V0], maximal power [Pmax], decrease in the ratio of horizontal-to-resultant force [DRF], and maximal ratio of horizontal-to-resultant force [RFpeak]). Futsal players showed a higher F0 than soccer players (effect size [ES] range: 0.11 to 0.74), while V0 (ES range: -0.48 to -1.15) and DRF (ES range: -0.75 to -1.45) was higher for soccer players. No significant differences were observed between soccer and futsal players for Pmax (ES range: -0.43 to 0.19) and RFpeak (ES range: -0.49 to 0.30). Men and high-level players presented an overall enhanced F-V profile compared to women and their lower-level counterparts, respectively. The higher F0 and lower V0 of futsal players could be caused by the specific game's demand (larger number of accelerations but of shorter distances compared to soccer). These results show that the sprint mechanical F-V profile is able to distinguish between soccer and futsal players.


#6 The temporal pattern of recovery in eccentric hamstring strength post-soccer specific fatigue
Reference: Res Sports Med. 2018 Oct 8:1-12. doi: 10.1080/15438627.2018.1523168. [Epub ahead of print]
Authors: Rhodes D, McNaughton L, Greig M
Summary: Eccentric hamstring strength is an aetiological risk factor for soccer injury. The temporal pattern of recovery post-exercise is critical in injury management. 18 male professional soccer players completed baseline assessments of eccentric hamstring strength at isokinetic speeds of 60, 150 and 300°· s-1. Post SAFT90 measures were repeated immediately, + 24 hrs, + 48 hrs and + 72 hrs. Main effects for recovery time and testing speed in average torque (AvT), peak torque (PT) and the corresponding angle (Ɵ) were supplemented by regression modelling to describe the temporal pattern of recovery. A main effect for isokinetic testing speed was observed in PT and AvT. A main effect for recovery time highlighted greater strength pre-exercise, with a quadratic pattern to temporal recovery highlighting minima achieved at between 40-48 hrs. Strength parameters are not fully recovered until 96 hrs post soccer specific fatigue, with implications for training design and injury management, particularly within fixture-congested periods.


#7 Manual therapy and early return to sport in football players with adductor-related groin pain: A prospective case series
Reference: Physiother Theory Pract. 2018 Oct 11:1-10. doi: 10.1080/09593985.2018.1531096. [Epub ahead of print]
Authors: Tak I PhD, MScPT, Langhout R MMT PT, Bertrand B MScPT, Barendrecht M MPTS, Stubbe J PhD, Kerkhoffs G PhD, MD, Weir A PhD, MBBS
Summary: The purpose was to study the clinical course including return to sport success rates of football players with adductor-related groin pain (ARGP) after manual therapy of the adductor muscles. Thirty-four football players with ARGP with median pre-injury Tegner scores of 9 (IQR 25-75: 9-9) were treated with manual therapy of the adductor muscles. Main outcome measures were numeric pain rating scale (NPRS), Hip and Groin Outcome Score (HAGOS) and global perceived effect (GPE) for treatment and patient satisfaction at 2, 6 and 12 weeks. Return to sport was documented. Pain during (NPRS 7 (6-8) and after (NPRS 8 (6-8) sports decreased to NPRS 1 (0.2-3) and 1 (0.8-3), respectively (p < 0.001). Within 2 weeks 82% of the players returned to pre-injury playing levels with improved (p < 0.001) HAGOS subscale scores. Eighty-five percent reported clinically relevant improvement, 82% reported to be satisfied. At 12 weeks, 88% had returned to pre-injury playing levels. HAGOS showed symptoms were still present. Early return to sport seems possible and safe after manual therapy of the adductor muscles in football players with ARGP in the short term. While the majority of injured football players return to sport within two weeks, caution is advised regarding effectiveness as hip and groin symptoms were still present and no control groups were available.


#8 Effects of pitch spatial references on players' positioning and physical performances during football small-sided games
Reference: J Sports Sci. 2018 Oct 11:1-7. doi: 10.1080/02640414.2018.1523671. [Epub ahead of print]
Authors: Coutinho D, Gonçalves B, Travassos B, Abade E, Wong DP, Sampaio J
Summary: The aim of this study was to identify the effects of adding spatial references during football small-sided games in youth players' tactical and physical performance. Twelve under-15 players performed a Gk+ 6v6+ Gk game under two playing conditions: (i) without spatial references (CONTROL condition); (ii) with spatial references, by dividing equally the pitch into three corridors and three sectors (experimental situation, LINES). Players' positional data was used to compute time-motion and tactical-related variables. The results revealed that performance under LINES situation increased the regularity in the zones occupied (~14%, Cohen's d: 0.5; ±0.3; p = 0.003) and in the distance between teammates' dyads (~19%, 0.9; ±0.2; p < 0.001). Oppositely, LINES condition decreased the longitudinal synchronization of players' displacements (0.4; ±0.2; p = 0.002), players' average speed (0.5; ±0.3; p = 0.002) and distance covered at lower (0.9; ±0.3; p < 0.001) and moderate speed (0.5; ±0.3; p < 0.001). Adding spatial references seems to promote a more structured pattern of play and increase positional regularity. However, coaches should be aware that this constraint may decrease the synchronization between players. Overall, these findings may be generalized to most invasion team sports.


#9 Top 50 most-cited articles in medicine and science in football
Reference: BMJ Open Sport Exerc Med. 2018 Oct 1;4(1):e000388. doi: 10.1136/bmjsem-2018-000388. eCollection 2018.
Authors: Brito J, Nassis GP, Seabra AT, Figueiredo P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6173236/pdf/bmjsem-2018-000388.pdf
Summary: The purpose was to conduct a comprehensive mapping analysis to the scientific literature published in football aiming to identify the areas of bigger interest and potential for further exploration. The data were obtained by a search conducted on the Web of Science. Articles were listed based on citation frequency. We used an open-source bibliometrix R-package for the comprehensive bibliometric analyses. The number of citations per article ranged from 251 to 869 (median 323; IQR 125). The yearly number of citations ranged from 8 to 54 (median 26; IQR 11). Most of the articles (76%) were of level III of evidence, 10% were level II and 14% were level IV. Within the top 50 most-cited articles, 40 articles were original research (37 observational and 3 experimental studies), 9 were review articles and 1 was a thesis. From the 40 original research articles, 50% involved elite players, 73% were exclusive to male players and 80% involved adult players only. The topic area with the highest number of articles was sports medicine (44%), followed by training and testing (32%), performance analysis (14%) and physiology (10%). No study within the top 50 was devoted to biomechanics, nutrition, sport psychology, coaching or social sciences. The lack of experimental studies within the top 50 most-cited articles in football clearly underpins how far we still are from establishing the theoretical and methodological guidelines for the applied science and medicine in football.


#10 Effect of the Fatigue on the Physical Performance in Different Small-Sided Games in Elite Football Players
Reference: J Strength Cond Res. 2018 Oct 5. doi: 10.1519/JSC.0000000000002858. [Epub ahead of print]
Authors: Calderón Pellegrino G, Paredes-Hernández V, Sánchez-Sánchez J, García-Unanue J, Gallardo L
Summary: Football players need to be able to perform high-intensity efforts of short duration with brief recovery periods. The aim of this study was to analyze the influence of the pitch dimension on high-intensity actions and the effect of a repeated sprint ability (RSA) test on the physical performance in different 4-against-4 (4v4) small-sided games (SSG) dimensions. Sixteen U-18 elite football players performed an RSA test between two 4v4 SSGs (pre and post) to induce fatigue and compare physical data. Speed, sprint number, accelerations, sprint distance, total distance covered, and total distance covered of the players at different intensities were evaluated in 3 different SSGs (125, 150, 250, and 300 m). Results revealed a significant detriment of physical performance in the 125-m SSG after RSA, mostly in number of sprints (-6.56; confidence interval [CI] 95%: -10.13 to -3.00; effect size [ES]: 1.13 p < 0.001), accelerations (-2.69; CI 95%: -5.13 to -0.24; ES: 0.68; p = 0.032), and sprint distance (-65.44 m; CI 95%: -103.73 to -27.16; ES: 1.20; p = 0.001). In bigger SSGs (250 and 300 m), higher distance at high intensity was covered and Vmax, Vmean, and sprint distance were greater. In summary, accelerations, sprint number, and fatigue were higher in smaller pitches, and higher velocities were reached in bigger SSGs. Football players should be aware that changes in pitch size can modify the physical performance on high-intensity actions in SSGs.

Sun

04

Nov

2018

Latest research in football - week 39 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Examination of Physical Fitness Parameters Between Professional and Amateur Greek Soccer Players During the Transition Period
Reference: J Strength Cond Res. 2018 Oct 4. doi: 10.1519/JSC.0000000000002770. [Epub ahead of print]
Authors: Bekris E, Pidoulas G, Pidoulas P, Gissis I, Katis A, Komsis S
Summary: The aim of the study was to compare physical fitness parameters between professional and amateur soccer players of different levels. The sample consisted of 381 soccer players divided in 4 experimental groups: first division professional players (n = 115), second division professional players (n = 70), third division semiprofessional players (n = 93), and amateur soccer players (n = 103). Players were tested for several physiological parameters at the end of the transition period. Analysis of variance showed significantly lower body fat and increased maximum oxygen consumption (V[Combining Dot Above]O2max) and velocity of maximum oxygen consumption (vV[Combining Dot Above]O2max) values for first division professional players compared with the other experimental groups (p < 0.05). Similarly, first division professional players showed higher performance during squat jump and countermovement jump test compared with the other experimental groups (p < 0.05). Significant differences on flexibility test were observed between amateur players and the other group (p < 0.05). The results of the study indicated that Greek soccer players at the highest level overcome in almost all the underexamination physiological parameters probably because of less absence from training and better implementation of training programs during the transition period.


#2 Individualizing Acceleration in English Premier League Academy Soccer Players
Reference: J Strength Cond Res. 2018 Oct 4. doi: 10.1519/JSC.0000000000002875. [Epub ahead of print]
Authors: Abbott W, Brickley G, Smeeton NJ, Mills S
Summary: Global thresholds are typically used to band acceleration dependent on intensity. However, global thresholds do not account for variation in individual capacities, failing to quantify true intensity of acceleration. Previous research has investigated discrepancies in high-speed distance produced using global and individual speed thresholds, not yet investigated for acceleration. The current aim was to investigate discrepancies between global and individual thresholds when quantifying acceleration tasks. Acceleration data were recorded for 31 professional soccer players, using 10-Hz Global positioning systems devices. Distances traveled performing low-, moderate-, and high-intensity acceleration were calculated for athletes using global and individual thresholds. Global acceleration thresholds for low-, moderate-, and high-intensity acceleration were classified as 1-2, 2-3, and >3 m·s, respectively, with individual thresholds classified as 25-50%, 50-75%, and >75% of maximum acceleration, respectively. Athletes were grouped low (LO), medium (ME), or high (HI) maximum accelerative capacity, determined using 3 maximal 40-m linear sprints. Two-way mixed-design analyses of variance were used to analyze differences in acceleration distances produced between analysis methods and athlete groups. No significant differences were identified between analysis methods for LO. For ME, no significant differences were demonstrated for low intensity. Moderate- and high-intensity acceleration distances were significantly higher for global compared with individual analysis method (p < 0.01). For HI, significantly higher acceleration distances were produced for all acceleration intensities using global thresholds (p < 0.01). Significant differences identified between analysis methods suggest practitioners must apply caution when using global thresholds. Global thresholds do not account for individual capacities and may provide an inaccurate representation of relative intensity of acceleration tasks.


#3 Operative Treatment of Proximal Rectus Femoris Injuries in Professional Soccer Players: A Series of 19 Cases
Reference: Orthop J Sports Med. 2018 Oct 2;6(10):2325967118798827. doi: 10.1177/2325967118798827. eCollection 2018 Oct.
Authors: Lempainen L, Kosola J, Pruna R, Puigdellivol J, Ranne J, Orava S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168727/pdf/10.1177_2325967118798827.pdf
Summary: Proximal rectus femoris (PRF) tears are relatively rare injuries among top-level athletes. PRF injuries can be avulsions of both tendon heads (direct and reflected heads) or of a single head, and some have a tendency to progress to recurrent injuries. The purpose was to describe a series of operatively treated PRF ruptures in professional soccer players. Nineteen cases of PRF injuries (18 patients, 1 bilateral) in professional soccer players who were treated surgically were retrospectively reviewed. Perioperative findings with return-to-play data were recorded. Of the PRF injuries, 10 total avulsions (both heads) and 9 single-head tears were seen on magnetic resonance imaging and were later confirmed during surgery. All 18 patients returned to their preinjury level of play (mean follow-up, 2.8 years [range, 1-11 years]). The repair of PRF tears in professional soccer players yielded good results and allowed all patients to return to their preinjury level of play.


#4 Relationship Between Heart Rate Variability and Acute: Chronic Load Ratio Throughout a Season in NCAA D1 Men's Soccer Players
Reference: J Strength Cond Res. 2018 Oct 4. doi: 10.1519/JSC.0000000000002853. [Epub ahead of print]
Authors: Sekiguchi Y, Huggins RA, Curtis RM, Benjamin CL, Adams WM, Looney DP, West CA, Casa DJ
Summary: The purpose of this study was twofold: (a) to examine the relationship between heart rate variability (HRV) and acute:chronic workload ratio (ACWR)-based training load (TL) metrics and (b) to examine relationships across various A:C ratio-based TL metrics. Heart rate variability in 23 male college soccer players (mean ± SD; age, 21 ± 1 years; body mass, 80.3 ± 5.8 kg; height, 181.9 ± 6.5 cm; %body fat, 11.9 ± 2.0%; and V[Combining Dot Above]O2max, 51.9 ± 5.0 ml·kg·min) was measured at 5 time points: week(W)1, W3, W7, W12, and W14 during the 2015 NCAA men's soccer season. Heart rate variability was calculated from beat to beat intervals using a heart rate monitor. Players donned a global position satellite-enabled device that measured the following TL metrics: session time (ST), Player Load (PL), PL·min, and total distance (TD). Acute:chronic workload ratio was calculated for each TL metric: ACWR-based ST (ACWRST), ACWR-based PL (ACWRPL), ACWR-based PL·min (ACWRPLM), and ACWR-based TD (ACWRTD): ACWR = week average TLs/mo average (30 ± 1 days) TLs. Relationships between HRV and ACWR-based each TL metric were evaluated using mixed effects models. Tukey pairwise comparisons were used to examine differences between types of ACWR-based TL metrics. An increase in ACWRST significantly reduced HRV throughout a season (-7.4 ± 3.6 m·s; p = 0.04). There were significant differences between ACWRPLM and ACWRST, ACWRPL and ACWRTD at W1, ACWRPLM and ACWRST at W3 (p < 0.05). In conclusion, ACWRST, ACWRPL, and ACWRTD were significantly different from ACWRPLM. ACWRST was found to significantly predict HRV; higher ACWRST was significantly associated with lower HRV. Therefore, tracking of the ACWR using ST may help to optimize athlete's physiological state throughout a season.


#5 The effects of a calf pump device on second half performance of a simulated soccer match in competitive youth players
Reference: J Sports Sci. 2018 Oct 4:1-9. doi: 10.1080/02640414.2018.1522947. [Epub ahead of print]
Authors: Béliard S, Cassirame J, Ennequin G, Coratella G, Tordi N
Summary: During soccer matches, performance decrements have been reported that relate to both physical abilities and technical skills. To investigate the effects of low-frequency electrical stimulation LFES (VeinoplusSport®, Ad Rem Technology, France) administered during half-time recovery on performance alterations during the second half. Twenty-two highly trained young players undertook a soccer-match simulation (SAFT90). During half-time, they were randomly assigned to LFES group or Placebo group. Each half was split into 3 bouts of 12 minutes. Following each bout, maximal strike speed (MSS), sprint test (ST), maximal sprint accelerations (MA) and metabolic power (MP) were determined in both groups. Arterial (AF) and venous flows (VF) were measured at rest and at the end of half-time. LEFS group exhibited beneficial effects on performance compared to the Placebo group with a likely effect for MSS, ST, MA, and a possible effect for MP. AF and VF increased statistically more in LEFS group compared to Placebo group. The use of specific calf-pump LFES during half-time of a youth simulated soccer match attenuated the decrease in performance during the second half compared to Placebo group. This effect is most marked at the beginning of the second half with regards to explosive parameters.


#6 Does Early Recruitment Predict Greater Physical Performance in Academy Soccer Players?
Reference: Sports (Basel). 2018 Sep 30;6(4). pii: E108. doi: 10.3390/sports6040108.
Authors: Hertzog M, Paul DJ, Nassis GP, Silva JR
Summary: The purpose of this longitudinal study was to investigate whether recruitment status influences neuromuscular and endurance performances in academy soccer players over a 2-year training period (from Under-16 to Under-18). Thirty-seven male soccer players from an elite academy were selected and divided in two cohorts according to their recruitment status: Early Recruitment group (ER; n = 16), training and competing for the academy since Under-14 and Under-15 age groups, and; Late Recruitment group (LR; n = 21) included in the academy training process at Under-16. Squat (SJ) and countermovement jump with (CMJwA) and without arms swing (CMJ), 10-m sprint time, and Vam-Eval test (MAV) were performed in three successive occasions always pre-season (Under-16, Under-17 and Under-18 age groups, T1, T2, and T3 respectively). A two-way (recruitment status × time) analysis of variance with repeated measurements was performed as well as the magnitude of difference using both effect size and magnitude-based inferences. There was no difference between ER and LR for MAV, 10 m-sprint, and SJ from T1 to T3. However, LR players presented non-significant small and possibly greater improvement in CMJ (ES = 0.4) and CMJwA (ES = 0.4) than ER players at T2. These data indicate that early recruitment is not likely to result in greater physical performance improvement at the age of 18.


#7 Relationship of Absolute and Relative Lower-Body Strength to Predictors of Athletic Performance in Collegiate Women Soccer Players
Reference: Sports (Basel). 2018 Sep 29;6(4). pii: E106. doi: 10.3390/sports6040106.
Authors: Andersen E, Lockie RG, Dawes JJ
Summary: The purpose of this study was to investigate the relationships between absolute and relative lower-body strength on predictors of athletic performance among Division II collegiate women's soccer players. Archived pre-season testing data for seventeen (n = 17) female National Collegiate Athletics Association (NCAA) Division II soccer players were analyzed, including: vertical jump, 3RM back squat, 505-agility, modified T-test, 10 m and 30 m sprint, and 20 m multistage fitness test (20 m MSFT). Relative strength was calculated based on the estimated 1RM back squat divided by the athlete's body mass. Significant correlations were discovered between absolute lower-body strength and 505-agility (Right: r = -0.51, p < 0.05; Left: r = -0.59, p < 0.05), modified T-test (r = -0.55, p < 0.05), 10 m and 30 m (r = -0.59, p < 0.05; r = -0.54, p < 0.05), and sprint performance. Relative lower-body strength showed significant correlations with vertical jump (r = 0.54, p < 0.05), 505-agility (Right: r = -0.58, p < 0.05; Left: r = -0.67, p < 0.01), modified T-test (r = -0.75, p < 0.01), 10 m and 30 m (r = -0.59 p < 0.05; r = -0.67, p < 0.01), and the 20 m MSFT (r = 0.58, p < 0.05). These results indicate that strength and conditioning coaches should emphasize the development of absolute and relative lower-body strength with their players to improve power, agility, and speed performance.


#8 Effects of the '11+ Kids' injury prevention programme on severe injuries in children's football: a secondary analysis of data from a multicentre cluster-randomised controlled trial
Reference: Br J Sports Med. 2018 Oct 2. pii: bjsports-2018-099062. doi: 10.1136/bjsports-2018-099062. [Epub ahead of print]
Authors: Beaudouin F, Rössler R, Aus der Fünten K, Bizzini M, Chomiak J, Verhagen E, Junge A, Dvorak J, Lichtenstein E, Meyer T, Faude O
Summary: The purpose of the study was to assess the effects of the injury prevention programme '11+ Kids' on reducing severe injuries in 7 to 13 year old football (soccer) players. Football clubs (under-9, under-11 and under-13 age groups) from the Czech Republic, Germany, the Netherlands and Switzerland were cluster-randomised (clubs) into an intervention (INT) and a control group (CON). INT replaced their usual warm-up by '11+ Kids' two times a week. CON followed their regular training regime. Match and training exposure and injury characteristics were recorded and injury incidence rates (IRs) and 95% CIs calculated. For the present analysis, only severe injuries (absence from training/match ≥28 days) were considered. Hazard ratios (HR) were calculated using extended Cox models. The overall IR of severe injuries per 1000 football hours was 0.33 (95% CI 0.25 to 0.43) in CON and 0.15 (95% CI 0.10 to 0.23) in INT. There was a reduction of severe overall (HR 0.42, 95% CI 0.24 to 0.72), match (0.41, 0.17 to 0.95) and training injuries (0.42, 0.21 to 0.86) in INT. The injury types that were prevented the most were: other bone injuries 66%, fractures 49% and sprains and ligament injuries 37%. Severe injuries located at the knee (82%), hip/groin (81%), the foot/toe (80%) and the ankle (65%) were reduced tremendously. '11+ Kids' has a large preventive effect on severe injuries by investing only 15 to 20 min per training session. The present results should motivate coaches to implement effective injury prevention programmes such as the '11+ Kids' in children's football.


#9 Jumping performance based on duration of rehabilitation in female football players after anterior cruciate ligament reconstruction
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Sep 28. doi: 10.1007/s00167-018-5154-5. [Epub ahead of print]
Authors: Arundale AJH, Kvist J, Hägglund M, Fältström A
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-018-5154-5.pdf
Summary: The purpose was to determine if female football players who had longer durations of rehabilitation, measured in months, after anterior cruciate ligament reconstruction would have lower tuck jump scores (fewer technique flaws) and smaller asymmetries during drop vertical jump landing. One-hundred-and-seventeen female football players, aged 16-25 years, after primary unilateral ACL reconstruction (median 16 months, range 6-39) were included. Athletes reported the duration of rehabilitation they performed after anterior cruciate ligament reconstruction. Athletes also performed the tuck jump and drop vertical jump tests. Outcome variables were: tuck jump score, frontal plane knee motion and probability of peak knee abduction moment during drop vertical jump landing. There was no difference in tuck jump score based on duration of rehabilitation (n.s.). No interaction (n.s.), difference between limbs (n.s.), or duration of rehabilitation (n.s.) was found for peak knee abduction moment during drop vertical jump landing. No interaction (n.s.) or difference between limbs (n.s.) was found for frontal plane knee motion, but there was a difference based on duration of rehabilitation (P = 0.01). Athletes with > 9 months of rehabilitation had more frontal plane knee motion (medial knee displacement) than athletes with < 6 months (P = 0.01) or 6-9 months (P = 0.03). As there was no difference in tuck jump score or peak knee abduction moment based on duration of rehabilitation, the results of this study press upon clinicians the importance of using objective measures to progress rehabilitation and clear athletes for return to sport, rather than time alone.

Fri

02

Nov

2018

Latest research in football - week 38 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Physical responses of professional soccer players during 4 vs. 4 small-sided games with mini-goals according to rule changes
Reference: Biol Sport. 2018 Mar;35(1):75-81. doi: 10.5114/biolsport.2018.70754. Epub 2017 Oct 12.
Authors: Giménez JV, Liu H, Lipińska P, Szwarc A, Rompa P, Gómez MA
Summary: The aim of this study was to investigate the influence of the number of ball touches authorised per game (one touch [T1], two touches [T2], and free touches [FT]) on the players' physical responses throughout the bouts in 4 vs 4 soccer small-sided games (SSGs) with mini-goals (without a goalkeeper). Fourteen professional Polish players (age 23.2±2.7 years, height 177.9±6.1 cm, weight: 73.2±6.9 kg, body fat 12.6±2%, playing experience: 14±5 years) completed nine series of 4 vs 4 SSGs. Each trial included three series of SSGs with a game duration of 4 minutes on an equal sized pitch (30x24 m; 720 m2; individual occupied area per player=90 m2). Differences in physical responses and time-motion characteristics of players were measured with the Global Positioning System (GPS) and assessed using a repeated measures ANOVA to compare the three game conditions and the magnitude-based inference to evaluate the pairwise comparison effects. The results showed that only the variables distance covered at low speed, time walking, time at low speed, and accelerations of >4 m/s² were statistically significantly different among game conditions. The pairwise comparisons only identified significant effects for distance covered at low speed (between FT and T2), for time walking (between FT and T1), for time at moderate and low speed (between FT and T2), and for accelerations of >4 m/s² (between FT and T1). The players' performances are affected by the ball touch constraint during SSGs with mini-goals. The results provide useful information for training and task design that replicate specific physical demands (i.e., accelerations of >4 m/s², time walking or running at a lower speed).


#2 Associations between wellness and internal and external load variables in two intermittent small-sided soccer games
Reference: Physiol Behav. 2018 Sep 17. pii: S0031-9384(18)30619-X. doi: 10.1016/j.physbeh.2018.09.008. [Epub ahead of print]
Authors: Clemente FM
Summary: The purpose of this study was to test the associations between wellness and internal and external load variables during two intermittent small-sided games (SSGs). Ten male amateur soccer players (age: 19.8±1.6 years; experience: 8.3±2.1 years; height: 177.4±3.8 cm; weight: 71.7±4.2 kg) voluntarily participated in this study. The 5 × 5 format was played in 3 × 6 min and 6 × 3 min regimens. Muscle soreness (DOMS), stress, fatigue, and sleep quality were rated before each session. Perceived exertion (RPE); mean heart rate (HRmean); total (TD), jogging (JD), running (RD), and sprinting (SD) distances; player's training load (PTL); and total accelerations (TAc) were monitored during SSGs. In the case of the 3 × 6' regimen, large negative correlations between DOMS and TD (-0.68, [-0.89; -0.20]), JD (-0.66, [-0.89; -0.17]) and SD (-0.63, [-0.88; -0.12]) were found, and very large negative correlations between DOMS and PTL (-0.84, [-0.95; -0.53]) were found. Very large (-0.73, [-0.91; -0.30] and large (-0.61, [-0.87; -0.09]) negative correlations between DOMS and HRmean and PTL, respectively, were observed during the 6 × 3' regimen. Regarding the associations between load variables, during the 6 × 3' regimen, RPE was very largely correlated with TD (0.77, [0.37; 0.93]), JD (0.70, [0.25; 0.90]) and largely correlated with TAc (0.67, [0.19; 0.89]). In the 3 × 6' regimen, large correlations were found between RPE and SD (0.62, [0.10; 0.87]) and TAc (0.61, [0.09; 0.87]). Overall, PTL was nearly perfectly correlated with TD (0.96, [0.86; 0.99]) and JD (0.94, [0.81; 0.98]), very largely correlated with TAc (0.87, [0.61; 0.96]), and largely correlated with RD (0.72, [0.29; 0.91]). The results of this study suggest that wellness status may influence workload in SSGs; in particular, DOMS may be moderately-to-largely detrimental to both internal and external load variables. Moreover, it was confirmed that RPE is moderately-to-largely correlated to objectively measured external load variables.


#3 Influence of contextual variables and the pressure to keep category on physical match performance in soccer players
Reference: PLoS One. 2018 Sep 20;13(9):e0204256. doi: 10.1371/journal.pone.0204256. eCollection 2018.
Authors: García-Unanue J, Pérez-Gómez J, Giménez JV, Felipe JL, Gómez-Pomares S, Gallardo L, Sánchez-Sánchez J
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0204256&type=printable
Summary: Previous studies have analysed the influence of contextual variables on performance and physical demands in soccer. However, the points needed to remain in the category have been an element that has not been analysed previously. The aim of the present study was to investigate the influence of match location, match period, strength of the opponent and the points required to keep category on physical performance in professional soccer players. Fourteen Spanish second B Division League matches played by a professional football team were analysed during the 2016/17 season using GPS devices. The 10 main players of each match used the GPS throughout the match. The variables of Total Distance (m), High Intensity Distance (m), High intensity Accelerations (n), Sprint Time (s) and Sprint Distance (m) were analysed. The most notable differences are found in Total Distance covered. Away games accumulated significantly more distance than those played at home, but only in the second half (+230.65 m, IC95%: 21.94 to 438.19, ES: 0.46, p = 0.031). There are no differences depending on the strength of the opponent. However, players covered greater distances during the first half in those matches that were played furthest from salvation (+235.86 m, 95% CI: 49.03 to 422.70, ES: 0.51, p = 0.014). Total Distance is the main parameter affected by situational variables. In addition, the pressure of being further away from saving the category increases the distance covered by players in a game.


#4 Heading in soccer increases serum neurofilament light protein and SCAT3 symptom metrics
Reference: BMJ Open Sport Exerc Med. 2018 Aug 27;4(1):e000433. doi: 10.1136/bmjsem-2018-000433. eCollection 2018.
Authors: Wallace C, Smirl JD, Zetterberg H, Blennow K, Bryk K, Burma J, Dierijck J, Wright AD, van Donkelaar P
Download link: https://bmjopensem.bmj.com/content/bmjosem/4/1/e000433.full.pdf
Summary: The purpose was to determine the effect of heading a soccer ball on serum neurofilament light (NF-L) protein, plasma tau protein and symptom metrics including total number of symptoms reported and symptom severity scores on the Standardized Concussion Assessment Tool- 3rd edition (SCAT3). Eleven male collegiate soccer players were recruited to take part in three experimental conditions including heading, sham and control conditions. Participants were required to perform 40 headers in 20 min in the heading condition, and control 40 soccer balls directed at them with their hands, chest or thigh in the sham condition. No ball contact was made during the control condition. Blood sampling and SCAT3 symptom assessments were completed prior to and 1 hour following conditions. A subset of participants returned 3 weeks following the heading condition for blood sampling. NF-L was elevated at 1 hour (p=0.004) and 1 month (p=0.04) following the heading condition, and at 1 hour (p=0.02) following the control condition. Tau levels remained unchanged following all conditions. The total number of symptoms (TS) and symptom severity (SS) scores from the SCAT3 were both elevated following the heading condition (p=0.01 and p=0.03, respectively). Both TS and SS decreased following sham (p=0.04 and p=0.04) and control conditions (p=0.04 and p=0.04). An acute bout of soccer heading is associated with increased NF-L concentrations at 1 hour and 1 month following the session and can lead to symptoms commonly reported following sport-related concussion.


#5 How sprinters accelerate beyond the velocity plateau of soccer players: waveform analysis of ground reaction forces
Reference: Scand J Med Sci Sports. 2018 Sep 19. doi: 10.1111/sms.13302. [Epub ahead of print]
Authors: Colyer SL, Nagahara R, Takai Y, Salo AIT
Summary: Forces applied to the ground during sprinting are vital to performance. This study aimed to understand how specific aspects of ground reaction force waveforms allow some individuals to continue to accelerate beyond the velocity plateau of others. Twenty-eight male sprint specialists and 24 male soccer players performed maximal-effort 60-m sprints. A 54-force-plate system captured ground reaction forces, which were used to calculate horizontal velocity profiles. Touchdown velocities of steps were matched (8.00, 8.25 and 8.50 m·s-1 ) and the subsequent ground contact forces were analysed. Mean forces were compared across groups and statistical parametric mapping (t-tests) assessed for differences between entire force waveforms. When individuals contacted the ground with matched horizontal velocity, ground contact durations were similar. Despite this, sprinters produced higher average horizontal power (15.7-17.9 W·kg-1 ) than the soccer players (7.9-11.9 W·kg-1 ). Force waveforms did not differ in the initial braking phase (0-~20% of stance). However, sprinters attenuated eccentric force more in the late braking phase and produced a higher anteroposterior component of force across the majority of the propulsive phase, for example from 31-82% and 92-100% of stance at 8.5 m·s-1 . At this velocity, resultant forces were also higher (33-83% and 86-100% of stance) and the force vector was more horizontally orientated (30-60% and 95-98% of stance) in the sprinters. These findings illustrate the mechanisms which allowed the sprinters to continue accelerating beyond the soccer players' velocity plateau. Moreover, these force production demands provide new insight regarding athletes' strength and technique training requirements to improve acceleration at high velocity.


#6 Outcome after Combined Lateral Extra-articular Tenodesis and Anterior Cruciate Ligament Revision in Professional Soccer Players
Reference: J Knee Surg. 2018 Sep 18. doi: 10.1055/s-0038-1672120. [Epub ahead of print]
Authors: Alessio-Mazzola M, Formica M, Russo A, Sanguineti F, Capello AG, Lovisolo S, Felli L
Summary: We report the functional outcome after combined anterior cruciate ligament (ACL) reconstruction and lateral extra-articular tenodesis (LET) for ACL re-rupture and high-grade pivot shift in professional soccer players. For this retrospective review, the medical records of 24 professional soccer players were analyzed. The mean age at surgery was 23.8 ± 4.2 years and the mean follow-up was 42.2 ± 16.9 months. Pre- and postoperative assessment included the KT-1000 Lachman test, pivot shift test, International Knee Documentation Committee (IKDC) subjective knee evaluation, Tegner activity scale (TAS), and Lysholm score. The rate of return to sports and the level of play at final follow-up were recorded. ACL revision was performed with an autologous bone-patellar tendon-bone autograft or a hamstring graft. LET was performed using an extra-articular MacIntosh procedure as modified by Arnold-Coker. Anterior-posterior laxity was significantly reduced at the final clinical assessment (p < 0.0001): 22 patients (91.7%) had a negative pivot shift and 2 (8.3%) had residual glide (+), with significant improvement (p < 0.0001). The mean subjective IKDC and Lysholm score improved from 69.5 ± 11.1 (range: 56-90) to 88.4 ± 8.9 (range: 62.1-100) and from 58.1 ± 11.7 (range: 33-72) to 97.4 ± 3.2 (range: 88-100), respectively, with significant improvement (p  < 0.0001) over preoperative values. The overall failure rate was 8.3%. There were no differences between mean preinjury and final TAS scores (p > 0.05). The rate of return to sports at the same level was 91.7% and the mean time to return to sports was 9.2 ± 2.2 months. Mid-term functional outcome after combined extra-articular reconstruction and ACL revision surgery was satisfactory, with a reduction in residual postoperative rotatory instability and degree of pivot shift.


#7 Efficacy of Injury Prevention Training Is Greater for High-Risk vs Low-Risk Elite Female Youth Soccer Players
Reference: Am J Sports Med. 2018 Sep 18:363546518795677. doi: 10.1177/0363546518795677. [Epub ahead of print]
Authors: De Ste Croix M, Hughes J, Ayala F, Taylor L, Datson N
Summary: The efficacy of robustness training for high- versus low-risk individuals within high-risk groups is currently unknown. The purpose was to explore the efficacy of robustness training on injury risk factors among female youth soccer players and to examine if high-risk athletes are greater responders to such training. A total of 125 elite youth female soccer players on the English FA talent pathway were randomly selected into a training group (n = 71) or a control group (n = 54). Relative leg stiffness, 2-dimensional knee valgus and knee flexion range of motion from a single-legged countermovement jump, and probability of high knee abduction moment (pKAM) risk were all determined before and after a 16-week robustness training program. For further analysis, participants in the training group were split into groups based on risk: high risk (pKAM >0.80, n = 33) and low risk (pKAM <0.55, n = 33). Magnitude-based inferences were used to explore differences between the control and intervention groups and the high- and low-risk groups. Magnitude-based inferences demonstrated significant beneficial effects in the training group for knee valgus, pKAM, and leg stiffness as compared with the control group. The control group demonstrated possible worthwhile differences in knee flexion range of motion as compared with the intervention group. The high-risk group demonstrated likely/very likely worthwhile differences versus the low-risk group for all parameters. Robustness training induces significant beneficial improvements in injury risk factors among female youth soccer players. The beneficial effects of this multidimensional program are greater for those classified as high risk.


#8 Functional Movement Patterns and Body Composition of High-Level Volleyball, Soccer and Rugby Players
Reference: J Sport Rehabil. 2018 Sep 17:1-20. doi: 10.1123/jsr.2018-0087. [Epub ahead of print]
Authors: Campa F, Piras A, Raffi M, Toselli S
Summary: Sports practice leads athletes to develop a specific body composition, coordination patterns and basic motor skills based on the different tactical and physical needs. This study aimed to present and compare a wide range of functional movement patterns and body composition (BC) parameters of high-level male athletes playing different sports, and to determine if there was a relationship between the parameters examined. Thirty volleyball, twenty-five soccer and thirty rugby players (age 25.9±5.0 years, BMI 25.6±4.1 kg/m2) participated in this study. Functional movement patterns and anthropometric measurements were collected by a physician specifically trained. BMI, fat mass, fat free mass, upper arm muscle and fat area, calf muscle and fat area, thigh muscle and fat area, and functional movement screen (FMS) scores. In addition to considering the FMS total score, we separated the screen into 3 parts: FMSmove, FMSflex and FMSstab. The rugby players showed a higher number of asymmetrical and dysfunctional movements than the other athletes (p <0.01), while the highest scores in FMSflex were obtained by the volleyball players (p <0.01). Additionally, most of the asymmetrical and painful movements in the athletes were measured on the shoulder mobility test. Muscle and fat areas differed significantly among the athletes (p <0.05). Significant associations were found between movement patterns and several BC variables. In particular, large negative correlations were measured between percentage of fat mass (r = -0.616; p <0.01), upper arm fat area (r = -0.519; p <0.01) and FMS total score. Functional movement patterns and BC differ in athletes according to the sport practiced. Furthermore, reaching an optimal BC is essential to achieve a satisfactory quality of movement.


#9 The Effect of a 20-Week Corrective Exercise Programme on Functional Movement Patterns in Youth Elite Male Soccer Players
Reference: J Sport Rehabil. 2018 Sep 17:1-18. doi: 10.1123/jsr.2018-0039. [Epub ahead of print]
Authors: Campa F, Spiga F, Toselli S
Summary: Poor functional movement patterns negatively affect the ability to perform fundamental movements with precision and efficiency, increasing injury risk in athletes. The purpose was to examine the effect of a 20-week corrective exercise programme during the competitive season on functional movement patterns in youth elite male soccer players. 65 youth elite male soccer players (age 15.89 ± 0.53 years; weight 67.42 ± 6.78 kg; stature 175.20 ± 6.34 cm) participated in this study. Two of four teams were randomly selected to take part in the corrective programme. Thus, the players were placed into two groups: corrective exercise programme (CEP) and control group (CON). Functional movement screen (FMS) was used to assess the presence of dysfunctional, asymmetrical and painful movements in the players before and after the intervention period. In addition to considering the FMS total score (FMStotal), we separated the screen into 3 parts: FMSmove, FMSflex and FMSstab. A repeated measures ANOVA was conducted to determine the effectiveness of the training programme on FMS scores. The chi-square (χ2) test was performed to determine whether there were significant changes in the frequencies of asymmetric and dysfunctional movements after 20 weeks. No athlete experienced severe injuries during the intervention period. There was a significant group by time interaction (P < 0.01) for FMStotal, FMSmove and FMSstab, in which only the CEP increased their scores after the intervention period (P < 0.05). A χ2 analysis showed a significant (P < 0.05) decrease in asymmetric and dysfunctional movements at the follow-up in CEP, while these changes were not observed in CON. Youth elite soccer players demonstrate a high prevalence of asymmetric movements during FMS testing, but their functional movement patterns can be improved during the competitive season following a specific corrective exercise programme.


#10 Leg strength and power in Polish striker soccer players
Reference: Acta Bioeng Biomech. 2018;20(2):109-116
Authors: Buśko K, Górski M, Nikolaidis PT, Mazur-Różycka J, Łach P, Staniak Z, Gajewski J
Summary: The main goal of the present study was to examine muscle strength and power of dominant and non-dominant leg, knee extensors and flexors, and their correlations with jumping performances in soccer players. A secondary aim was to evaluate muscle sense. 31 male professional strikers (age 20.9 ± 2.3 years, body mass 75.1 ± 6.6 kg, body height 179.5 ± 4.7 cm) participated in the study. The power output of lower extremities and the height of rise of the body mass centre during vertical jumps were measured using a force plate. The maximum muscle torque of the flexors and extensors of the knee were measured under isometric conditions using a special isometric torquemeter. Force sense was measured in isometric conditions in two tests: (a) fifty percent of the maximal voluntary contraction was set as a value of target force and the participants were instructed to reproduce the target force, (b) the participants attempted to develop a torque reproducing a sine course within the range of 10 to 50% of MVC performed. A direct relationship was observed between the peak muscle torque in knee extensors developed during isokinetic contraction at all velocities and power and height of three types of vertical jumps ( p <0.05). No correlation was observed between jumping performance and muscle torque under isometric condition. No differences were found in strength and jumping abilities as well as in force sense between dominant and non-dominant legs. This study offered a comprehensive and complete evaluation of leg muscle strength, sense and power, with the use of using force plate and isokinetic dynamometry.


