Blog archive

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.

Sun

06

Jan

2019

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, acceleration distance, and acceleration counts. For the ARs, there was no association between the CODA test with high-intensity running or acceleration (P>0.05). However, the 5×30 m sprint test was associated with HIR count during the entire match (E -12.9, 95% CI -25.4 to -0.4) and the 5-min period with the highest HIR count (E -2.02, 95% CI -3.55 to -0.49). For the FRs, the 6×40 m fitness test was not associated with running performance during matches (P>0.05). In conclusion, performance in these tests had weak or no associations with accelerations or HIR in top Norwegian referees during match play.


#6 The effects of an enrichment training program for youth football attackers
Reference: PLoS One. 2018 Jun 13;13(6):e0199008. doi: 10.1371/journal.pone.0199008. eCollection 2018.
Authors: Coutinho D, Santos S, Goncalves B, Travassos B, Wong DP, Schollhorn W, Sampaio J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5999098/pdf/pone.0199008.pdf
Summary: The aim of this study was to identify the effects of a complementary training program based on differential learning approach in the physical, technical, creative and positioning performance of youth football attackers. Fifteen players were allocated into the control (U15C = 9, age: 13.9±0.5 years; U17C = 6, age: 16.1±0.7 years) and the experimental (U15E = 9, age: 14.2±0.8 years; U17E = 6, age: 15.8±0.5 years) groups. The experimental groups participated in 10-weeks of a complementary training program based on differential learning approach to improve physical literacy and players' tactical behavior. Variables studied encompassed: motor (vertical jump, speed and repeated change-of direction), technical (pass, dribble and shot), creative (fluency, attempts, versatility) and positioning-related variables (stretch index, spatial exploration index and regularity of the lateral and longitudinal movements). Results revealed that U15E improved both the jump and repeated change-of-direction performance, while the U17E have only improved the jump performance. The U15E showed improvements in all technical variables (small to large effects), and in the fluency and versatility (moderate effects), while the U17 have only improved the successful shots (large effects). From a positional perspective, there was a moderate increase in the stretch index, and decreased longitudinal and lateral regularity (small to moderate effects) in the U15E compared to the U15C. In turn, the U17E revealed a moderate increase of the spatial exploration index and a small decrease in the stretch index. Overall, the results suggest that the complementary training program was effective for the development of the overall performance of the U15E attackers, while more time and/or variability may be needed for older age groups. Nevertheless, the overall higher values found in experimental groups, may suggest that this type of complementary training program improves performance.


#7 The Adductor Strengthening Programme prevents groin problems among male football players: a cluster-randomised controlled trial
Reference: Br J Sports Med. 2018 Jun 10. pii: bjsports-2017-098937. doi: 10.1136/bjsports-2017-098937. [Epub ahead of print]
Authors: Haroy J, Clarsen B, Wiger EG, Oyen MG, Serner A, Thorborg K, Holmich P, Andersen TE, Bahr R
Summary: Groin injuries represent a considerable problem in male football. Previous groin-specific prevention programmes have not shown a significant reduction in groin injury rates. An exercise programme using the Copenhagen Adduction exercise increases hip adduction strength, a key risk factor for groin injuries. However, its preventive effect is yet to be tested. The aim of the study was to evaluate the effect of a single-exercise approach, based on the Copenhagen Adduction exercise, on the prevalence of groin problems in male football players. 35 semiprofessional Norwegian football teams were cluster-randomised into an intervention group (18 teams, 339 players) and a control group (17 teams, 313 players). The intervention group performed an Adductor Strengthening Programme using one exercise, with three progression levels, three times per week during the preseason (6-8 weeks), and once per week during the competitive season (28 weeks). The control group were instructed to train as normal. The prevalence of groin problems was measured weekly in both groups during the competitive season using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. The average prevalence of groin problems during the season was 13.5% (95% CI 12.3% to 14.7%) in the intervention group and 21.3% (95% CI 20.0% to 22.6%) in the control group. The risk of reporting groin problems was 41% lower in the intervention group (OR 0.59, 95% CI 0.40 to 0.86, p=0.008). The simple Adductor Strengthening Programme substantially reduced the self-reported prevalence and risk of groin problems in male football players.