#11 Nordic Hamstring Strength of Highly Trained Youth Football Players and Its Relation to Sprint Performance
Reference: J Strength Cond Res. 2018 Sep 19. doi: 10.1519/JSC.0000000000002800. [Epub ahead of print]
Authors: Markovic G, Sarabon N, Boban F, Zoric I, Jelcic M, Sos K, Scappaticci M
Summary: We aimed to characterize Nordic hamstring (NH) strength and bilateral NH strength asymmetry in highly trained youth footballers and to investigate the relationship between NH strength and sprint performance. Twenty-two adult and 133 highly trained youth footballers in the age groups U12-U18 participated in this study. Eccentric hamstring strength was assessed using the NH device. Youth footballers (n = 119) also performed 20-m sprint test. Age-related changes in absolute and relative NH strength, and bilateral NH strength asymmetry were analyzed using 1-way analysis of variance. The linear relationship between relative NH strength and sprint performance was established using a Pearson correlation analysis. Significant age-related increases (F = 3.6-18.9; all p < 0.01) in NH strength were reported for all units except N·kg (F = 1.9; p = 0.08). The largest differences in absolute NH strength were seen between U15 and U16 groups. Bilateral NH strength asymmetry varied from 8 to 16% (F = 1.8; p = 0.09) across all age groups. A large correlation between NH strength and sprint performance was observed (r = -0.52; p < 0.01). Our results indicate that NH strength increases nonlinearly with players' age, with the highest values observed in U16 group. Furthermore, bilateral NH strength asymmetry varied nonsignificantly between 8 and 16%. Finally, 27% of variance of sprint performance of youth footballers could be explained by relative NH strength. The reported NH strength data could be used as normative standards during testing and training of youth football players. Present results also suggest that coaches should pay close attention to eccentric hamstring function in youth footballers.


#12 Venous versus capillary sampling for total creatine kinase assay: Effects of a simulated football match
Reference: PLoS One. 2018 Sep 20;13(9):e0204238. doi: 10.1371/journal.pone.0204238. eCollection 2018.
Authors: de Oliveira DCX, Frisselli A, de Souza EG, Stanganelli LCR, Deminice R
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0204238&type=printable
Summary: Capillary rather than venipuncture may be a simpler and less invasive blood collection protocol that would increase the number of potential sampling tests. However, if capillary sampling can be used as an alternative to venipuncture to determine changes in plasma, total creatine kinase (CK) activity in response to a football training session is poorly known. This study aims to determine whether capillary blood sampling would provide representative measures of total CK activity compared to venipuncture in response to a football training session-induced elevated CK plasma levels. Twenty-two players from an under-19 football team performed a simulated football match with 11 players on each team for 90 minutes total duration (two halves of 45 minutes with 15 minutes rest between). Venous and ear lobe capillary blood samples were collected before and after (24h and 48h) the training session. Athletes retested for three consecutive days after exercise during the recovery week. The simulated match significantly increased (P< 0.05) total CK activity as determined in both venous (1.7-fold) and capillary (1.9-fold) blood sampling. Total CK activity determined using capillary samples demonstrated significant correlation (r = 0.85; P < 0.01) and an elevated concordance Lin index (pc = 0.80) when compared to venous sampling total CK. The Bland-Altman plot showed capillary sampling CK overestimated venous CK levels by 130 U/L (61%), with moderated variance and low bias. Our results demonstrated that capillary sampling for total CK activity assay may be considered a reliable alternative to venipuncture to determine changes in plasma total CK activity in response to a football training session.


#13 Motivational Climate in Youth Football Players
Reference: Behav Sci (Basel). 2018 Sep 15;8(9). pii: E83. doi: 10.3390/bs8090083.
Authors: Castro-Sánchez M, Zurita-Ortega F, Ubago-Jiménez JL, Ramírez-Granizo IA, Chacón-Cuberos R
Download link: www.mdpi.com/2076-328X/8/9/83/pdf
Summary:  In recent decades, the psychology of sport has gained special relevance in this field, due to the influence of psychological variables on sports performance and the regularity of sports practice. The aim of this research is to analyse the motivational climate of footballers. This study uses a descriptive cross-sectional design on a sample of 156 adolescent football players, using an ad-hoc questionnaire for the recording of socio-demographic variables and the PMCSQ-2 questionnaire on motivational climate in sport. The results of the present investigation indicate that footballers are more oriented towards task than ego, sportsmen who compete in Honor Division being the those who are more oriented towards ego and those of National Division being more oriented towards task. The main conclusion of this research is those who are the motivational climate is related to the division in which the players compete.


#14 Comparative Effects of Tensioning and Sliding Neural Mobilization on Static Postural Control and Lower Limb Hop Testing in Football Players
Reference: J Sport Rehabil. 2018 Sep 17:1-24. doi: 10.1123/jsr.2017-0374. [Epub ahead of print]
Authors: Ferreira J, Bebiano A, Raro D, Martins J, Silva AG
Summary: Context Sliding and tensioning neural mobilization are used to restore normal function of the nervous system, but impose different stresses to it. Particularly, sliding induces greater nerve excursion than tensioning. Conceivably, they might impact nervous system function differently. Objective To compare the effects of tensioning neural mobilization versus sliding neural mobilization of the dominant lower limb on static postural control and hop testing. Design Randomized, parallel and double blinded trial. Setting/Participants Thirty-seven football players. Intervention(s) Participants were randomized into two groups: sliding neural mobilization (n=18) or tensioning neural mobilization (n=19) targeting the tibial nerve. Main Outcome Measures Static postural sway was assessed with a force plate and functional performance with hop tests. Measurements were taken at baseline, after the intervention and at 30 minutes follow up. Results There was a significant effect of time for the center of pressure total displacement and velocity (p<0.05), for the single leg hop test (p<0.05), the 6 meters timed hop test (p<0.05) and the crossover hop test (p<0.05), but no significant effect of the intervention. Conclusion Sliding and tensioning neural mobilization improved postural control and hop testing in football players, and improvements remained 30 minutes after the intervention. Additional research examining the influence of neural mobilization on sensory motor impairments, postural control and functional performance is needed.

Fri

02

Nov

2018

Latest research in football - week 37 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Dynamic balance asymmetries in pre-season injury-prevention screening in healthy young soccer players using the Modified Star Excursion Balance Test-a pilot study
Reference: J Phys Ther Sci. 2018 Sep;30(9):1141-1144. doi: 10.1589/jpts.30.1141. Epub 2018 Sep 4.
Authors: Gkrilias P, Zavvos A, Fousekis K, Billis E, Matzaroglou C, Tsepis E
Summary: The purpose of this preliminary study was to investigate whether young players with no history of injury, have developed early asymmetries in dynamic balance ability tested via the recommended for screening in sports, Modified Star Excursion Balance Test (MSEBT). Twenty-four young healthy male soccer players participated in the study having at least 4 years of systematic soccer training. The Waterloo Footedness Questionnaire was used to discriminate the stability dominant leg (STAB) from the non-stability dominant leg (NSTAB). Dynamic balance was assessed via the MSEBT. Participants, after familiarization, made 3 attempts in each direction for both legs: a) Anterior (AN), b) Posterolateral (PL) and c) Posteromedial (PM). The sole statistically significant performance asymmetry was in the PL direction, in favor of the STAB (94.5 ± 13.3 cm vs. 98.1 ± 10.4 cm). The results of this pilot study showed a potential for developing dynamic balance asymmetries, in soccer players at the age of 13-14 years. Since asymmetry was significant in only one direction, further long term monitoring would be helpful to evaluate whether this is a growing functional deficit, potentially involving any of the other two directions of testing or if it is alleviated with increasing training age. These asymmetries could comprise an injury risk factor.


#2 Energy Balance Coexists With Disproportionate Macronutrient Consumption Across Pretraining, During Training, and Posttraining Among Indian Junior Soccer Players
Reference: Pediatr Exerc Sci. 2018 Sep 12:1-10. doi: 10.1123/pes.2017-0276. [Epub ahead of print]
Authors: Cherian KS, Sainoji A, Nagalla B, Yagnambhatt VR
Summary: The purpose was to evaluate energy expenditure, energy intake, and nutrient adequacy of Indian junior soccer players. Forty junior national-level soccer players (Under-12 and Under-16 age groups) were assessed for 3-day weighed food records and 3-day energy expenditure. Energy and nutrient intake was analyzed from food records, and energy expenditure was measured using a portable metabolic analyzer and activity records. Nutrient adequacy was determined by comparing intake with prevailing recommendations. Players exhibited no significant difference between energy intake (boys = 3062 [340.9] and girls = 2243 [320.3] kcal·d-1) and expenditure (boys = 2875 [717.3] and girls = 2442 [350.3] kcal·d-1). Across age groups, the Under-12 boys showed positive energy balance as against energy deficits in Under-16. Girls showed energy deficits, although not significant. There were 58% of girls showing energy availability <30 kcal·kg-1 fat-free mass, of which 37% were Under-16 players. Carbohydrates contributed to >60% of energy expenditure among 95.2% boys and 73.7% girls. Among 52.4% boys and 47.4% girls, <25% of energy expenditure was contributed by fat. More than 95% players consumed <1 g·kg-1 carbohydrates pretraining and 100% of them consumed >1.2 g·kg-1 carbohydrates posttraining. Junior soccer players consumed more than recommended carbohydrates in the diet, although not aligning with the pretraining, during training, and posttraining meal requirements. Considering the energy deficits observed among Under-16 players, a suitable dietary modification is warranted.


#3 Effects of Plyometric and Directional Training on Physical Fitness Parameters in Youth Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-22. doi: 10.1123/ijspp.2018-0545. [Epub ahead of print]
Authors: Michailidis Y, Tabouris A, Metaxas T
Summary: The aim of this study is to investigate whether the combination of a soccer training session, plyometric training (PT) and change of direction (COD) exercises would enhance soccer ability to a greater extent than training on its own in youth soccer players. Thirty-one youth players participated in this study (age 12±0.8 years). Players were randomly separated into 2 groups: control group (CG, n=14) and intervention group (INTG) which performed extra PT and COD exercises (INTG, n=17). The duration of the training program was 6 weeks. Sprint 10m, 30m, countermovement jump (CMJ), squat jump (SJ), long jump (LJ), multiple 5-bound (5MB), T-test, and YO-YO intermitted endurance test 1 (YYIET1) were measured pre and post of the training program. The performance in acceleration, T-test and LJ improved in both groups (P=0.03, P=0.002 and P=0.001, respectively). SJ performance increased in INTG (15.2 %, P=0.003) and slightly decreased in CG (P=0.003). The performances of the 2 groups differed significantly in SJ and LJ (P=0.003 and P=0.038, respectively). This study supports that a short-term combined program of PT and COD exercises can improve jumping ability, acceleration, and endurance parameters in youth soccer players. The small training effect could be explained when taking into account the level of the participants, the duration of the program and the low volume of COD exercises that were used.


#4 Presleep Casein Protein Ingestion: Acceleration of Functional Recovery in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-24. doi: 10.1123/ijspp.2018-0385. [Epub ahead of print]
Authors: Abbott W, Brett A, Cockburn E, Clifford T
Summary: This study examined whether consuming casein protein (CP) before sleep would enhance recovery after a night-time soccer match in professional players. In a randomized, crossover design, ten professional soccer players from the reserve squad of a team in the highest tier of English soccer consumed 40 g of CP or 40 g of carbohydrates (CON) 30 min pre-sleep after a soccer match (kick off 19:00). To assess recovery, countermovement jump (CMJ) height, reactive strength index (RSI), muscle soreness (MS), and the adapted Brief Assessment of Mood Questionnaire (BAM+) were measured before, 12, 36 and 60 h after each match. Dietary intake across the testing period was also recorded. There were unclear differences in external load in the matches and dietary intake between CON and CP. CP had a most likely and likely beneficial effect on CMJ recovery at 12 and 36 h post-match (CP -1.6; ±1.2% vs. CON -6.6; ±1.7%; -4.1; ±2.3% vs. -0.4; ±1.1%, respectively). RSI recovery was most likely enhanced with CP at 12 and 36 h post-match and muscle soreness, as measured with a visual analogue scale (mm), was most likely greater in CON vs. CP at 12 h post (72; ±17 vs. 42; ±20 mm). BAM+ was possibly lower in CON at 36 h post but unaffected at other time points. Pre-sleep CP accelerates functional recovery in professional soccer players and therefore provides a practical means of attenuating performance deficits in the days after a match.


#5 Determining the Relationship Between Internal Load Markers and Non-Contact Injuries in Young Elite Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-19. doi: 10.1123/ijspp.2018-0466. [Epub ahead of print]
Authors: Raya-González J, Nakamura FY, Castillo D, Yanci J, Fanchini M
Summary: The purpose was to examine the association and predictive ability of internal load markers with regards to non-contact injuries in young elite soccer players. Twenty-two soccer players (18.6 ± .6 years) who competed in the Spanish U19 League participated in the study. During a full season, non-contact injuries were recorded and, using session rating of perceived exertion (s-RPE), internal weekly load (sum of load of all training sessions and matches for each week) and acute:chronic workload ratio (typically, acute = current week and chronic = rolling 4 week average) were calculated. A Generalized Estimating Equation analysis was used to examine association of weekly and acute:chronic load ratio markers with a non-contact injury in the subsequent week. Load variables were also analyzed for predictive ability with Receiver Operating Characteristic (ROC) curve and area under the curve (AUC). No association was found for weekly load (CI 1.00, .99 to 1.00) and acute:chronic load ratio (CI .16, .01 to 1.84) with respect to injury occurrence. In addition, the analyzed load markers showed poor ability to predict injury occurrence (AUC<.50). The results of this study suggest that internal load markers are not associated with non-contact injuries in young soccer players and present poor predictive capacity with regards to the latter.


#6 Physical Characteristics of Elite Youth Female Soccer Players Characterized by Maturity Status
Reference: J Strength Cond Res. 2018 Sep 7. doi: 10.1519/JSC.0000000000002795. [Epub ahead of print]
Authors: Emmonds S, Scantlebury S, Murray E, Turner L, Robsinon C, Jones B
Summary: The purpose of this study was to investigate the influence of maturity status on the physical characteristics of youth female soccer players. One hundred fifty-seven players from 3 elite soccer academies in England completed assessments of anthropometry, strength (isometric midthigh pull), lower-body power (countermovement jump [CMJ]), aerobic capacity (Yo-Yo intermittent recovery test level 1), change of direction (CoD: 505-left/right), and speed (10 and 30 m). Each player was classified into 1 of 6 maturity groups based on their estimated years from peak height velocity (YPHV). Magnitude-based inferences were used to assess for the practical significance between consecutive groups. Speed, CoD time, CMJ, and aerobic capacity were all possibly most likely better in more mature players. However, there was a likely difference in relative peak force between maturity groups -0.5 YPHV (27.13 ± 4.24 N·Kg) and 0.5 YPHV (24.62 ± 3.70 N·Kg), which was associated with a likely difference in 10-m sprint time (-0.5 YPHV: 2.00 ± 0.12 vs. 0.5 YPHV 2.08 ± 0.16 seconds) and unclear changes in CMJ and CoD time. Findings provide novel comparative data for this cohort relative to maturity status and can be used by strength and conditioning coaches to inform the design of training programs for youth female soccer players. Strength and conditioning coaches should be aware that youth female soccer players may experience a decrease in relative strength around peak height velocity, which may impact upon the speed, CoD time, and CMJ of players.


#7 Post-football Gonathrosis: Injuries and Surgeries are A Risk
Reference: Cureus. 2018 Jul 10;10(7):e2953. doi: 10.7759/cureus.2953.
Authors: Ali Khan MM, Siddiqui AA, Yaqoob U, Yaqub MD, Khan OJ, -Ul-Haq F
Summary: Football is one of the most popular sports in the world. Many studies have shown there is a high incidence of gonarthrosis in football players. The reason for this increase is said to be injuries to the meniscus, the anterior cruciate ligament (ACL) and the resulting surgeries. The incidence is significantly increased in players with knee injuries. The knee is also the most commonly injured site in football and the most common cause of surgery in football players. Together these injuries, particularly of the ACL or meniscus and the resulting surgeries, increase the risk of developing gonarthrosis in post-football years.


#8 Validity of Session Rating of Perceived Exertion Assessed via the CR100® Scale to Track Internal Load in Elite Youth Football Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-14. doi: 10.1123/ijspp.2018-0432. [Epub ahead of print]
Authors: Naidu SA, Fanchini M, Cox A, Smeaton J, Hopkins WG, Serpiello FR
Summary: The purpose of the study was to assess the convergent validity of the Borg CR100® scale to track internal training load (TL) in youth football players. Nineteen youth football players (age 15 ± 1 y, height 175.9 ± 12.3 cm, body mass 69 ± 15.4 kg) were monitored for 27 sessions, including training and games. Internal training load was assessed via session rating of perceived exertion (sRPE) and two heart rate (HR)-based methods; Banister's training impulse (TRIMP) and Edwards' TL. The correlations between sRPE and HR-based TL, the differences in individual player intercepts and slopes, and the differences between types of sessions (training vs. games) were assessed using a general linear mixed model with magnitude-based inferences. Correlations between sRPE and Banister's TRIMP were very large at overall group level (r=0.77, 90% confidence limits (CL) 0.72 to 0.80), and individual level (range 0.70 - 0.95). Correlations between sRPE and Edwards' TL were very large at overall group level (r=0.84, 90% CL 0.82 to 0.86), and large to very large at individual level (range 0.64 - 0.93). A very likely small difference was found in the comparison between games and training sessions for the relationship between sRPE and Banister's TRIMP. The Borg CR100® scale is a valid method for monitoring training load in youth football players.


#9 There are more football injury prevention reviews than randomised controlled trials. Time for more RCT action!
Reference: Br J Sports Med. 2018 Sep 10. pii: bjsports-2018-099373. doi: 10.1136/bjsports-2018-099373. [Epub ahead of print]
Authors: Bricca A, Juhl CB, Bizzini M, Andersen TE, Thorborg K


#10 Quantification of a Professional Football Team's External Load Using a Microcycle Structure
Reference: J Strength Cond Res. 2018 Sep 7. doi: 10.1519/JSC.0000000000002816. [Epub ahead of print]
Authors: Martín-García A, Gómez Díaz A, Bradley PS, Morera F, Casamichana D
Summary: The aims of this study were to (a) determine the external load of a football team across playing position and relative to competition for a structured microcycle and (b) examine the loading and variation the day after competition for players with or without game time. Training and match data were obtained from 24 professional football players who belonging to the reserve squad of a Spanish La Liga club during the 2015/16 season using global positioning technology (n = 37 matches and n = 42 training weeks). Training load data were analyzed with respect to the number of days before or after a match (match day [MD] minus or plus). Training load metrics declined as competition approached (MD-4 > MD-3 > MD-2 > MD-1; p < 0.05; effect sizes [ES]: 0.4-3.1). On the day after competition, players without game time demonstrated greater load in a compensatory session (MD + 1C) that replicated competition compared with a recovery session (MD + 1R) completed by players with game time (MD + 1C > MD + 1R; p < 0.05; ES: 1.4-1.6). Acceleration and deceleration metrics during training exceeded 50% of that performed in competition for MD + 1C (80-86%), MD-4 (71-72%), MD-3 (62-69%), and MD-2 (56-61%). Full backs performed more high-speed running and sprint distance than other positions at MD-3 and MD-4 (p < 0.05; ES: 0.8-1.7). The coefficient of variation for weekly training sessions ranged from ∼40% for MD-3 and MD-4 to ∼80% for MD + 1R. The data demonstrate that the external load of a structured microcycle varied substantially based on the players training day and position. This information could be useful for applied sports scientists when trying to systematically manage load, particularly compensatory conditioning for players without game time.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.


#11 Normative Data and Physical Determinants of Multiple Sprint Sets in Young Soccer Players Aged 11-18 Years: Effect of Maturity Status
Reference: J Strength Cond Res. 2018 Sep 19. doi: 10.1519/JSC.0000000000002810. [Epub ahead of print]
Authors: Selmi MA, Sassi RH, Yahmed MH, Giannini S, Perroni F, Elloumi M
Summary: The aims of the study were: (a) to establish normative data for repeated-sprint sets (RSS) test based on the maturity status (age at peak height velocity [PHV]) and (2) to investigate the relationship between anthropometrical variables (stature, sitting height, body mass, and body fat percentage), RSS (2 × 5 × 20 m with 15-second recovery between sprints and 1-minute recovery between sets), and fitness tests {squat jump, countermovement jump, standing long jump, standing triple jump, 5-jump test, and 20-m shuttle run (multistage shuttle run test [MSRT])}. Young male soccer players (n = 262; age: 14.5 ± 2.9 years) were evaluated and classified into 4 groups according to their maturity status: pre-PHV, circum-PHV1, circum-PHV2, post-PHV. An analysis of variance and Bonferroni post hoc were used to determine maturity group differences (p ≤ 0.05), whereas Pearson's correlation was used between variables. Repeated-sprint sets' indices (sum of sprint times [SST] and best sprint time [BST]) were significantly different between the maturity groups. Significant correlations between SST with body mass (from -0.73 to -0.33) and MSRT (from -0.49 to -0.30) among each maturity group were found. With the different maturity groups, correlations between SST (s), BST (s), and vertical jump (cm) (r = -0.63 to -0.25 and r = -0.68 to -0.23) and horizontal jump (m) (r = -0.70 to -0.38 and r = -0.63 to -0.43) were observed. Repeated-sprint sets' values improve during maturation of young soccer players and the correlations between RSS and fitness tests vary through the maturity groups. This information could be useful for the coach to identify talent and to prescribe specific physical training to improve performance.


#12 Effects of Two Different Tapering Protocols on Fitness and Physical Match Performance in Elite Junior Soccer Players
Reference: J Strength Cond Res. 2018 Sep 19. doi: 10.1519/JSC.0000000000002861. [Epub ahead of print]
Authors: Krespi M, Sporiš G, Trajković N
Summary: The purpose of this study was to determine the effects of 2 different tapering protocols on fitness and physical match performance in elite junior soccer players. One-hundred fifty-eight elite junior soccer players (mean age: 17.1 ± 0.79 years; mean height: 177.9 ± 6.64 cm; mean body mass: 71.3 ± 7.96 kg; and mean body mass index: 22.5 ± 1.66 kg·m) were randomly assigned to 2 groups: an exponential (n = 79) and a linear tapering (n = 79) group. Training sessions were conducted 3 times per week for 8 weeks. After 4 weeks of training and 4 weeks of tapering, participants were assessed in terms of body composition, physical fitness, and distance covered within a match. Both groups showed similar changes for body composition. The exponential group showed better improvement than the linear group in the 5- and 30-m sprints, countermovement jump, and V[Combining Dot Above]O2max (p < 0.05). The exponential tapering group had larger changes (p < 0.05) than the linear group in medium running (8-13 km·h) (6%; effect size = 0.26 compared with 5.5%; effect size = 0.22) and sprinting (>18 km·h) (26%; effect size = 0.72 compared to 21.7%; effect size = 0.60). The results show that exponential tapering produced better effects on speed, power, and endurance abilities than the linear protocol. Our results confirmed the reports of others that suggest that volume is the optimal variable to manipulate while maintaining both the intensity and the frequency of sessions.

Thu

01

Nov

2018

Latest research in football - week 36 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 King-Devick test normative reference values and internal consistency in youth football and soccer athletes
Reference: Scand J Med Sci Sports. 2018 Aug 28. doi: 10.1111/sms.13286. [Epub ahead of print]
Authors: Moran RN, Covassin T
Summary: The King-Devick (K-D) test has gained popularity as a sideline concussion assessment tool, comprising of visual tracking and saccadic eye movements. However, limited normative data exists for youth athletes under the age of 13. The purpose of this study was to establish normative reference values and examine the internal consistency of the K-D test in youth athletes. The K-D test was administered to 422 youth football and soccer athletes prior to their respective season. The average K-D score was 54.29±11.5 seconds. Across the two trials, 55% of participants committed at least one error. Overall, the K-D test demonstrated a high internal consistency (Cronbach α = 0.92) when administered at baseline. Inter-item correlations revealed a moderate to strong relationship between test cards and trials (r range= 0.71 to 0.95; p<0.001), along with test cards and baseline K-D time (r range= 0.85 to 0.94; p<0.001). Although the K-D test was consistent during baseline testing, the high percentage of errors at baseline makes the K-D test questionable for post-concussion comparisons.


#2 Epidemiological Findings of Soccer Injuries During the 2017 Gold Cup
Reference: Orthop J Sports Med. 2018 Aug 20;6(8):2325967118791754. doi: 10.1177/2325967118791754. eCollection 2018 Aug.
Authors: Chahla J, Sherman B, Cinque M, Miranda A, Garrett WE, Chiampas G, O'Malley H, Gerhardt MB, Mandelbaum BR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6102768/pdf/10.1177_2325967118791754.pdf
Summary: Surveillance programs are vital to analyze the cause and nature of lesions and ultimately establish protocols of action to lower injury rates. The purpose of the study was to evaluate the adherence of team doctors to an electronic surveillance system and determine the incidence and characteristics of injuries among soccer players participating in the 2017 Gold Cup.All data were collected from the electronic medical reports submitted during each match of the 2017 Gold Cup. Twelve teams participated in the tournament (each with 23  the team physician after each injury. Each report contained the player's number, the exact time of injury (minute of play), the location and diagnosis of injury as indicated by a previously defined code, and its severity in terms of the number of days of absence from training and match play. The electronic reporting system had a response rate of 100.0%, with 97.2% of questions answered completely. The mean age of injured players was 27 years (range, 21-35 years) and was not statistically significantly different from the overall mean player age (P > .05). There were no significant differences in the frequency of injuries when analyzed by player position (P = .743). The overall rate of injuries was 1.04 per match, with the most common injuries being contusions (42.3%), sprains (7.7%), strains (7.7%), and fractures (7.7%). These injuries were more commonly the result of contact (75.0%) than noncontact (25.0%) mechanisms (P < .001). Injuries most commonly occurred between the 60th and 75th minute of play when comparing all 15-minute time intervals (P = .004). This study supports the use of electronic injury reporting, which demonstrated a high level of adherence among an international cohort of team physicians and has significant potential for improving injury surveillance and tracking responses to prevention programs. Injury rates in the Gold Cup were similar to those in previous studies and demonstrated the highest rates late in the second half of the game, specifically between the 60th and 75th minute of play.


#3 Altered lower limb kinematics and muscle activities in soccer players with chronic ankle instability
Reference: Phys Ther Sport. 2018 Aug 9;34:28-35. doi: 10.1016/j.ptsp.2018.08.003. [Epub ahead of print]
Authors: Kunugi S, Masunari A, Koumura T, Fujimoto A, Yoshida N, Miyakawa S
Summary: The purpose was to examine the lower limb kinematics and muscle activities in diagonal single-leg rebound jump in soccer players with chronic ankle instability (CAI). Thirty male collegiate soccer players participated: 15 with CAI were compared with 15 without CAI, matched by physical description. In the diagonal single-leg rebound jump, participants stood on one leg on a 30-cm high box, hopped down diagonally (45°) onto a force plate, and jumped vertically as high as possible with hands on their hips. Hip, knee, and ankle kinematics were acquired using a motion capture system. The activity of the gluteus medius, hip adductor, and lower leg muscles was recorded using electromyography. Jump performance was calculated using a force plate. The CAI group had (i) decreased hip adduction, knee flexion, external rotation, and dorsiflexion angle; (ii) reduced hip adductor and peroneus muscle activations; and (iii) reduced jump height and short flight time. Male collegiate soccer players with CAI showed altered kinematics and muscle activities during a diagonal single-leg rebound jump; this may adversely affect rebound jump performance.


#4 Match-Play and Performance Test Responses of Soccer Goalkeepers: A Review of Current Literature
Reference: Sports Med. 2018 Aug 24. doi: 10.1007/s40279-018-0977-2. [Epub ahead of print]
Authors: White A, Hills SP, Cooke CB, Batten T, Kilduff LP, Cook CJ, Roberts C, Russell M
Summary: Goalkeepers are typically the last defensive line for soccer teams aiming to minimise goals being conceded, with match rules permitting ball handling within a specific area. Goalkeepers are also involved in initiating some offensive plays, and typically remain in close proximity to the goal line while covering ~ 50% of the match distances of outfield players; hence, the competitive and training demands of goalkeepers are unique to their specialised position. Indeed, isolated performance tests differentiate goalkeepers from outfield players in multiple variables. With a view to informing future research, this review summarised currently available literature reporting goalkeeper responses to: (1) match play (movement and skilled/technical demands) and (2) isolated performance assessments (strength, power, speed, aerobic capacity, joint range of motion). Literature searching and screening processes yielded 26 eligible records and highlighted that goalkeepers covered ~ 4-6 km on match day whilst spending ~ 98% of time at low-movement intensities. The most decisive moments are the 2-10 saves·match-1 performed, which often involve explosive actions (e.g. dives, jumps). Whilst no between-half performance decrements have been observed in professional goalkeepers, possible transient changes over shorter match epochs remain unclear. Isolated performance tests confirm divergent profiles between goalkeepers and outfield players (i.e. superior jump performance, reduced [Formula: see text]2max values, slower sprint times), and the training of soccer goalkeepers is typically completed separately from outfield positions with a focus primarily on technical or explosive drills performed within confined spaces. Additional work is needed to examine the physiological responses to goalkeeper-specific training and match activities to determine the efficacy of current preparatory strategies.


#5 Return to Competition After Surgery for Herniated Lumbar Disc in Professional Football Players
Reference: Clin J Sport Med. 2018 Aug 28. doi: 10.1097/JSM.0000000000000662. [Epub ahead of print]
Authors: Tencone F, Minetto MA, Tomaello L, Giannini A, Roi GS
Summary: The purpose was to investigate the prevalence and outcomes of surgery for lumbar disc herniation in professional football players. A period of 10 seasons of the Italian Football First League (Serie A) was retrospectively investigated. Thirty-three teams (for a total of 1960 players) took turns in the 10 seasons, and 42 team doctors were requested to provide information about the number of players who underwent surgery for lumbar disc herniation. Prevalence and match incidence of the lumbar discectomy, proportion of players returning to competition after surgery, recovery time and preintervention and postintervention number of appearances in official matches were analyzed. Eleven players underwent the surgical intervention during the considered period. The prevalence of the surgical treatment was 0.6%, whereas the match incidence was 0.09 cases/1000 match hours. All players returned to competitions 6.0 (3.5-7.7) months after surgery, with no significant difference between different roles. The number of appearances in official matches was comparable during the seasons before and after surgery. The lumbar discectomy must be considered a rare surgical procedure performed in professional football players. All players returned to competitions after surgery. The postintervention number of appearances in official matches was comparable with the preintervention one.


#6 Early return to playing professional football following fixation of 5th metatarsal stress fractures may lead to delayed union but does not increase the risk of long-term non-union
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 28. doi: 10.1007/s00167-018-5104-2. [Epub ahead of print]
Authors: Miller D, Marsland D, Jones M, Calder J
Summary: 5th metatarsal stress fractures are frequently encountered in professional football. There is concern that early return to play following intra-medullary screw fixation may lead to an increased risk of delayed union. The purpose of the study was to assess whether an early return to play after surgical fixation of 5th metatarsal fractures in professional football players is a risk factor for delayed union and the effect of this on the ultimate clinical outcome. Retrospective review of prospectively collected data of a series of 37 professional football players following intramedullary screw fixation of 5th metatarsal stress fractures. End points included time of return to play and to radiological union of the fracture. At a minimum follow-up of 24 months the mean return to play was 10.5 weeks and mean time to complete radiological union was 12.7 weeks. Return to play at 8 weeks or less resulted in a higher risk of delayed radiological union (24% at 3 months), but this neither prevented the athlete from continuing to play football nor did it affect the ultimate risk of non-union (3% overall). A re-fracture occurred in 1 patient (3%) at 10 months who previously had complete radiographic union at 9 weeks. Intramedullary screw fixation of 5th metatarsal stress fractures leads to a predictable time of return to play and a low rate of non-union. If players return to play at 8 weeks or less a persistent line may be expected in up to a quarter of patients. However, if asymptomatic this radiological finding does not mean that athletes must avoid playing football as ultimately a good outcome is expected with low rates of non-union and refracture.


#7 Injury incidence in semi-professional football claims for increased need of injury prevention in elite junior football
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 25. doi: 10.1007/s00167-018-5119-8. [Epub ahead of print]
Authors: Loose O, Fellner B, Lehmann J, Achenbach L, Krutsch V, Gerling S, Jansen P, Angele P, Nerlich M, Krutsch W
Summary: Injuries are a common occurrence in football. Sufficient epidemiological data are available in professional football but not in salaried semi-professional football. This study investigates the injury incidence at different levels of semi-professional football with focus on junior football. The data were based on injury reports provided by players and medical staff over the 2015-2016 season, which corresponded to the consensus statement for data samples in football. This study investigated the injury incidence and prevalence of five skill levels of semi-professional football (the fourth to the seventh league and elite junior football). 1130 players had sustained 2630 injuries over the 2015-2016 season. The overall injury incidence was 9.7 per 1000 h football exposure; prevalence with at least one injury was 79%. The highest overall injury incidence in elite junior football was 10.4 in 1000 h football exposure. The fifth league had the lowest incidence with 9.0 in 1000 h football (p < 0.05). Traumatic injuries most often occurred in the fourth league (3.9 in 1000 h football). The body areas most affected by traumatic injury were knees, ankles and thighs. Elite junior players had a significantly higher incidence of overuse complaints (7.4 in 1000 h football) than the fourth league (5.4, p = 0.005). The body areas most affected by overuse complaints were the lower back, thigh and groin. No differences were found between the different positions on field. Salaried semi-professional football involves a high overall injury incidence. The highest incidence, particularly of overuse injuries, was seen in elite junior football. These findings should be incorporated in specific injury prevention training or screenings beginning in junior football.


#8 Neurocognitive Performance of 425 Top-Level Football Players: Sport-specific Norm Values and Implications
Reference: Arch Clin Neuropsychol. 2018 Aug 25. doi: 10.1093/arclin/acy056. [Epub ahead of print]
Authors: Prien A, Junge A, Brugger P, Straumann D, Feddermann-Demont N
Summary: Concussion diagnosis and management in sports largely relies on neurocognitive testing. In the absence of baseline assessment, only norm values of the general population are available for comparison with scores of concussed athletes. To evaluate whether (elite) sport specific norm values are needed, cognitive performance was compared between top-level football players and the general population. Cognitive performance of 425 top-level football players was evaluated using the computerized test battery CNS Vital Signs. Players were split into two age groups (15-19 and 20-29 years) and test results were compared with a norm sample (n = 268) by means of age-standardized scores using Cohen's d effect size statistics. The younger age group outperformed the norm sample in all domains, with small to moderate effects on tests of processing speed (d = 0.58, 95% CI = 0.31,0.85), cognitive flexibility (d = 0.27, 95% CI = 0.01,0.53) and psychomotor speed (d = 0.97, 95% CI = 0.69,1.24). In the older age group, no differences were found on four out of six domains; a moderate positive effect was found for psychomotor speed (d = 0.74, 95% CI = 0.54,0.93), a small negative effect for reaction time (d = -0.47, 95% CI = -0.66,-0.28). Relative to the norm, older football players scored lower than younger football players on all test domains. Cognitive performance of elite football players may be different from the general population. It is recommended to use football-specific norm scores for comparison with test results of concussed players, and to choose an adequate control group when investigating effects of contact sport on cognition. Studies with older/retired football players are needed to further analyze potential sport-specific age effects.


#9 Match Related Time Course of Perceived Recovery in Youth Football Players
Reference: Int J Sports Physiol Perform. 2018 Aug 30:1-16. doi: 10.1123/ijspp.2017-0521. [Epub ahead of print]
Authors: Paul DJ, Tomazoli G, Nassis GP
Summary: The aim of the study was to i) examine the reproducibility of the perceived recovery scale (PRS) in football players ii) describe the time course of the PRS in response to a football match. Methods Twenty trained youth players (mean ± SD; age 16.2 ± 1.2 y, height 1.75 ± 0.07 m, body mass 64.0 ± 7.8 kg) took part in the study. PRS was collected - 2 hrs, - 30 mins before and +15 mins, +3 hrs and +24 hrs after an international football match. Players were categorised into two groups based on their playing time (≤45 and 90 mins). Reproducibility of the PRS was high (ICC = 0.83, TE = 0.59, CV = 9.9%) between the two pre-match measures. Overall, PRS was lower at +15 mins (4.0 ± 1.5, p< 0.01; ES=2.2) and + 3 hrs (4.7 ± 1.6, p< 0.01; ES=1.5) compared to -30 mins (7.1 ± 1.3), while +15 mins was lower than +24 hrs (6.1 ± 1.3, p<0.01; ES=1.5). No differences between groups for PRS scores at any of the time points. The perceived recovery scale is a reproducible method for monitoring perceptions of recovery to football activity and sensitive to time course changes relating to a match. The scale is an easy and efficient tool that can be used to monitor an aspect of recovery.


#10 Accurate Prediction Equation to Assess Body Fat in Male and Female Adolescent Football Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Aug 30:1-23. doi: 10.1123/ijsnem.2018-0099. [Epub ahead of print]
Authors: Lozano-Berges G, Matute-Llorente Á, Gómez-Bruton A, González-Agüero A, Vicente-Rodríguez G, Casajús JA
Summary: The aims of this study were (a) to determine which of the most used anthropometric equations was the most accurate to estimate percentage of body fat (%BF), (b) to develop a new specific anthropometric equation, and (c) to validate this football-specific equation. A total of 126 (13.3±0.6 y) football players (86 males) participated in the present study. Participants were divided into two groups: 98 players were included in the assessment of existing equations and in the development of the new prediction equation; and 28 were used to validate it. %BF was measured with dual-energy X-ray absorptiometry (DXA) and also estimated with six different %BF anthropometric equations: Johnston, Slaughter, Carter, Faulkner, Deurenberg and Santi-Maria. Paired t-tests were used to analyze differences between methods. A football-specific equation was developed by a stepwise linear-regression. The existing anthropometric equations showed significant bias for %BF when compared to DXA (p<.001; constant error [CE] ranged from -4.57 to 9.24%; standard error of estimate [SEE] ranged from 2.46 to 4.20). On the other hand, the developed football-specific equation was %BF = 11.115 + 0.775(triceps skinfold) + 0.193(iliac-crest skinfold) - 1.606(sex). The developed equation demonstrated neither %BF differences (p=.121; CE=0.57%; SEE=0.36) when compared to DXA, presenting a high cross-validation prediction power (R2=0.85). Published anthropometric equations were not accurate to estimate %BF in adolescent football players. Due to the fact that the developed football-specific equation showed neither differences nor heteroscedasticity when compared to DXA, this equation is recommended to assess %BF in adolescent football players.


#11 Comparative effects of single vs. double weekly plyometric training sessions on jump, sprint and COD abilities of elite youth football players
Reference: J Sports Med Phys Fitness. 2018 Aug 28. doi: 10.23736/S0022-4707.18.08804-7. [Epub ahead of print]
Authors: Bianchi M, Coratella G, Dello Iacono A, Beato M
Summary: Plyometrics are widely implemented as training methodology for enhancing functional sports performance. Although several studies have analysed the plyometrics effects due to training plans with a frequency of 2-3 times a week, few of them provided evidence supporting an equal efficiency of similar training programs implementing lower training frequency such as one training session a week. Twenty-one players (elite academy, Switzerland) were included in the current study (mean ± SD; age 17 ± 0.8 years, weight 70.1 ± 6.4 kg, height 177.4 ± 6.2 cm). This study used a randomised pre-post parallel group trial design. The participants were assigned to either a low-volume plyometric training group (LPG = 10 participants) or a high-volume plyometric training group (HPG = 11 participants). A long jump test, a single-leg triple hop test, sprint (10, 30 and 40 m) and 505 change of directions (COD) test were performed. Exercise-induced meaningful changes in performance for both LPG and HPG occurred after the training. LPG and HPG reported improvements in long jump (ES=1.0 and 0.77), triple hop right (ES=0.32 and 0.28), triple hop left (ES=0.46 and 0.32), 10 m sprint (ES=0.62 and 1.0). Both LPG and HPG are effective training modalities inducing benefits in jump and sprint tests for elite young football players. Fitness coaches and sports scientists could integrate their training plans with the protocols described in this study.


#12 Prediction of Attendance Demand in European Football Games: Comparison of ANFIS, Fuzzy Logic, and ANN
Reference: Comput Intell Neurosci. 2018 Aug 7;2018:5714872. doi: 10.1155/2018/5714872. eCollection 2018.
Authors: Şahin M, Erol R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6109553/pdf/CIN2018-5714872.pdf
Summary: An artificial neural network (ANN), adaptive neurofuzzy inference system (ANFIS) models, and fuzzy rule-based system (FRBS) models are developed to predict the attendance demand in European football games, in this paper. To determine the most successful method, each of the methods is analyzed under different situations. The Elman backpropagation, feed-forward backpropagation, and cascade-forward backpropagation network types are developed to determine the outperforming ANN model. The backpropagation and hybrid optimization methods are used for training fuzzy inference system (FIS) to determine the outperforming ANFIS model. The fuzzy logic model is developed after experimenting different forms of membership functions. To this end, the data of 236 soccer games are used to train the ANN and ANFIS models, and 2017/2018 season's data of these clubs are used to test all of the models. The results of all models are compared with each other and real past data. To assess the performance of each model, two error measures that are Mean Absolute Percent Error (MAPE) and Mean Absolute Deviation (MAD) are implemented. These measures reveal that the ANN model that has Elman network type outperforms the other models. Finally, the results emphasize that the proposed ANN model can be effectively used for prediction purposes.


#13 Exercise loading for cardiopulmonary assessment and evaluation of endurance in amputee football players
Reference: J Phys Ther Sci. 2018 Aug;30(8):960-965. doi: 10.1589/jpts.30.960. Epub 2018 Jul 24.
Authors: Mikami Y, Fukuhara K, Kawae T, Sakamitsu T, Kamijo Y, Tajima H, Kimura H, Adachi N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110228/pdf/jpts-30-960.pdf
Summary: It is difficult for amputees to perform conventional cardiopulmonary exercise testing. Values were determined for two-legged, one-legged, and two-armed exercise testing in healthy adult males (Study 1), for comparison with preliminary measurements of endurance in amputee football players (Study 2). In Study 1, cardiopulmonary exercise testing was performed in healthy adult males. Correlations between oxygen uptake in two-legged and one-legged/two-armed exercise were calculated and a comparison was made between one-legged exercise and two-armed exercise for each measured value. In Study 2, cardiopulmonary exercise testing was performed on male amputee football players using a two-arm-driven ergometer. The measured values obtained for healthy adult males and amputee football players were compared. In Study 1, peak work rate and peak heart rate values of healthy participants were significantly higher in two-armed exercise than in one-legged exercise. The correlation between peak oxygen uptake values for two-legged and one-legged exercise was decreased. In Study 2, peak work rate of two-armed exercise was significantly higher in amputee football players than in healthy participants.  Study 1 suggested that musculoskeletal factors might have greater significance for one-legged exercise than for two-armed exercise. Study 2 suggested that para-sports, including amputee football, may contribute to physical strength and health maintenance in lower leg amputees.

Sun

28

Oct

2018

Latest research in football - week 35 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Relative Age Effect in the 10 Best Leagues of Male Professional Football of the Union of European Football Associations (UEFA)
Reference: J Sports Sci Med. 2018 Aug 14;17(3):409-416. eCollection 2018 Sep.
Authors: Yagüe JM, de la Rubia A, Sánchez-Molina J, Maroto-Izquierdo S, Molinero O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090398/pdf/jssm-17-409.pdf
Summary: The aim of the present research was to observe the relative age effect on professional soccer players of the ten best leagues of the Union of European Football Associations (UEFA), according to the IFFHS (International Federation of Football History and Statistics). The sample consisted of 5201 professional players who participated in the professional leagues during the 2016-2017 season. The birth date of each player was classified in four quartiles (Q1, Q2, Q3 and Q4). The frequencies (fr) and percentages (%) of the birth quartiles were analyzed. The chi square test (X2) and degrees of freedom (gl) were performed to check the differences in the intergroup distribution. Likewise, odd ratios were calculated for the different quartiles, where Q4 was the reference group according to the different leagues studied, playing positions (goalkeeper, defender, midfielder and forward) and classification (first four places, half-of the table and four last places). To calculate the size of the effect on the nominal variables, the Cramer V test was carried out. The results confirmed a greater representation of players born in Q1 and Q2, indicating statistically significant values (p < 0.05) for all the leagues studied, except in the Eerste Klasse A (Belgium). This significance was repeated for the demarcation variables in the field, with a greater effect in the case of the midfielders. Finally, the RAE also affected the three groups according to teams´ classification. The conclusions confirm the effect of the RAE in the sample studied, which would require a review of the talent selection processes in football in order to balance the chances of success of players born at the end of the year.


#2 Is Plantar Loading Altered During Repeated Sprints on Artificial Turf in International Football Players?
Reference: J Sports Sci Med. 2018 Aug 14;17(3):359-365. eCollection 2018 Sep.
Authors: Girard O, Millet GP, Thomson A, Brocherie F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090389/pdf/jssm-17-359.pdf
Summary: We compared fatigue-induced changes in plantar loading during the repeated anaerobic sprint test over two distinct distance intervals. Twelve international male football outfield players (Qatar Football Association) completed 6 × 35-m sprints (10 s of active recovery) on artificial turf with their football boots. Insole plantar pressure distribution was continuously recorded and values (whole foot and under 9 foot zones) subsequently averaged and compared over two distinct distance intervals (0-17.5 m vs. 17.5-35 m). Sprint times increased (p <0.001) from the first (4.87 ± 0.13 s) to the last (5.63 ± 0.31 s) repetition, independently of the distance interval. Contact area (150 ± 23 vs. 158 ± 19 cm2; -5.8 ± 9.1%; p = 0.032), maximum force (1910 ± 559 vs. 2211 ± 613 N; -16.9 ± 18.2%; p = 0.005) and mean pressure (154 ± 41 vs. 172 ± 37 kPa; -13.9 ± 19.0%; p = 0.033) for the whole foot were lower at 0-17.5 m vs. 17.5-35 m, irrespectively of sprint number. There were no main effects of sprint number or any significant interactions for any plantar variables of the whole foot. The distance interval × sprint number × foot region interaction on relative loads was not significant. Neither distance interval nor fatigue modified plantar pressure distribution patterns. Fatigue led to a decrement in sprint time but no significant change in plantar pressure distribution patterns across sprint repetitions.


#3 Time-use and environmental determinants of dropout from organized youth football and tennis
Reference: BMC Public Health. 2018 Aug 16;18(1):1022. doi: 10.1186/s12889-018-5919-2.
Authors: Deelen I, Ettema D, Kamphuis CBM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6097310/pdf/12889_2018_Article_5919.pdf
Summary: Many adolescents drop out of organized sports. Lack of motivation and competing priorities are known as important reasons for dropout. However, time use factors as well as environmental determinants have been largely neglected in the current literature on dropout from youth sports. The aim of this study is to investigate how (changes in) time use and characteristics of the physical environment determine dropout from football and tennis among adolescents. Data on time use and background characteristics were collected through online surveys in 2015 and 2016 among adolescents aged 13-21 (N = 2555), including both the dropped outs and those who still continued membership of their football or tennis clubs. Physical environmental determinants (travel distance to the sports club, and neighbourhood density) were measured objectively. Binary logistic regression analyses were carried out for football and tennis separately to examine the associations between time use (time spent on various activities and changes related to the school and job situation), and environmental factors on the probability of dropping out from sports. Time spent on sports outside the context of the sports club, and time spent on social or voluntary activities at the sports club was positively associated with continuing being football and tennis members. Tennis players who changed schools or participated in two sports at the same time had a higher probability of dropping out, whereas tennis players who travelled greater distances from home to the tennis club were less likely to drop out. Determinants of dropout differed between football and tennis. However, time use variables were important predictors of dropout from football as well as tennis, whereas environmental determinants hardly contributed to the prediction of dropout. To keep youths involved in organized sports, this study recommends that sports professionals should: 1) offer flexibility in training and competition schedules, 2) stimulate participation in social activities and voluntary work at the sports club, 3) pay special attention to their needs and preferences, and 4) encourage possibilities to practice and play sports outside of regular training hours, for instance at the sports club or at playgrounds or parks in the neighbourhood.


#4 The effect of playing status, maturity status, and playing position on the development of match skills in elite youth football players aged 11-18 years: A mixed-longitudinal study
Reference: Eur J Sport Sci. 2018 Aug 17:1-12. doi: 10.1080/17461391.2018.1508502. [Epub ahead of print]
Authors: Saward C, Morris JG, Nevill ME, Sunderland C
Summary: This mixed-longitudinal study examined the development of match skills in elite male youth footballers (aged 11-18 years), while considering the effect of playing status, maturity status, and playing position. Across two seasons, 126 elite male youth footballers were assessed in 1-10 competitive matches (401 player-matches). For each match, the on-the-ball actions of each player were recorded using a notation system. The match skills observed were frequencies of successful passes, on-target shots, dribbles, crosses, clearances, and tackles/blocks/interceptions. Multilevel Poisson analysis was used to model the development of players, with regard to each match skill. Modelling revealed significant (p < .05) age-related changes in the frequency of several match skills. That is, dribbles increased, on-target shots, crosses and tackles/blocks/interceptions decreased, whereas changes in successful passes were position-specific. Players retained by an academy performed more dribbles compared to released players (p < .05) (e.g. retained vs. released 18-year-old centre forward = 4.1 vs. 2.0 dribbles per hour), and retained defenders performed more tackles/blocks/interceptions than released defenders (p < .05) (e.g. retained vs. released 18-year-old, on-time maturing centre back = 12.5 vs. 10.2 tackles/blocks/interceptions per hour). Moreover, compared to on-time maturing players, early maturing players performed more tackles/blocks/interceptions (p < .05) (e.g. on-time vs. early maturing retained 18-year-old centre back = 12.5 vs. 15.2 tackles/blocks/interceptions per hour). Playing position affected all match skills (p < .05). The developmental profiles of match skills presented here may support experts in identifying and developing talented footballers across a wide age range, while considering the influence of maturity status and playing position.


#5 Evaluation of Muscle Injuries in Professional Football Players: Does Coach Replacement Affect the Injury Rate?
Reference: Clin J Sport Med. 2018 Aug 15. doi: 10.1097/JSM.0000000000000640. [Epub ahead of print]
Authors: Dönmez G, Kudaş S, Yörübulut M, Yıldırım M, Babayeva N, Torgutalp ŞŞ
Summary: The objective was to assess the incidence and characteristics of muscle injuries in professional football players and to assess if coach dismissal may be related with muscle injuries within 1-month period from the dismissal. One hundred eighteen male football players from the Turkis first league participated in this study. Data on time-loss muscle injuries confirmed using magnetic resonance imaging were recorded, including type, body part, duration, and lay-off time, and training session and match exposure times. The muscle injury rate was evaluated at 2 weeks and 30 days after coach dismissal. In total, 124 muscle injuries were recorded, with injury incidences of 2.3 muscle injuries per 1000 hours of exposure overall, 1.2 in training sessions, and 13.6 in matches. Injury time loss ranged from 3 to 67 days (median, 13 days). Eighteen percent of the injuries (n = 23) were recurrent; no association was found between recurrence rate and the player's age or position (P = 0.15, P = 0.27, respectively). Recurrent injuries caused more severe injuries (26.1%, P = 0.02) and longer median lay-off time (P = 0.01). During the study, teams A and B replaced 7 and 3 coaches, respectively. The injury incidence increased to 5.3 per 1000 hours of exposure in the 2 weeks after the coach dismissal, and decreased to 4.5 within 1 month of coach dismissal. Given the link between coach dismissal and increased rates of muscle strain injuries, increased attentiveness to preventing muscle injuries during coaching transitions and to the impact of new training regimens is required by trainers and medical teams.


#6 Overuse injuries are prevalent in children's competitive football: a prospective study using the OSTRC Overuse Injury Questionnaire
Reference: Br J Sports Med. 2018 Aug 14. pii: bjsports-2018-099218. doi: 10.1136/bjsports-2018-099218. [Epub ahead of print]
Authors: Leppänen M, Pasanen K, Clarsen B, Kannus P, Bahr R, Parkkari J, Haapasalo H, Vasankari T
Summary: The purpose was to investigate the prevalence and burden of overuse injuries in children's football as well as player characteristics and their association with overuse injury risk. This investigation is based on the control arm (10 clubs) of a randomised controlled trial investigating prevention of injuries in youth football. We conducted a prospective 20-week follow-up study on overuse injuries among Finnish football players (n=733, aged 9-14 years). Each week, we sent a text message to players' parents to ask if the player had sustained any injury during the past week. Players with overuse problem were interviewed over the phone using an overuse injury questionnaire. The main outcome measures were prevalence of all overuse injuries and substantial overuse injuries (those leading to moderate or severe reductions in participation or performance) and injury severity. The average response rate was 95%. In total, 343 players (46.8%) reported an overuse problem while in the study. The average weekly prevalence of all overuse problems and substantial overuse problems was 12.8% and 6.0%, respectively. Injuries affecting the knee had the highest weekly prevalence (5.7% and 2.4% for all and substantial knee problems, respectively). Girls had a higher likelihood of knee problems (OR 2.70; 95% CI 1.69 to 4.17), whereas boys had a higher likelihood of heel problems (OR 2.82; 95% CI 1.07 to 7.44). The likelihood of reporting an overuse problem increased with age (OR 1.21; 95% CI 1.00 to 1.47). Overuse injuries are prevalent in children's competitive football. Knee overuse injuries represent the greatest burden on participation and performance.


#7 Communication quality between the medical team and the head coach/manager is associated with injury burden and player availability in elite football clubs
Reference: Br J Sports Med. 2018 Aug 13. pii: bjsports-2018-099411. doi: 10.1136/bjsports-2018-099411. [Epub ahead of print]
Authors: Ekstrand J, Lundqvist D, Davison M, D'Hooghe M, Pensgaard AM
Download link: https://bjsm.bmj.com/content/bjsports/early/2018/08/21/bjsports-2018-099411.full.pdf
Summary: We investigated medical staff interpretations and descriptions of internal communication quality in elite football teams to determine whether internal communication was correlated with injuries and/or player availability at training and matches. Medical staff from 36 elite football clubs across 17 European countries produced 77 reports at four postseason meetings to provide their perceptions of internal communications in their teams. They also recorded data on individual players' exposure to football and time-loss injuries. The injury burden and incidence of severe injuries were significantly higher in teams with low quality of communication between the head coach/manager and the medical team (scores of 1-2 on a 5-point Likert scale) compared with teams with moderate or high-quality scores (scores of 3-5; p=0.008 for both). Teams with low scores had 4%-5% lower training attendance (76% vs 83%, p=0.001) and less availability at matches (82% vs 88%, p=0.004) compared with teams with moderate or high communication quality scores. The quality of internal communication within a team was correlated with injury rates, training attendance and match availability.


#8 An Augmented Perceptual-Cognitive Intervention Using a Pattern Recall Paradigm With Junior Soccer Players
Reference: Front Psychol. 2018 Aug 23;9:1260. doi: 10.3389/fpsyg.2018.01260. eCollection 2018.
Authors: Schorer J, Schapschröer M, Fischer L, Habben J, Baker J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6115512/pdf/fpsyg-09-01260.pdf
Summary: In sport, perceptual skill training software is intended to assist tactical training in the field. The aim of this field study was to test whether "laboratory-based" pattern recall training would augment tactical skill training performed on the field. Twenty-six soccer players between 14 and 16 years of age from a single team participated in this study and were divided into three groups. The first received field training on a specific tactical skill plus cognitive training sessions on the pattern recall task. The second performed only the field training while the third group served as a control group and had field training on other topics. The task on the pre-, post-, and retention-tests was to recall specific soccer patterns displayed on a computer screen. Results showed significant changes between pre- and post-test performance. There was no significant interaction between groups and tests but the effect size was large. From pre- to retention-test, there was a significant difference between tests and an interaction between groups and tests, but no main effect difference between groups. On the basis of significance testing only retention was affected by the additional training, however, descriptive results and effect sizes from pre- to post-test were as expected and suggested there were learning benefits. Together these results indicate that augmented perceptual-cognitive training might be beneficial, but some limitations in our study design (e.g., missing field test, missing placebo group, etc.) need to be improved in future work.


#9 Effect of a 6-week supervised detraining period on bone metabolism markers and their association with ergometrics and components of the hypothalamic-pituitary-gonadal (HPG) axis in professional male soccer players
Reference: J Bone Miner Metab. 2018 Sep 5. doi: 10.1007/s00774-018-0947-7. [Epub ahead of print]
Authors: Koundourakis NE, Androulakis N, Dermitzaki E, Venihaki M, Margioris AN
Summary: The aim of this study was to examine the effect of a supervised 6-week detraining period on bone metabolism markers, and their association with ergometrics, and components of the hypothalamic-pituitary-gonadal (HPG) axis in elite male professional soccer players. Sixty-seven soccer players (mean age ± SD 23.4 ± 5.2 years) that were following a supervised training program participated in this study. Players were tested twice: immediately after the conclusion of the competition period, and following the detraining period, for the determination of bone-turnover rates, ergometrics, and components of the HPG-axis. The detraining period resulted in significant reduction in osteocalcin [OC] (p < 0.001), C-terminal propeptide of collagen type-I [CICP] (p = 0.002), and bone-alkaline-phosphatase [b-ALP] (p < 0.001) values, while C-terminal telopeptide [CTX] was increased (p < 0.001). No significant relationships were apparent between bone biomarkers and body weight, body-fat %, total testosterone, free testosterone, estradiol, follicle-stimulating hormone, and luteinizing hormone in both experimental sessions (p > 0.05). Similarly, despite the deterioration in ergometrics after detraining (all p < 0.001), no significant correlations were evident (p > 0.05) between bone biomarkers and maximal oxygen consumption, squat jump, countermovement jump, and 20 m sprint performance, and also between % change of bone biomarkers and ergometrics, apart from a weak relationship (p = 0.041) between OC and VO2max of questionable value. Our results suggest that the 6-week soccer off-season detraining period in our study negatively affected bone physiology as reflected by the suppression of bone-formation rate and a parallel induction of bone resorption. The cause of this acute alteration of bone-turnover rates is not related to the examined components of the HPG-axis, although parallels is not associated with the changes in ergometrics.


#10 Epidemiology of Upper Extremity Soccer Injuries Among High School- and College-Aged Players in the United States: An Analysis of the 1999-2016 NEISS Database
Reference: Sports Health. 2018 Sep 5:1941738118795483. doi: 10.1177/1941738118795483. [Epub ahead of print]
Authors: Durand WM, Goodman AD, Giglio P, Etzel C, Owens BD
Summary: Although lower extremity injuries are more common than upper extremity injuries in high school- and college-aged soccer players, upper extremity injuries may be equally severe. The epidemiology of upper extremity injuries is poorly characterized in this population.  The authors hypothesis that upper extremity injuries are an important contributor to soccer-related morbidity among high school- and college-aged players. The National Electronic Injury Surveillance System (NEISS) is a nationally representative sample of 100 hospital emergency departments (EDs). Each record contains demographic and injury information. Records from 1999 to 2016 were analyzed, including patients between the ages of 14 and 23 years with a soccer-related injury sustained at school or during an athletic event. A total of 1,299,008 high school- or college-aged patients presented to the ED for a soccer-related injury from 1999 to 2016, of which 20.4% were in the upper extremity. Patients were predominantly male (58.0%) and high school-aged (81.4%). Males constituted a greater proportion of upper extremity injuries when compared with other injury locations (63.5% male for upper extremity). Upper extremity injuries were more likely to be fractures (43.7% vs 13.9%) and dislocations (7.1% vs 3.4%) and less likely to be strains/sprains (27.8% vs 56.6%). Males suffered more shoulder dislocations (81.8% males among patients with shoulder dislocation vs 57.8% among those with other injuries), finger dislocations (72.0% vs 58.0%), upper arm fractures (74.9% vs 57.6%), and forearm fractures (68.3% vs 57.3%). Upper extremity injuries are frequent in high school- and college-aged soccer players presenting to the ED. Efforts to reduce soccer-related injuries should include strategies targeting the upper extremity, perhaps reducing the incidence of high-energy falls. Efforts to reduce soccer-related injuries should include strategies targeting upper extremity injuries, particularly among males and college-aged players.


#11 Pathogenic Factors Associated With Osgood-Schlatter Disease in Adolescent Male Soccer Players: A Prospective Cohort Study
Reference: Orthop J Sports Med. 2018 Aug 28;6(8):2325967118792192. doi: 10.1177/2325967118792192. eCollection 2018 Aug.
Authors: Watanabe H, Fujii M, Yoshimoto M, Abe H, Toda N, Higashiyama R, Takahira N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6113738/pdf/10.1177_2325967118792192.pdf
Summary: A previous cross-sectional study reported that pathogenic factors associated with Osgood-Schlatter disease (OSD) in adolescent athletes include increased quadriceps muscle tightness, lower leg malalignment, and development of apophysitis in the tibial tuberosity. The purpose was to confirm these pathogenic factors associated with OSD in a longitudinal study with regard to physical function and performance. In this study, 37 boys (mean age, 10.2 ± 0.4 years) were recruited from 2 soccer teams at an elementary school. This cohort study was conducted over an observation period of 1 year, with measurements recorded at baseline, followed by screening for OSD every 6 months. Variables evaluated at baseline included physical function (morphometry, joint flexibility, and lower extremity alignment), presence of Sever disease, and kicking motion. Pathogenic factors associated with OSD in the support leg of adolescent male soccer players included height, weight, body mass index, quadriceps femoris muscle tightness in the kicking and support legs, and gastrocnemius muscle tightness, soleus muscle tightness, and medial longitudinal arch in the support leg. Additional factors included a diagnosis of Sever disease and distance from the lateral malleolus of the support leg's fibula to the center of gravity during kicking. The onset of OSD was found to be affected by many factors, including developmental stage, physical attributes, and pre-existing apophysitis. In particular, a diagnosis of Sever disease and backward shifting of the center of gravity during kicking increased the risk of the subsequent onset of OSD, suggesting that these factors are very important as a possible focus for interventions.


#12 Inter-individual Variability in Responses to 7 Weeks of Plyometric Jump Training in Male Youth Soccer Players
Reference: Front Physiol. 2018 Aug 20;9:1156. doi: 10.3389/fphys.2018.01156. eCollection 2018.
Authors: Ramirez-Campillo R, Alvarez C, Gentil P, Moran J, García-Pinillos F, Alonso-Martínez AM, Izquierdo M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6109752/pdf/fphys-09-01156.pdf
Summary: The purpose of this study was to compare the inter-individual variability in the effects of plyometric jump training (PJT) on measures of physical fitness (sprint time, change of direction speed, countermovement jump, 20- and 40-cm drop jump reactive strength index, multiple five bounds distance, maximal kicking distance, and 2.4-km time trial) in youth soccer players who completed a PJT program versus players who completed soccer training only. In a single-blinded study, participants aged between 10 and 16 years were randomly divided into a PJT group (n = 38) and a control group (n = 38). The experimental group participated in a PJT program twice weekly for 7 weeks, whereas the control group continued with their regular soccer training sessions. Between-group differences were examined using a Mann-Whitney U test. Nonresponders where defined as individuals who failed to demonstrate any beneficial change that was greater than two times the typical error of measurement from zero. The results indicated that the mean group improvement for all physical fitness measures was greater (p < 0.05) in the PJT group (Δ = 0.4 to 23.3%; ES = 0.04 to 0.58) than in the control group (Δ = 0.1 to 3.8%; ES = 0.02 to 0.35). In addition, a significantly greater (p < 0.05) number of responders across all dependent variables was observed in the PJT group (from 4 up to 33 responders) than in the control group (from 0 up to 9 responders). In conclusion, compared to soccer training only, PJT induced greater physical fitness improvements in youth soccer players, with a greater number of responders for all the physical fitness tests related to jumping, speed, change of direction speed, endurance, and kicking technical ability.


#13 Heart Rate and Perceived Experience Differ Markedly for Children in Same- versus Mixed-Gender Soccer Played as Small- and Large-Sided Games
Reference: Biomed Res Int. 2018 Aug 5;2018:7804642. doi: 10.1155/2018/7804642. eCollection 2018.
Authors: Póvoas S, Randers MB, Krustrup P, Larsen MN, Pereira R, Castagna C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6098911/pdf/BMRI2018-7804642.pdf
Summary: This study examines heart rate (HR) and perceived experience during same- versus mixed-gender soccer played as small- (SSG) and large-sided (LSG) games. HR, rating of perceived exertion (RPE), and fun scores were determined in 134 pupils (50 girls, 84 boys) randomly assigned to same- and mixed-genders formats playing 2x15-min of SSG (2v2, 4v4) and LSG (12v12) in a random order (~50 m2/player). HR was lower (p≤0.03) for girls when playing together with boys than when playing alone (71±10 versus 77±7%HRmax), while being similar for boys playing mixed- or same-gender games (74±7 versus 77±4%HRmax). Boys perceived less fun when playing together with girls than when playing alone (4.4±2.3 versus 6.3±2.3, p<0.001). Irrespective of gender, higher (p<0.001) HRmean, %time>80%HRmax, and RPE were observed during 2v2 (78±9%HRmax, 43±33%, 5.5±2.5) and 4v4 (76±9%HRmax, 39±32%, 5.5±2.7) than during 12v12 (70±10%HRmax, 23±27%, 3.8±2.9). Cardiovascular strain was lower for girls when playing together with boys than when playing alone in LSG. SSG were more intense than LSG when girls played mixed-gender games and when boys played mixed- and same-gender games. When boys played mixed-gender games, SSG were considered more fun than LSG. Physical education teachers and coaches should consider gender and game format differences when using soccer.

Thu

25

Oct

2018

Latest research in football - week 34 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Changes in biomechanical knee injury risk factors across two collegiate soccer seasons using the 11+ prevention program
Reference: Scand J Med Sci Sports. 2018 Aug 17. doi: 10.1111/sms.13278. [Epub ahead of print]
Authors: Arundale AJH, Silvers-Granelli HJ, Marmon A, Zarzycki R, Dix C, Snyder-Mackler L
Summary: The 11+ injury prevention program effectively reduces injuries in high school aged female soccer player, but the mechanism of the 11+ is unknown, particularly whether it impacts biomechanical risk factors associated with knee injuries. The purpose was to report the changes in hip and knee biomechanics with use of the 11+ over two soccer seasons. Two collegiate women's soccer teams performed the 11+ for two soccer seasons. A control team was followed for one season. Athletes performed motion analysis of a drop vertical jump during preseason and postseason. Both groups had meaningful increases in peak knee abduction angle over the first season, and there were no meaningful changes in peak knee abduction moment over either season. The control group had bilateral decreases in knee flexion angle. The program did not seem to systematically impact biomechanical risk factors associated with knee injuries, with increase in peak knee abduction angle no bilateral changes in frontal or transverse hip motion. The 11+ may have mitigated clinically meaningful decreases in knee flexion, however as ACL injuries do not occur purely in the sagittal plane, it is unclear the impact of these changes. The results of this study indicate that the 11+ may require some modifications to impact landing biomechanics and potentially risky movement patterns, particularly when used in collegiate women over multiple seasons


#2 Timing Training in Female Soccer Players: Effects on Skilled Movement Performance and Brain Responses
Reference: Front Hum Neurosci. 2018 Aug 2;12:311. doi: 10.3389/fnhum.2018.00311. eCollection 2018.
Authors: Sommer M, Häger CK, Boraxbekk CJ, Rönnqvist L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082929/pdf/fnhum-12-00311.pdf
Summary: Although trainers and athletes consider "good timing skills" critical for optimal sport performance, little is known in regard to how sport-specific skills may benefit from timing training. Accordingly, this study investigated the effects of timing training on soccer skill performance and the associated changes in functional brain response in elite- and sub-elite female soccer players. Twenty-five players (mean age 19.5 years; active in the highest or second highest divisions in Sweden), were randomly assigned to either an experimental- or a control group. The experimental group (n = 12) was subjected to a 4-week program (12 sessions) of synchronized metronome training (SMT). We evaluated effects on accuracy and variability in a soccer cross-pass task. The associated brain response was captured by functional magnetic resonance imaging (fMRI) while watching videos with soccer-specific actions. SMT improved soccer cross-pass performance, with a significant increase in outcome accuracy, combined with a decrease in outcome variability. SMT further induced changes in the underlying brain response associated with observing a highly familiar soccer-specific action, denoted as decreased activation in the cerebellum post SMT. Finally, decreased cerebellar activation was associated with improved cross-pass performance and sensorimotor synchronization. These findings suggest a more efficient neural recruitment during action observation after SMT. To our knowledge, this is the first controlled study providing behavioral and neurophysiological evidence that timing training may positively influence soccer-skill, while strengthening the action-perception coupling via enhanced sensorimotor synchronization abilities, and thus influencing the underlying brain responses.


#3 Somatotype Hormone Levels and Physical Fitness in Elite Young Soccer Players over a Two-Year Monitoring Period
Reference: J Sports Sci Med. 2018 Aug 14;17(3):455-464. eCollection 2018 Sep.
Authors: Hammami MA, Ben Abderrahman A, Rhibi F, Nebigh A, Coppalle S, Ravé G, Tabka Z, Zouhal H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090385/pdf/jssm-17-455.pdf
Summary: The effect of two soccer-training seasons on the growth, development and somatotype hormone concentrations of elite youth soccer players were evaluated. Eighteen elite soccer players and 18 age-matched non-athletic control subjects participated in the study. Anthropometric-measurements, aerobic and anaerobic performance tests and serum concentrations of insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), and growth hormone (GH) were assessed at 5 time points across two competitive seasons. Soccer players revealed higher GH, IGF-1 and IGFBP-3 than the control group across all-time points. Significant moderate correlations were observed only in soccer players between hormonal concentrations (IGF-1 and IGFBP-3) and the jumping tests (r = 0.45-0.48; p < 0.01). Somatotropic axis hormones, anthropometric and physical parameters increased to a greater degree with growth and soccer training combined compared to growth alone. Results from this investigation revealed that intense training did not impair growth or development in these young soccer players across 2-year period.


#4 Effects of Spatiotemporal Constraints and Age on the Interactions of Soccer Players when Competing for Ball Possession
Reference: J Sports Sci Med. 2018 Aug 14;17(3):379-391. eCollection 2018 Sep.
Authors: Menuchi MRTP, Moro ARP, Ambrósio PE, Pariente CAB, Araújo D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090386/pdf/jssm-17-379.pdf
Summary: Although there are several descriptions of interpersonal coordination in soccer teams, little is known about how such coordination is influenced by space and time constraints. In this study, we analyzed variations in interpersonal coordination under different marking intensities and across different age groups. Marking intensity was manipulated by changing the players' game space and time of ball possession in a conditioned soccer game known as rondo. Five participants in each age category (U13, U15, U17, and U20) performed rondo tasks in four experimental conditions, in a total of 134 trials. The dependent variables considered were pass performance and eco-physical variables capturing the player-environment coupling, such as coupling of the marking between players. Our results demonstrate that in soccer: (1) markers and passers are tightly coupled; (2) the marker-passer coupling emerges from a flexible and adaptive exchange of passes; (3) the marker-passer coupling is stronger in markings of higher intensity and older age groups. Thus, the interactions between soccer players in marking can be analyzed as an emerging and self-organized process in the context of group performance.


#5 Behaviours of shooter and goalkeeper interact to determine the outcome of soccer penalties
Reference: Scand J Med Sci Sports. 2018 Aug 15. doi: 10.1111/sms.13276. [Epub ahead of print]
Authors: Hunter AH, Angilletta MJ Jr, Wilson RS
Summary: During a soccer penalty, the shooter's strategy and the goalkeeper's strategy interact to determine the outcome. However, most models of penalty success overlook its interactive nature. Here, we quantified aspects of shooter and goalkeeper strategies that interact to influence the outcome of soccer penalties - namely, how the speed of the shot affects the goalkeeper's leave-time or shot-blocking success, and the effectiveness of deceptive strategies. We competed 7 goalkeepers and 17 shooters in a series of penalty shootout competitions with a total of 1278 shot taken. Each player was free to use any strategy within the rules of a penalty shot and game-like pressure was created via monetary incentive for goal-scoring (or blocking). We found that faster shots lead to earlier leave-times and were less likely blocked by goalkeepers, and-unlike most previous studies-that deceptive shooting strategies did not decrease the likelihood goalkeepers moved in the correct direction. To help identify optimal strategies for shooter's and goalkeepers, we generated distributions and mathematical functions sport scientist can use to develop more comprehensive models of penalty success.


#6 Recreational soccer as sport medicine for middle-aged and older adults: a systematic review
Reference: BMJ Open Sport Exerc Med. 2018 Aug 9;4(1):e000336. doi: 10.1136/bmjsem-2017-000336. eCollection 2018.
Authors: Luo H, Newton RU, Ma'ayah F, Galvão DA, Taaffe DR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6089298/pdf/bmjsem-2017-000336.pdf
Summary: Strategies to prevent or attenuate the age-related decline in physical and physiological function and reduce chronic disease risk factors are of clinical importance. The objective was to examine the health benefits of recreational soccer in middle-aged and older adults. All available records up until 9 June 2017 in PubMed, Web of Science, SPORTDiscus, MEDLINE, Embase, CINAHL Plus, PsycINFO and Cochrane Library databases were utilize.  Eligibility criteria for selecting studies were: All randomised trials with or without a control group (randomised controlled trials or randomised uncontrolled trials) and non-randomised controlled trials that used recreational soccer, which includes small-sided soccer games, as the sole or principal intervention, and reported relevant effects in untrained/sedentary, healthy or unhealthy adults aged 40 years and above were included. Five trials described in 13 articles were included, which scored 6-9 out of 12 points on the modified Delphi quality rating scale. The duration was from 12 to 52 weeks, with various frequencies, volumes and game formats performed both outdoors and indoors with men and women. The trials indicate that recreational soccer may result in improvement in cardiovascular function, body composition and functional ability, although no significant changes were observed in postural balance. Recreational soccer should be considered an alternative exercise modality for untrained, healthy or unhealthy middle-aged and older adults of both sexes to maintain an active lifestyle and mitigate a wide array of physical and physiological age-related changes.


#7 Effects of short-term in-season break detraining on repeated-sprint ability and intermittent endurance according to initial performance of soccer player
Reference: PLoS One. 2018 Aug 15;13(8):e0201111. doi: 10.1371/journal.pone.0201111. eCollection 2018.
Authors: Rodríguez-Fernández A, Sánchez-Sánchez J, Ramirez-Campillo R, Rodríguez-Marroyo JA, Villa Vicente JG, Nakamura FY
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0201111&type=printable
Summary: The objective was to better understand the detraining effects in soccer, the purpose of the study was to analyse if performance level of soccer players modulate repeated-sprint ability (RSA) and intermittent endurance changes during 2-weeks of detraining (i.e., in-season break). Seventeen professional and sixteen young elite soccer players of two different teams performed, before and after 2-weeks of detraining, the RSA test and the Yo-Yo Intermittent Recovery Test, level 1 (YYIR1). Before detraining, professional players perform better (p < 0.05) RSA best time (RSAbest) than young players. A decrease (p < 0.05) in RSAbest, RSA total time (RSAtotal) and mean time (RSAmean) performance was observed in both teams, without changes in RSA fatigue index (Sdec). No significant changes in distance covered during YYIR1 was observed in any team. Before detraining, faster players from both teams (FG) (following the median split technique, soccer players with RSAbest ≤ 3.95 s) performed better (p < 0.01) in RSAtotal, RSAmean and RSAbest, but worse (p < 0.01) in Sdec. Although FG and the slower players (SG, RSAbest > 3.95 s) showed a worse (p < 0.05) RSAtotal, RSAbest and RSAmean performance after detraining (ES = 1.5, 1.4 and 2.9; ES = 0.6, 1.2 and 0.6; for FG and SG, respectively), the deterioration was greater in the FG for RSAbest (p < 0.05) and RSAtotal (ES = 1.46). After detraining, FG improved (p < 0.05) Sdec performance. In conclusion, a 2-week in-season break (detraining) period induced a worse RSA, with no effect on intermittent endurance in professional and elite young soccer players, with greater detrimental effects on RSAtotal and RSAbest in FG. In addition, Sdec does not seem to be sensitive to changes in RSA after a 2-week in-season break.


#8 Enhancing motor learning of young soccer players through preventing an internal focus of attention: The effect of shoes colour
Reference: PLoS One. 2018 Aug 15;13(8):e0200689. doi: 10.1371/journal.pone.0200689. eCollection 2018.
Authors: De Giorgio A, Sellami M, Kuvacic G, Lawrence G, Padulo J, Mingardi M, Mainolfi L
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0200689&type=printable
Summary: The purpose of this research was to assess how the motor learning skills in 7-years old soccer players can be improved by preventing an internal focus of attention via the use coloured shoes. We painted the classic black soccer shoes in six areas corresponding to six regions of the foot with which it is possible to interact with the ball. Thirty-four 7-years-old soccer players were randomized to two groups (Coloured n = 17 and Black, n = 17) to perform four basic football manoeuvres/tasks: reception (RECP), passing (PASS), ball management (MAGT), and shooting (SHOT). We found highly significant differences (P<0.001) in all four performance tests: mean(sd) RECP: 0.82(0.07) vs. 0.45(0.12); PASS: 0.85(0.07) vs. 0.47(0.09); MAGT: 0.91(0.09); SHOT: 1.00(1.00) vs. 0.44(0.16). Colored shoes appear to draw children's attention away from body centered cues without explicit verbal communications. We propose that this cognitive adaptation enhanced the technical gesture by preventing the negative processes associated with action constraining when adopting an internal focus attention (perhaps by allowing the foot to adapt to surfaces and movements more naturally than conditions that promote a focus on the body movement). Consequently, this type of coloured footwear could be used during childhood to allow children to enhance the performance of basic football exercises through preventing action constraining and promoting intuitive (non-body centered) action knowledge.


#9 Electromyographic analysis of hip adductor muscles in soccer instep and side-foot kicking
Reference: Sports Biomech. 2018 Aug 13:1-12. doi: 10.1080/14763141.2018.1499800. [Epub ahead of print]
Authors: Watanabe K, Nunome H, Inoue K, Iga T, Akima H
Summary: A possible link between soccer-specific injuries, such as groin pain and the action of hip adductor muscles has been suggested. This study aimed to investigate neuromuscular activation of the adductor magnus (AM) and longus (AL) muscles during instep and side-foot soccer kicks. Eight university soccer players performed the two types of kick at 50%, 75% and 100% of the maximal ball speed. Surface electromyography (EMG) was recorded from the AM, AL, vastus lateralis (VL) and biceps femoris (BF) muscles of both kicking and supporting legs and the kicking motions were three-dimensionally captured. In the kicking leg, an increase in surface EMG with an increase in ball speed during instep kicking was noted in the AM muscle (p < 0.016), but not in AL, VL or BF muscles (p > 0.016). In the supporting leg, surface EMG of both AM and AL muscles was significantly increased with an increase in the ball speed before ball impact during both instep and side-foot kicks (p < 0.016). These results suggest that hip adductor muscles markedly contribute to either the kicking or supporting leg to emphasise the action of soccer kicks.


#10 Meniscal fixation is a successful treatment for hypermobile lateral meniscus in soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 11. doi: 10.1007/s00167-018-5080-6. [Epub ahead of print]
Authors: Steinbacher G, Alentorn-Geli E, Alvarado-Calderón M, Barastegui D, Álvarez-Díaz P, Cugat R
Summary: The purpose was to report the outcomes (subjective function, return to play, complications and reoperations) of arthroscopic all-inside meniscal fixation in a large sample of soccer players with hypermobile lateral meniscus. Between 2010 and 2015, 55 patients undergoing surgical treatment for hypermobile lateral meniscus at Mutualidad Catalana de Futbolistas (Barcelona, Spain) were identified. Patients with open physes, associated injuries, discoid meniscus, or clinical follow-up less than 6 months were excluded. Once identified, all patients were contacted over the phone to collect cross-sectional data on International Knee Documentation Committee (IKDC) score, postoperative Tegner score, and postoperative visual analogue scale (VAS) for pain. In addition, complications and reoperations were retrospectively collected. Forty-six cases (in 45 patients) with a mean (SD) age of 26.3 (9.5) years and mean (SD; range) follow-up of 43 (19.5; 8-73) months were included. The pre- and post-operative median (range) Tegner score was 9 (6-9) and 8 (0-9), respectively. Compared to the preoperative period, the postoperative Tegner score was equal in 27/46 (59%) cases and lower in 16/46 (35%) cases (3 missing values). Return to play was possible in 38/46 (82%) cases, from which 27/46 (59%) corresponded to the same pre-injury activity level. Postoperatively, the median (range) VAS for pain was 1 (0-9), and the mean (SD) subjective IKDC was 86.2 (16.7). Three of the 46 cases (6.5%) required a reoperation because of pain in one patient (meniscal suture failure) and meniscal tear in two patients. All-inside meniscal fixation is a successful treatment for hypermobile lateral meniscus, which allows acceptable return to play and good function in soccer players at a low reoperation rate. However, according to the present cross-sectional case series, players should be advised that return to the same pre-injury activity level is achieved in only 27 of 46 (59%) of the cases. Surgeons facing with the difficult problem of hypermobile lateral meniscus in soccer players should consider meniscus fixation as an easy and successful option.


#11 Attitudes and Experiences of Men with Prostate Cancer on Risk in the Context of Injuries Related to Community-based Football - A Qualitative Study
Reference: J Aging Phys Act. 2018 Aug 17:1-24. doi: 10.1123/japa.2018-0089. [Epub ahead of print]
Authors: Rørth M, Tjørnhøj-Thomsen T, Cormie P, Oliffe JL, Midtgaard J
Summary: While football training may be a potent strategy for health promotion in older men, the considerable risk of injuries may constitute a barrier for referral of clinical populations. The current study explored the attitudes of men with prostate cancer on risk in the context of injuries related to participating in a community-based football program. Four videotaped focus group interviews, and three individual in-depth telephone interviews were carried out with men with prostate cancer (n=35; mean age 68.8). Thematic networks technique was used to derive the global theme Injury-induced reinforced masculinity comprising five sub-themes: "Part of the game", "A good story to tell", "Like boys again", "An old, carefree body", and "Camaraderie". Collectively, these themes explained how football injuries may reflect masculine ideals in some men with prostate cancer. The study indicates that injuries are largely acceptable to men with prostate cancer, especially those in search of a means for expressing their masculinity.

Wed

24

Oct

2018

Latest research in football - week 33 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Speed synchronization, physical workload and match-to-match performance variation of elite football players
Reference: PLoS One. 2018 Jul 24;13(7):e0200019. doi: 10.1371/journal.pone.0200019. eCollection 2018.
Authors: Gonçalves B, Coutinho D, Travassos B, Folgado H, Caixinha P, Sampaio J
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0200019&type=printable
Summary: This study aimed to: (i) examine whether the speed synchronization and physical performance of an elite football team changed between the first and the second half, using match time blocks of 15-min, and (ii) explore the match-to-match variation of players' speed synchronization performance. Twenty-eight outfield elite footballers participated in 51 official matches. Positional data were gathered and used to calculate the total distance covered as a physical workload indicator. For all the outfield teammate dyad combinations (45 pairs), it was processed the percentage of time that players' speed was synchronized during walking, jogging and running using relative phase (Hilbert Transform). Also, the match-to-match variation of the players' speed synchronization, expressed in coefficient of variation was computed. The differences in the total distance covered from all players within the different match's time block periods revealed a moderate decrease in the distance covered in the last 15-min of the match compared to the first 15-min (-6.5; ±1.07%, most likely: change in means with 95% confidence limits). However, when compared the last minutes from both halves a small increase was observed (2.7; ±1.2%, likely) from first to second half. The synchronization of the players' speed displacements revealed small to moderate decreases in the % of synchronization in the second half periods for the jogging and running speed, while the opposite was found for the walking speed (~13 to 24% more, most likely). The playing position analysis for the walking zone showed similar trends between the groups, with small to moderate higher values in the second half, with the exception of [30'-45'] vs [75'-90'] in the midfielder's dyads and in [15'-30'] vs [60'-75'] match periods for forwards. Similar trend was found during the running speed, in which small to moderate higher synchronization was found during the first half periods, with the exception of [15'-30'] vs [60'-75'] and [30'-45'] vs [75'-90'] in midfielder's dyads. Regarding to the match-to-match variation of the players' speed synchronization, overall results showed small to moderate increases in coefficient of variation during jogging and running displacements from the beginning to the end of the match (32.1; ±13.2% increase in jogging and 26.2; ±10.5% in running, both comparisons most likely). The higher distance covered during most of the first half periods and the higher dyadic synchronization at high speeds might have limited players' performance in the second half. In addition, the decrease trend in speed synchronization during the second half periods might have resulted from accumulated muscular and mental fatigue towards the match. Within, the match-to-match variation in tactical-related variables increased across the match duration, with especial focus in the midfielder dyads. Dyadic speed synchronization might provide relevant information concerning the individual and collective performance.


#2 Kinematic and kinetic analysis of the goalkeeper's diving save in football
Reference: J Sports Sci. 2018 Jul 23:1-9. doi: 10.1080/02640414.2018.1499413. [Epub ahead of print]
Authors: Ibrahim R, Kingma I, de Boode VA, Faber GS, van Dieën JH
Summary: Kinetics and full body kinematics were measured in ten elite goalkeepers diving to save high and low balls at both sides of the goal, aiming to investigate their starting position, linear and angular momentum, and legs' contribution to end-performance. Our results showed that goalkeepers adopted a starting position with a stance width of 33 ± 1% of leg length, knee flexion angle of 62 ± 18° and hip flexion angle of 63 ± 18°. The contralateral leg contributed more than the ipsilateral leg to COM velocity (p < 0.01), both for the horizontal (2.7 ± 0.1 m·s-1 versus 1.2 ± 0.1 m·s-1) and for the vertical component (3.1 ± 0.3 m·s-1 versus 0.4 ± 0.2 m·s-1). Peak horizontal and peak angular momenta were significantly larger (p < 0.01) for low dives than for high dives with a mean difference of 55 kg·m·s-1 and 9 kg·m2·s-1, respectively. In addition, peak vertical momentum was significantly larger (p < 0.01) for high dives with a mean difference between dive heights of 113 kg·m·s-1. Coaches need to highlight horizontal lateral skills and exercises (e.g. sideward push-off, sideward jumps), with emphasis on pushing-off with the contralateral leg, when training and assessing goalkeeper's physical performance.


#3 High knee loading in male adolescent pre-professional football players: Effects of a targeted training programme
Reference: J Sci Med Sport. 2018 Jul 5. pii: S1440-2440(18)30320-7. doi: 10.1016/j.jsams.2018.06.016. [Epub ahead of print]
Authors: Lagas IF, Meuffels DE, Visser E, Groot FP, Reijman M, Verhaar JAN, de Vos RJ
Summary: The objective was to assess whether targeted neuromuscular exercises can decrease knee loading of adolescent pre-professional footballers with high knee loading as identified with the field-based Drop Vertical Jump Test (DVJT). We undertook a prospective controlled trial, conducted between August and November 2016 at Erasmus Medical Centre, The Netherlands. Pre-professional football players (aged 14-21years) were evaluated at baseline and after 12weeks follow-up with the field-based DVJT. The field-based DVJT is a standardised test in which a player drops from a box and jumps up immediately after landing; knee load is calculated based on five parameters. Players with high knee load (probability≥0.75) from one club performed regular training(control group), and players with high knee load from another other club performed targeted neuromuscular exercises for 12weeks (intervention group). The difference of change in knee load between both groups after 12weeks was the primary outcome measure. Of 107 eligible players, 75 had a high knee loading. Knee loading decreased in both groups after 12weeks of training, but change in probability of high knee load was not significantly different between both groups (95% Confidence Interval [-0.012-0.082], p=0.139). Targeted neuromuscular exercises had no additional effect in decreasing knee loading of adolescent male pre-professional football players compared to regular training.


#4 Implicit learning increases shot accuracy of football players when making strategic decisions during penalty kicking
Reference: Hum Mov Sci. 2018 Jul 18;61:72-80. doi: 10.1016/j.humov.2018.07.004. [Epub ahead of print]
Authors: Navarro M, van der Kamp J, Schor P, Savelsbergh GJP
Summary: Implicit learning has been proposed to improve athletes' performance in dual-task situations. Yet, only a few studies tested this with a sports-relevant dual-task. Hence, the current study aimed to compare the effects of implicit and explicit training methods on penalty kicking performance. Twenty skilled football players were divided in two training groups and took part in a practice phase to improve kicking accuracy (i.e., without a goalkeeper) and in a post-test in order to check penalty kick performance (i.e., accuracy including a decision to kick to the side opposite the goalkeeper's dive). Results found that the implicit and explicit training method resulted in similar levels of decision-making, but after implicit training this was achieved with higher kicking accuracy. Additionally, applications for football players and coaches are discussed.


#5 Osteogenic impact of football training in 55- to 70-year-old women and men with prediabetes
Reference: Scand J Med Sci Sports. 2018 Jul 26. doi: 10.1111/sms.13252. [Epub ahead of print]
Authors: Skoradal MB, Helge EW, Jørgensen NR, Mortensen J, Weihe P, Krustrup P, Mohr M
Summary: The effects of football training on bone health were examined in 55- to 70-year-old sedentary women and men with prediabetes. Patients (n = 50) with prediabetes (age; 61 ± 9 years, BMI 29.7 ± 0.6 kg/m2 , body fat content; 37 ± 1%, VO2max ; 22.7 ± 0.8 mL/min/kg and mean arterial pressure; 104 ± 3 mm Hg) were randomized into a football training group (FTG; n = 27, 14 women) and a control group (CON; n = 23, 11 women). At baseline, 73% and 24% were diagnosed with femur osteopenia and osteoporosis, respectively. FTG performed football training twice weekly 30-60-minute sessions in 16 weeks, and both FTG and CON received professional dietary advice. Pre- and post-intervention whole-body and regional bone mineral content (BMC) and density (BMD) were determined with DXA-scans, and venous blood samples were drawn and analyzed for plasma bone turnover markers. Change scores were greater (P < 0.05) in FTG compared to CON in leg BMD (0.023 ± 0.005 vs -0.004 ± 0.001 g/cm2 ) and in leg BMC (32 ± 8 vs -4 ± 6 g). Between-group changes in favor of FTG (P < 0.05) also occurred in the femur neck BMD (3.2%) and femur shaft BMD (2.5%). Whole-body BMC and BMD were unchanged in both groups during the intervention. In FTG, resting plasma osteocalcin, P1NP, and CTX-1 rose (P < 0.05) by 23 ± 8, 52 ± 9 and 38 ± 7%, with greater change scores (P < 0.05) than in CON. Finally, P1NP (formation)/CTX-1 (resorption) ratio increased (P < 0.05) in FTG (127 ± 15 vs 150 ± 11) from pre- to post-intervention, with no change in CON (124 ± 12 and 123 ± 12). In conclusion, football training provides a powerful osteogenic stimulus and improves bone health in 55- to 70-year-old women and men diagnosed with prediabetes.


#6 Comparison of the lumbopelvic rhythm among adolescent soccer players with and without low back pain
Reference: Int J Sports Phys Ther. 2018 Apr;13(2):171-176.
Authors: Tojima M, Torii S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6063066/pdf/ijspt-13-171.pdf
Summary: Hip-spine incoordination can cause low back pain (LBP) in adolescents. Hip-spine coordination, including the lumbopelvic rhythm (LPR) and the lumbar-hip ratio (LHR), can be used to assess lower limb and spine function. However, there are no reports of the values of LPR or LHR in adolescent soccer players with and without LBP. The purpose of this study was to clarify the effect of LBP on LPR and LHR during trunk extension among adolescent soccer players. One hundred and nine adolescent soccer players were recruited and divided into two groups, one with and one without LBP. Using three-dimensional motion analysis, participants range of motion (ROM) of the lumbar spine (LS) and hip during trunk and hip extension was measured to calculate the LPR and LHR. Paired, two-tailed t-tests were used to compare the LS and hip ROM between the non-LBP and LBP groups, two-way repeated measures analysis of variance was used to compare time with the non-LBP and LBP groups for LHR, and linear prediction was used to describe the LPR. The maximum LS ROM in the LBP group was significantly less than that in the non-LBP group by 6.6 ° (p = .005). There was no difference in the maximum hip ROM between the groups (p = .376). The LHR did not change during trunk extension (F [4, 428] = 1.840, p = .120), the mean LHR was 4.6 in the non-LBP group and 3.7 in the LBP group, and there was no difference between the groups (p = .320). The linear function of the LPR indicated, that when the hip joint was extended by 1 °, the LS extended by 3.2 ° in the non-LBP group (R2 = .997, p < .001) and 2.8 ° in the LBP group (R2 = .999, p < .001). LBP inhibited lumbar motion relative to hip extension as LPR was smaller in the LBP group than in the non-LBP group. However, there was no difference between the groups in LHR because inter-individual variability affected the LHR.


#7 Foot and Soccer Referees': A Pilot Study Searching "Performance" Throughout Prevention
Reference: Front Physiol. 2018 Jul 25;9:1009. doi: 10.3389/fphys.2018.01009. eCollection 2018.
Authors: Gianturco L, Bodini BD, Gianturco V, Pregliasco FE, Cascio M, Serafin A, Turiel M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6069454/pdf/fphys-09-01009.pdf
Summary: Soccer refereeing is a "not-conventional" sport in which aerobic workload is prevalent. Along the years, several studies have attempted to define best markers of referees' performance. Many studies focused their attention on field tests and their relationship with aerobic power. Instead, in this study, starting by a medical assessment satisfying the FIFA 11+ criteria for injuries prevention, we have investigated the foot of soccer referees and we have also wanted to find possible and/or unexpected improvements in performance. As performance marker, we have used the referral field test for soccer referees that is internationally validated and known as Yo-Yo test (YYiR1). While standardized foot posture index (FPI) questionnaire was used for screening foot referees conditions (40 young, all men by sex, with mean age 23.47 ± 4.36). Analyzing collected data, we have demonstrated by means of Read-Cressie Chi square test that neutral FPI is an important favor item affecting YYiR1 results. Further studies will be necessary in order to confirm our pilot investigation.


#8 Outcomes of Cardiac Screening in Adolescent Soccer Players
Reference: N Engl J Med. 2018 Aug 9;379(6):524-534. doi: 10.1056/NEJMoa1714719.
Authors: Malhotra A, Dhutia H, Finocchiaro G, Gati S, Beasley I, Clift P, Cowie C, Kenny A, Mayet J, Oxborough D, Patel K, Pieles G, Rakhit D, Ramsdale D, Shapiro L, Somauroo J, Stuart G, Varnava A, Walsh J, Yousef Z, Tome M, Papadakis M, Sharma S
Summary: Reports on the incidence and causes of sudden cardiac death among young athletes have relied largely on estimated rates of participation and varied methods of reporting. We sought to investigate the incidence and causes of sudden cardiac death among adolescent soccer players in the United Kingdom. From 1996 through 2016, we screened 11,168 adolescent athletes with a mean (±SD) age of 16.4±1.2 years (95% of whom were male) in the English Football Association (FA) cardiac screening program, which consisted of a health questionnaire, physical examination, electrocardiography, and echocardiography. The FA registry was interrogated to identify sudden cardiac deaths, which were confirmed with autopsy reports. During screening, 42 athletes (0.38%) were found to have cardiac disorders that are associated with sudden cardiac death. A further 225 athletes (2%) with congenital or valvular abnormalities were identified. After screening, there were 23 deaths from any cause, of which 8 (35%) were sudden deaths attributed to cardiac disease. Cardiomyopathy accounted for 7 of 8 sudden cardiac deaths (88%). Six athletes (75%) with sudden cardiac death had had normal cardiac screening results. The mean time between screening and sudden cardiac death was 6.8 years. On the basis of a total of 118,351 person-years, the incidence of sudden cardiac death among previously screened adolescent soccer players was 1 per 14,794 person-years (6.8 per 100,000 athletes). Diseases that are associated with sudden cardiac death were identified in 0.38% of adolescent soccer players in a cohort that underwent cardiovascular screening. The incidence of sudden cardiac death was 1 per 14,794 person-years, or 6.8 per 100,000 athletes; most of these deaths were due to cardiomyopathies that had not been detected on screening. (Funded by the English Football Association and others.).


#9 Nesfatin-1 and irisin levels in response to the soccer matches performed in morning, afternoon and at night in young trained male subjects
Reference: Cell Mol Biol (Noisy-le-grand). 2018 Jul 30;64(10):130-133.
Authors: Ozcelik O, Algul S, Yilmaz B
Summary: This study aimed to investigate the potential effects of acute soccer matches performed in morning, afternoon and at night on both nesfatin-1 and irisin levels in trained subjects. Total of 20 male subjects performed in soccer matches at three different times of day: morning, afternoon, and night. Pre- and post-match venous blood samples were taken, and levels of both nesfatin-1 and irisin were analysed using the enzyme-linked immunosorbent assay (ELISA). Following all matches, the subjects' irisin levels increased significantly in all subjects (p &lt; 0.0001). Nesfatin-1 levels were also increased after the matches; however, the increase was statistically significant for morning (P=0.01) and night-time (p=0.009). The subjects' nesfatin-1 levels did not increase in all subjects and decrease of nesfatin-1 levels observed in some subjects after matches. This study finds that soccer matches performed different workout times have strong stimulatory effects on irisin levels in all subjects but nesfatin-1 response varied among the subjects and it did not change significantly in afternoon match.


#10 Are soccer matches dangerous for patients with heart disease? The HeartAtaque trial - a prospective pilot study
Reference: Rev Port Cardiol. 2018 Aug;37(8):645-653. doi: 10.1016/j.repc.2017.09.024. Epub 2018 May 22.
Authors: Martins JL, Adrega T, Santos L, Afreixo V, Viana J, Santos J
Summary: Behavioral and emotional factors are triggers of cardiovascular events (CVEs). It is uncertain whether soccer fans, particularly individuals with coronary artery disease (CAD), are at increased risk for CVEs. The purpose was to assess the effect of watching soccer matches in patients with known CAD on the incidence of CVEs according to the match result. We prospectively assessed 82 male soccer fans with a history of acute coronary syndrome during 23 matches of the 2015/2016 season. Each individual was assessed by Holter monitoring on the day of their team's match and on the control day. The primary endpoint was the composite of death, stroke, reinfarction, angina or sustained arrhythmia. Secondary endpoints assessed were episodes of non-sustained supraventricular or ventricular arrhythmia and mean heart rate (HR). Participants' mean age was 61±10 years. Compared with the control day, despite a significant increase in HR (p<0.001) that was independent of the result (p>0.97), the number of CVEs did not differ according to the result (p>0.05). Moreover, the number of non-sustained episodes of supraventricular and ventricular arrhythmia did not differ when stratified according to the match result (p>0.05). The match result was not associated with a difference in incidence of CVEs in patients with a past history of CAD, with ischemic and arrhythmic substrate, who watched soccer matches on television.


#11 Longevity and cardiovascular mortality of Polish elite football players
Reference: Kardiol Pol. 2018 Aug 9. doi: 10.5603/KP.a2018.0173. [Epub ahead of print]
Authors: Gajda J, Śmigielski W, Śmigielski J, Pakos E, Drygas W
Download link: https://ojs.kardiologiapolska.pl/kp/article/download/KP.a2018.0173/9831
Summary: Despite the wide popularity of football, there is a paucity of scientific evidence explaining the relationship between being a competitive footballer and life expectancy AIM: The study analyses and compares cause-specific mortality between Polish elite footballers (men) and the general male population. A retrospective method of analysis is employed to study a sample of 455 elite footballers who died between 1990 and 2015. The cause of death was established based on the official statistics of Polish Central Statistical Office. The comparative sample consists of men in the general male population in Poland who died in the sampled period being at least 25 years of age at the time of death. The mean age at death turned out to be higher for footballers than controls (70.2 vs 67.4 years). Cardiovascular diseases were a more common cause of death among footballers than in the general male population in both the under 65-group and the above- 65-group (46.9% to 32.3% and 61.3% to 53.3%, respectively). A closer analysis of cause-specific cardiovascular mortality revealed that acute myocardial infarction caused more deaths (OR=1.31; CI 95%: [1.02-1.68]) and hypertensive disease less deaths (OR=0.20; CI 95%: [0.05-0.79]) among athletes than in the general male population. The study results point to excess cardiovascular mortality among Polish elite footballers. A trend analysis has shown, however, that its level is falling.


#12 The Use of Microtechnology to Quantify the Peak Match Demands of the Football Codes: A Systematic Review
Reference: Sports Med. 2018 Aug 7. doi: 10.1007/s40279-018-0965-6. [Epub ahead of print]
Authors: Whitehead S, Till K, Weaving D, Jones B
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0965-6.pdf
Summary: Quantifying the peak match demands within the football codes is useful for the appropriate prescription of external training load. Wearable microtechnology devices can be used to identify the peak match demands, although various methodologies exist at present. This systematic review aimed to identify the methodologies and microtechnology-derived variables used to determine the peak match demands, and to summarise current data on the peak match demands in the football codes. A systematic search of electronic databases was performed from earliest record to May 2018; keywords relating to microtechnology, peak match demands and football codes were used. Twenty-seven studies met the eligibility criteria. Six football codes were reported: rugby league (n = 7), rugby union (n = 5), rugby sevens (n = 4), soccer (n = 6), Australian Football (n = 2) and Gaelic Football (n = 3). Three methodologies were identified: moving averages, segmental and 'ball in play'. The moving averages is the most commonly used (63%) and superior method, identifying higher peak demands than other methods. The most commonly used variables were relative distance covered (63%) and external load in specified speed zones (57%). This systematic review has identified moving averages to be the most appropriate method for identifying the peak match demands in the football codes. Practitioners and researchers should choose the most relevant duration-specific period and microtechnology-derived variable for their specific needs. The code specific peak match demands revealed can be used for the prescription of conditioning drills and training intensity.


#13 Different neuromuscular parameters influence dynamic balance in male and female football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 7. doi: 10.1007/s00167-018-5088-y. [Epub ahead of print]
Authors: López-Valenciano A, Ayala F, De Ste Croix M, Barbado D, Vera-Garcia FJ
Summary: The purpose of the study was to analyse the relationship between several parameters of neuromuscular performance with unilateral dynamic balance measured through the Y-Balance test, as well as to determine the possible sex-related differences. The Y-Balance test, isokinetic (concentric and eccentric) knee flexion and extension strength, isometric hip abduction and adduction strength, lower extremity joint range of motion (ROM) (hip, knee and ankle) and core stability were assessed in male (n = 88) and female (n = 44) professional football players. A stepwise multivariate linear least square regression with backward elimination analysis was carried out to identify a group of factors that were independently associated with balance performance in both sexes. Passive hip flexion and ankle dorsiflexion with knee flexed ROM were the main factors that retained a significant association to dominant (R2 = 23.1) and non-dominant (R2  = 33.5) balance scores for males. For females, core stability, hip abduction isometric peak torque, passive hip abduction and ankle dorsiflexion with knee flexed ROM variables retained a significant association with balance scores for both, dominant (R2 = 38.2) and non-dominant (R2 = 46.9) legs. Training interventions aimed at improving or maintaining unilateral dynamic balance in male football players should include, among other things, stretching exercises for the posterior chain of the lower extremity. However, females should also include exercises for strength and mobility of the hip abductors and core stability (especially in the frontal plane). This knowledge would allow clinicians and sport practitioners to develop more effective and tailored unilateral dynamic balance training interventions in male and female football players, possibly improving performance and reducing the risk of injury.

Fri

19

Oct

2018

Hamburger SV team warm-up

The footage below shows the pre-match warm-up of the Hamburger SV players before their game against SV Darmstadt '98.

Thu

18

Oct

2018

Latest research in football - week 32 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Age-Matched Z-Scores for Longitudinal Monitoring of Center of Pressure Speed in Single-Leg Stance Performance in Elite Male Youth Soccer Players
Reference: J Strength Cond Res. 2018 Jul 26. doi: 10.1519/JSC.0000000000002765. [Epub ahead of print]
Authors: Huurnink A, Fransz DP, de Boode VA, Kingma I, van Dieën JH
Summary: Coordination of corrective motor actions is considered important for soccer performance and injury prevention. A single-leg stance (SLS) test assesses the integrity and proficiency of the sensorimotor control system, quantified by center of pressure averaged speed (COPspeed). We aimed to provide age-matched z-scores for COPspeed in elite male youth soccer players. Second, we assessed a threshold for abnormal long-term change in performance, i.e., critical difference (CD). In a youth academy program, 133 soccer players of 9-18 years were tested twice for both legs (2 repetitions), and one repetition follow-up was conducted at 5.8 months (SD 2.7). Linear regression between age and COPspeed was performed to provide age-matched z-scores. Variance of differences in z-scores at baseline and between sessions was used to estimate the CD up to 5 repetitions. Intraclass correlation coefficients (ICCs) were assessed within and between sessions. The age significantly affected COPspeed (p < 0.0001), with lower values in older players (95% confidence interval; 3.45-9.17 to 2.88-5.13 cm·s, for 9 and 18 years, respectively). The z-score CD ranged from 1.72 (one repetition) to 1.34 (5 repetitions). The ICC of z-scores was 0.88 within session and 0.81 between sessions. In conclusion, the SLS performance in elite male youth soccer players improves with age. We determined age-matched z-scores of COPspeed, which reliably determined performance according to age. The CD allows for detection of abnormal variations in COPspeed to identify players with a (temporary) deterioration of sensorimotor function. This could be applied to concussion management, or to detect underlying physical impairments.


#2 Profiling the Responses of Soccer Substitutes: A Review of Current Literature
Reference: Sports Med. 2018 Jul 26. doi: 10.1007/s40279-018-0962-9. [Epub ahead of print]
Authors: Hills SP, Barwood MJ, Radcliffe JN, Cooke CB, Kilduff LP, Cook CJ, Russell M
Summary: Depending upon competition regulations, the laws of soccer allow between three and an unlimited number of substitutions that can be made on either a permanent or rolling basis. Substitutes are typically introduced to minimise/offset the effects of fatigue, alter tactics, replace players deemed as underperforming or injured, and/or give playing time to youth players or to squad members returning from injury. While the match-day practices of substitutes include participation in the pre-match warm-up, and sporadic periods of rewarm-up activity, it is currently unclear as to whether these pre-entry preparations facilitate optimal match performance thereafter. Acknowledging the contextual factors that possibly influence substitutes' performance, this review summarises the presently available literature on soccer substitutes, and makes recommendations for future research. Literature searching and screening yielded 13 studies, which have typically focused on characterising: (1) the patterns, including timing, of substitutes' introduction; (2) indices of match-performance; and (3) the emotional experiences of soccer substitutes. The majority of substitutions occur after the first-half has ended (i.e. at half-time or during the second-half), with introduced players exceeding the second-half physical performances of those who started the match. Observations of progressive improvements in running performance as playing time increases, and findings that substitutes mostly experience negative emotions, highlight the potential inadequacies of pre-match preparations, and present future research opportunities. Additional work is therefore needed to confirm these findings and to determine the efficacy of current preparation strategies, thereby providing opportunities to assess then address substitutes' pre-pitch entry preparations, on-field performance and emotional responses.


#3 Leg Fracture Associated with Synostosis of Interosseous Membrane During Running in A Soccer Player
Reference: Transl Med UniSa. 2018 Mar 31;17:1-5. eCollection 2017 Jul.
Authors: Oliva F, Buharaja R, Iundusi R, Tarantino U
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6056250/pdf/tm-17-01.pdf
Summary: Leg fractures may occur frequently in sport injuries but it is very rare to find this kind of injury associated with interosseous membrane synostosis. This case report describes a unique case of 42 B1.2 fracture of the leg associated with an interosseous membrane synostosis and literature review on Pubmed, Google scholar and Medscape. A 26 year old male amateur soccer player came to our attention at the emergency room after a fall while he was running without any direct trauma following a referred ankle sprain. X-ray and CT scan of the left leg showed a comminuted displaced fracture of the lower middle third of tibial and peroneus diaphysis, and moreover, a fracture of peroneal malleolus associated with a bone bridge between the tibia and fibula. The patient was treated with a surgical osteosynthesis the day after trauma. We think that the interosseous membrane plays an important role in biomechanics of the leg even during running. To our knowledge, this is the first case reported which show the fractures of the tibia and fibula associated with an ipsilateral synostosis of the interosseous membrane.


#4 Dynamics of Recovery of Physiological Parameters After a Small-Sided Game in Women Soccer Players
Reference: Front Physiol. 2018 Jul 11;9:887. doi: 10.3389/fphys.2018.00887. eCollection 2018.
Authors: Mascarin RB, De Andrade VL, Barbieri RA, Loures JP, Kalva-Filho CA, Papoti M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6050376/pdf/fphys-09-00887.pdf
Summary: Training methods based on small-sided game (SSG) seem to promote physiological and tactical benefits for soccer players as they present characteristics more specific to the game. Thus, the main objective of the present study was to analyze the hormonal, biochemical, and autonomic parameters in an acute manner and the recovery dynamics (up to 72 h after) in a SSG. Thirteen professional female soccer players participated in the study (18.8 ± 0.8 years, body mass 59.4 ± 6.2 kg, and height 1.68 ± 0.05 m). During and after the SSG session (4 min × 4 min separated by 3 min of passive interval and 120 m2 coverage per player), autonomic modulation was analyzed in the time and frequency domains using heart rate variability, and blood samples (5 ml) were collected before (0 h) and after (10 min and 24, 48, 72 h) the SSG for biochemical and hormonal analysis. The SSG induced an increase effect for LF (low frequency) (92,52%; Very likely increase) and a decrease effect for HF (high frequency) values (-65,72%; Very likely decrease), after 10 min of recovery. The LF/HF increase after 10 min of recovery (386,21%; Very likely increase). The RMSSD (square root of the mean squared differences of the successive N-N intervals) and pNN50 (measure of the number of adjacent NN intervals which differ by more than 50 ms) values presented a decrease effect 10 min after SSG (61,38%; Very likely decrease and-90%; Very likely decrease). The CK (creatine kinase) values presented no changes 10 min after SSG. The LDH (lactate dehydrogenase) values presented an increase effect 10 min after the SSG (19,22%; Likely increase). Both testosterone and cortisol concentrations presented the same behavior after SSG, where no alterations were observed with after 10 min (<0,37%; Most likely trivial). The SSG promoted significant cardiovascular stress that was restored within the first 24 h of recovery. Parasympathetic parameters continued to increase while sympathetic parameters declined significantly during the 72 h of recovery. In addition, the reduced game did not alter biochemical or hormonal responses during the 72 h.


#5 Effective injury forecasting in soccer with GPS training data and machine learning
Reference: PLoS One. 2018 Jul 25;13(7):e0201264. doi: 10.1371/journal.pone.0201264. eCollection 2018.
Authors: Rossi A, Pappalardo L, Cintia P, Iaia FM, Fernàndez J, Medina D
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0201264&type=printable
Summary: Injuries have a great impact on professional soccer, due to their large influence on team performance and the considerable costs of rehabilitation for players. Existing studies in the literature provide just a preliminary understanding of which factors mostly affect injury risk, while an evaluation of the potential of statistical models in forecasting injuries is still missing. In this paper, we propose a multi-dimensional approach to injury forecasting in professional soccer that is based on GPS measurements and machine learning. By using GPS tracking technology, we collect data describing the training workload of players in a professional soccer club during a season. We then construct an injury forecaster and show that it is both accurate and interpretable by providing a set of case studies of interest to soccer practitioners. Our approach opens a novel perspective on injury prevention, providing a set of simple and practical rules for evaluating and interpreting the complex relations between injury risk and training performance in professional soccer.


#6 Mixed-methods pre-match cooling improves simulated soccer performance in the heat
Reference: Eur J Sport Sci. 2018 Jul 24:1-10. doi: 10.1080/17461391.2018.1498542. [Epub ahead of print]
Authors: Aldous JWF, Chrismas BCR, Akubat I, Stringer CA, Abt G, Taylor L
Summary: This investigation examined the effects of three pre-match and half-time cooling manoeuvres on physical performance and associated physiological and perceptual responses in eight University soccer players during a non-motorised treadmill based individualised soccer-specific simulation [intermittent soccer performance test (iSPT)] at 30°C. Four randomised experimental trials were completed; following 30-min (pre-match) and 15-min (half-time) cooling manoeuvres via (1) ice slurry ingestion (SLURRY); (2) ice-packs placed on the quadriceps and hamstrings (PACKS); (3) mixed-methods (MM; PACKS and SLURRY concurrently); or no-cooling (CON). In iSPT first half, a moderate increase in total (Mean ± Standard Deviation: 108 ± 57 m, qualitative inference: most likely, Cohen's d: 0.87, 90%CL: ±0.31), high-speed (56 ± 46 m, very likely, 0.68 ± 0.38) and variable run (15 ± 5 m, very likely, 0.81 ± 0.47) distance covered was reported in MM compared with CON. Additionally, pre-match reductions in thermal sensation (-1.0 ± 0.5, most likely, -0.91 ± 0.36), rectal (-0.6 ± 0.1°C, very likely, -0.86 ± 0.35) and skin temperature (-1.1 ± 0.3°C, very likely, -0.88 ± 0.42) continued throughout iSPT first half. Physical performance during iSPT first half was unaltered in SLURRY and PACKS compared to CON. Rectal temperature was moderately increased in SLURRY at 45-min (0.2 ± 0.1°C, very likely, 0.67 ± 0.36). Condition did not influence any measure in iSPT second half compared to CON. Only MM pre-match cooling augmented physical performance during iSPT first half, likely due to peripheral and central thermoregulatory factors favourably influencing first half iSPT performance. Further practical half-time cooling manoeuvres which enhance second half performance are still required.


#7 Association Between the Force-Velocity Profile and Performance Variables Obtained in Jumping and Sprinting in Elite Female Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Jul 24:1-21. doi: 10.1123/ijspp.2018-0233. [Epub ahead of print]
Authors: Marcote-Pequeño R, García-Ramos A, Cuadrado-Peñafiel V, González-Hernández JM, Gómez MÁ, Jiménez-Reyes P
Summary: The aims of this study were (I) to quantify the magnitude of the association between the same variables of the force-velocity (FV) profile and the performance variables (unloaded squat jump [SJ] height and 20 m sprint time) obtained during the jumping and sprinting testing procedures, and (II) to determine which mechanical capacity (i.e., maximum force [F0], maximum velocity [V0] or maximum power [Pmax]) presents the highest association with the performance variables. The FV profile of 19 elite female soccer players (age: 23.4±3.8 years, height: 166.4±5.6 cm, body mass: 59.7±4.7 kg) was determined during the jumping and sprinting tasks. The F0, V0, FV slope, Pmax, and FV imbalance (difference respect to the optimal FV profile in jumping and the decrease in the ratio of horizontal force production in sprinting) were determined for each task. Very large correlations between both tasks were observed for Pmax (r= 0.75) and the performance variables (r= -0.73), moderate correlations for V0 (r= 0.49), while the F0 (r= -0.14), the FV slope (r= -0.09), and the FV imbalance (r= 0.07) were not significantly correlated between both tasks. The Pmax obtained during each specific task was the mechanical capacity most correlated with its performance variable (r= 0.84 in jumping and r= 0.99 in sprinting). The absence of significant correlations between some of the FV relationship parameters suggests that for an individualized training prescription based on the FV profile both jumping and sprinting testing procedures should be performed with elite female soccer players.


#8 Acute Avulsion of the Iliac Crest Apophysis in an Adolescent Indoor Soccer
Reference: J Belg Soc Radiol. 2015 Dec 30;99(2):20-24. doi: 10.5334/jbr-btr.876.
Author: Coulier B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6032651/pdf/jbsr-99-2-876.pdf
Summary: We report a typical case of acute avulsion of the anterior iliac crest apophysis diagnosed in an indoor football player. The injury occurred as a result of a sudden twist of the trunk while kicking. Plain radiographs made the diagnosis. Complementary CT with 3D reconstructions was preferred to ultrasound because of the very strong habitus - 110 kilograms for 1,73 meter - of the 15-year old adolescent. CT confirmed that occult chronic mechanical stress on the iliac apophysis had preceded the acute avulsion and also emphasized the crucial role of the tensor fascia lata in the mechanism of the injury. The patient was successfully treated conservatively. The case is presented with a short review of the literature.


#9 Can Squat Jump Performance Differentiate Starters vs. Nonstarters in Division I Female Soccer Players?
Reference: J Strength Cond Res. 2018 Aug;32(8):2348-2355. doi: 10.1519/JSC.0000000000002053.
Authors: Magrini MA, Colquhoun RJ, Sellers JH, Conchola EC, Hester GM, Thiele RM, Pope ZK, Smith DB
Summary: Although soccer is predominately an endurance sport, high velocity movements may be an important indicator of athletic success. The purpose of this investigation was to establish whether squat jumps (SJs) can differentiate starters from nonstarters with a female collegiate division I soccer team. Eighteen female division I soccer athletes were separated into 2 groups: 9 starters (age: 19.5 ± 1.0; mass = 64.8 ± 11.5 kg; height = 167.5 ± 7.7 cm; games started = 18.2 ± 4.7; and minutes played = 1633.8 ± 478.2 minutes) and 9 nonstarters (age: 19.4 ± 1.4 years; mass = 63.3 ± 4.2 kg; height = 164.7 ± 6.8 cm; games started 0.7 ± 1.3; and minutes played 158.2 ± 269.3 minutes). Each athlete performed 3 maximal SJs at a starting knee angle of 110° without arm swing. Each participant's SJ height, mean power (MP), peak power (PP), mean velocity (MV), and peak velocity (PV) were measured during each attempt by a linear position transducer. No statistically significant differences (p ≥ 0.05) in MP and PP between the starters and nonstarters were observed. However, starters performed significantly better than nonstarters in SJ height (p = 0.002), MV (p = 0.025), and PV (p = 0.015). In addition, SJ height was strongly correlated with MV (r = 0.628) and PV (r = 0.647). These findings suggest that SJ height, MV, and PV may be important variables for discriminating differences between starters and nonstarters in division I female soccer athletes and a strong indicator of explosive performance.


#10 Quantified Soccer Using Positional Data: A Case Study
Reference: Front Physiol. 2018 Jul 6;9:866. doi: 10.3389/fphys.2018.00866. eCollection 2018.
Authors: Pettersen SA, Johansen HD, Baptista IAM, Halvorsen P, Johansen D
Download link:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6043664/pdf/fphys-09-00866.pdf
Summary: Performance development in international soccer is undergoing a silent revolution fueled by the rapidly increasing availability of athlete quantification data and advanced analytics. Objective performance data from teams and individual players are increasingly being collected automatically during practices and more recently also in matches after FIFA's 2015 approval of wearables in electronic performance and tracking systems. Some clubs have even started collecting data from players outside of the sport arenas. Further algorithmic analysis of these data might provide vital insights for individual training personalization and injury prevention, and also provide a foundation for evidence-based decisions for team performance improvements. This paper presents our experiences from using a detailed radio-based wearable positioning data system in an elite soccer club. We demonstrate how such a system can detect and find anomalies, trends, and insights vital for individual athletic and soccer team performance development. As an example, during a normal microcycle (6 days) full backs only covered 26% of the sprint distance they covered in the next match. This indicates that practitioners must carefully consider to proximity size and physical work pattern in microcycles to better resemble match performance. We also compare and discuss the accuracy between radio waves and GPS in sampling tracking data. Finally, we present how we are extending the radio-based positional system with a novel soccer analytics annotation system, and a real-time video processing system using a video camera array. This provides a novel toolkit for modern forward-looking soccer coaches that we hope to integrate in future studies.


#11 Acute high-intensity exercise test in soccer athletes affects salivary biochemical markers
Reference: Free Radic Res. 2018 Jul 20:1-6. doi: 10.1080/10715762.2018.1481288. [Epub ahead of print]
Authors: Rodrigues de Araujo V, Lisboa P, Boaventura G, Caramez F, Pires L, Oliveira E, Moura E, Casimiro-Lopes G
Summary: Saliva has been reported as a potential biological fluid for biochemical monitoring. This study investigated salivary markers of exercise intensity, oral mucosal immunity, and redox homeostasis in soccer athletes subjected to an acute high-intensity interval exercise (HIIE) protocol characterised by a repeated sprint ability test. Thirty-two professional soccer athletes were recruited and saliva aliquots were collected at rest and immediately after HIIE protocol. When compared with pre-test values we observed that HIIE protocol induced moderate changes for total protein (p = .015; effect size (ES) = 0.51; smallest worthwhile change (SWC)factor = 5.7) and for cortisol levels (p < .0001; ES = 0.49; SWCfactor = 3.9). Lactate levels showed very large changes (p < .000; ES = 1.35; SWCfactor  = 10.8), while Ig-A alterations were considered unclear. Besides, transferrin changes were trivial and maintained its levels at rest and after HIIE below the proposed threshold of 0.5 mg/dL. Regarding redox homeostasis we observed unclear effects for TBARs, MDA, GSH, GSSG, CAT, and SOD while uric acid showed large decreases (p = .005; ES = 0.80; SWCfactor  = -5.4). HIIE protocol as a physical test conducted in soccer athletes increased salivary concentration of exercise intensity markers, such as lactate, total protein, and cortisol, but did not affect Ig-A levels. Redox homeostasis in saliva seems to be more related with uric acid levels as a possible key factor TBARs homeostasis.

Wed

17

Oct

2018

Hamburger SV Goalkeeper Warm-up

As the title proposes, the video below shows the pre-march warm-up of the HSV goalkeeper.

 

The footage was taken before the game against SV Darmstadt '98 (2nd German division).

Tue

16

Oct

2018

Latest research in football - week 31 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Validity of the RSA-RANDOM Test for Young Soccer Players
Reference: Int J Sports Med. 2018 Jul 19. doi: 10.1055/a-0637-2094. [Epub ahead of print]
Authors: Martin V, Sanchez-Sanchez J, Ramírez-Campillo R, Nakamura FY, Gonzalo-Skok O
Summary: The present study aimed to examine the reliability, usefulness, responsiveness, age-related differences and construct validity of a novel decision-making RSA test (RSA-RANDOM test) in young soccer players. Twenty-five young male soccer players performed the RSA-RANDOM test on 2 occasions separated by 5-7 days to assess test-retest reliability and determine a priori usefulness. Furthermore, the same players executed the RSA-RANDOM test 4 times throughout the season to analyse responsiveness. Forty-five players (U-13 to U-17) were evaluated in such test to examine age-related differences. Finally, 9 players were used to determine the construct validity of the test. Reliability scores showed a high intraclass correlation coefficient (ICC=0.88 to 0.90) and low coefficient of variation (CV=1.0-1.2%). The responsiveness of the RSA-RANDOM test was good, as the typical short- (1.2-1.9%), mid- (1.4-2.4%) and long-term (2.3-3.2%) changes in RSA-RANDOM performance were higher than the CV. Age-related differences analysis showed better RSA-RANDOM performance as age increased in young soccer players. Low (r=-0.50) to moderate (r=-0.75) relationships were found between the RSA-RANDOM test variables (RSA best and mean times) with high-intensity and total distance covered, respectively. A novel decision-making RSA test (RSA-RANDOM) has shown to be reliable and valid in young soccer players.


#2 Prior Knowledge of the Grading Criteria Increases Functional Movement Screen Scores in Youth Soccer Players
Reference: J Strength Cond Res. 2018 Jul 17. doi: 10.1519/JSC.0000000000002724. [Epub ahead of print]
Authors: Bryson A, Arthur R, Easton C
Summary: We sought to determine whether familiarity with the grading criteria of the Functional Movement Screen (FMS) impacted the outcome score in elite youth soccer players. Thirty-two trained male youth soccer players (aged 17 ± 1 years) participated in a randomized control trial. Participants were randomly assigned to evenly sized control and experimental groups, who each completed the FMS on 2 separate occasions. Participants in the experimental group were provided the FMS grading criteria between their first and second screens. Time-synchronized video footage was used to grade the FMS using standardized criteria. Structured interviews were then conducted with selected participants (n = 4) in the experimental group to establish athletes' perception of the FMS. The experimental group had a large increase in overall FMS score from the first to the second screen in comparison with the control group (Δ2.0 ± 1.0, p < 0.001, d = 1.3). Scores for the deep squat, hurdle step, and rotary stability tests components of the FMS all increased in the experimental group in comparison with the control group (p < 0.05). Thematic analysis of the interview data suggested that the participants in the experimental group improved their understanding between good and poor technique during the FMS. These findings support the notion that FMS scores are influenced by awareness of the grading criteria. As a consequence, the FMS may not be suitable for objectively predicting injury in youth soccer players.


#3 Articular and peri-articular hip lesions in soccer players. The importance of imaging in deciding which lesions will need surgery and which can be treated conservatively?
Reference: Eur J Radiol. 2018 Aug;105:227-238. doi: 10.1016/j.ejrad.2018.06.012. Epub 2018 Jun 20.
Authors: Di Pietto F, Chianca V, Zappia M, Romano S
Summary: Soccer is one of the most popular sports worldwide engaging millions of participants each year. During play, injuries occur rather frequently and most of them involve the hip joint and the surrounding structure. In professional athletes, injuries are often complex scenarios and in the case of misdiagnosis, patients' return to play is delayed or it may progress to a more serious injury with consequent damage for their career and for the soccer team. The most frequent articular pathologies are Femoro-acetabular impingement and labral tears. Stress fracture, avulsion, ischiofemoral impingement, subspine impingement, athletic pubalgia, muscle injuries and Morel-Levallèe lesion are the most frequent hip peri-articular pathologies whereas snapping hip may be both intra- or extra-articular pathology. With an increasing number of football players, the radiologist plays a crucial role in the detection and characterization of the extent of the injuries. This article reviews the current imaging concepts frequently seen in injuries around the hips of professional football players focusing in particular on the most suitable therapeutic approaches, whether surgical or conservative.


#4 Relative Age Effect, Biological Maturation, and Coaches' Efficacy Expectations in Young Male Soccer Players
Reference: Res Q Exerc Sport. 2018 Jul 17:1-7. doi: 10.1080/02701367.2018.1486003. [Epub ahead of print]
Authors: Peña-González I, Fernández-Fernández J, Moya-Ramón M, Cervelló E
Summary: The talent identification and selection process in young male soccer players is mainly focused on anthropometrics and physical performance, but social factors are also considered in this process. The purpose of this study was to test the existence of the relative age effect and its possible influence on anthropometrics and physical performance and to analyze coaches' efficacy expectations. Data for 564 young male soccer players (Mage = 13.7 ± 1.5 years; Mweight = 53.7 ± 11.6 kg; Mheight = 160.2 ± 11.6 cm) included their birth quartile, maturity status, anthropometrics, a physical test battery, and coaches' efficacy expectations. Early-born players were overrepresented (p < .05). Early-born players were not statistically taller, heavier, or better at physical performance (p > .05) when maturation and chronological age were controlled as confounding factors. However, coaches expected more from early-born players (p < .05), and the inferential analysis showed likely to very likely worthwhile differences between the coaches' expectations for players born in the first quartile of the year and those born in the fourth quartile of the year. Anthropometrical and physical performance variables were not affected by birth quartile, and coaches' efficacy expectations were related to the relative age effect.


#5 Effect of Dehydration on Passing Decision Making in Soccer Athletes
Reference: Res Q Exerc Sport. 2018 Jul 17:1-8. doi: 10.1080/02701367.2018.1488026. [Epub ahead of print]
Authors: Fortes LS, Nascimento-Júnior JRA, Mortatti AL, Lima-Júnior DRAA, Ferreira MEC
Summary: It seems that dehydration may impair decision-making performance in athletes. This study aimed to investigate the influence of dehydration on passing decision-making performance in soccer players. Participants were 40 male soccer players (Mage = 22.3 ± 2.3 years) who agreed to participate in the study and were randomly assigned to the following conditions: control (CON), dehydration (DEH), and euhydration (EUH). The players played in 2 games of 90 min in duration (2 45-min halves) followed by 2 15-min halves (overtime) with and without proper hydration. The Game Performance Assessment Instrument (GPAI) was considered for the analysis of passing decision making. The GPAI analysis indicated effective reduction in the decision-making index in the DEH condition compared with the EUH and CON conditions, F(2, 38) = 31.4, p < .05, ES = 0.8. In conclusion, dehydration may be considered a mediating factor in the passing decision-making performance of male soccer athletes.


#6 Altered landing mechanics are shown by male youth soccer players at different stages of maturation
Reference: Phys Ther Sport. 2018 Jul 7;33:48-53. doi: 10.1016/j.ptsp.2018.07.001. [Epub ahead of print]
Authors: Read PJ, Oliver JL, Myer GD, De Ste Croix MBA, Belshaw A, Lloyd RS
Summary: Examine the effects of maturation on single leg jumping performance in elite male youth soccer players. 347 male youth players classified as either pre, circa or post-peak height velocity (PHV) participated in this study. Single leg countermovement jump (SLCMJ) height, peak vertical landing forces (pVGRF), knee valgus and trunk side flexion were used as outcome measures. Vertical jump height and absolute pVGRF increased with each stage of maturation (p < 0.001; d = 0.85-2.35). Relative to body weight, significantly higher landing forces were recorded on the left leg in circa versus post-PHV players (p < 0.05; d = -0.40). Knee valgus reduced with maturation but the only notable between-group differences were shown in post-PHV players (p < 0.05; d = 0.67); however, greater ipsilateral lateral trunk flexion angles was also present and these differences were significantly increased relative to circa-PHV players (p < 0.05; d = 0.85). Periods of rapid growth are associated with landing kinetics which may heighten injury risk. While reductions in knee valgus were displayed with maturation; a compensatory strategy of greater trunk lateral flexion was evident in post-PHV players and this may increase the risk of injury.


#7 Alternative assessment of knee joint muscle balance of soccer players through total work-based hamstring: quadriceps ratios
Reference: Eur J Sport Sci. 2018 Jul 14:1-7. doi: 10.1080/17461391.2018.1495271. [Epub ahead of print]
Authors: Minozzo F, Lopez P, Machado CLF, Wilhelm EN, Grazioli R, Pinto RS
Summary: Isokinetic hamstring-to-quadriceps (H:Q) ratios are frequently used to assess knee muscle strength imbalances and risk of injuries/re-injuries. The use of peak torque (PT) or total work (TW) to estimate joint stability may lead to different results because of the differences between these two neuromuscular variables. Thus, the current study aimed to compare the conventional and functional H:Q ratios calculated by PT and TW. Ninety-three male professional soccer players from Brazilian first division teams performed isokinetic concentric and eccentric contractions of the quadriceps and the hamstrings at 60°/s. Muscle strength balance was calculated using the conventional torque ratio (CTR) and conventional work ratio (CWR), functional torque ratio (FTR) and functional work ratio (FWR) were highly and moderately correlated between them (r = 0.83 and r = 0.73, respectively). The Wilcoxon statistical test revealed significant differences between CTR and CWR, as well as FTR and FWR (p < 0.05). T-test demonstrated significant differences in mean CTR-CWR and FTR-FWR, whereas Bland-Altman plots showed non-consistent bias. In addition, the chi-square test demonstrated significant differences between players below the conventional reference values and functional reference values (p < 0.001). In conclusion, TW ratios seem to provide distinct and additional information regarding the H:Q strength balance in professional soccer players. Moreover, taking into account that TW captures torque information throughout the entire range of motion, it is possible that TW ratios represent a more comprehensive assessment of muscle strength imbalance.


#8 Injuries in girls' soccer and basketball: a comparison of high schools with and without athletic trainers
Reference: Inj Epidemiol. 2018 Jul 16;5(1):29. doi: 10.1186/s40621-018-0159-6.
Authors: Pierpoint LA, LaBella CR, Collins CL, Fields SK, Dawn Comstock R
Download link: https://link.springer.com/content/pdf/10.1186%2Fs40621-018-0159-6.pdf
Summary: Sports injuries impose physical and economic burdens on high school athletes, yet only 37% of high schools have access to a fulltime certified athletic trainer (AT). Although intuitively there are multiple benefits of AT coverage, research demonstrating the measurable effect of AT coverage on rates and patterns of injury is limited. Our objective was to investigate the epidemiology of girls' basketball and soccer injuries in high schools with and without an AT. We compared data captured by two similar sports injury surveillance systems during the 2006/07-2008/09 academic years. High School Reporting Information Online (RIO) included a national sample of schools with ATs, and the Sports Injury Surveillance System (SISS) included a sample of Chicago public high schools without ATs. Overall injury rates were higher in schools without ATs than schools with ATs in girls' soccer (RR: 1.73, 95% CI: 1.51-2.00) and basketball (RR: 1.22, 95% CI: 1.03-1.45). Recurrent injury rates were even higher in schools without ATs compared to schools with ATs in soccer (RR: 6.00 95% CI: 4.54-7.91) and basketball (RR: 2.99, 95% CI: 2.12-4.14). Conversely, concussion rates were higher in schools with ATs than schools without ATs in soccer (RR: 8.05, 95% CI: 2.00-32.51) and basketball (RR: 4.50, 95% CI: 1.43-14.16). Other injury patterns were similar between the two samples. This study demonstrated the effectiveness of AT coverage of high school girls' soccer and basketball, both in reducing overall and recurrent injury rates and in identifying athletes with concussions. Future studies should evaluate the effect of ATs on other high school sports and on youth sports to determine if these findings are generalizable across sports and age groups.


#9 Laterality Influences Agility Performance in Elite Soccer Players
Reference: Front Physiol. 2018 Jun 29;9:807. doi: 10.3389/fphys.2018.00807. eCollection 2018.
Authors: Zouhal H, Abderrahman AB, Dupont G, Truptin P, Le Bris R, Le Postec E, Coppalle S, Ravé G, Brughelli M, Bideau B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033993/pdf/fphys-09-00807.pdf
Summary: Laterality (i.e., handedness, footedness, and eyedness) could have an impact on highly repeated soccer movements and thus, could influence performance. The purpose of this study was to examine the laterality of high-level football players and its effects on 180° left and right U-turn movements. Handedness, footedness, and eyedness were determined in 72 elite football players (EFP, 18.2 ± 2.2 years) from the Stade Rennais Football Club (French League 1) and 9 amateur football players (AFP, 19.6 ± 2.1 years). Players performed a visual-motor task on a synthetic pitch consisting of 180° left and right rotations as fast as possible in response to a visual light on a computer screen. Movement times and reactive times for each left and right rotation were recorded with an accelerometer and video display. Laterality profiles showed a majority (χ2 = 9.42, df = 2, p = 0.031) of crossed formulas (i.e., dominant leg or hand is controlateral to the dominant eye) for EFP (53 ± 7%) and a majority of non-crossed formulas for AFP (63 ± 9%). Reaction times were significantly faster (p = 0.028, effect size = 0.148, trivial) in EFP right-eyed (568.2 ± 55.5 ms) than in AFP (610.0 ± 43.9 ms). For the left rotation and for right-footed players, movement times were significantly different (p = 0.043, effect size = 0.413, small) between EFP (1.15 ± 0.07 s) and AFP (1.17 ± 0.07 s). A significant difference (p < 0.033) was observed between footedness and rotation movement times in the EFP. Our results showed that laterality profiles differed between EFP and AFP. Hence, in EFP, reaction times depended on the side of the visual stimulus. Moreover, leg laterality of EFP influenced 180° left or right rotation speed. Our results indicate the importance of determining laterality in soccer players and identifying deficits in performance when turning.


#10 Mediating Effects of Parents' Coping Strategies on the Relationship Between Parents' Emotional Intelligence and Sideline Verbal Behaviors in Youth Soccer
Reference: J Sport Exerc Psychol. 2018 Jun 1;40(3):153-162. doi: 10.1123/jsep.2017-0318. Epub 2018 Jul 14.
Authors: Teques P, Calmeiro L, Martins H, Duarte D, Holt NL
Summary: The overall purpose of this study was to examine the mediating effects of parents' coping strategies on the relationship between parents' emotional intelligence and sideline verbal behaviors during their children's soccer games. Participants were 232 parents (120 mothers and 110 fathers) of youth soccer players age 9-13 years. Observations in situ were carried out at 30 soccer games during a soccer tournament. At the end of the game, parents were approached and asked to complete the Emotional Intelligence Scale and the Brief COPE scale. Structural-equation-modeling analyses revealed that adaptive and maladaptive coping mediated the relationship between regulation of emotion and parents' praise/encouragement, and negative and derogatory comments during the game. In addition, game result moderated the relationships between emotional intelligence, coping strategies, and parent behaviors. Emotional regulation and adaptive coping may promote desirable parent sideline behaviors and reduce undesirable behaviors.


#11 Goalkeepers' Reputations Bias Shot Placement in Soccer Penalties
Reference: J Sport Exerc Psychol. 2018 Jun 1;40(3):128-134. doi: 10.1123/jsep.2017-0358. Epub 2018 Jul 14.
Authors: Müller F, Best JF, Cañal-Bruland R
Summary: Research has demonstrated that in addition to minor changes in goalkeepers' position or height, goalkeeper reputation seems to influence penalty takers' shot placement. However, this evidence is based on correlative designs. Here, the authors experimentally manipulated both height and reputation to examine their causal impact on actual shot placement. Penalty takers performed kicks facing goalkeepers of different height (tall vs. short) and reputation (high vs. low) projected on a life-size screen. Results showed that tall goalkeepers were judged as taller than short goalkeepers. Likewise, high-reputation goalkeepers were judged as taller than low-reputation goalkeepers. An important finding was that reputation also influenced shot placement. When facing high-reputation goalkeepers, penalty takers aimed farther away from the goalkeeper and missed the goal more often. It follows that reputation affects both height estimates of goalkeepers and, most important, shot placement. Consequently, manipulating perceived reputation of goalkeepers provides an avenue for sport professionals to subtly influence shot placement of penalty takers.


#12 Physical growth in young Chilean football players: Proposal of percentiles based on chronological and biological age
Reference: Arch Argent Pediatr. 2018 Aug 1;116(4):e508-e514. doi: 10.5546/aap.2018.eng.e508. [Article in English, Spanish; Abstract available in Spanish from the publisher]
Authors: Carrasco López S, Gómez-Campos R, Méndez Cornejo J, Morales L, Urra-Albornoz C, Cossio-Bolañosb M
Download link: http://www.sap.org.ar/docs/publicaciones/archivosarg/2018/v116n4a10e.pdf
Summary: The aim were to a) To compare physical growth to the 2012 American standard from the Centers for Disease Control and Prevention (CDC); b) to analyze physical growth by chronological and biological age; c) to propose physical growth charts based on chronological and biological age. Methodology. A descriptive (cross-sectional) study was conducted in young Chilean football players based on weight, standing height, and sitting height. These were compared to the CDC- 2012 standard. Percentiles were developed using the LMS method. A total of 642 young Chilean football players aged 13.0-18.9 years were studied. Their body weight was lower than that of the CDC standard from 13.0 to 18.9 years old (p < 0.05), whereas their height showed no significant differences in the initial age categories (13.0- 13.9 and 14.0-14.9 years). Differences started to be observed as of 15.0 years old up to 18.9 years old (p < 0.05). In relation to chronological age, weight explained 31%; standing height, 16%; and sitting height, 0.09%, whereas in relation to biological age, weight explained 51%; standing height, 40%; and sitting height, 54%. Percentiles were developed based on chronological and biological age. These youth showed different physical growth patterns compared to the CDC-2012 standard. Their assessment reflects better explanatory percentages for biological age than for chronological age. The proposed percentiles may be an alternative to keep track of the physical growth patterns of young football players in sports settings in the short, medium, and long term.


#13 Mechanisms of acute adductor longus injuries in male football players: a systematic visual video analysis
Reference: Br J Sports Med. 2018 Jul 13. pii: bjsports-2018-099246. doi: 10.1136/bjsports-2018-099246. [Epub ahead of print]
Authors: Serner A, Mosler AB, Tol JL, Bahr R, Weir A
Summary: Change of direction and kicking have been described as the main actions resulting in adductor longus injury. Video descriptions of inciting events are lacking. The purpose was to perform a standardised visual video analysis of a series of acute adductor longus injuries in football. Video footage was reviewed by players, and assessed independently by five sports medicine professionals. Inciting events were described and categorised using standardised scoring, including playing situation, player/opponent behaviour, movement and body positions. Videos of acute adductor longus injuries in 17 professional male football players were analysed. Most injuries occurred in non-contact situations (71%), following a quick reaction to a change in play (53%). Injury actions were: change of direction (35%), kicking (29%), reaching (24%) and jumping (12%). Change of direction and reaching injuries were categorised as closed chain movements (59%), characterised by hip extension and abduction with external rotation. Kicking and jumping injuries were categorised as open chain (41%), characterised by a change from hip extension to hip flexion, and hip abduction to adduction, with external rotation. Acute adductor longus injuries in football occur in a variety of situations. Player actions can be categorised into closed (change of direction and reaching) and open (kicking and jumping) chain movements involving triplanar hip motion. A rapid muscle activation during a rapid muscle lengthening appears to be the fundamental injury mechanism for acute adductor longus injuries.

Mon

08

Oct

2018

Latest research in football - week 30 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The competence-supportive and competence-thwarting role of athlete leaders: An experimental test in a soccer context
Reference: PLoS One. 2018 Jul 11;13(7):e0200480. doi: 10.1371/journal.pone.0200480. eCollection 2018.
Authors: Fransen K, Vansteenkiste M, Vande Broek G, Boen F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6040764/pdf/pone.0200480.pdf
Summary: The aim of this experiment was to study the growth-promoting and adverse impact of athlete leaders' competence-supportive and-thwarting behavior on the motivation and performance of team members. Male soccer players (N = 144; MAge = 14.2) were allocated to ad-hoc teams of five soccer players. These teams participated in two sessions, being randomly exposed to an athlete leader who acted either competence-supportive, competence-thwarting, or neutral during the second session. When the athlete leader was competence-supportive (versus competence-thwarting), his teammates' intrinsic motivation and performance increased (versus decreased) compared with the control condition. The leader's impact on intrinsic motivation was fully accounted for by team members' competence satisfaction. These findings recommend coaches to invest in the competence-supportive power of their athlete leaders to establish an optimally motivating and performance-enhancing team environment.


#2 Match Running Performance of Elite Soccer Players: V[Combining Dot Above]O2max and Players Position Influences
Reference: J Strength Cond Res. 2018 Jul 9. doi: 10.1519/JSC.0000000000002646. [Epub ahead of print]
Author: Metaxas TI
Summary: The aims of this study were (a) to assess the relationship between laboratory-measured VO2max with total distance covered in a soccer match, (b) to assess the relationship between laboratory-measured VO2max with the distance covered at a different running intensity in a soccer match, (c) to quantify different intensity running in various playing positions, and (d) to determine the differences of running performance between halves. Analyzed match running performance of the Greek elite (n = 14) soccer players using a global positioning system within the second division professional league. No correlation was found between VO2max and match running performance at any velocity. The players covered greater distances in the first half at all speed levels except walking. In the first half, they covered a greater distance than in the second half (1,533 vs. 1,297 m, p < 0.001; 879 vs. 708 m, p < 0.001; 433 vs. 359 m, p < 001; 185 vs. 152 m, p < 0.01; 81.4 vs. 65.5 m, p < 0.001) when jogging, running, high-intensity running, fast running, sprint and total, respectively. Wide players covered greater distances at fast running (p < 0.001) and sprint zone than the players who played at the axon of the field (348 vs. 297 and 186 vs. 113 m, respectively). In addition, midfielders covered a greater distance at high-intensity running zone and at fast running zone than the defenders and forwards (1,768 vs. 1,372 m, p < 0.01 and 1,768 vs. 1,361 m, p < 0.01; 686 vs. 878 m, p < 0.01 and 709 vs. 878 m, p < 0.05, respectively). The results demonstrate that match running performance and the distance covered depends on the tactical role of each player in the team. These data provide valuable information for coaches regarding the running profile of the Greek elite soccer players that could be used to design a more effective training program.


#3 Relationships Between Eccentric and Concentric Knee Strength Capacities and Maximal Linear Deceleration Ability in Male Academy Soccer Players
Reference: J Strength Cond Res. 2018 Jul 9. doi: 10.1519/JSC.0000000000002739. [Epub ahead of print]
Authors: Harper DJ, Jordan AR, Kiely J
Summary: The purpose of this study was to investigate the relationships between maximal linear deceleration ability, and knee flexor (KF) and knee extensor (KE) strength. Fourteen male academy soccer players completed a 30-m linear sprint, a maximal linear deceleration test, and eccentric and concentric KF and KE contractions in both dominant leg (DL) and nondominant leg (NDL) at slower (60°·s) and faster (180°·s) angular velocities on an isokinetic dynamometer. Maximal linear deceleration ability was evaluated using distance-to-stop (DEC-DTS) and time-to-stop (DEC-TTS), with isokinetic peak torque representing KF and KE strength capacity. Relationships were established using Pearson's correlation coefficients (r) with magnitude-based inferences used to describe the uncertainty in the correlation. Both concentric KE and KF strength at 180°·s in the NDL had the highest correlations with deceleration ability (r = -0.76 and r = -0.78, respectively). In the DL, concentric KE and KF strength at 180°·s also had very likely large correlations with deceleration ability (r = -0.54 and -0.55, respectively). All correlations between eccentric KF strength and deceleration ability were unclear. At 180°·s, correlations between eccentric KE strength and deceleration ability were also unclear; however, at 60°·s, both DL (r = -0.63 to -0.64) and NDL (r = -0.54 to -0.55) had very likely large correlations with deceleration ability. These findings provide novel insights into the unilateral KF and KE strength capacities underpinning the ability to decelerate rapidly from high-sprint velocities.


#4 Creative decision making and visual search behavior in skilled soccer players
Reference: PLoS One. 2018 Jul 10;13(7):e0199381. doi: 10.1371/journal.pone.0199381. eCollection 2018.
Authors: Roca A, Ford PR, Memmert D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039007/pdf/pone.0199381.pdf
Summary: The ability to produce creative solutions is a key part of expert performance. The aim of this study was to identify the visual search behaviors that underpin superior creative performance of skilled soccer players during simulated 11-a-side match play. Players (N = 44) were required to interact with a representative life-size video-based simulation of attacking situations whilst in possession of the ball. Clips were occluded at a key moment and they were required to play the ball in response to each situation presented. Moreover, they were required to name other additional actions they could execute for each situation. Creative performance on the task was measured using the three criteria of originality, flexibility, and fluency of decisions. Visual search behaviors were examined using a portable eye-movement registration system. Players were classified as most- (n = 11) or least-creative (n = 11) based on their performance on the representative task. The most-creative players produced more appropriate, original, flexible, and fluid decisions compared to least-creative players. The creativity-based differences in judgment were underpinned by differences in visual search strategy. Most-creative players employed a broader attentional focus including more fixations of shorter duration and towards more informative locations of the display compared with least-creative players. Moreover, most-creative players detected teammates in threatening positions earlier in the attacking play. Creative performance is underpinned by different underlying visual processes when compared to less-creative performance, which appears to be crucial in facilitating more creative solutions.


#5 Association between trunk pain and lower extremity pain among youth soccer players: a cross-sectional study
Reference: BMC Sports Sci Med Rehabil. 2018 Jul 6;10:13. doi: 10.1186/s13102-018-0102-8. eCollection 2018.
Authors: Sogi Y, Hagiwara Y, Yabe Y, Sekiguchi T, Momma H, Tsuchiya M, Kuroki K, Kanazawa K, Koide M, Itaya N, Yoshida S, Yano T, Itoi E, Nagatomi R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035452/pdf/13102_2018_Article_102.pdf
Summary: Soccer is a high-intensity sport with a high injury rate. Among youth soccer players, lower extremity pain is a major problem that could be associated with trunk function. This study investigated the association between lower extremity pain and trunk pain among youth soccer players. A cross-sectional study involving youth soccer players participating in the Miyagi Amateur Sports Association was conducted using a self-reported questionnaire. A multiple logistic regression analysis was used to examine the association between trunk pain and lower extremity pain. Covariates were sex, age, body mass index, height increase, number of days of training per week, practice time per day on weekdays or weekends, competition levels, frequency of participation in games, and previous injuries. The final study population comprised 1139 youth soccer players (age, 6-15 years; male, 94.2%). Lower extremity pain with concomitant trunk pain occurred in 61.8% (42/68). Trunk pain was significantly associated with lower extremity pain (adjusted odds ratio [OR], 6.82; 95% confidence interval [CI], 3.99-11.67). Back pain and hip pain were significantly associated with knee pain (adjusted OR [95% CI]: 7.63 [3.70-15.76] and 3.84 [1.89-7.83], respectively), ankle pain (adjusted OR [95% CI]: 9.03 [4.42-18.44] and 5.43 [2.77-10.62], respectively), and both knee and ankle pain (adjusted OR [95% CI]: 13.67 [6.01-31.09] and 5.98 [2.56-13.97], respectively). Trunk pain was associated with lower extremity pain among youth soccer players. Clinicians and coaches should consider comorbidities while treating those players.


#6 Influence of Situational Variables, Team Formation, and Playing Position on Match Running Performance and Social Network Analysis in Brazilian Professional Soccer Players
Reference: J Strength Cond Res. 2018 Jul 4. doi: 10.1519/JSC.0000000000002725. [Epub ahead of print]
Authors: Aquino R, Carling C, Palucci Vieira LH, Martins G, Jabor G, Machado J, Santiago P, Garganta J, Puggina E
Summary: The purpose of this study was to investigate the independent and interactive effects of situational variables, opposition team formation, and playing position on running performance and network analysis in Brazilian professional soccer players (n = 22). Global positioning system technology was used to determine total distance covered, mean speed, maximum running speed, and distance covered in 6 speed ranges. Social network analysis was used to assess interpersonal coordination (team interactions characterized as successful passes [n = 3,033] between teammates). Observations of match running performance (n = 129) and network analysis (n = 108) were obtained. The main results were: (a) no interactive effects between team formation and playing position were observed for running and network variables (unclear to possibly); (b) matches played at home or against "weaker" opponents presented greater running demands and individual/global metrics of network analysis (likely to almost certain); (c) match outcome demonstrated influence only for running performance; matches in which the reference team won resulted in higher values than in matches lost; (d) when the reference team competed in 1-4-4-2 formation, this resulted in greater running demands than 1-4-2-3-1 formation (likely to almost certain); (e) reduced values of running performance variables were reported in central defenders compared with other positions. Central/external midfielders reported greater closeness/betweenness centrality, outdegree, and eigenvector compared with central/external defenders and forwards (likely to almost certain). The results from this study provide practical information to potentially impact on physical, tactical, and technical training.


#7 Isometric Midthigh Pull Characteristics in Elite Youth Male Soccer Players: Comparisons by Age and Maturity Offset
Reference: J Strength Cond Res. 2018 Jul 4. doi: 10.1519/JSC.0000000000002673. [Epub ahead of print]
Authors: Morris RO, Jones B, Myers T, Lake J, Emmonds S, Clarke ND, Singleton D, Ellis M, Till K
Summary: The purpose of this study was to (a) provide comparative isometric midthigh pull (IMTP) force-time characteristics for elite youth soccer players and (b) determine the effect of age and maturation on IMTP force-time characteristics. Elite male youth soccer players (U12 n = 51; U13 n = 54; U14 n = 56; U15 n = 45; U16 n = 39; and U18 n = 48) across 3 maturity offset groups (Pre n = 117; circa n = 84; and Post-peak height velocity n = 92) performed 2 maximal IMTP trials on a portable force platform (1,000 Hz). Absolute and relative values for peak force (PF) and impulse over 100 and 300 ms were analyzed. A full Bayesian regression model was used to provide probable differences similar to that of a frequentist p value. Advanced age and maturation resulted in superior IMTP force-time characteristics. Peak force demonstrated high probabilities of a difference between all consecutive age groups (p > 0.95). For absolute and relative impulse (100 and 300 ms), only 2 consecutive age groups (U14-15's and U16-18's) demonstrated high probabilities of a difference (p > 0.95) with large effects (d = 0.59-0.93). There were high probable differences between all maturity offset groups for PF and impulse with medium to large effects (d = 0.56-3.80). These were also reduced when expressed relative to body mass (relative PF and relative impulse). This study provides comparative IMTP force-time characteristics of elite male youth soccer players. Practitioners should consider individual maturation status when comparing players given the impact this has on force expression.


#8 Running Intensities in Elite Youth Soccer by Age and Position
Reference: J Strength Cond Res. 2018 Jul 4. doi: 10.1519/JSC.0000000000002728. [Epub ahead of print]
Authors: Duthie GM, Thornton HR, Delaney JA, Connolly DR, Serpiello FR
Summary: The purpose of this investigation was to examine differences between the peak running speed, acceleration, and metabolic power of elite youth soccer across a range of age levels by position. Ninety-six elite junior soccer players were assessed between 2015 and 2017. Ninety-six elite junior soccer players (at time of match: age, 15.8 ± 0.9 years; body mass, 69.1 ± 8.0 kg) were assessed during 61 games within the 2015, 2016, and 2017 season, for a total of 441 individual match observations (4.8 ± 3.3 matches per player, range 1-13). Participants were classified by age group: under 15 (U15, n = 121, 14.7 ± 0.3 years), under 16 (U16, n = 176, 15.8 ± 0.3 years), or under 17 (U17, n = 144, 16.7 ± 0.4 years), and according to their playing position: Attacker (ATT), Defender (DEF), Mid-Fielder (MID), or Wide (WIDE). Participants wore global positioning system units during each match, where speed (m·min), acceleration/deceleration (m·s), and metabolic power (Pmet) were established. A 1- to 10-minute moving average was applied to establish the intercept (c) and slope (n) of running intensity variables as a power law y = cx relationship. Linear mixed models were used to examine differences in the intercept and slope between age group and player position. There were no substantial differences in peak (intercept) or decline (slope) in running intensity between playing levels. Several differences were observed in the peak running speeds (m·min), particularly peak running speeds of ATT and DEF being substantially lower than the MID. Despite variability between positions, we suggest that the magnitude of these differences would not warrant the prescription of different running intensities across positions at the elite junior level. These findings describe the peak running intensities of elite junior soccer, useful in the monitoring and prescription of training to ensure that players are prepared for the most demanding periods of competition.


#9 Influence of opponent standard on activity profile and fatigue development during preseasonal friendly soccer matches: a team study
Reference: Res Sports Med. 2018 Jul 9:1-12. doi: 10.1080/15438627.2018.1492400. [Epub ahead of print]
Authors: Rago V, Silva J, Mohr M, Randers M, Barreira D, Krustrup P, Rebelo A
Summary: We examined the influence of competitive standard of the opponent on activity profile and fatigue during preseason friendly soccer matches. Time motion analysis was performed in a male professional soccer team (N = 14) during six friendly games played against professional, semi-professional and amateur-level opponents (PL, SPL and AL). The reference team covered higher acceleration distance, acceleration and deceleration > 2 m· s-2 distance against PL than AL (ES = 0.77 to 0.91). Acceleration and deceleration distance > 2 m· s-2 was also higher (ES = 0.66 to 0.84) against SPL than AL. Greater decreases in total distance, distance> 16 km· h-1 and > 22 km· h-1, total acceleration and deceleration, acceleration and deceleration distance > 2 m· s-2 (ES = 0.84 to 2.20) were also observed during PL compared to AL opponent. Playing against a stronger opponent seems to be more physically demanding, with special emphasis on events related with change of velocity (accelerations and decelerations). Declines in physical performance appear more evident against a higher opponent.


#10 Monitoring collegiate soccer players during a congested match schedule: Heart rate variability versus subjective wellness measures
Reference: Physiol Behav. 2018 Jul 5;194:527-531. doi: 10.1016/j.physbeh.2018.07.001. [Epub ahead of print]
Authors: Rabbani A, Baseri MK, Reisi J, Clemente FM, Kargarfard M
Summary: The aims of this study were a) to examine within-group changes of wellness and heart rate variability measures and b) to compare their sensitivity to a congested match schedule in collegiate soccer players (n = 8). Wellness (Hooper index and its subsets) and heart rate variability (Ln rMSSD, SDNN) measures were assessed after selected low-load (training sessions) and high-load (a congested match schedule) phases. Session rating of perceived exertion (sRPE) was computed for training and match sessions. A very likely large difference in accumulated sRPE was observed between low-load and high-load phases (+148.4%, 90% confidence interval CI [87.3; 229.5%]); effect size, ES, 2.16 [1.49; 2.82]. While the Hooper index showed an almost certainly moderate increase (+49.8%, [33.9; 67.5%]), ES, 1.05 [0.76; 1.34], heart rate variability measures (i.e., Ln rMSSD and SDNN) only changed with a possible trivial effect (range -2.1; 8.2%, [-7.1; 16.7%]), ES, -0.15; 0.15 [-0.50; 0.44]. The Hooper index showed a moderately higher sensitivity than Ln rMSSD to a congested match schedule (34.7%, [26.9; 41.6%], ES, 0.81 [0.60; 1.03]). Relationships between changes in the Hooper index and some of its subsets (∆Hooper index, ∆sleep, and ∆fatigue), with changes in mean sRPE (∆sRPE) were very large (range r = 0.72; 0.89). However, small associations were observed between changes in heart rate variability (∆Ln rMSSD, and ∆SDNN) and ∆sRPE (range r = -0.21; 0.10). This study suggests the use of subjective wellness indices, instead of heart rate variability measures, to monitor collegiate soccer players during congested match schedules.

Mon

08

Oct

2018

Latest research in football - week 29 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Influence of intense training cycle and psychometric status on technical and physiological aspects performed during the small-sided games in soccer players
Reference: Res Sports Med. 2018 Jul 3:1-12. doi: 10.1080/15438627.2018.1492398. [Epub ahead of print]
Authors: Selmi O, Marzouki H, Ouergui I, BenKhalifa W, Bouassida A
Summary: The study investigated the effect of intense training cycle (IT) of early season preparation period (SPP) and psychological status on technical and physiological parameters during small-sided games (SSG) and the relationships between these variables. Sixteen professional soccer players participated in the study (mean±SD: age: 24.5±4.1). Training load (TL), Total quality recovery (TQR) and well-being indices were performed daily. TL increased progressively (%TL=31.56 [AU]). Physiological variables did not change after IT and were not influenced by well-being indices and TQR. Technical aspects were negatively altered after IT (p<0.05). TL was significantly correlated with successful passes (r=-0.57, p=0.02), interceptions (r=-0.83, p<0.001) and lost balls (r=0.73, p=0.002). Well-being and TQR were related to successful passes, interceptions and lost passes [(r=-0.55, p=0.03; r=-0.75, p=0.001; r=-0.69, p=0.004); (r=0.54, p=0.03; r=-0.76, p=0.001; r=-0.69, p=0.004), respectively]. TL, Well-being indices and TQR represent a useful strategy for coaches to control technical aspects in soccer players during SPP.


#2 Effects of traditional balance and slackline training on physical performance and perceived enjoyment in young soccer players
Reference: Res Sports Med. 2018 Jul 2:1-12. doi: 10.1080/15438627.2018.1492392. [Epub ahead of print]
Authors: Trecroci A, Cavaggioni L, Lastella M, Broggi M, Perri E, Iaia FM, Alberti G
Summary: The aim of this study was to evaluate the effects of 12-week balance and slackline training programs on physical performance and perceived enjoyment scale in young soccer players. Forty-one preadolescent soccer players were assigned to two experimental groups performing traditional balance (BLT) or slackline training (SLT), and a control group. Pre-post assessment encompassed Balance Error Scoring System (BESS), Star Excursion Balance test (SEBT), sprint with 90° turns (S90), and countermovement jump (CMJ). The rate of perceived enjoyment scale (PACES) was applied at the end of the experimental period. SLT and BLT improved similarly in BESS, SEBT and S90. No changes were detected in the CMJ. Regarding PACES score, SLT presented significantly higher values than BLT. Young athletes may benefit from a motivating training approach, thus, a designed program based on slackline drills should be preferable to improve physical performance in terms of balance and change of direction ability in preadolescent soccer players.


#3 Contextual factors on physical demands in professional women's soccer: Female Athletes in Motion study
Reference: Eur J Sport Sci. 2018 Jul 1:1-6. doi: 10.1080/17461391.2018.1491628. [Epub ahead of print]
Authors: Vescovi JD, Falenchuk O
Summary: The aim of this study was to examine the impact of contextual factors on relative locomotor and metabolic power distances during professional female soccer matches. Twenty-eight players (forwards, n = 4; midfielders, n = 12; defenders, n = 12) that competed in a 90-min home and away match (regular season only). The generalised estimating equations (GEE) was used to evaluate relative locomotor and metabolic power distances for three contextual factors: location (home vs. away), type of turf (natural vs. artificial), and match outcome (win, loss and draw). No differences were observed for home vs. away matches. Moderate-intensity running (20.0 ± 1.0 m min-1 and 16.4 ± 0.9 m min-1), high-intensity running (8.6 ± 0.4 m min-1 and 7.3 ± 0.4 m min-1) and high-metabolic power (16.3 ± 0.5 m min-1 and 14.4 ± 0.5 m min-1) distances were elevated on artificial turf compared to natural grass, respectively. Relative sprint distance was greater during losses compared with draws (4.3 ± 0.4 m min-1 and 3.4 ± 0.3 m min-1). Overall physical demands of professional women's soccer were not impacted by match location. However, the elevation of moderate and high-intensity demands while playing on artificial turf may have implications on match preparations as well as recovery strategies.


#4 Exercise training in overweight and obese children: Recreational football and high-intensity interval training provide similar benefits to physical fitness
Reference: Scand J Med Sci Sports. 2018 Jul 6. doi: 10.1111/sms.13241. [Epub ahead of print]
Authors: Cvetković N, Stojanović E, Stojiljković N, Nikolić D, Scanlan AT, Milanović Z
Summary: This study compared the effects of recreational football and high-intensity interval training (HIIT) on body composition, muscular fitness, and cardiorespiratory fitness in overweight and obese children. Forty-two overweight/obese males aged 11-13 years [body mass index (BMI) >20.5 kg/m2 ] were randomly assigned to a recreational football training group (n = 14; 157.9 ± 5.8 cm; 63.7 ± 12.6 kg), HIIT group (n = 14; 163.8 ± 9.4 cm; 71.5 ± 10.5 kg), or nontraining control group (n = 14; 162.7 ± 9.3 cm; 67.4 ± 16.1 kg). Physical fitness components were measured at baseline and after 12 weeks of training at the same time of the day and under similar conditions, including body composition, muscular fitness (lower-body power, change-of-direction speed, and flexibility), and cardiovascular fitness (Yo-Yo Intermittent Endurance test distance, resting heart rate, and blood pressure). Lean body mass (4.3%, ES = 0.40; 95% CI: -0.48, 1.29; P = .382) and muscle mass 4.4% (ES = 0.40; 95% CI: -0.48, 1.29; P = .378) very likely increased in the recreational football group, while possible improvements were observed in the HIIT group (lean body mass: 2.5%, ES = 0.22; 95% CI: -0.62, 1.06; P = .607, muscle mass: 2.8%, ES = 0.23; 95% CI: -0.61, 1.07; P = .594). Only trivial increases were observed in the control group for lean body mass (0.5%, ES = 0.05; 95% CI: -0.70, 0.79; P = .906) and muscle mass (1.1%, ES = 0.09; 95% CI: -0.65, 0.83; P = .814). Significant differences were found between the recreational football and control groups in post-training body mass (P = .034) and body mass index (P = .017). Body fat very likely decreased in the recreational football group (-7.7%, ES = -0.41; 95% CI: -1.29, 0.48; P = .376) and possibly decreased in the HIIT group (-5.2%, ES = -0.22; 95% CI: -1.05, 0.62; P = .607), with a trivial reduction in the control group (-1.1%, ES = -0.04; 95% CI: -0.78, 0.70; P = .914). Very likely increases in lower-body power were evident in the recreational football (17.0%, ES = 0.76; 95% CI: -0.15, 1.66; P = .107) and control groups (16.1%, ES = 0.55; 95% CI: -0.20, 1.31; P = .156), while small improvements were observed in the HIIT group (6.0%, ES = 0.24; 95% CI: -0.60, 1.08; P = .580, possible). Likely to most likely improvements in Yo-Yo Intermittent Endurance test performance and change-of-direction speed were noted in the recreational football group (Yo-Yo: 79.8%, ES = 1.09; 95% CI: 0.16, 2.03; P = .025, change-of-direction speed: -10.6%, ES = -1.05; 95% CI: -1.98, -0.12; P = .031) and the HIIT group (Yo-Yo: 81.2%, ES = 1.03; 95% CI: 0.15, 1.92; P = .025, change-of-direction speed: -5.4%, ES = -0.91; 95% CI: -1.79, -0.04; P = .045). Diastolic blood pressure likely decreased in the recreational football (-8.6%, ES = -0.74; 95% CI: -1.64, 0.17; P = .116) and HIIT groups (-9.8%, ES = -0.57; 95% CI: -1.40, 0.30; P = .195), with a possible increase in the control group (1.2%, ES = 0.21; 95% CI: -0.53, 0.96; P = .068). Recreational football and HIIT elicited improvements in all muscular and cardiorespiratory fitness measures. In contrast, the control group, which performed only physical education classes, increased body mass, BMI, and fat mass. Therefore, additional activities such as recreational football or HIIT might counter the prevalence of overweight and obesity in children.


#5 Bowlegs and Intensive Football Training in Children and Adolescents
Reference: Dtsch Arztebl Int. 2018 Jun 15;115(24):401-408. doi: 10.3238/arztebl.2018.0401.
Authors: Thaller PH, Fürmetz J, Chen F, Degen N, Manz KM, Wolf F.
Summary: In many countries around the world, football (association football, or "soccer" predominantly in North America) is the sport most commonly played by children and adolescents. It is widely thought that football players are more likely to develop genu varum (bowlegs); an association with knee arthritis also seems likely. The goals of this systematic review and meta-analysis are to provide an overview of the available evidence on genu varum after intensive soccer training in childhood and adolescence, and to discuss the possible pathogenetic mechanisms. We systematically searched the PubMed, Medline, Embase, and Coch- rane Library databases for studies of the relation between leg axis development and intensive football playing during the growing years. Controlled studies employing the intercondylar distance (ICD) as the target variable were evaluated in a meta-analysis, with the mean difference as a measure of effect strength. This meta-analysis included 3 studies with a total of 1344 football players and 1277 control individuals. All three studies individually showed a signifi- cant difference in the mean ICD values of the two groups. The pooled effect esti- mator for the mean difference was 1.50 cm (95% confidence interval [0.53; 2.46]). Two further studies that could not be included in the meta-analysis had similar con- clusions. Asymmetrical, varus muscle forces and predominantly varus stress on the osseous growth plates neighboring the knee joint, especially during the prepubertal growth spurt, seem to be the cause of this phenomenon. Intensive soccer playing during the growing years can promote the devel- opment of bowlegs (genu varum) and, in turn, increase the risk of knee arthritis. Phy- sicians should inform young athletes and their parents of this if asked to advise about the choice of soccer as a sport for intensive training. It cannot be concluded, however, that football predisposes to bowlegs when played merely as a leisure activity.


#6 The Impact of an External Load of Football Equipment on Dynamic Balance as Assessed by the Modified Star Excursion Balance Test
Reference: Int J Exerc Sci. 2018 Jun 1;11(4):797-805. eCollection 2018.
Authors: Denehey T, Marshall T, Spaccarotella K, Andzel W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033501/pdf/ijes-11-4-797.pdf
Summary: Ankle sprains are common injuries, especially for football players, and may result in ankle instability, which can limit performance and increase injury risk. Ankle stability return to play criteria is often assessed under loaded conditions, even though previous research suggests loaded conditions affect dynamic balance. The purpose of this study was to evaluate dynamic balance under loaded conditions. A modified Star Excursion Balance Test (SEBT), incorporating anterior, posterior medial and posterior lateral reach directions under the loaded condition of NCAA Division III football equipment was evaluated. Thirty male collegiate football players completed the modified SEBT under loaded and non-loaded conditions. Scores for the three reach directions on the SEBT were computed for loaded and non-loaded conditions. Repeated measures ANOVA was used to compare reach directions under loaded and non-loaded. Under loaded conditions, participants had significantly shorter posterior lateral reach distances for the left (98.05 ± 12.73 cm vs. 89.30 ± 10.45 cm, p = 0.00) and right (103.77 ± 12.78 cm vs. 99.07 ± 13.50 cm, p = 0.00) legs and significantly shorter reach distances for the right leg in both the anterior direction (84.58 ± 5.64 cm vs. 80.57 ± 13.73 cm, p = 0.02) and composite dynamic balance score (105.99 ± 12.99 vs. 102.30 ± 14.28, p = 0.009). The addition of 6.2 kg of external load significantly affected dynamic balance assessed by the modified Star Balance Excursion Test. These findings suggest that return to support assessments should involve sport-specific conditions when determining readiness of return to play.


#7 Effects of Football Simulated Fatigue on Neuromuscular Function and Whole-body Response to Disturbances in Balance
Reference: Scand J Med Sci Sports. 2018 Jul 7. doi: 10.1111/sms.13261. [Epub ahead of print]
Authors: Behan FP, Willis S, Pain MTG, Folland JP
Summary: The effect of football specific fatigue on explosive neuromuscular performance and dynamic balance has received little attention in the literature despite the potential consequences for injury risk. This study aimed to investigate the effect of fatigue induced by simulated football match-play on maximal and explosive knee flexor (KF) and knee extensor (KE) torque, and thus the maximal and explosive KF/KE ratio, as well as the effect of fatigue induced by simulated football match-play on whole-body response to disturbances in balance. Fifteen male team sports players (mean ± SD: age 24.2±4.2 years; stature 1.79±0.09 m; body mass, 77.3±10.7 kg) underwent ~90 minutes of the modified Loughborough Intermittent Shuttle Test (LIST; fatiguing exercise condition) or seated rest (control condition) on separate days. Maximal and explosive isometric KF and KE voluntary torque (MVT/ EVT) were assessed pre and post condition. Maximal and explosive KF/KE ratios were calculated. Centre of mass (COM) response (displacement) to unexpected anterior and posterior platform perturbations were also assessed pre and post condition. Football simulated fatigue resulted in reduced KF (15%) and KE (12%) MVT (p≤0.002) but was not found to reduce EVT of either muscle group, or explosive KF/KE ratio. Football simulated fatigue resulted in impaired balance response (11% increase in COM displacement) to unexpected perturbation in the posterior (p=0.002) but not the anterior direction. Impaired response to dynamic disturbances in balance, rather than explosive torque or changes in muscle balance (H/Q ratios) may be a contributory factor towards increased injury risk in the latter portion of football games, and likely highlights the influence of fatigue on sensory/proprioceptive processes.


#8 Football training over 5 years is associated with preserved femoral bone mineral density in men with prostate cancer
Reference: Scand J Med Sci Sports. 2018 Jul 12. doi: 10.1111/sms.13242. [Epub ahead of print]
Authors: Uth J, Fristrup B, Haahr RD, Brasso K, Helge JW, Rørth M, Midtgaard J, Helge EW, Krustrup P
Summary: This study investigated the association between long-term adherence to football training and retaining bone mineralization and physical capacity in men with prostate cancer (PCa) managed with androgen deprivation therapy (ADT). Patients completing follow-up at 32 weeks in the FC Prostate Randomized Controlled Trial (RCT) in 2012 or 2013 were invited to 5-year follow-up assessments in May 2017 (n = 30). Changes in physiological outcomes over time between the football participants (FTG) and nonparticipants (CON) were examined. Twenty-two men accepted the invitation of which 11, aged 71.3 ± 3.8 years, had continued to play self-organized football 1.7 (SD 0.5) times per week for 4½ years (±8 months). At 5 years, right femoral neck bone mineral density (BMD) had improved significantly in the FTG compared to CON (P = .028). No other significant between-group differences were observed. In FTG, RHR decreased by 4.3 bpm (P = .009) with no changes in CON. Muscle mass, knee-extensor muscle strength, VO2 max, and postural balance decreased in both groups. In FTG, the fraction of training time with HR between 80%-90% or >90% of HRmax was 29.9% (SD 20.6) and 22.8% (SD 28.7), respectively. Average distance covered during 3 × 20 minutes of football training was 2524 m (SD 525). Football training over a 5-year period was associated with preserved femoral neck BMD in elderly men with PCa managed on ADT. Intensity during football training was >80% of HRmax for 51% of training time after 5 years. Body composition and physical capacity deteriorated over 5 years regardless of football participation.


#9 Heading and unintentional head impacts have opposing associations with Patient Reported Outcomes in amateur soccer players
Reference: Res Sports Med. 2018 Jul 13:1-11. doi: 10.1080/15438627.2018.1492396. [Epub ahead of print]
Authors: Hunter LE, Ifrah C, Zimmerman ME, Kim M, Lipton RB, Stewart WF, Lipton ML
Summary: The effects of soccer-related head impacts, beyond overt concussions, on Patient Reported Outcomes (PROs) have not been explored to date. Generalized estimating equations were employed to determine the association between soccer-related head impacts (headers in the prior 2 weeks, unintentional head impacts in the prior 2 weeks, headers in the prior 12 months and lifetime concussions) on PROs including depression, anxiety, sleep disturbance and sleep impairment. Compared to players with no unintentional head impacts in the prior 2 weeks, players with one unintentional exposure reported more symptoms of anxiety (p = 0.002) and players with 2+ exposures reported more symptoms of depression (p = 0.006) and anxiety (p < 0.001). In contrast, players in the 3rd Quartile of 12 mo. headers reported less anxiety (p = 0.001), sleep disturbance (p = 0.002) and sleep impairment (p < 0.001) compared to those in the 1st quartile. Unintentional head impacts are associated with worse PROs while more headers are paradoxically associated with better PROs.


#10 Development of an Educational Program for Non-Professional Soccer Coaches in Charge of Community-Based Soccer in Men with Prostate Cancer: a Qualitative Study
Reference: Sports Med Open. 2018 Jul 13;4(1):31. doi: 10.1186/s40798-018-0147-y.
Authors: Bjerre ED, Leth M, Hammer NM, Midtgaard J
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-018-0147-y
Summary: While clinical trials have demonstrated the benefits of structured exercise for prostate cancer survivors, few attempts have been made to investigate and implement sustainable community-based exercise programs supporting adoption of long-term physical activity behavior. Against this background, the aims of this study was to explore the perspectives of experts and stakeholders on the development of a training course and intervention manual used to support the delivery of community-based soccer training in men with prostate cancer (the FC Prostate Community [FCPC] trial). A two-step qualitative design including triangulation of methods, data sources, and researchers. Step 1 comprised key informant interviews with clinical and scientific experts (n = 4). Step 2 included stakeholder focus group interviews with nurses (n = 5), non-professional soccer coaches and club representatives (n = 5), and prostate cancer survivors (n = 7). Four themes emerged from the analysis of the key informant interviews: The Coach's Qualifications, Structure of the Training, Prevention of Injuries, and A Non-Patient Environment, which informed development of the training course and intervention manual. The stakeholders added the importance of clarifying the Responsibility of the Coach, the value of Positive Competition, and Social Inclusion of the prostate cancer survivors in the club. Based on these results, we present the final templates for the training course and intervention manual. No general set of rules or safety measures to promote or optimize the delivery of community-based exercise in cancer survivors is recommended. However, the general principles related to the necessary clarification of the coach's responsibility in relation to the prevention and management of injuries and participant adherence through a non-patient environment may be transferable to the training and education of other groups of lay persons in charge of delivering exercise interventions to other clinical subpopulations in a non-hospital setting.


#11 Association between knee-to-hip flexion ratio during single-leg vertical landings, and strength and range of motion in professional soccer players
Reference: Sports Biomech. 2018 Jul 12:1-10. doi: 10.1080/14763141.2018.1494207. [Epub ahead of print]
Authors: Leporace G, Tannure M, Zeitoune G, Metsavaht L, Marocolo M, Souto Maior A
Summary: The aim of this study was to test the correlation between knee-to-hip flexion ratio during a single leg landing task and hip and knee strength, and ankle range of motion. Twenty-four male participants from a professional soccer team performed a continuous single leg jump-landing test during 10s, while lower limb kinematics data were collected using a motion analysis system. After biomechanical testing, maximal isometric hip (abduction, extension, external rotation), knee extension and flexion strength were measured. Maximum ankle dorsiflexion range of motion was assessed statically using the weight bearing lunge test. Pearson correlation coefficients were calculated to determine the associations between the predictor variables (knee and hip strength, and ankle ROM) and the main outcome measure (knee-to-hip flexion ratio). Correlation between knee-to-hip flexion ratio and hip abductors strength was significant (r = -0.47; p = 0.019). No other significant correlations were observed among the variables (p > 0.05). These results demonstrated that a lower hip abductors strength in male soccer players was correlated with a high knee-to-hip flexion ratio during landing from a single leg jump, potentially increasing knee overload by decreasing energy absorption at the hip. The results provide a novel proposal for the functioning of hip muscles to control knee overload.

Sun

23

Sep

2018

Latest research in football - week 28 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Knee osteoarthritis in professional football is related to severe knee injury and knee surgery
Reference: Inj Epidemiol. 2018 Jun 18;5(1):26. doi: 10.1186/s40621-018-0157-8.
Authors: Gouttebarge V, Aoki H, Kerkhoffs GMMJ
Download link: https://link.springer.com/content/pdf/10.1186%2Fs40621-018-0157-8.pdf
Summary: As a consequence of severe knee injuries, knee osteoarthritis (OA) seems prevalent in retired professional footballers. However, some epidemiological data remain missing, for instance whether knee OA is also prevalent in current professional footballers, whether knee OA is associated with knee injuries and surgeries, and whether knee OA leads to a lower level of functioning. Therefore, three research questions were answered: (i) what is the prevalence of knee osteoarthritis (OA) among current and retired professional footballers? (ii) is severe knee injury or knee surgery associated with knee OA among current and retired professional footballers? (iii) what are the consequences of knee OA on physical knee function among current and retired professional footballers? An observational study based on a cross-sectional design by means of questionnaires was conducted. Participants were current and retired professional footballers recruited by the World Players' Union (FIFPro). Information about severe knee injury and knee OA was gathered (medical record or team doctor), while physical knee function was assessed through a validated scale. A total of 1360 participants (964 current and 396 retired professional footballers) were enrolled in the study (response rate of 54%). Prevalence of knee OA was 13% among current players and 28% among retired players (p < 0.01), being higher among older players. Current and retired professional footballers were nearly twice as likely to suffer from knee OA by every additional severe knee injury and by every additional knee surgery (risk ratio: 1.72-1.96; p < 0.01). Current and retired professional footballers with knee OA reported a lower level of physical knee function than current and retired players without OA (p < 0.01), their physical knee function being also lower than reference values (adult population, young athletic population and amateur footballers). The prevalence of knee OA was higher among retired than among current professional footballers and reached up to 40%, leading to negative consequences for their physical knee function. Current and retired professional footballers were nearly twice as likely to suffer from knee OA by every additional severe knee injury and by every additional knee surgery incurred during their career. Management of knee OA should be prioritized among professional footballers, especially to prevent the worsening of the condition during their retirement years.


#2 Match Demands of National Collegiate Athletic Association Division I Men's Soccer
Reference: J Strength Cond Res. 2018 Jul 2. doi: 10.1519/JSC.0000000000002719. [Epub ahead of print]
Authors: Curtis RM, Huggins RA, Looney DP, West CA, Fortunati A, Fontaine GJ, Casa DJ
Summary: This study aimed to profile positional movement characteristics of National Collegiate Athletic Association (NCAA) Division I male soccer players. Eighteen Division I male soccer players were monitored using global positioning systems, inertial movement, and heart rate (HR) technology during 24 matches over a full competitive season (N = 235 observations). Positional groups were classified as either a forward (F), center midfield (CM), wide midfield (WM), or defender (D). Movement was profiled by locomotor (walking [0-7.19 km·h], jogging [7.20-14.39 km·h], running [14.40-21.59 km·h], and sprinting [>21.6 km·h]), and acceleration/deceleration characteristics (low intensity [0-1.99 m·s], moderate intensity [2-3.99 m·s], and high intensity [>4 m·s]). Players averaged distances of 9,367 ± 2,149 m per match at speeds of 91 ± 20 m·min and physiological intensities of 78 ± 8 %HRmax. Center midfields demonstrated the highest average speeds (97 ± 20 m·min) and covered the most distance (9,941 ± 2,140 m). Wide midfields accumulated the most sprint distance (391 ± 145 m) and high-intensity accelerations (129 ± 30 n)/decelerations (96 ± 24 n). Several practically meaningful differences exist between positions for internal and external load metrics. Match loads seen in NCAA Division I soccer vary from reports of professional soccer; however, the effects of match regulation, structure, and congestion, which are unique to NCAA soccer, require further investigation. Physical and physiological load monitoring of NCAA soccer may aid coaches and practitioners in the periodization of training programs leading up to and during a competitive soccer season. These data speak to the necessity for examining both internal and external loads by position.


#3 Promoting additional activity in youth soccer: a half-longitudinal study on the influence of autonomy-supportive coaching and basic psychological need satisfaction
Reference: J Sports Sci. 2018 Jul 5:1-9. doi: 10.1080/02640414.2018.1495394. [Epub ahead of print]
Authors: Gjesdal S, Wold B, Ommundsen Y
Summary: This study investigated the relationships between perceptions of coach autonomy support, basic psychological need satisfaction and the frequency at which youth soccer players engage in additional soccer activity outside of team sessions. We employed structural equation modelling to test a two-wave (T1 and T2) half-longitudinal study to see if basic psychological need satisfaction mediated the relationship between coach autonomy support and additional soccer activity across a competitive season. The sample consisted of 527 youth soccer players, aged 10-15 years. Results revealed moderate to strong temporal stability for autonomy, competence, relatedness and frequency of additional soccer activity. Furthermore, no support is offered for mediation as T1 coach autonomy support was not related to any of the three basic needs at T2 when accounting for their T1 levels. However, a positive relationship between T1 autonomy and T2 additional soccer activity emerged. This suggests that those who experience high levels of autonomy in the team setting at the start of the season report an increased frequency of additional activity at the end of the season. Results are discussed in light of the Self-Determination Theory and the Trans-Contextual Model.


#4 The effect of two different speed endurance training protocols on a multiple shuttle run performance in young elite male soccer players
Reference: Res Sports Med. 2018 Jul 4:1-14. doi: 10.1080/15438627.2018.1492402. [Epub ahead of print]
Authors: Vitale JA, Povia V, Vitale ND, Bassani T, Lombardi G, Giacomelli L, Banfi G, La Torre A
Summary: There is not enough evidence on the impact of different speed endurance training regimes on footballers' ability to perform multiple shuttle run performance. This study examined the effect of 4 weeks of speed endurance maintenance (SEM) and speed endurance production (SEP) training on the 5-meter multiple shuttle run test (5-m MST) performance in young elite soccer players. A parallel two-groups, longitudinal design was used. Fifteen players were divided to either SEM (8 repetitions of 20-s all-out sprint interspersed with 40 s of recovery) or SEP (8 repetitions of 20-s all-out bout interspersed with 120 s of recovery) training group. SEM improved the ability to tolerate fatigue and maintained the performance development during the 5-m MST while SEP increased only the 1st sprint showing, simultaneously, an increased fatigue index and performance decrement. The selection of which training regimes to prioritize should be based on the players' characteristics and individual game requirements Abbreviations: SEP: Speed Endurance Production; SEM: Speed Endurance Maintenance; PRE: Baseline; POST: End of experimental protocol; 5-m MST: 5-meters Multiple Shuttle Run Test; TD: Total Distance; FI: Fatigue Index; MSTdec: Percentage Decrement Score; BMI: Body Mass Index.


#5 Recreational soccer practice among adults, in Brazilian capitals, 2011-2015
Reference: Epidemiol Serv Saude. 2018 Jul 2;27(2):e2017284. doi: 10.5123/S1679-49742018000200013. [Article in English, Portuguese; Abstract available in Portuguese from the publisher]
Authors: Lima DF, Piovani VGS, Lima LA
Download link: http://www.scielo.br/pdf/ress/v27n2/en_2237-9622-ress-27-02-e2017284.pdf
Summary: The aim of the study was to describe the profile of recreational adult soccer players who lived in the Brazilian capitals in the period from 2011 to 2015. A sample of adults were interviewed by the Surveillance System for Risk and Protective Factors for Chronic Diseases by Telephone Survey - VIGITEL (2011 to 2015). 11.812 adults (11.375 men and 437 women) pointed to soccer as their main leisure physical exercise, with higher prevalence in the North region (32%) and lower in the South region (10%) of the country; the average reduction of soccer players 3.4% for every 5 years over age (95%CI 2.9;4.1); from 2011 to 2015, there was decrease in the number of soccer players, -1.4% per year (95%CI -0,7;2,2). Tthe practice of soccer was predominantly male, presented an inverse relationship with the increase of age, more prevalent in the Northern region and less prevalent in the Southern region.


#6 Left ventricular function during exercise in trained pre-adolescent soccer players
Reference: Scand J Med Sci Sports. 2018 Jul 3. doi: 10.1111/sms.13258. [Epub ahead of print]
Authors: Unnithan VB, Rowland TW, George K, Lord R, Oxborough D
Summary: It is unclear, what the underlying cardiovascular mechanisms are that give rise to the high level of aerobic fitness seen in youth soccer players. The aim of the study was to evaluate global and regional markers of systolic and diastolic function in a group of pre-adolescent soccer players during an incremental exercise test. Twenty-two, male soccer players (SP) from two professional soccer clubs (age: 12.0 ± 0.3 years) volunteered for the study. Fifteen recreationally active boys (CON), of similar age (age: 11.7 ± 0.2 years) were also recruited. All boys underwent a cycle ergometer test to exhaustion. Cardiac dimensions were determined using M-mode echocardiography. During submaximal and maximal exercise, continuous-wave Doppler ultrasound techniques were used to derive stroke volume (SVIndex). Tissue-Doppler imaging was used to quantify systolic (S'adj) and diastolic function (E; E'adj and E/E') at rest and both submaximal and maximal exercise intensities. Speckle tracking echocardiography was used to determine peak longitudinal ε at submaximal exercise intensities. SP demonstrated significantly (P ≤ 0.05) greater peak VO2 values than CON (SP: 48.0 ± 5.0 vs CON: 40.1 ± 7.5 mL·kg-1 ·min-1 ). Allometrically scaled to body surface area left ventricular end-diastolic volume (LVEDV) was larger (P ≤ 0.05) in the SP (51.3 ± 9.0) compared to CON (44.6 ± 5.8 mL·BSA1.5 ). At the same relative, submaximal exercise intensities, the SP demonstrated greater SVIndex, cardiac output (QIndex) and E. No differences were noted for peak longitudinal ε during submaximal exercise. Factors that augment pre-load and LV volume appear to determine the superior aerobic fitness seen in the soccer players.


#7 Operative Outcomes of Grade 3 Turf Toe Injuries in Competitive Football Players
Reference: Foot Ankle Int. 2018 Jun 1:1071100718775967. doi: 10.1177/1071100718775967. [Epub ahead of print]
Authors: Smith K, Waldrop N
Summary: Turf toe is a term used to describe a hyperextension injury to the first metatarsophalangeal joint. Although the vast majority of turf toe injuries can be treated successfully without operative intervention, there are instances where surgery is required to allow the athlete to return to play. Although there is a plethora of literature on turf toe injuries and nonoperative management, there are currently few reports on operative outcomes in athletes. We obtained all cases of turf toe repair according to the ICD-10 procedural code. The inclusion criteria included: age greater than 16, turf toe injury requiring operative management and at least a varsity level high school football player. The charts were reviewed for age, BMI, level of competition, injury mechanism, football position, setting of injury and playing surface. In addition, we recorded the specifics of the operative procedure, a listing of all injured structures, the implants used and the great toe range of motion at final follow-up visit. The AOFAS Hallux score and VAS was used postoperatively as our outcome measures. Our patient population included 15 patients. The average follow-up time was 27.5 months. The average patient was 19.3 years old with a body mass index of 32.3. The average playing time missed was 16.5 weeks. The average dorsiflexion range of motion at the final follow-up was 42.3 degrees. At final follow-up, the average AOFAS Hallux score was 91.3. The average VAS pain score was 0.7 at rest and 0.8 with physical activity. Complete turf toe injuries are often debilitating and may require operative management to restore a pain-free, stable, and functional forefoot. This study represents the largest cohort of operatively treated grade 3 turf toe injuries in the literature and demonstrates that good clinical outcomes were achieved with operative repair.


#8 Load distribution on the foot and lofstrand crutches of amputee football players
Reference: Gait Posture. 2018 Jun 9;64:169-173. doi: 10.1016/j.gaitpost.2018.06.008. [Epub ahead of print]
Authors: Tatar Y, Gercek N, Ramazanoglu N, Gulmez I, Uzun S, Sanli G, Karagozoglu C, Cotuk HB
Summary: Amputee football is a worldwide popular sport with positive physical and psychological effects on the disabled. Amputee players use their hands dominantly for locomotion. However, the effect of using upper extremity which is not accommodated to loading is not very well known. The objective of this study was to determine the load distribution of amputee football players during walking, running and kicking the ball. This study was conducted with 15 certified amputee football players (age 24.5 ± 5.8 years, body weight 62.3 ± 10.9 kg, height 171.6 ± 7.7 cm). The loads on their non-amputated lower extremity were measured with F-Scan mobile system sensors inserted in their shoes, and the loads on their upper extremities were measured with F-Grip system sensors affixed to the gloves. The participants were asked to walk, run and kick the ball using Lofstrand Crutches. The maximum loading on the upper extremities during walking, running and kicking the ball varied between 111% and 175% of the body weight. While loading during walking and running was similar, the loading on the upper extremity during kicking the ball exceeded that of walking by 58.1% and running by 47.4%. The maximum loading on the non-amputated lower extremity varied between 134% and 196% of the body weight. Loading during running was 46.2% higher than that of walking. The loading on the foot during kicking the ball was 45.7% higher than that of walking. The loading on the foot during running and kicking were similar. Walking-running-kicking the ball with LC resulted in unusual loading particularly on the upper extremity. During running, the increased loading was transferred to the foot rather than the hands. During kicking, the loading increased extremely and was mainly transferred to the hands. The frequent repetition of kicking during the game may therefore increase the incidence of upper extremity injuries.

Sun

23

Sep

2018

Latest research in football - week 27 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Demands of a Women's College Soccer Season
Reference: Sports (Basel). 2018 Feb 23;6(1). pii: E16. doi: 10.3390/sports6010016.
Authors: Gentles JA, Coniglio CL, Besemer MM, Morgan JM, Mahnken MT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969200/pdf/sports-06-00016.pdf
Summary: The purpose of this study was to use GPS, accelerometers, and session rating of perceived exertion (sRPE) to examine the demands of a Division II women's soccer team. Data was collected on 25 collegiate Division II women's soccer players over an entire regular season (17 matches and 24 practices). ZephyrTM BioHarnesses (BHs) were used to collect tri-axial acceleration information and GPS derived variables for all matches and practices. Acceleration data was used to calculate Impulse Load, a measure of mechanical load that includes only locomotor related accelerations. GPS was used to quantify total distance and distance in six speed zones. Internal Training Loads were assessed via sRPE. Mean Impulse Load, total distance, and sRPE during match play was 20,120 ± 8609 N·s, 5.48 ± 2.35 km, and 892.50 ± 358.50, respectively. Mean Impulse Load, total distance, and sRPE during practice was 12,410 ± 4067 N·s, 2.95 ± 0.95 km, and 143.30 ± 123.50, respectively. Several very large to nearly perfect correlations were found between Impulse Load and total distance (r = 0.95; p < 0.001), Impulse Load and sRPE (r = 0.84; p < 0.001), and total distance and sRPE (r = 0.82; p < 0.001). This study details the mechanical demands of Division II women's soccer match play. This study also demonstrates that Impulse Load is a good indicator of total distance.



#2 Seasonal Variations in Physical Fitness and Performance Indices of Elite Soccer Players
Reference: Sports (Basel). 2018 Feb 13;6(1). pii: E14. doi: 10.3390/sports6010014.
Authors: Meckel Y, Doron O, Eliakim E, Eliakim A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969193/pdf/sports-06-00014.pdf
Summary: The aim of the study was to investigate seasonal variations in fitness and performance indices of professional male soccer players. Eighteen professional male soccer players (age range 22⁻32 years) completed three similar sets of tests at three stages of the season: before preseason; after preseason and the middle of the competitive in-season. A significant decrease in body mass and percent fat was found during the preseason. A significant improvement (p < 0.05) was found in the vertical jump (preseason: 37.0 ± 5.3, post-preseason: 39.0 ± 4.8, mid-season: 40.3 ± 5.5 cm), the 4 × 10-m agility test (preseason: 8.1 ± 0.2, post-preseason: 7.9 ± 0.2, mid-season: 8.1 ± 0.3 s), flexibility (preseason: 45.2 ± 8.8, post-preseason: 48.2 ± 7.0, mid-season: 49.9 ± 6.9 cm) and aerobic capacity (preseason: 52.7 ± 6.6, post-preseason: 56.4 ± 6.0, mid-season: 57.4 ± 5.4 mL/kg/min) during preseason, with no further change during mid-season. Repeated sprint test (RST) (6 × 30-m) performance indices showed significant deterioration (p < 0.05) in ideal sprint time (IS; preseason: 21.8 ± 1.0, post-preseason: 23.0 ± 0.8, mid-season: 23.2 ± 0.8 s) and total sprint time (TS; preseason: 22.5 ± 0.7, post-preseason: 23.5 ± 0.6, mid-season: 23.8 ± 0.6 s) during preseason, with no further changes during mid-season. However, performance decrement (PD) significantly decreased during the preseason with no change during mid-season. The findings suggest that while power training was probably responsible for the anaerobic fitness improvement, the high-volume training led to improvement in aerobic fitness during the preseason. However, the low-intensity aerobic-type training, coupled with the high total training load, may have led to fatigue and decreases in IS and TS during the preseason.


#3 The Influence of Playing Position and Contextual Factors on Soccer Players' Match Differential Ratings of Perceived Exertion: A Preliminary Investigation
Reference: Sports (Basel). 2018 Feb 12;6(1). pii: E13. doi: 10.3390/sports6010013.
Authors: Barrett S, McLaren S, Spears I, Ward P, Weston M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969182/pdf/sports-06-00013.pdf
Summary: (1) Background: Differential RPE (dRPE) separates scores for breathlessness (RPE-B), leg muscle exertion (RPE-L) and technical/cognitive exertion (RPE-T). Limited information for dRPE is available in soccer match play, yet these measurements may help inform practitioners training and recovery strategies. This preliminary study investigated the effects of playing position and contextual factors on elite soccer players' dRPE. (2) Methods: Thirty-two male English Premier League players recorded dRPE scores 15⁻30 min post-match for RPE-B, RPE-L, and RPE-T. Data were analysed using linear mixed models, with magnitude-based inferences subsequently applied. (3) Results: Overall, the mean ± SD for the dRPE were 63 ± 23 arbitrary units (au) (RPE-B), 67 ± 22 au (RPE-L), and 60 ± 24 au (RPE-T). Full Backs reported substantially higher RPE-B, RPE-L and RPE-T when compared to all other positions. Substantially higher RPE-T scores were reported for matches played against Top teams compared to Bottom (10 au; 90% Confidence Interval 5 to 15 au) and Middle (10 au; 4 to 15 au) ranked teams. The effects of match result and location on dRPE were not substantial. (4) Conclusions: Positional differences were observed following soccer match play for RPE-B, RPE-L and RPE-T. Full backs had substantially higher dRPE then any other position, with all players reporting increased RPE-T when playing teams at the Top of the league. These findings can help practitioners monitor internal load responses and support the prescription of training and recovery sessions.


#4 Relationships and Predictive Capabilities of Jump Assessments to Soccer-Specific Field Test Performance in Division I Collegiate Players
Reference: Sports (Basel). 2016 Dec 3;4(4). pii: E56. doi: 10.3390/sports4040056.
Authors: Lockie RG, Stage AA, Stokes JJ, Orjalo AJ, Davis DL, Giuliano DV, Moreno MR, Risso FG, Lazar A, Birmingham-Babauta SA, Tomita TM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968899/pdf/sports-04-00056.pdf
Summary: Leg power is an important characteristic for soccer, and jump tests can measure this capacity. Limited research has analyzed relationships between jumping and soccer-specific field test performance in collegiate male players. Nineteen Division I players completed tests of: leg power (vertical jump (VJ), standing broad jump (SBJ), left- and right-leg triple hop (TH)); linear (30 m sprint; 0⁻5 m, 5⁻10 m, 0⁻10, 0⁻30 m intervals) and change-of-direction (505) speed; soccer-specific fitness (Yo-Yo Intermittent Recovery Test Level 2); and 7 × 30-m sprints to measure repeated-sprint ability (RSA; total time (TT), performance decrement (PD)). Pearson's correlations (r) determined jump and field test relationships; stepwise regression ascertained jump predictors of the tests (p < 0.05). All jumps correlated with the 0⁻5, 0⁻10, and 0⁻30 m sprint intervals (r = -0.65⁻-0.90). VJ, SBJ, and left- and right-leg TH correlated with RSA TT (r = -0.51⁻-0.59). Right-leg TH predicted the 0⁻5 and 0⁻10 m intervals (R² = 0.55⁻0.81); the VJ predicted the 0⁻30 m interval and RSA TT (R² = 0.41⁻0.84). Between-leg TH asymmetry correlated with and predicted left-leg 505 and RSA PD (r = -0.68⁻0.62; R² = 0.39⁻0.46). Improvements in jumping ability could contribute to faster speed and RSA performance in collegiate soccer players.


#5 Coalitional Physical Competition : Acute Salivary Steroid Hormone Responses among Juvenile Male Soccer Players in Hong Kong
Reference: Hum Nat. 2018 Jun 16. doi: 10.1007/s12110-018-9321-7. [Epub ahead of print]
Authors: McHale TS, Chee WC, Chan KC, Zava DT, Gray PB
Summary: A large body of research links testosterone and cortisol to male-male competition. Yet, little work has explored acute steroid hormone responses to coalitional, physical competition during middle childhood. Here, we investigate testosterone, dehydroepiandrosterone (DHEA), androstenedione, and cortisol release among ethnically Chinese boys in Hong Kong (N = 102), aged 8-11 years, during a soccer match (n = 84) and an intrasquad soccer scrimmage (n = 81), with 63 participants competing in both treatments. The soccer match and intrasquad soccer scrimmage represented out-group and in-group treatments, respectively. Results revealed that testosterone showed no measurable change. DHEA increased during both treatments in the majority of participants and the degree of change had no relation to independent variables (e.g., performance, age, treatment, outcome) or covariate measures (Body Mass Index, Pubertal Development Scale). Most boys experienced androstenedione increases during match play, but no significant differences during the intrasquad soccer scrimmage competitions. The magnitude of change differed significantly between treatments and was positively associated with age. These latter findings suggest boys' androstenedione responses may be sensitive to competitor type (i.e., unknown competitors vs. peers). For most subjects, cortisol significantly increased during match play, decreased during the intrasquad soccer scrimmage, and differed significantly between treatments, suggesting each treatment promoted a different psychological state among competitors. Cortisol/DHEA molar ratio decreased during the intrasquad scrimmage, suggestive of a more relaxed mental state. These data shed new light on potential proximate mechanisms associated with coalitional competition among prepubescent boys, with relevance to adrenarche and life history theory.


#6 Prevalence of femoroacetabular impingement and effect of training frequency on aetiology in paediatric football players
Reference: Hip Int. 2018 Jun 1:1120700018781939. doi: 10.1177/1120700018781939. [Epub ahead of print]
Authors: Polat G, Arzu U, Dinç E, Bayraktar B
Summary: The aim of this study was to determine the prevalence of asymptomatic radiographic findings of femoroacetabular impingement (FAI) in paediatric football players in different age groups and to investigate aetiological factors. Paediatric male athletes between 10 and 17 years of age from 8 soccer teams were recruited. In addition to an annual control check-up, anteroposterior pelvis and frog-leg radiographs as well as the curriculum vitae of the athletes, their injuries, and real-time complaints were recorded. The alpha angle, lateral centre-edge angle, Tönnis angle, and collodiaphyseal angle were measured and morphological abnormalities were noted. There were 214 male football players with a mean age of 13.4 ± 3.2 years included in the study. In the morphological analysis of hips, there was FAI in 30% of the athletes. In the analysis of FAI prevalence in 3 subgroups based on age (Group 1: 10-12 years [ n = 25], Group 2: 13-15 years [ n = 104], Group 3: 16-17 years [ n = 85]), there was 0% FAI in Group 1, 19.1% in Group 2 and 60% in Group 3. In the analysis of aetiological factors, there was no significant difference between the right and left hips of players regarding alpha angles and FAI prevalence. However, the prevalence of FAI was higher in players who had been playing football for 3 years or more and who had been training for 12.5 hours/week or more. Training for 12.5 hours or more per week in paediatric football players doubled the risk development of FAI morphology.


#7 Return to play, performance and career duration after ACL rupture: a case-control study in in the five biggest football nations in Europe
Reference: Scand J Med Sci Sports. 2018 Jun 21. doi: 10.1111/sms.13245. [Epub ahead of print]
Authors: Niederer D, Engeroff T, Wilke J, Vogt L, Banzer W
Summary: A media-based collection and further analysis of relative return to play (RTP) rates and the corresponding quality of play after anterior cruciate ligament (ACL) rupture in top level football was the aim of our study. In the 5-year case-control study, male players from the first two leagues of the five European countries top leagues, who sustained a total ACL rupture during the season 2010/11 and/or 2011/12, were included. For them and a matched control sample (ratio 1:2), data were retrieved from the publicly available and validated media-based platforms (transfermarkt.de & whoscored. com) until the end of season 2016/17. Injury and return to play-specific data were calculated as rate ratios (RR) to compare the injured and matched control athletes rates and as a survival analysis (log-rank-test; career duration). Overall, 132 ACL-injuries in 125 players occurred. The RTP rate was 98.2%, the RTP to same level was 59.4%. Five years post RTP, 69.9% of the ACL group were still engaged in football (RR = 87%), 40.9% at the same level (RR = 72%). Survival analysis revealed a systematic group difference in career duration compared to controls (Cox-Mantel's Chi² =5.8; p= .016). Game performance (scoring points, p < .001; rates/number of completed passes, p = .048; and minutes played, p < .001) was lower in the ACL athletes than in the matching group in the RTP and post RTP seasons. Although absolute and relative RTP rates after ACL reconstruction are high in professional football, career duration and performance quality are lower than in the reference group. This article is protected by copyright. All rights reserved.


#8 Effects of Training and Competition Load on Neuromuscular Recovery, Testosterone, Cortisol, and Match Performance During a Season of Professional Football
Reference: Front Physiol. 2018 Jun 7;9:668. doi: 10.3389/fphys.2018.00668. eCollection 2018.
Authors: Rowell AE, Aughey RJ, Hopkins WG, Esmaeili A, Lazarus BH, Cormack SJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6000155/pdf/fphys-09-00668.pdf
Summary: Training load and other measures potentially related to match performance are routinely monitored in team-sport athletes. The aim of this research was to examine the effect of training load on such measures and on match performance during a season of professional football. Training load was measured daily as session duration times perceived exertion in 23 A-League football players. Measures of exponentially weighted cumulative training load were calculated using decay factors representing time constants of 3-28 days. Players performed a countermovement jump for estimation of a measure of neuromuscular recovery (ratio of flight time to contraction time, FT:CT), and provided a saliva sample for measurement of testosterone and cortisol concentrations 1-day prior to each of 34 matches. Match performance was assessed via ratings provided by five coaching and fitness staff on a 5-point Likert scale. Effects of training load on FT:CT, hormone concentrations and match performance were modeled as quadratic predictors and expressed as changes in the outcome measure for a change in the predictor of one within-player standard deviation (1 SD) below and above the mean. Changes in each of five playing positions were assessed using standardization and magnitude-based inference. The largest effects of training were generally observed in the 3- to 14-day windows. Center defenders showed a small reduction in coach rating when 14-day a smoothed load increased from -1 SD to the mean (-0.31, ±0.15; mean, ±90% confidence limits), whereas strikers and wide midfielders displayed a small increase in coach rating when load increased 1 SD above the mean. The effects of training load on FT:CT were mostly unclear or trivial, but effects of training load on hormones included a large increase in cortisol (102, ±58%) and moderate increase in testosterone (24, ±18%) in center defenders when 3-day smoothed training load increased 1 SD above the mean. A 1 SD increase in training load above the mean generally resulted in substantial reductions in testosterone:cortisol ratio. The effects of recent training on match performance and hormones in A-League football players highlight the importance of position-specific monitoring and training.


#9 In-Season Variations in Head Impact Exposure among Youth Football Players
Reference: J Neurotrauma. 2018 Jun 19. doi: 10.1089/neu.2018.5699. [Epub ahead of print]
Authors: Urban JE, Kelley ME, Espeland MA, Davenport EM, Whitlow CT, Powers AK, Maldjian JA, Stitzel JD
Summary: Head impact exposure (HIE) is often summarized by the total exposure measured during the season and does not indicate how the exposure was accumulated, or how it varied during the season. Therefore, the objective of this study is to compare HIE during preseason, the first and second halves of the regular season, and playoffs in a sample of youth football players (n=119, ages 9-13). Athletes were divided into one of four exposure groups based on quartiles computed from the distribution of risk-weighted cumulative exposure (RWECP). Mean impacts per session and mean 95th percentile linear and rotational acceleration in practices and games were compared across the four exposure groups and time frames using mixed effects models. Within games, the mean 95th percentile accelerations for the entire sample ranged from 47.2 g and 2331.3 rad/s2 during preseason to 52.1 g and 2533.4 rad/s2 during the second half of regular season. Mean impacts per practice increased from preseason to the second half of regular season and declined into playoffs among all exposure groups; however, the variation between time frames was not greater than 2 impacts per practice. Time of season had a significant relationship with mean 95th percentile linear and rotational acceleration in games (both p=0.01) but not with practice accelerations or impacts/session. The in-practice mean levels of 95th percentile linear and rotational acceleration remained fairly constant across the four time frames, but in games these changed over time depending on exposure group (interactions p<0.05). The results of this study improve our understanding of in-season variations in HIE in youth football and may inform important opportunities for future interventions.


#10 The "Football is Medicine" platform-scientific evidence, large-scale implementation of evidence-based concepts and future perspectives
Reference: Scand J Med Sci Sports. 2018 Jun 19. doi: 10.1111/sms.13220. [Epub ahead of print]
Authors: Krustrup P, Williams CA, Mohr M, Hansen PR, Helge EW, Elbe AM, de Sousa M, et al.
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13220

Sun

23

Sep

2018

Latest research in football - week 26 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 The Validity of External:Internal Training Load Ratios in Rested and Fatigued Soccer Players
Reference: Sports (Basel). 2018 May 19;6(2). pii: E44. doi: 10.3390/sports6020044.
Authors: Akubat I, Barrett S, Sagarra ML, Abt G
Summary: The purpose was to examine the relationship of external:internal training load ratios with fitness and assess the impact of fatigue. Ten soccer players performed a lactate threshold test followed by two soccer simulations (BEAST90mod) 48 h apart. Recovery (TQR) and muscle soreness (DOMS) was measured before each trial. Internal Training load (TL) (iTRIMP) and external load total distance (TD), high intensity distance (HID), PlayerLoad&trade; (PL) mean metabolic power (MMP) high metabolic power distance (HP) were collected for each trial and external:internal ratios produced. The relationships between ratios and velocity at lactate threshold (vLT) and velocity at Onset of Blood Lactate Accumulation (vOBLA) were examined in both trials along with changes in ratios. Total Quality of Recovery and DOMS showed large changes. There were trivial to large decreases in TL from trial 1 to 2. Moderate increases in ratios for TD:iTRIMP, PL:iTRIMP and MMP:iTRIMP were seen but only small/trivial for HP:iTRIMP and HID:iTRIMP. In rested conditions all ratios show large relationships with vLT and vOBLA. However vLT vs. HID:iTRIMP; PL:iTRIMP; HP:iTRIMP and vOBLA vs. TD:iTRIMP; PL:iTRIMP; MMP:iTRIMP became weaker under fatigue. Acute changes in the ratios have implications for the use of ratios as fitness measures but also as indicators of fatigue.


#2 Non-Linear Resistance Training Program Induced Power and Strength but Not Linear Sprint Velocity and Agility Gains in Young Soccer Players
Reference: Sports (Basel). 2018 May 14;6(2). pii: E43. doi: 10.3390/sports6020043.
Authors: Barbalho M, Gentil P, Raiol R, Del Vecchio FB, Ramirez-Campillo R, Coswig VS
Summary: The present study evaluated the effects of resistance training (RT) following a non-linear periodization model in the physical fitness of young soccer athletes. Young soccer players (n = 23) were allocated into two groups: an RT group (RTG), and the control group (CON). The RTG underwent 15 weeks of non-linear RT periodization in three weekly sessions in addition to their specific soccer training. The CON continued performing the specific soccer training. Before and after the training period, all of the subjects performed one-repetition maximum (RM) tests for speed, agility, and power (vertical and horizontal jump). The RTG obtained significant gains in one-RM tests (before 64.1 ± 5.8 kg, after 79.1 ± 3.3 kg) and power (vertical jump (before 56 ± 2.7 cm, after 61.3 ± 1.7 cm) and horizontal jump (before 184.5 ± 5.5 cm, after 213.6 ± 3.2 cm)). In contrast, the CON group presented a non-significant increase in one-RM tests and horizontal jump, and a significant reduction in vertical jump (before 55.4 ± 2.2 cm, after 51.3 ± 1.5 cm). Neither group presented significant gains in speed (CON: p = 0.27; RTG: p = 0.72) and agility (CON: p = 0.19; RTG: p = 0.58). Our data suggest that non-linear RT should be inserted into the routine of young soccer athletes for improving strength and power without impairing speed and agility.


#3 Directional Change Mediates the Physiological Response to High-Intensity Shuttle Running in Professional Soccer Players
Reference: Sports (Basel). 2018 Apr 24;6(2). pii: E39. doi: 10.3390/sports6020039.
Authors: Tang R, Murtagh C, Warrington G, Cable T, Morgan O, O'Boyle A, Burgess D, Morgans R, Drust B
Summary: The purpose of this study was to investigate the influence that different frequencies of deceleration and acceleration actions had on the physiological demands in professional soccer players. Thirteen players were monitored via microelectromechanical devices during shuttle running protocols which involved one, three, or seven 180 degree directional changes. Heart rate exertion (HRE) (1.1 ± 0.7) and rating of perceived exertion (RPE) (5 ± 1) were significantly higher for the protocol which included seven directional changes when compared to the protocols which included one (HRE 0.5 ± 0.3, ES = 1.1, RPE 3 ± 0, ES = 2.7) or three (HRE 0.5 ± 0.2, ES = 1.1, RPE 3 ± 1, ES = 1.9) directional changes (p < 0.05). The gravitational force (g-force) as measured through accelerometry (ACC) also showed a similar trend when comparing the seven (8628.2 ± 1630.4 g) to the one (5888.6 ± 1159.1 g, ES = 1.9) or three (6526.9 ± 1257.6 g, ES = 1.4) directional change protocols (p < 0.05). The results of this study suggest that increasing the frequency of decelerations and accelerations at a high intensity running (HIR) speed alters the movement demands and elevates the physiological responses in professional players. This data has implications for the monitoring of physical performance and implementation of training drills.


#4 The Influence of Fatigued Core Muscles on Head Acceleration during Headers in Soccer
Reference: Sports (Basel). 2018 Apr 11;6(2). pii: E33. doi: 10.3390/sports6020033.
Authors: Becker S, Frohlich M, Kelm J, Ludwig O
Summary: The core muscles play a central role in stabilizing the head during headers in soccer. The objective of this study was to examine the influence of a fatigued core musculature on the acceleration of the head during jump headers and run headers. Acceleration of the head was measured in a pre-post-design in 68 soccer players (age: 21.5 ± 3.8 years, height: 180.0 ± 13.9 cm, weight: 76.9 ± 8.1 kg). Data were recorded by means of a telemetric 3D acceleration sensor and with a pendulum header. The treatment encompassed two exercises each for the ventral, lateral, and dorsal muscle chains. The acceleration of the head between pre- and post-test was reduced by 0.3 G (p = 0.011) in jump headers and by 0.2 G (p = 0.067) in run headers. An additional analysis of all pretests showed an increased acceleration in run headers when compared to stand headers (p < 0.001) and jump headers (p < 0.001). No differences were found in the sub-group comparisons: semi-professional vs. recreational players, offensive vs. defensive players. Based on the results, we conclude that the acceleration of the head after fatiguing the core muscles does not increase, which stands in contrast to postulated expectations. More tests with accelerated soccer balls are required for a conclusive statement.


#5 Relationships between Linear Speed and Lower-Body Power with Change-of-Direction Speed in National Collegiate Athletic Association Divisions I and II Women Soccer Athletes
Reference: Sports (Basel). 2018 Apr 4;6(2). pii: E30. doi: 10.3390/sports6020030.
Authors: Lockie RG, Dawes JJ, Jones MT
Summary: This study investigated relationships that linear speed and lower-body power have on change-of-direction (COD) speed in collegiate women soccer players. Data from two Division I (n = 39) and one Division II (n = 18) schools were analyzed. Subjects were assessed in: power (vertical jump (VJ); jump height, peak anaerobic power measured in watts (PAPw), power-to-body mass ratio (P:BM); linear speed (10-m sprint); and COD speed (modified T-test (MTT), 505, COD deficit). Independent samples T-tests derived significant between-group differences, with effect sizes (d) calculated. Pearson&rsquo;s correlations determined relationships between COD speed, linear speed, and power, with regression equations calculated. Division I players demonstrated superior 505, COD deficit, VJ height, PAPw, and P:BM (d = 1.09⁻2.21). Division II players were faster in the MTT (d = 1.51). For all players, the 505 correlated with the 10-m sprint (r = 0.39⁻0.53) and VJ height (r = -0.65⁻0.66), while the COD deficit related to the 10-m sprint (r = -0.77⁻0.82). The regression data supported these results. Division I players were superior in the 505 and COD deficit, and expressed their power in the 180 deg; 505 task. Division II players should enhance lower-body power and the ability to perform 180 deg; direction changes.


#6 Inevitable Relative Age Effects in Different Stages of the Selection Process among Male and Female Youth Soccer Players
Reference: Sports (Basel). 2018 Mar 31;6(2). pii: E29. doi: 10.3390/sports6020029.
Authors: Lagestad P, Steen I, Dalen T
Summary: The relative age effect (RAE) in the selection of young soccer players is a well-known phenomenon. The purpose of this study was to examine the relative age effect existing despite strategies that have been implemented to avoid its presence in the selection process. We also aimed to investigate the RAE during the three different selection stages for B13, B14 (boys), and G13, G14 (girls), and gender differences in the RAE. This was achieved by collecting data from everyone who played soccer in Troendelag, and data that would illuminate the RAE during the three stages of selection for the regional teams of the 2015/2016 season. Mann⁻Whitney U-tests and Chi-square tests were used as statistical methods. The main finding of this study is that, despite the intention to reduce RAE in the selection process according to the criterion that at least 40% of the players should be born in the second half of the year, both the early-born boys and girls are more likely to be selected. The results also show that the RAE occurs gradually, and the longer the players are in the selection process the more prominent it is. This study highlights the importance of being aware of the RAE when selecting young players.


#7 Relationships between Sprint Ability and Endurance Capacity in Soccer Referees
Reference: Sports (Basel). 2018 Mar 30;6(2). pii: E28. doi: 10.3390/sports6020028.
Authors: Sanchez-Garcia M, Sanchez-Sanchez J, Rodriguez-Fernandez A, Solano D, Castillo D
Summary: The aim of this study was to analyze the association between sprint ability and endurance capacity in soccer referees. Twenty-three Spanish officials participated in this study. Each referee undertook, in this order, a 40 m linear straight sprinting test (40 m Sprint) and the Yo⁻Yo intermittent recovery level 1 test (YYIR1) interspersed with a 8 min of self-administered rest. The results in the 40 m Sprint test showed that the time spent by referees was 5.56 ± 0.27 s and achieved a maximum velocity of 31.46 ± 2.85 km·h-1. Furthermore, during the YYIR1 the referees covered 1213.91 ± 432.26 m. The distance covered at YYIR1 was moderately correlated to the velocity achieved in the 40 m Sprint test (r = -0.404, p < 0.05). These results suggest that the ability to reach high speeds is a limiting factor in YYIR1 performance.


#8 The Impact of 120 Minutes of Match-Play on Recovery and Subsequent Match Performance: A Case Report in Professional Soccer Players
Reference: Sports (Basel). 2018 Mar 13;6(1). pii: E22. doi: 10.3390/sports6010022.
Authors: Winder N, Russell M, Naughton RJ, Harper LD
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969194/pdf/sports-06-00022.pdf
Summary: The influence of a match including extra-time (ET) on subsequent 90 min match performance and recovery has not been investigated. Four professional soccer players played in three competitive matches in a 7-day period: matches one (MD1) and three (MD3) lasted 90 min and match 2 (MD2) lasted 120 min (i.e., included ET). Physical (total and high-intensity (HI) distance covered, accelerations and decelerations, and mechanical load) and technical performances (pass and dribble accuracy) were analyzed throughout match-play. Subjective measures of recovery and countermovement jump (CMJ) height were made 36⁻42 h post-match. Post-MD2, there were very or most likely harmful effects of ET on CMJ height (-6 ± 9%), muscle soreness (+18 ± 12%), and fatigue (+27 ± 4%) scores, and overall wellness score (-13 ± 5%) compared to post-MD1. Furthermore, there were very likely harmful effects on muscle soreness (+13 ± 14%), wellness scores (-8 ± 10%), and CMJ height (-6 ± 9%) post-MD3 vs. post-MD1. There was a possibly harmful effect of ET on HI distance covered during MD3, along with reductions in pass (-9.3%) and dribble (-12.4%) accuracy. An ET match negatively impacted recovery 36 h post-match. Furthermore, in some players, indices of performance in a 90 min match played 64 h following ET were compromised, with subsequent recovery also adversely affected.


#9 Can Genetics Predict Sports Injury? The Association of the Genes GDF5, AMPD1, COL5A1 and IGF2 on Soccer Player Injury Occurrence
Reference: Sports (Basel). 2018 Mar 5;6(1). pii: E21. doi: 10.3390/sports6010021.
Authors: McCabe K, Collins C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969195/pdf/sports-06-00021.pdf
Summary: Genetics plays an integral role in athletic performance and is increasingly becoming recognised as an important risk factor for injury. Ankle and knee injuries are the most common injuries sustained by soccer players. Often these injuries result in players missing training and matches, which can incur significant costs to clubs. This study aimed to identify genotypes associated with ankle and knee injuries in soccer players and how these impacted the number of matches played. 289 soccer players, including 46 professional, 98 semi-professional and 145 amateur players, were genetically tested. Ankle and knee injuries and the number of matches played were recorded during the 2014/15 season. Four genes were assessed in relation to injury. Genotypes found to be associated with injury included the TT (nucleobase) genotype of the GDF5 gene, TT and CT (nucleobase) genotypes of AMPD1 gene, TT genotype of COL5A1 and GG (nucleobase) genotype of IGF2 gene. These genes were also associated with a decrease in the number of matches played.

Thu

30

Aug

2018

Latest research in football - week 25,5 - 2018

As in previous literature update, here are the rest of the Basel publications.

#1 Seasonal Variation of Agility, Speed and Endurance Performance in Young Elite Soccer Players
Reference: Sports (Basel). 2017 Feb 4;5(1). pii: E12. doi: 10.3390/sports5010012.
Authors: Dragijsky M, Maly T, Zahalka F, Kunzmann E, Hank M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969008/pdf/sports-05-00012.pdf
Summary: The aim of this study was to investigate changes in the linear running speed (LRS) for 30 m, change of direction speed (CODS), and endurance in young elite Czech soccer players. The following tests were conducted to assess CODS and endurance: Agility 505 turning toward the dominant (A505DL) and non-dominant lower limb (A505NL); Illinois Agility Test (IAT); and intermittent test (Yo-Yo IRT1). During the soccer season, we investigated performance at the following time periods: the start (t₁) and the end of the pre-season period (t₂); during (t₃) and at the end of the competitive period (t₄). Repeated measurement analysis of variance revealed a significant effect of time period on selected fitness parameters (p < 0.05). Post hoc analysis for test A505DL revealed significant improvements of performance at t₃ (2.71 ± 0.08 s) and t₄ (2.72 ± 0.06 s) compared to t₁ (2.81 ± 0.09 s). A505NL was significantly different between t₁ (2.83 ± 0.09 s) and t₂ (2.76 ± 0.09 s), t₃ (2.7 ± 0.07 s) and t₄ (2.71 ± 0.09 s). Performance of CODS at t₁ for the IAT (18.82 ± 0.56 s) was significantly lower (p < 0.05) than any other time period (t₂ = 18.52 ± 0.63 s, t₃ = 17.94 ± 0.51 s, t₄ = 17.89 ± 0.66 s). The power of LRS was significantly different at t₃ (4.99 ± 0.15 s), and t₄ (4.98 ± 0.17 s) compared to t₁ (5.15 ± 0.21 s), and t₂ (5.07 ± 0.14 s). For the Yo-Yo IRT1 test, we observed a significant increase in performance between t₁ (625.26 ± 170.34 m), t₂ (858.95 ± 210.55 m), and t₃ (953.68 ± 229.88 m). These results show the impact of soccer season time period on young soccer player performance and may further serve as a basis for comparison with similar research conducted by peers. These results may aid sports practice for clinicians, conditioning coaches, soccer coaches and physiotherapeutic coaches.


#2 Seasonal Variation of Agility, Speed and Endurance Performance in Young Elite Soccer Players
Reference: Sports (Basel). 2017 Feb 4;5(1). pii: E12. doi: 10.3390/sports5010012.
Authors: Dragijsky M, Maly T, Zahalka F, Kunzmann E, Hank M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969008/pdf/sports-05-00012.pdf
Summary: The aim of this study was to investigate changes in the linear running speed (LRS) for 30 m, change of direction speed (CODS), and endurance in young elite Czech soccer players. The following tests were conducted to assess CODS and endurance: Agility 505 turning toward the dominant (A505DL) and non-dominant lower limb (A505NL); Illinois Agility Test (IAT); and intermittent test (Yo-Yo IRT1). During the soccer season, we investigated performance at the following time periods: the start (t₁) and the end of the pre-season period (t₂); during (t₃) and at the end of the competitive period (t₄). Repeated measurement analysis of variance revealed a significant effect of time period on selected fitness parameters (p < 0.05). Post hoc analysis for test A505DL revealed significant improvements of performance at t₃ (2.71 ± 0.08 s) and t₄ (2.72 ± 0.06 s) compared to t₁ (2.81 ± 0.09 s). A505NL was significantly different between t₁ (2.83 ± 0.09 s) and t₂ (2.76 ± 0.09 s), t₃ (2.7 ± 0.07 s) and t₄ (2.71 ± 0.09 s). Performance of CODS at t₁ for the IAT (18.82 ± 0.56 s) was significantly lower (p < 0.05) than any other time period (t₂ = 18.52 ± 0.63 s, t₃ = 17.94 ± 0.51 s, t₄ = 17.89 ± 0.66 s). The power of LRS was significantly different at t₃ (4.99 ± 0.15 s), and t₄ (4.98 ± 0.17 s) compared to t₁ (5.15 ± 0.21 s), and t₂ (5.07 ± 0.14 s). For the Yo-Yo IRT1 test, we observed a significant increase in performance between t₁ (625.26 ± 170.34 m), t₂ (858.95 ± 210.55 m), and t₃ (953.68 ± 229.88 m). These results show the impact of soccer season time period on young soccer player performance and may further serve as a basis for comparison with similar research conducted by peers. These results may aid sports practice for clinicians, conditioning coaches, soccer coaches and physiotherapeutic coaches.


#3 Functional Assessment and Injury Risk in a Professional Soccer Team
Reference: Sports (Basel). 2017 Jan 22;5(1). pii: E9. doi: 10.3390/sports5010009.
Authors: Gomez-Piqueras P, Gonzalez-Villora S, Sainz de Baranda Andujar MDP, Contreras-Jordan OR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969000/pdf/sports-05-00009.pdf
Summary: At the last World Conference on Sport and Physical Therapy celebrated in Bern (Switzerland, 2015), it was confirmed that the functional skills of an athlete are a very important variable to be considered in the recovery of an injury. On the other hand, its use as a predictive risk tool still lacks solid evidence. The purpose of this study was to determine whether a battery of functional tests (FPT) could be used as a preliminary measure for the season in order to identify the injury risk in a professional soccer team in the Spanish Second Division B League. Fifty-two soccer players (ages of 25.3 ± 4.6 years, 10.33% ± 0.9% fat) were functionally assessed during two seasons (2012⁻2013 and 2013⁻2014) and analyzed from an injury perspective. A total of 125 injuries were recorded. The sample was grouped based on the number of injuries and the required absence days. Except for the bipodal vertical jump (CMJ), none of the functional tests revealed differences among the groups. The correlation study between the functional condition and the suffered injuries did not show any significant results.


#4 Soccer and Relative Age Effect: A Walk among Elite Players and Young Players
Reference: Sports (Basel). 2017 Jan 11;5(1). pii: E5. doi: 10.3390/sports5010005.
Authors: Sierra-Diaz MJ, Gonzalez-Villora S, Pastor-Vicedo JC, Serra-Olivares J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969014/pdf/sports-05-00005.pdf
Summary: Grouping people according to chronological age is popular in fields such as education and sport. Athletes who are born in the first months of the year usually have cognitive and physical development differences in contrast to those born in the last months of the same year. That is why competitive teams tend to select older players more often than youngsters. Age differences between athletes born in the same year as well as an over-representation of older players are known as the Relative Age Effect. This effect is extensively described in young and elite team sports such as basketball, volleyball or, ice-hockey, as well as in soccer. The purpose of this study is to examine the state-of-the-art of the Relative Age Effect in youth and elite soccer players. This review summarizes recent research articles on the Relative Age Effect related to competitive soccer from 2010 to 2016. The systematic literature search was conducted in four databases: SPORTDiscus, Medline, EBSCO host and Google Scholar. Although causes and final solutions have not been clearly achieved yet, it is necessary to continue investigating this phenomenon in order to provide a starting point for future research.


#5 Goal Format in Small-Sided Soccer Games: Technical Actions and Offensive Scenarios of Prepubescent Players
Reference: Sports (Basel). 2016 Nov 25;4(4). pii: E53. doi: 10.3390/sports4040053.
Authors: Pulling C, Twitchen A, Pettefer C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968898/pdf/sports-04-00053.pdf
Summary: The aim of this study was to investigate the influence of the number of goal-posts and the positioning of goal-posts used within small-sided games on the frequency of technical actions and offensive scenarios performed by prepubescent players within soccer. The participants were eight male prepubescent soccer players (12.1 ± 0.5 years). The participants were video recorded for 20 min playing four different formats of 4v4 small-sided games: (1) standard two goal game; (2) four goal game, one goal in each corner; (3) two goal game with goal-posts positioned 9.14 m/10 yd infield, scoring only through the back of the goal; (4) four goal-game, one goal positioned 9.14 m/10 yd infield in each corner, scoring through either the front or back of each goal. Chi-squared tests of independence were utilized to statistically explore the impact of the different small-sided game formats. There were significant associations (p < 0.05) observed between the different small-sided game formats and the frequency of turns, dribbles, shots, goals and overlaps performed. For example, players performed more turns in small-sided game format two and more shots during small-sided game format four. It is suggested coaches should consider using a variation of the number and positioning of goal-posts in small-sided games as an effective training tool in the development of prepubescent soccer players. This will enable coaches to vary the focus of sessions, and develop specific technical and tactical actions within a situation similar to that of real match-play.


#6 Relationship between Procedural Tactical Knowledge and Specific Motor Skills in Young Soccer Players
Reference: Sports (Basel). 2016 Nov 17;4(4). pii: E52. doi: 10.3390/sports4040052.
Authors: Aquino R, Marques RFR, Petiot GH, Goncalves LGC, Moraes C, Santiago PRP, Puggina EF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968894/pdf/sports-04-00052.pdf
Summary: The purpose of this study was to investigate the association between offensive tactical knowledge and the soccer-specific motor skills performance. Fifteen participants were submitted to two evaluation tests, one to assess their technical and tactical analysis. The motor skills performance was measured through four tests of technical soccer skills: ball control, shooting, passing and dribbling. The tactical performance was based on a tactical assessment system called FUT-SAT (Analyses of Procedural Tactical Knowledge in Soccer). Afterwards, technical and tactical evaluation scores were ranked with and without the use of the cluster method. A positive, weak correlation was perceived in both analyses (rho = 0.39, not significant p = 0.14 (with cluster analysis); and rho = 0.35; not significant p = 0.20 (without cluster analysis)). We can conclude that there was a weak association between the technical and the offensive tactical knowledge. This shows the need to reflect on the use of such tests to assess technical skills in team sports since they do not take into account the variability and unpredictability of game actions and disregard the inherent needs to assess such skill performance in the game.


#7 Comparıson of the Heart Rate and Blood Lactate Responses of Different Small Sided Games in Young Soccer Players
Reference: Sports (Basel). 2016 Sep 29;4(4). pii: E48. doi: 10.3390/sports4040048.
Authors: Koklu Y, Alemdaroglu U
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968902/pdf/sports-04-00048.pdf
Summary: The purpose of this study was to compare the percentage of maximum heart rate (%HRmax), blood lactate (La-), and rating of perceived exertion (RPE, CR-10) responses across different formats of small-sided games (SSG) in elite young soccer players. Fourteen players (average age 16.7 ± 0.6 years; height 177.6 ± 4.1 cm; body mass 66.3 ± 4.7 kg; average training age 6.7 ± 1.6 years; percentage of body fat 8.4 ± 2.6%) volunteered to perform the YoYo intermittent recovery test (level 1) and eight bouts of soccer drills including 2-a-side, 3-a-side, and 4-a-side games without goalkeepers in random order at two-day intervals. Heart rates were monitored throughout the SSGs, whereas the RPE and venous blood lactate were determined at the end of the last bout of each SSG. The differences in La-, %HRmax, and RPE either across the different SSGs or between the bouts were identified using 3 × 8 (games × exercise bouts) two-way analysis of variance with repeated measures. Significant differences were found in terms of La-, RPE, and %HRmax among the different types of SSG (p ≤ 0.05). 3-a-side and 4-a-side games elicited significantly higher responses than 2-a-side games in terms of %HRmax (p ≤ 0.05), whereas 4-a-side games resulted in significantly lower La- and RPE responses compared to 2-a-side and 3-a-side games. The results of this study show that physiological responses differ according to the numbers of players involved in small-sided games. Therefore, it can be concluded that 3-a-side and 4-a-side games could be more effective in improving high intensity aerobic performance than 2-a-side games, which in turn are more appropriate for developing anaerobic performance.


#8 Physiological Characteristics of Incoming Freshmen Field Players in a Men's Division I Collegiate Soccer Team
Reference: Sports (Basel). 2016 Jun 8;4(2). pii: E34. doi: 10.3390/sports4020034.
Authors: Lockie RG, Davis DL, Birmingham-Babauta SA, Beiley MD, Hurley JM, Stage AA, Stokes JJ, Tomita TM, Torne IA, Lazar A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968924/pdf/sports-04-00034.pdf
Summary: Freshmen college soccer players will have lower training ages than their experienced teammates (sophomores, juniors, seniors). How this is reflected in field test performance is not known. Freshmen (n = 7) and experienced (n = 10) male field soccer players from the same Division I school completed soccer-specific tests to identify potential differences in incoming freshmen. Testing included: vertical jump (VJ), standing broad jump, and triple hop (TH); 30-m sprint, (0⁻5, 5⁻10, 0⁻10, and 0⁻30 m intervals); 505 change-of-direction test; Yo-Yo Intermittent Recovery Test Level 2 (YYIRT2); and 6 × 30-m sprints to measure repeated-sprint ability. A MANOVA with Bonferroni post hoc was conducted on the performance test data, and effect sizes and z-scores were calculated from the results for magnitude-based inference. There were no significant between-group differences in the performance tests. There were moderate effects for the differences in VJ height, left-leg TH, 0⁻5, 0⁻10 and 0⁻30 m sprint intervals, and YYIRT2 (d = 0.63⁻1.18), with experienced players being superior. According to z-score data, freshmen had meaningful differences below the squad mean in the 30-m sprint, YYIRT2, and jump tests. Freshmen soccer players may need to develop linear speed, high-intensity running, and jump performance upon entering a collegiate program.


#9 Heart Rate Responses during Small Sided Games and Official Match-Play in Soccer
Reference: Sports (Basel). 2016 May 30;4(2). pii: E31. doi: 10.3390/sports4020031.
Authors: Asci A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968916/pdf/sports-04-00031.pdf
Summary: Small sided games (SSGs) are a match specific type of training. In addition, there is an insufficient number of studies that compare heart rate (HR) responses of SSGs and official match-play (OM). The purpose of this study was to investigate the heart rate responses during SSGs and OM in young soccer players. Twenty-two male soccer players (mean ± SD; age 17.4 ± 0.9 years, height 174.9 ± 6.6 cm, body weight 67.7 ± 8.1 kg) volunteered to participate in this study. The first session included anthropometric measurements and a maximum running test (RT). Following the RT session, all players participated in five different randomly ordered SSG sessions (3-, 4-, 5-, 7- and 9-a-side with goalkeepers). OMs were also monitored in the fourth week of the study. A one-way multivariate repeated-measures analysis of variance (MANOVA) was then conducted to evaluate the differences between the SSGs and OM. The results showed that 3-a-side elicited significantly higher HR and %HRmax than other SSGs and OM, whereas 9-a-side resulted in significantly lower HR and %HRmax compared to other SSG formats and OM (p < 0.05). In conclusion, 3-a-side, 4-a-side and 5-a-side SSG formats provide players with the opportunity to spend sufficient proportion of time spent in high intensity zones that are specific to match demands.


#10 Relationship of Two Vertical Jumping Tests to Sprint and Change of Direction Speed among Male and Female Collegiate Soccer Players
Reference: Sports (Basel). 2016 Feb 16;4(1). pii: E11. doi: 10.3390/sports4010011.
Authors: McFarland IT, Dawes JJ, Elder CL, Lockie RG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968930/pdf/sports-04-00011.pdf
Summary: In collegiate level soccer acceleration, maximal velocity and agility are essential for successful performance. Power production is believed to provide a foundation for these speed qualities. The purpose of this study was to determine the relationship of change of direction speed, acceleration, and maximal velocity to both the counter movement jump (CMJ) and squat jump (SJ) in collegiate soccer players. Thirty-six NCAA Division II soccer players (20 males and 16 females) were tested for speed over 10 and 30 m, CODS (T-test, pro agility) and power (CMJ, SJ). Independent t-tests (p ≤ 0.05) were used to derive gender differences, and Pearson's correlations (p ≤ 0.05) calculated relationships between the different power and speed tests. Female subjects displayed moderate-to-strong correlations between 30 m, pro agility and T-test with the CMJ (r = -0.502 to -0.751), and SJ (r = -0.502 to -0.681). Moderate correlations between 10 and 30 m with CMJ (r = -0.476 and -0.570) and SJ (r = -0.443 and -0.553, respectively) were observed for males. Moderate to strong relationships exist between speed and power attributes in both male and female collegiate soccer players, especially between CMJ and maximal velocity. Improving stretch shortening cycle (SSC) utilization may contribute to enhanced sport-specific speed.

#11 Effect of New Zealand Blackcurrant Extract on Performance during the Running Based Anaerobic Sprint Test in Trained Youth and Recreationally Active Male Football Players
Reference: Sports (Basel). 2017 Sep 15;5(3). pii: E69. doi: 10.3390/sports5030069.
Authors: Godwin C, Cook MD, Willems MET
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968969/pdf/sports-05-00069.pdf
Summary: It was observed previously that New Zealand blackcurrant (NZBC) extract reduced slowing of the maximal 15 m sprint speed during the Loughborough Intermittent Shuttle Test. We examined the effect of NZBC extract on the performance of the Running Based Anaerobic Sprint Test (RAST, 6 × 35-m sprints with 10 seconds passive recovery) in trained youth and recreationally active football players. Fifteen recreationally active (University team) (age: 20 ± 1 years, height: 174 ± 19 cm, body mass: 80 ± 13 kg) and nine trained youth players (English professional club) (age: 17 ± 0 years, height: 178 ± 8 cm, body mass: 69 ± 9 kg, mean ± SD) participated in three testing sessions. Prior to the RASTs, participants consumed two capsules of NZBC extract (600 mg∙day-1 CurraNZ®) or placebo (P) for 7 days (double blind, randomised, cross-over design, wash-out at least 14 days). Ability difference between groups was shown by sprint 1 time. In the placebo condition, trained youth players had faster times for sprint 1 (5.00 ± 0.05 s) than recreationally active players (5.42 ± 0.08 s) (p < 0.01). In trained youth players, there was a trend for an effect of NZBC extract (p = 0.10) on the slowing of the sprint 1 time. NZBC extract reduced slowing of the sprint 5 time (P: 0.56 ± 0.22 s; NZBC: 0.35 ± 0.25, p = 0.02) and this was not observed in recreationally active players (P: 0.57 ± 0.48 s; NZBC: 0.56 ± 0.33, p = 0.90). For fatigue index, expressed as a % change in fastest sprint time, there was a strong trend to be lower in both trained youth and recreationally active players combined by NZBC extract (P: -13 ± 7%; NZBC: -11 ± 6%, p = 0.06) with 12 participants (five trained youth) experiencing less fatigue. New Zealand blackcurrant extract seems to benefit repeated sprint performance only in trained football players.


#12 Body Composition Evaluation Issue among Young Elite Football Players: DXA Assessment
Reference: Sports (Basel). 2017 Feb 23;5(1). pii: E17. doi: 10.3390/sports5010017.
Authors: Leao C, Simoes M, Silva B, Clemente FM, Bezerra P, Camoes M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969018/pdf/sports-05-00017.pdf
Summary: Accurate assessment of body composition is an important issue among athletes. Different methodologies generate controversial results, leading to a deep uncertainty on individual exercise prescriptions. Thus, this study aims to identify the differences between field methods, such as bioelectrical impedance (BIA) and skinfold assessment, with a clinical method, highly accurate, dual-energy X-ray absorptiometry (DXA), among elite young football players. Thirty-eight male football players with a mean (sd) age of 16.7 (0.87) years, involved in the Portuguese national competition of U16 (n = 13) and U19 (n = 25), were evaluated and objective measures of body composition, muscle strength and football skills were collected by trained specialists. Body composition was assessed using BIA (Tanita BC-418, Tanita Corp., Tokyo, Japan), in agreement with all the evaluation premises. Additionally, all athletes were evaluated using the clinical method DXA (Hologic Inc., Waltham, MA, USA). Among the U19 athletes, three skinfold sites (SKF) were assessed: chest, abdomin and thigh. The Spearman correlation coefficients and the mean difference between methods were calculated. The agreement between both methods was analyzed using Bland-Altman plots. Among the evaluated athletes, lower mean values of body fat % were found using BIA as a method of body composition assessment compared with DXA (12.05 vs. 15.58 for U16; 11.97 vs. 14.16 for U19). Despite the moderate correlation between methods (r = 0.33) to estimate the percentage of total fat, the median of the difference (DXA vs. BIA) was relevant in clinical terms, with 2.90% and 1.47% for U16 and U19 athletes, respectively. Stronger correlations were found between the sum of the SKF and DXA fat estimation (r = 0.68). The Bland-Altman plots showed a clear underestimation in the evaluations using the BIA, namely among athletes with better body composition profiles (8%⁻12% of fat). Using BIA, an underestimation of body fat assessment was observed among 94.5% of the athletes with less than 12% body fat mass. Among the evaluated athletes, fat mass was underestimated at a median value of 2.21% using BIA in comparison with DXA. The sum of the SKF showed a stronger correlation with the reference method (DXA) (r = 0.68) than BIA.


#13 Content Validity and Psychometric Properties of the Nomination Scale for Identifying Football Talent (NSIFT): Application to Coaches, Parents and Players
Reference: Sports (Basel). 2017 Jan 1;5(1). pii: E2. doi: 10.3390/sports5010002.
Authors: Prieto-Ayuso A, Pastor-Vicedo JC, Contreras-Jordan O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969006/pdf/sports-05-00002.pdf
Summary: The identification of football talent is a critical issue both for clubs and the families of players. However, despite its importance in a sporting, economic and social sense, there appears to be a lack of instruments that can reliably measure talent performance. The aim of this study was to design and validate the Nomination Scale for Identifying Football Talent (NSIFT), with the aim of optimising the processes for identifying said talent. The scale was first validated through expert judgment, and then statistically, by means of an exploratory factor analysis (EFA), confirmatory factor analysis (CFA), internal reliability and convergent validity. The results reveal the presence of three factors in the scale's factor matrix, with these results being confirmed by the CFA. The scale revealed suitable internal reliability and homogeneity indices. Convergent validity showed that it is teammates who are best able to identify football talent, followed by coaches and parents. It can be concluded that the NSIFT is suitable for use in the football world. Future studies should seek to confirm these results in different contexts by means of further CFAs.


#14 The Effect of Recovery Duration on Technical Proficiency during Small Sided Games of Football
Reference: Sports (Basel). 2016 Jul 8;4(3). pii: E39. doi: 10.3390/sports4030039.
Authors: McLean S, Kerherve H, Naughton M, Lovell GP, Gorman AD, Solomon C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968888/pdf/sports-04-00039.pdf
Summary: The aim of this study was to determine the effect of increasing the duration of the recovery periods separating serial bouts of small sided games (SSG) of football on technical skills (TS). Twelve semi-professional footballers (mean ± SD; age 21 ± 3 years; VO2peak 64 ± 7 mL∙min∙kg-1; playing experience 15 ± 3 years) completed two SSG sessions, consisting of 3 vs. 3 players and 6 bouts of 2 min, separated by either 30 s recovery (REC-30) or 120 s recovery (REC-120). Sixteen TS, including passing, possession, and defensive related variables, and exercise intensity (heart rate, rating of perceived exertion, time motion descriptors) during the bouts were measured. Repeated measures ANOVA were used to determine differences between-conditions, for TS. The number of successful tackles was significantly higher, and the average time each team maintained possession was significantly lower in REC-120 compared to REC-30. There were no significant differences for all other TS variables, or exercise intensity measures between REC-30 and REC-120. Overall, a four-fold increase in the duration of recovery separating SSG bouts did not alter the technical skill execution of players. The experience and skill level of the players, combined with an apparent regulation of effort through pacing, may have assisted in the maintenance of technical skill execution.


#15 Analysis of Physiological, Technical, and Tactical Analysis during a Friendly Football Match of Elite U19
Reference: Sports (Basel). 2016 Jun 16;4(2). pii: E35. doi: 10.3390/sports4020035.
Authors: Ortega JI, Evangelio C, Clemente FM, Martins FML, Gonzalez-Villora S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968927/pdf/sports-04-00035.pdf
Summary: The main objective was to analyze a friendly match of youth elite soccer players identifying the variance of tactical and physiological response parameters during the game. In addition, detecting the impact of both halves on player performance. For the purposes of this study twenty-two U19 players were analyzed playing 11v11. Activity profile, heart rate (HR and HRmax), grouped in five different zones were analyzed via Bluetooth technology, technical performance was analyzed by the Team Sport Assessment Procedure (TSAP), and tactical performance was measured by Social Network Analysis. A comparison of heart rate responses showed significant main effects in the halves (p = 0.001; η p 2 = 0.623). A comparison between tactical position and technical performance had significant main effects (p = 0.001; η p 2 = 0.390). Tactical position showed statistically significant effects on tactical prominence (p = 0.002; η p 2 = 0.296). Therefore, fatigue is a component distinguished in technical/tactical parameters, such as volume of play and efficiency index. Results suggest that fatigue effects may constrain technical performance and, for that reason, the use of instruments to monitor the fatigue effect during matches may be suggested.


#16 "You're Not Born with Talent" Talented Girls' and Boys' Perceptions of Their Talents as Football Players
Reference: Sports (Basel). 2016 Jan 27;4(1). pii: E6. doi: 10.3390/sports4010006.
Authors: Saether SA, Mehus I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968932/pdf/sports-04-00006.pdf
Summary: Generally in sports, there is a strong assumption of a connection between skill level in young age and adulthood. Studies have mainly focused on the coaches' understanding and role in identifying and developing talent. In this article we turn our attention towards the athletes' perspectives, interviewing talented young football players (five boys and five girls) about their perceptions of their own talent and development. The objective of the article is to investigate how boys and girls perceive their talent and to discuss how various perceptions influence coaching practice in talent development. We introduce the following questions: (a) do the players use a static or dynamic perception of their own talent and (b) do the players consider specific or general skills to be most important in their skill development? Results show that the boys have a more static perception of talent compared to the girls. Furthermore, the boys in this study stress the importance of highly specified skills. The girls have a more balanced view on what is important, but tend to stress the importance of basic skills. The study suggests two potential implications. First, the coaches should be aware of the possible vulnerability following players' static perception of talent. Second, an exclusive focus on specified skills might make for less optimal preparation for the changing demands young players meet when moving through the different levels of play on their way to high level football. In future research it would be interesting to investigate how players with a lower skill level, not yet regarded as talent, perceive their talent and skill development.


#17 Effects of Video-Based Visual Training on Decision-Making and Reactive Agility in Adolescent Football Players
Reference: Sports (Basel). 2015 Dec 31;4(1). pii: E1. doi: 10.3390/sports4010001.
Authors: Nimmerichter A, Weber NJR, Wirth K, Haller A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968940/pdf/sports-04-00001.pdf
Summary: This study investigated the trainability of decision-making and reactive agility via video-based visual training in young athletes. Thirty-four members of a national football academy (age: 14.4 ± 0.1 years) were randomly assigned to a training (VIS; n = 18) or a control group (CON; n = 16). In addition to the football training, the VIS completed a video-based visual training twice a week over a period of six weeks during the competition phase. Using the temporal occlusion technique, the players were instructed to react on one-on-one situations shown in 40 videos. The number of successful decisions and the response time were measured with a video-based test. In addition, the reactive-agility sprint test was used. VIS significantly improved the number of successful decisions (22.2 ± 3.6 s vs. 29.8 ± 4.5 s; p < 0.001), response time (0.41 ± 0.10 s vs. 0.31 ± 0.10 s; p = 0.006) and reactive agility (2.22 ± 0.33 s vs. 1.94 ± 0.11 s; p = 0.001) pre- vs. post-training. No significant differences were found for CON. The results have shown that video-based visual training improves the time to make decisions as well as reactive agility sprint-time, accompanied by an increase in successful decisions. It remains to be shown whether or not such training can improve simulated or actual game performance.

Thu

30

Aug

2018

Latest research in football - week 25 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Short-Term Plyometric Jump Training Improves Repeated-Sprint Ability in Prepuberal Male Soccer Players
Reference: J Strength Cond Res. 2018 Jun 14. doi: 10.1519/JSC.0000000000002703. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Fernandez-Fernandez J, Sammoud S, Bouguezzi R, Prieske O, Granacher U
Summary: This study examined the effects of a short-term (i.e., 8 weeks) combined horizontal and vertical plyometric jump training (PJT) program in combination with regular soccer-specific training as compared with soccer-specific training only on jump and change of direction (CoD) performances, speed, and repeated-sprint ability (RSA) in prepuberal male soccer players. Twenty-four players were recruited and randomly assigned to either a PJT group (PJTG; n = 13; 12.7 ± 0.2 years) or an active control group (CONG; n = 11; 12.7 ± 0.2 years). The outcome measures included tests for the assessment of jump performance (drop jump from 20- to 40-cm height [DJ20 and DJ40] and 3-hop test [THT]), speed (20-m sprint), CoD (T-test), and RSA (20-m repeated shuttle sprint). Data were analyzed using magnitude-based inferences. Within-group analyses revealed large performance improvements in the T-test (d = -1.2), DJ20 (d = 3.7), DJ40 (d = 3.6), THT (d = 0.6), and the RSAtotal (d = -1.6) in the PJTG. Between-group analyses showed greater performance improvements in the T-test (d = -2.9), 20-m sprint time (d = -2.0), DJ20 (d = 2.4), DJ40 (d = 2.0), THT (d = 1.9), RSAbest (d = -1.9), and the RSAtotal (d = -1.9) in the PJTG compared with CONG. Eight weeks of an in-season PJT in addition to regular soccer-specific training induced larger increases in measures of physical fitness in prepuberal male soccer players compared with regular soccer-specific training only. More specifically, PJT was effective in improving RSA performance.


#2 Fitness Monitoring in Elite Soccer Players: Group vs. Individual Analyses
Reference: J Strength Cond Res. 2018 Jun 14. doi: 10.1519/JSC.0000000000002700. [Epub ahead of print]
Authors: Rabbani A, Kargarfard M, Twist C
Summary: The aims of this study were to (a) examine changes in group and individual HR measures during a submaximal warm-up test, and (b) investigate the relationship between accumulated internal training loads and HR changes during an in-season phase among elite soccer players (n = 14). Before and after an in-season phase (24 days), exercise HR (HRex) and HR recovery (HRR) expressed either as the number of beats recovered (HRR60s) or as the mean HR (HRpost1) during 1 minute of recovery were analyzed. Heart rate measures were expressed as the % of maximal HR. Session rating of perceived exertion (sRPE) was computed for all training/match sessions. Group and individual HR changes were analyzed using magnitude-based inferences. Pearson correlation coefficients were also used to examine the relationships. Group analyses of HR changes revealed there were possibly to likely trivial changes in all HR measures. When analyzing individual data, no substantial change was observed for HRR60s%. However, substantial changes in HRex% and HRpost1% were observed for 4/14 and 5/14 players, respectively. The relationships between HRex% and HRpost1% were nearly perfect (r = 0.90, confidence limits [0.82-0.95]). The associations between changes in HRex% and HRpost1% were also nearly perfect (r = 0.92, 0.80-0.97). A very large inverse correlation was observed between HRex% and accumulated sRPE (r = -0.75, -0.44 to -0.90). This study highlights the value of conducting individual vs. group aerobic fitness monitoring. This study also showed the importance of how HRR is reported when aerobic fitness monitoring of elite soccer players.


#3 Segmental decompressive fasciotomy for acute non-traumatic compartment syndrome in a professional soccer player: case report
Reference: Rev Bras Ortop. 2018 Feb 15;53(2):244-247. doi: 10.1016/j.rboe.2018.02.001. eCollection 2018 Mar-Apr.
Authors: Baumfeld D, Pereira AL, Lage CFG, Miura GM, Gomes YVT, Nery C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6001402/pdf/main.pdf
Summary: Acute compartment syndrome in athletes is a rare orthopedic emergency associated with strenuous exercise. It is often diagnosed late and can lead to severe complications and high morbidity. This report describes the case of a young soccer player with acute compartment syndrome with no history of trauma, diagnosed and treated 24 h after the onset of symptoms, through minimally invasive decompressive fasciotomy, with good postoperative evolution.


Seems like I have missed those ones last year (strange,but anyway just in case), here they are!

#4 Balance Performance as Observed by Center-of-Pressure Parameter Characteristics in Male Soccer Athletes and Non-Athletes
Reference: Sports (Basel). 2017 Nov 8;5(4). pii: E86. doi: 10.3390/sports5040086.
Authors: Thompson LA, Badache M, Cale S, Behera L, Zhang N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969037/pdf/sports-05-00086.pdf
Summary: Static balance has a relevant influence on athletic performance as well as on reducing the risk of injury. The main goal of this study was to assess soccer athlete versus non-athlete balance performance via displacement and velocity parameters extracted from the center-of-pressure (COP) position time series. In order to accomplish our goal, we investigated standing balance in two male groups with unimpaired balance: non-athletes (n = 12) and collegiate varsity soccer athletes (n = 12). In order to make the standing balancing task more or less difficult, we altered participant base-of-support, as well as vision, yielding static (quiet stance) test conditions increasing in difficulty. From the COP position time series, displacement and velocity parameters were computed and plotted as a function of increasing test condition difficulty level. COP parameters showed steeper increases with increased test difficulty in non-athletes compared to athletes; this demonstrated athletes' better ability to control their balance. We concluded that balance performance could be characterized via COP displacement and velocity response curves. This study lends new insights into how COP parameters can be utilized to determine and characterize improvements in balance between un-impaired subject populations (athletes versus non-athletes).


#5 Executive Function and the P300 after Treadmill Exercise and Futsal in College Soccer Players
Reference: Sports (Basel). 2017 Sep 26;5(4). pii: E73. doi: 10.3390/sports5040073.
Authors: Won J, Wu S, Ji H, Smith JC, Park J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969040/pdf/sports-05-00073.pdf
Summary: Although a body of evidence demonstrates that acute exercise improves executive function, few studies have compared more complex, laboratory-based modes of exercise, such as soccer that involve multiple aspects of the environment. Twelve experienced soccer players (24.8 ± 2 years) completed three counterbalanced 20 min sessions of (1) seated rest; (2) moderate intensity treadmill exercise; and (3) a game of futsal. Once heart rate returned to within 10% of pre-activity levels, participants completed the Stroop Color Word Conflict Task while reaction time (RT) and P300 event-related potentials were measured. Reaction time during Stroop performance was significantly faster following the futsal game and treadmill exercise compared to the seated rest. The P300 amplitude during Stroop performance was significantly greater following futsal relative to both treadmill and seated-rest conditions. These findings suggest that single bouts of indoor soccer among college-aged soccer players, compared to treadmill and seated-rest conditions, may engender the greatest effect on brain networks controlling attention allocation and classification speed during the performance of an inhibitory control task. Future research is needed to determine if cognitively engaging forms of aerobic exercise may differentially impact executive control processes in less experienced and older adult participants.


#6 Effects of Heart Rate vs. Speed-Based High Intensity Interval Training on Aerobic and Anaerobic Capacity of Female Soccer Players
Reference: Sports (Basel). 2017 Aug 4;5(3). pii: E57. doi: 10.3390/sports5030057.
Authors: Arazi H, Keihaniyan A, EatemadyBoroujeni A, Oftade A, Takhsha S, Asadi A, Ramirez-Campillo R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968964/pdf/sports-05-00057.pdf
Summary: The purpose of this study was to compare the effects of two types of high-intensity interval training (HIIT) programs on aerobic and anaerobic capacity of female soccer players. Regional-level female athletes were randomly divided into heart rate-based HIIT (n = 8; age 23.4 ± 1.1 year) and speed-based HIIT groups (n = 8; age 23.4 ± 1.3 year). Athletes trained three days per week for six weeks. Before and after training, each athlete's performance was assessed directly through the Hoff test, 30-15 Intermittent Fitness Test (VIFT), and repeated-sprint ability test (RAST); maximal oxygen consumption (VO₂max), power and fatigue were estimated indirectly. Both experimental groups improved power, fatigue index and VO₂max after training (p < 0.05). It was noteworthy that the speed-based group had greater gains in minimal power (effect size (ES): 3.99 vs. 0.75), average power (ES: 2.23 vs. 0.33), and fatigue index (ES: 2.53 vs. 0.17) compared to heart rate-based group (p < 0.05). In conclusion, both heart rate-based and speed-based HIIT induced meaningful improvements in power, VO₂max, and fatigue index in female soccer players, although the speed-based HIIT group achieved greater gains in power and fatigue index compared to the heart rate-based group.


#7 The Role of Eccentric Strength in 180° Turns in Female Soccer Players
Reference: Sports (Basel). 2017 Jun 17;5(2). pii: E42. doi: 10.3390/sports5020042.
Authors: Jones PA, Thomas C, Dos'Santos T, McMahon JJ, Graham-Smith P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968983/pdf/sports-05-00042.pdf
Summary: Previous studies have reported an association between eccentric strength (ECC-STR) and change of direction (COD) ability. Little is known about how ECC-STR facilitates COD maneuvers. The aim of this study was to examine the role of ECC-STR during a 180° COD task in 18 female soccer players. Each player performed six trials of a 180° COD task whereby three-dimensional motion data from 10 Qualisys Pro-Reflex infrared cameras (240 Hz) and ground reaction forces (GRFs) from two AMTI force platforms (1200 Hz) were collected. Relative eccentric knee extensor (ECC-EXT) and flexor (ECC-FLEX) peak torque was collected from both limbs at 60°·s-1 using a Kin Com isokinetic dynamometer. Large correlations were revealed between COD performance (time to complete 5 m approach, 180° turn, 5 m return) and ECC-EXT (R = -0.674) and ECC-FLEX (R = -0.603). Moderate to large correlations were observed between approach velocity (AV) and COD performance (R = -0.484) and ECC-EXT (R = 0.724). Stronger participants (n = 9) recorded significantly (p < 0.05) faster AV (4.01 ± 0.18 vs. 3.74 ± 0.24 m·s-1, d = 1.27) and a greater reduction in velocity (-1.55 ± 0.17 vs. -1.37 ± 0.21 m·s-1, d = -0.94) during penultimate contact than weaker (n = 9) subjects. Greater ECC-STR is associated with faster COD performance in female soccer players, as stronger players are better able to decelerate during penultimate contact from faster approach velocities.


#8 Nutrition and Supplementation in Soccer
Reference: Sports (Basel). 2017 May 12;5(2). pii: E28. doi: 10.3390/sports5020028.
Authors: Oliveira CC, Ferreira D, Caetano C, Granja D, Pinto R, Mendes B, Sousa M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968974/pdf/sports-05-00028.pdf
Summary: Contemporary elite soccer features increased physical demands during match-play, as well as a larger number of matches per season. Now more than ever, aspects related to performance optimization are highly regarded by both players and soccer coaches. Here, nutrition takes a special role as most elite teams try to provide an adequate diet to guarantee maximum performance while ensuring a faster recovery from matches and training exertions. It is currently known that manipulation and periodization of macronutrients, as well as sound hydration practices, have the potential to interfere with training adaptation and recovery. A careful monitoring of micronutrient status is also relevant to prevent undue fatigue and immune impairment secondary to a deficiency status. Furthermore, the sensible use of evidence-based dietary supplements may also play a role in soccer performance optimization. In this sense, several nutritional recommendations have been issued. This detailed and comprehensive review addresses the most relevant and up-to-date nutritional recommendations for elite soccer players, covering from macro and micronutrients to hydration and selected supplements in different contexts (daily requirements, pre, peri and post training/match and competition).


#9 Detection and Selection of Behavioral Patterns Using Theme: A Concrete Example in Grassroots Soccer
Reference: Sports (Basel). 2017 Mar 13;5(1). pii: E20. doi: 10.3390/sports5010020.
Authors: Amatria M, Lapresa D, Arana J, Anguera MT, Jonsson GK
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969010/pdf/sports-05-00020.pdf
Summary: Observational methodology provides a rigorous yet flexible framework for capturing behaviors over time to allow for the performance of subsequent diachronic analyses of the data captured. Theme is a specialized software program that detects hidden temporal behavioral patterns (T-patterns) within data sets. It is increasingly being used to analyze performance in soccer and other sports. The aim of this study was to show how to select and interpret T-patterns generated by the application of three "quantitative" sort options in Theme and three "qualitative" filters established by the researchers. These will be used to investigate whether 7-a-side (F7) or 8-a-side (F8) soccer is best suited to the learning and skills development needs of 7- and 8-year-old male soccer players. The information contained in the T-patterns generated allowed us to characterize patterns of play in children in this age group. For both formats, we detected technical-tactical behaviors showing that children of this age have difficulty with first-touch actions and controlling the ball after a throw-in. We also found that ball control followed by a pass or a shot at the goal are common in the central corridor of the pitch. Further, depth of play is achieved by ball control, followed by dribbling and a pass or shot. In F8, we saw that depth of play was achieved through ball control, followed by dribbling and passing of one or more opponents leading to a pass or shot. However, in F7, we saw that players succeeded in advancing from their goal area to the rival goal area through a sequence of actions.


#10 Functional Movement Screen Scores and Physical Performance among Youth Elite Soccer Players
Reference: Sports (Basel). 2017 Feb 21;5(1). pii: E16. doi: 10.3390/sports5010016.
Authors: Silva B, Clemente FM, Camoes M, Bezerra P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969015/pdf/sports-05-00016.pdf
Summary: This study had two main objectives: (1) to determine if differences in Functional Movement Screen (FMS) scores exist between two levels of competition; and (2) to analyze the association between FMS individual and overall scores and physical performance variables of lower-limb power (jumps), repeated sprint ability and shot speed. Twenty-two Under 16 (U16) and twenty-six Under 19 (U19) national competitive soccer players participated in this study. All participants were evaluated according to anthropometrics, FMS, jump performance, instep kick speed and anaerobic performance. There were no significant differences in the individual FMS scores between competitive levels. There were significant negative correlations between hurdle step (right) and Running-based Anaerobic Sprint Test (RAST) power average ( ρ = -0.293; p = 0.043) and RAST fatigue index (RAST FatIndex) ( ρ = -0.340; p = 0.018). The hurdle step (left) had a significant negative correlation to squat jump (SJ) ( ρ = -0.369; p = 0.012). Rotary stability had a significant negative correlation to RAST fatigue index (Right: ρ = -0.311; p = 0.032. Left: ρ = -0.400; p = 0.005). The results suggest that individual FMS scores may be better discriminants of performance than FMS total score and established minimal association between FMS scores and physical variables. Based on that, FMS may be suitable for the purposes of determining physical function but not for discriminating physical performance.


#11 Differences in the Dominant and Non-Dominant Knee Valgus Angle in Junior Elite and Amateur Soccer Players after Unilateral Landing
Reference: Sports (Basel). 2017 Feb 13;5(1). pii: E14. doi: 10.3390/sports5010014.
Authors: Ludwig O, Simon S, Piret J, Becker S, Marschall F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969013/pdf/sports-05-00014.pdf
Summary: More than 70% of all knee injuries in soccer occur in non-contact situations. It is known that increased lower limb dynamic knee valgus is associated with such situations. Little has been found out about differences in knee kinematics of the dominant (kicking) and non-dominant (supporting) leg during a single leg landing. A total of 114 male adolescent soccer players (age 14.6 ± 1.1 years) from elite (N = 66) and amateur soccer clubs (N = 48) performed a single leg drop landing down from a box. For each leg, the two-dimensional dynamic knee valgus angle (DKVA) was calculated. Paired t-tests were used to statistically determine significant differences between dominant and non-dominant leg DKVA, and t-tests were calculated between the two performance groups. Statistically significant differences (p < 0.05) were identified for the DKVA between the dominant and non-dominant leg for both amateur and elite players, showing a greater DKVA for the dominant leg. Group differences for the DKVA between amateur and elite players were not found, neither for the dominant, nor for the non-dominant leg. It can be concluded that the non-dominant leg showed more stable dynamics than the dominant leg during unilateral landing regardless of the player's performance level. This could be due to adaptions to sport-specific requirements. Therefore, it is recommended that programs to prevent knee injuries among soccer players consider the dynamics of each leg individually.

Tue

07

Aug

2018

Latest research in football - week 24 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Sex Differences in Physical Capacities of German Bundesliga Soccer Players
Reference: J Strength Cond Res. 2018 Jun 20. doi: 10.1519/JSC.0000000000002662. [Epub ahead of print]
Authors: Cardoso de Araujo M, Baumgart C, Jansen CT, Freiwald J, Hoppe MW
Summary: Sex differences in physical capacities of elite soccer players have received limited attention. Therefore, this study investigated sex differences in linear and nonlinear sprint, squat and countermovement jump, core endurance, as well as incremental and intermittent endurance capacities in German Bundesliga soccer players. A total of 76 field players (29 women) were tested for the mentioned anaerobic- and aerobic-related physical capacities in a noninterventional cross-sectional design. The largest sex differences were evident in the explosive- and intermittent endurance-related capacities, with women presenting largely to extremely largely lower values in sprints, jumps, and intermittent endurance (effect size [ES] ≥1.77, p < 0.01). The differences in the total core endurance, running velocity at 2 and 4 mmol·L capillary blood lactate (v2 and v4), maximal heart rate (HR) (ES ≤ 0.72, p ≥ 0.06), and distance covered during the incremental endurance test (ES = 1.09, p = 0.01) were trivially to moderately lower for women. However, women had small to moderately higher ventral and dorsal core endurance (ES ≤ 0.69, p ≥ 0.07) and largely higher relative HR at the lactate thresholds (ES ≥ 1.54, p < 0.01). The individual data of female players showed more variability. Some individual data of women overlapped those of men, most evident in the total core endurance and v2. The findings indicate that there are sex differences in physical capacities according to the underlying amount of anaerobic and aerobic energy supply. The sex specificities should be considered to optimize training and testing procedures for soccer players.


#2 Developmental Changes in Isometric Strength: Longitudinal Study in Adolescent Soccer Players
Reference: Int J Sports Med. 2018 Jun 20. doi: 10.1055/s-0044-100389. [Epub ahead of print]
Authors: Duarte JP, Valente-Dos-Santos J, Coelho-E-Silva MJ, Malina RM, Deprez D, Philippaerts R, Lenoir M, Vaeyens R
Summary: This study aimed to examine longitudinal changes in isometric strength of the knee extensors (ImKE) and knee flexors (ImKF) at 30° and 60°. The sample was composed of 67 players aged 11.0-13.9 years at baseline over five years. Stature, body mass, skinfolds, and isometric strength (ImKE30°, ImKF30°, ImKE60° and ImKF60°) were measured. Fat mass and fat-free mass (FFM) were derived from skinfolds. Skeletal age was obtained using TW2 RUS. Multilevel random effects regression analyses extracted developmental polynomial models. An annual increment on chronological age (CA) corresponded to 5.6 N (ImKE30°: ), 2.7 N (ImKF30°: ), 4.6 N (ImKE60°: ) and 1.5 N (ImKF60°). An increment of 1 kg in FFM predicted isometric strength as follows: 1.2 N (ImKE30°), 2.1 N (ImKF30°), 3.1 N (ImKE60°) and 2.0 N (ImKF60°). The following equations were obtained: ImKE30°=5.759×CA+1.163×FFM; ImKF30°=-19.369+2.691×CA+0.693×CA2+2.108×FFM; ImKE60°=4.553×CA+3.134×FFM; and, ImKF60°=-19.669+1.544×CA+2.033×FFM. Although skeletal maturity had a negligible effect on dependent variables, age and body size, based on FFM, were relevant longitudinal predictors. During adolescence, systematic assessment of knee extensors and knee flexors are strongly recommended to prevent impairment of knee muscle groups.


#3 Assessing Cardiorespiratory Fitness of Soccer Players: Is Test Specificity the Issue?-A Review.
Reference: Sports Med Open. 2018 Jun 19;4(1):28. doi: 10.1186/s40798-018-0134-3.
Authors: Jemni M, Prince MS, Baker JS
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-018-0134-3
Summary: It is important that players and coaches have access to objective information on soccer player's physical status for team selection and training purposes. Physiological tests can provide this information. Physiological testing in laboratories and field settings are very common, but both methods have been questioned because of their specificity and accuracy respectively. Currently, football players have their direct aerobic fitness assessed in laboratories using treadmills or cycle ergometers, whilst indirect measures (using estimation of aerobic performance) are performed in the field, typically comprising multiple shuttle runs back and forth over a set distance. The purpose of this review is to discuss the applied techniques and technologies used for evaluating soccer players' health and fitness variables with a specific focus on cardiorespiratory testing. A clear distinction of the functionality and the specificity between the field tests and laboratory tests is well established in the literature. The review findings prioritize field tests over laboratory tests, not only for commodity purpose but also for motivational and specificity reasons. Moreover, the research literature suggests a combination of various tests to provide a comprehensive assessment of the players. Finally, more research needs to be conducted to develop a specific and comprehensive test model through the combination of various exercise modes for soccer players.


#4 Correlation between Match Performance and Field Tests in Professional Soccer Players
Reference: J Hum Kinet. 2018 Jun 13;62:213-219. doi: 10.1515/hukin-2017-0171. eCollection 2018 Jun.
Authors: Redkva PE, Paes MR, Fernandez R, da-Silva SG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006532/pdf/hukin-62-213.pdf
Summary: The aim of this study was to investigate possible correlations between aerobic and anaerobic fitness (in field tests) with performance during a 90 min friendly match, through the following variables: total distance covered, maximal running speed, number of high-intensity actions and number of sprints. Eighteen professional soccer players from a Brazilian elite team (age 23 ± 3 years, body mass 77.5 ± 8.9 kg) participated in the study. The athletes performed a Yo-Yo Endurance Test (aerobic fitness) and a Running Anaerobic Sprint Test (six maximal 35 m efforts separated by 10 s of passive recovery, anaerobic fitness). Data were collected during friendly matches using a GPS with 5 Hz technology. To establish the correlation between the variables determined during the matches, the Pearson correlation coefficient was used (significance level of p ≤ 0.05). A high correlation was found between distance covered in the Yo-Yo endurance test and total distance covered (r = 0.72; p < 0.05), number of high-intensity actions (r = 0.78; p < 0.05) and number of sprints (r = 0.88; p < 0.01) in the soccer matches. The RAST variables did not relate to the standards set during the matches (p < 0.05). From the results of the present study, it may be concluded that there is no correlation between RAST and friendly match data variables. However, better results in the Yo-Yo endurance test correlate with total distance, number of high-intensity actions and sprints during matches.


#5 The Impact of Nonlinear Pedagogy on Decision-Making and Execution in Youth Soccer Players According to Game Actions
Reference: J Hum Kinet. 2018 Jun 13;62:185-198. doi: 10.1515/hukin-2017-0169. eCollection 2018 Jun.
Authors: Praxedes A, Del Villar F, Pizarro D, Moreno A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006529/pdf/hukin-62-185.pdf
Summary: The aim of this study was to analyze the effect of a teaching program, based on Non-Linear Pedagogy, on decision-making and performance in youth soccer players as a function of the type of play action. Our participants were 19 players from the U12 age category. The teaching program, which was based on the application of modified games characterized by a numerical superiority in attack, was used for 14 training sessions. This program was conducted in two phases (preparation-for-intervention and intervention). Decision-making and execution for pass and dribbling actions were evaluated through the Game Performance Evaluation Tool. The results showed significant differences in favour of the experimental group in decision-making (p < .000) and the execution of passes (p = .003) after the intervention. However, such differences were not found for dribbling (decision-making, p = .402 and execution, p = .143). These findings demonstrate the effectiveness of this type of program for teaching actions with a high tactical component, such as the pass, and a different approach must be considered in actions with a high technical component, such as dribbling. It is necessary to continue developing studies in this line to clarify these issues.


#6 Seasonal Body Composition Variation Amongst Elite European Professional Soccer Players: An Approach of Talent Identification
Reference: J Hum Kinet. 2018 Jun 13;62:177-184. doi: 10.1515/hukin-2017-0132. eCollection 2018 Jun.
Authors: Owen AL, Lago-Penas C, Dunlop G, Mehdi R, Chtara M, Dellal A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006533/pdf/hukin-62-177.pdf
Summary: The primary aim of the investigation was to study the seasonal changes in body composition in elite European soccer players and identify key playing positional differences. Twenty-two players (age = 24 ± 3.7 years, body height = 180.45 ± 5.12 cm, body mass = 76.66 ± 5.34 kg) were tested. Players' mass (kg), lean body mass (LBM), fat free mass (FFM), fat mass (FM), muscle girths (MG) and sum of 8 skinfolds (mm) were measured across 5 time points (T0 = Start of pre-season training; T1 = End of pre-season training; T2 = Mid-season; T3 = End of mid-season break; T4 = End of season). Players were divided into their tactical positional roles for analysis. The specific positions they were divided into included defenders (n = 8), midfielders (n = 8) and forwards (n = 6). Assessment of training and matchplay exposure were also recorded. Sites-4, Sites-7, Sites-8 and Fat Mass decreased dramatically from T0 to T1 and T2 in all playing positions (p < 0.01), while no remarkable differences were found between T2, T3 and T4. Except for defenders, calf girth and lean mass were higher in T2, T3 and T4 compared to T0 and T1 (p < 0.01). Midfielders were found to be leaner than forwards and defenders in all data collection time point sessions. Defenders showed higher values in calf girth and lean body mass than midfielders and forwards. It can be concluded from this investigation that there are large variances n positional body composition profiles amongst professional European soccer players. Furthermore, significant changes are prevalent and occur across the season from LBM, FFM, MG and skinfold assessment amongst European elite level soccer players.


#7 Soccer Small-Sided Games Activities Vary According to the Interval Regime and their Order of Presentation within the Session
Reference: J Hum Kinet. 2018 Jun 13;62:167-175. doi: 10.1515/hukin-2017-0168. eCollection 2018 Jun.
Authors: Sanchez-Sanchez J, Ramirez-Campillo R, Carretero M, Martin V, Hernandez D, Nakamura FY
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006548/pdf/hukin-62-167.pdf
Summary: In order to investigate the physical demands of widely used in soccer small-sided games (SSGs), we compared game variations performed under different interval (fixed or variable) and timing regimens (beginning or end of a training session). Twelve male players wore GPS devices during the SSGs to record total distance, relative distance, distance at different speeds, and maximum velocity variables. Four variations of SSGs (4x4) were randomly applied: beginning of a training session with fixed and variable recovery, or end of a training session with fixed and variable recovery. During the beginning or end of a training session settings with fixed recovery duration, 2-min of playing and 2-min of recovery were provided. During the beginning and end of a training session settings with variable recovery, athletes kept playing until a goal was scored, or up to 2-min if no goals were scored. Results were analysed using MANOVA. Total distance and relative distance were higher in the beginning compared to end of training sessions for both fixed and variable recovery duration (small to moderate effect sizes). Distance at various speed ranges (i.e., 13-18 km/h and >18 km/h) was higher (p ≤ 0.01) at the beginning than at the end of training sessions with variable recovery. In addition, distance >18 km/h was higher at the beginning of a training session with variable recovery than fixed recovery and at the end of a training session with variable recovery than fixed recovery. In conclusion, several physical demand characteristics are affected by the moment of SSG application, while others respond to the recovery regime during SSGs, thus providing indications to the coaches to prescribe the intended training intensity by manipulating the context.


#8 Changes in Effective Playing Space when Considering Sub-Groups of 3 to 10 Players in Professional Soccer Matches
Reference: J Hum Kinet. 2018 Jun 13;62:145-155. doi: 10.1515/hukin-2017-0166. eCollection 2018 Jun.
Authors: Goncalves B, Folgado H, Coutinho D, Marcelino R, Wong D, Leite N, Sampaio J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006547/pdf/hukin-62-145.pdf
Summary: Success in soccer is much dependent on how players and teams create and restrict space and time. In match situations, players constitute small sub-groups to improve their collective synchronization and achievement of specific goals. This study aimed to identify changes in the effective playing space (EPS, defined as the smallest polygonal area delimited by the peripheral outfield players) when considering sub-groups of 3 to 10 players. Twenty outfield professional players participated in this study. The EPS, its regularity pattern (measured by the approximate entropy), coefficient of variation and players' mean speed were calculated for sub-groups of 3, 4, 5, 6, 7, 8, 9 and 10 players, considering the smallest inter-player distance as the criterion. The EPS presented a most likely increase with a higher number of players, especially considering the transition from 3 to 4 players (~440% of variation, very large). As the EPS increased with the number of players, the correspondent regularity presented a trend of a most likely increase (from EPS3 vs. EPS4: ~25%, very large; to EPS9 vs. EPS10: ~11%, moderate). The mean speed results suggest that players may achieve different states of collective coordination, mainly between ~6 to 8 km.h-1. Overall, three different match scenarios should require additional attention when aiming to design more match transferable tasks: i) transition from EPS3 to EPS4; ii) transition from EPS4 up to EPS8; and iii) transition from EPS8 to EPS9. These results help to understand match self-organized behaviours and, consequently, allow to optimize task characteristics in practice sessions.


#9 The Reliability of Technical and Tactical Tagging Analysis Conducted by a Semi-Automatic VTS in Soccer
Reference: J Hum Kinet. 2018 Jun 13;62:103-110. doi: 10.1515/hukin-2017-0162. eCollection 2018 Jun.
Authors: Beato M, Jamil M, Devereux G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006549/pdf/hukin-62-103.pdf
Summary: The Video Tracking multiple cameras system (VTS) is a technology that records two-dimensional position data (x and y) at high sampling rates (over 25 Hz). The VTS is of great interest because it can record external load variables as well as collect technical and tactical parameters. Performance analysis is mainly focused on physical demands, yet less attention has been afforded to technical and tactical factors. Digital.Stadium® VTS is a performance analysis device widely used at national and international levels (i.e. Italian Serie A, Euro 2016) and the reliability evaluation of its technical tagging analysis (e.g. shots, passes, assists, set pieces) could be paramount for its application at elite level competitions, as well as in research studies. Two professional soccer teams, with 30 male players (age 23 ± 5 years, body mass 78.3 ± 6.9 kg, body height 1.81 ± 0.06 m), were monitored in the 2016 season during a friendly match and data analysis was performed immediately after the game ended. This process was then replicated a week later (4 operators conducted the data analysis in each week). This study reports a near perfect relationship between Match and its Replication. R2 coefficients (relationships between Match and Replication) were highly significant for each of the technical variables considered (p < 0.001). In particular, a high score of interclass correlation and a small coefficient of variation were reported. This study reports meaningless differences between Match and its Replication (intra-day reliability). We concluded that the semi-automatic process behind the Digital.Stadium® VTS was more than capable of recording technical tagging data accurately.


#10 Changes in Injury Risk Mechanisms after Soccer-Specific Fatigue in Male Youth Soccer Players
Reference: J Hum Kinet. 2018 Jun 13;62:33-42. doi: 10.1515/hukin-2017-0157. eCollection 2018 Jun.
Authors: Lehnert M, Croix MS, Xaverova Z, Botek M, Varekova R, Zaatar A, Lastovicka O, Stastny P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006546/pdf/hukin-62-033.pdf
Summary: The aim of this study was to examine the acute effects of soccer specific fatigue on muscular and neuromuscular function in male youth soccer players. Elite soccer players (n = 20; age 15.7 ± 0.5 y; body height 177.75 ± 6.61 cm; body mass 67.28 ± 8.29 kg) were measured before and after soccer specific exercise (SAFT90). The reactive strength index (RSI) was determined by a drop jump test, leg stiffness (LS) by a 20 sub-maximal two-legged hopping test, and a functional hamstring to quadriceps strength ratio from isokinetic concentric and eccentric strength of the dominant and non-dominant leg (measured at angular velocities of 1.05 rad · s-1 and 3.14 rad · s-1). Metabolic response to the SAFT90 was determined by blood lactate and perceived exertion was assessed by the Borg scale. After simulated match play, a significant decrease in absolute LS (t = 4.411; p < 0.001; ω2 = 0.48) and relative LS (t = 4.326; p < 0.001; ω2 = 0.49) was observed and the RSI increased significantly (t = 3.806; p = 0.001; ω2 = 0.40). A reduction in LS found after the SAFT90 indicates possible reduction in dynamic knee stabilization. However, if we consider the changes in other observed variables, the present study did not clearly confirm that fatigue induced by a soccer specific protocol increased the risk of ACL and hamstring injury. This may be attributed to the simulated rather than actual match play used in the present study.


#11 Age and maturity related differences in motor coordination among male elite youth soccer players
Reference: J Sports Sci. 2018 Jun 18:1-8. doi: 10.1080/02640414.2018.1488454. [Epub ahead of print]
Authors: Rommers N, Mostaert M, Goossens L, Vaeyens R, Witvrouw E, Lenoir M, D'Hondt E
Summary: This study investigated differences in generic and soccer specific motor coordination, as well as speed and agility depending on age and maturity in elite youth soccer players (U10-U15, N = 619). Measurements included body height, body weight and sitting height to estimate age at peak height velocity (APHV); three Körperkoordinationstest für Kinder subtests (i.e. jumping sideways (JS), moving sideways (MS), balancing backwards (BB)) to assess generic motor coordination; the UGent dribbling test for soccer specific motor coordination; a 5m/30m sprint and T-test for speed and agility, respectively. Age specific z-scores of the predicted APHV identified players as earlier, on time or later maturing. (M)ANOVA analyses showed significant age by maturity interaction effects for the speed and agility test cluster, revealing maturity related differences in U14 and U15 players. Next to an overall higher performance with age for all test clusters (η2 0.080-0.468), earlier maturing players outperformed their later maturing peers in 5m/30m sprinting. The opposite was seen for JS and BB. So, players' maturity status should be taken into account to adequately value performance in talent identification. Also, the focus on characteristics that appear to be minimally biased by an earlier maturational timing (i.e. motor coordination) should be increased.

Fri

03

Aug

2018

Latest research in football - week 23 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 The Occurrence of Repeated High Acceleration Ability (RHAA) in Elite Youth Football
Reference: Int J Sports Med. 2018 Jun 5. doi: 10.1055/a-0608-4738. [Epub ahead of print]
Authors: Serpiello FR, Duthie GM, Moran C, Kovacevic D, Selimi E, Varley MC
Summary: The aim of the present study was to investigate the occurrence of Repeated High-Acceleration Ability (RHAA) bouts in elite youth football games using 10-Hz GPS devices and two relative thresholds derived from players' actual maximal acceleration. Thirty-six outfield soccer players (age 14.9±0.6 years) participated in the study. Players wore 10-Hz GPS units during 41 official games. High accelerations were defined as efforts commencing above a threshold corresponding to 70% (T70%) or 80% (T80%) of the average 5-m acceleration obtained during a 40-m sprint test; RHAA bouts were defined as ≥3 efforts with ≤45 s recovery between efforts. Results were analysed via generalised linear mixed model and magnitude-based inferential statistics. On average, 8.0±4.6 and 5.1±3.5 bouts were detected in an entire game using T70% and T80%, respectively. When all positions were analysed together, there was a very-likely small difference in the number of RHAA bouts between first and second half for T70% and T80%, respectively. RHAA bouts occur frequently in elite youth football, with small differences between halves and between playing positions within the first or second half in most variables assessed.


#2 Importance of Reactive Agility and Change of Direction Speed in Differentiating Performance Levels in Junior Soccer Players: Reliability and Validity of Newly Developed Soccer-Specific Tests
Reference: Front Physiol. 2018 May 15;9:506. doi: 10.3389/fphys.2018.00506. eCollection 2018.
Authors: Pojskic H, Aslin E, Krolo A, Jukic I, Uljevic O, Spasic M, Sekulic D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5962722/pdf/fphys-09-00506.pdf
Summary: Agility is a significant determinant of success in soccer; however, studies have rarely presented and evaluated soccer-specific tests of reactive agility (S_RAG) and non-reactive agility (change of direction speed - S_CODS) or their applicability in this sport. The aim of this study was to define the reliability and validity of newly developed tests of the S_RAG and S_CODS to discriminate between the performance levels of junior soccer players. The study consisted of 20 players who were involved at the highest national competitive rank (all males; age: 17.0 ± 0.9 years), divided into three playing positions (defenders, midfielders, and forwards) and two performance levels (U17 and U19). Variables included body mass (BM), body height, body fat percentage, 20-m sprint, squat jump, countermovement jump, reactive-strength-index, unilateral jump, 1RM-back-squat, S_CODS, and three protocols of S_RAG. The reliabilities of the S_RAG and S_CODS were appropriate to high (ICC: 0.70 to 0.92), with the strongest reliability evidenced for the S_CODS. The S_CODS and S_RAG shared 25-40% of the common variance. Playing positions significantly differed in BM (large effect-size differences [ES]; midfielders were lightest) and 1RM-back-squat (large ES; lowest results in midfielders). The performance levels significantly differed in age and experience in soccer; U19 achieved better results in the S_CODS (t-test: 3.61, p < 0.05, large ES) and two S_RAG protocols (t-test: 2.14 and 2.41, p < 0.05, moderate ES). Newly developed tests of soccer-specific agility are applicable to differentiate U17 and U19 players. Coaches who work with young soccer athletes should be informed that the development of soccer-specific CODS and RAG in this age is mostly dependent on training of the specific motor proficiency.


#3 The Betting Odds Rating System: Using soccer forecasts to forecast soccer
Reference: PLoS One. 2018 Jun 5;13(6):e0198668. doi: 10.1371/journal.pone.0198668. eCollection 2018.
Authors: Wunderlich F, Memmert D
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0198668&type=printable
Summary: Betting odds are frequently found to outperform mathematical models in sports related forecasting tasks, however the factors contributing to betting odds are not fully traceable and in contrast to rating-based forecasts no straightforward measure of team-specific quality is deducible from the betting odds. The present study investigates the approach of combining the methods of mathematical models and the information included in betting odds. A soccer forecasting model based on the well-known ELO rating system and taking advantage of betting odds as a source of information is presented. Data from almost 15.000 soccer matches (seasons 2007/2008 until 2016/2017) are used, including both domestic matches (English Premier League, German Bundesliga, Spanish Primera Division and Italian Serie A) and international matches (UEFA Champions League, UEFA Europe League). The novel betting odds based ELO model is shown to outperform classic ELO models, thus demonstrating that betting odds prior to a match contain more relevant information than the result of the match itself. It is shown how the novel model can help to gain valuable insights into the quality of soccer teams and its development over time, thus having a practical benefit in performance analysis. Moreover, it is argued that network based approaches might help in further improving rating and forecasting methods.


#4 Data concerning isometric lower limb strength of dominant versus not-dominant leg in young elite soccer players
Reference: Data Brief. 2018 Jan 31;17:414-418. doi: 10.1016/j.dib.2018.01.022. eCollection 2018 Apr.
Authors: Rouissi M, Chtara M, Bragazzi NL, Haddad M, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988318/pdf/main.pdf
Summary: The present data article describes the isometric lower limb strength of dominant leg versus not-dominant leg measured with handheld dynamometer (HHD) in a sample of 31 young elite soccer players (age 16.42 ± 0.45 years; height 169.00 ± 0.50 cm; leg length 94.80 ± 3.32 cm; body-mass 67.04 ± 5.17 kg).


#5 The Construct Validity of the CODA and Repeated Sprint Ability Tests in Football Referees
Reference: Int J Sports Med. 2018 Jun 14. doi: 10.1055/a-0577-4073. [Epub ahead of print]
Authors: Riiser A, Andersen V, Castagna C, Arne Pettersen S, Saeterbakken A, Froyd C, Ylvisaker E, Naess Kjosnes T, Fusche Moe V
Summary: As of 2017, the international football federation introduced the change of direction ability test (CODA) and the 5×30 m sprint test for assistant referees (ARs) and continued the 6×40 m sprint test for field referees (FRs) as mandatory tests. The aim of this study was to evaluate the association between performance in these tests and running performance during matches at the top level in Norway. The study included 9 FRs refereeing 21 matches and 19 ARs observed 53 times by a local positioning system at three stadiums during the 2016 season. Running performance during matches was assessed by high-intensity running (HIR) distance, HIR counts, accelerati