#8 Football is medicine: it is time for patients to play!
Reference: Br J Sports Med. 2018 Jun 9. pii: bjsports-2018-099377. doi: 10.1136/bjsports-2018-099377. [Epub ahead of print]
Authors: Krustrup P, Krustrup BR
Download link: http://bjsm.bmj.com/content/bjsports/early/2018/06/09/bjsports-2018-099377.full.pdf


#9 Are There Differences in Elite Youth Soccer Player Work Rate Profiles in Congested vs. Regular Match Schedules?
Reference: J Strength Cond Res. 2018 Jun 21. doi: 10.1519/JSC.0000000000002702. [Epub ahead of print]
Authors: Zanetti V, Carling C, Aoki MS, Bradley PS, Moreira A
Summary: Official international tournaments in which youth soccer players participate can involve very congested schedules. Yet, no information regarding physical and technical match performance during congested vs. regular (noncongested) cycles is available. In this study, accelerations, decelerations, mean metabolic power (MP), and technical performance (offensive and defensive variables) were compared across very congested match (VCM; 10 international matches played over 3 successive days, including 2 days with 2 consecutive matches separated by a 4- to 5-hour interval) and 10 regular (noncongested match [NCM]) match periods in elite male Under 15 (U15, n = 11) and Under 17 (U17, n = 13) soccer players. Players wore a 15-Hz Global Positioning System unit with a 100-Hz triaxial accelerometer. The session rating of perceived exertion (RPE) were assessed 30 minutes after match. Results showed a higher number of accelerations per minute observed in VCM vs. NCM (U15; 2.27 ± 0.35 vs. 2.12 ± 0.23; effect size [ES] = 0.49; U17; 2.27 ± 0.41 vs. 2.01 ± 0.31; ES = 0.69). Decelerations per minute were higher during VCM (U15; 1.99 ± 0.27 vs. 1.84 ± 0.25; ES = 0.55; and U17; 1.98 ± 0.35 vs. 1.80 ± 0.27; ES = 0.56). Mean MP was higher in the VCM (U15; 0.42 ± 0.06 vs. 0.37 ± 0.02; ES = 1.08; U17; 0.46 ± 0.03 vs. 0.30 ± 0.03; ES = 1.94). Technical actions per minute were higher in the VCM for U17 (ES = 1.60 and 1.37, for offensive and defensive performance, respectively) but lower (during VCM) for U15 (ES = 3.59 and 0.28, for offensive and defensive performance). U15 reported a higher session RPE in the VCM (7.9 ± 0.5 AUs vs. 6.9 ± 0.5 AUs). The findings suggest that running activity in these youth players was unaffected overall in tournaments with congested schedules, and that the intensity of match-play was actually greater than in regular match schedules.


#10 Personality and Risk Taking in Sports: A Focus on Unintentional and Intentional Head Impacts in Amateur Soccer Players
Reference: Clin J Sport Med. 2018 Jun 21. doi: 10.1097/JSM.0000000000000627. [Epub ahead of print]
Authors: Levitch CF, Ifrah C, Kim M, Stewart WF, Lipton RB, Zimmerman ME, Lipton ML
Summary: In soccer, unintentional and intentional (heading) head impacts are associated with concussive symptoms and cognitive dysfunction. We examined whether personality traits were associated with these behaviors in soccer players. Participants completed study visits at the Albert Einstein College of Medicine. A total of 307 adult amateur soccer players, recruited from New York City and the surrounding area, completed 737 HeadCount-2w questionnaires. Personality traits (intellect/imagination, conscientiousness, extraversion, agreeableness, and neuroticism) were assessed with the Mini-International Personality Item Pool questionnaire at the baseline study visit were used as predictor variables. Main outcome variables were an online questionnaire (HeadCount-2w) to ascertain frequency of intentional head impacts and occurrence of unintentional head impacts every 3 to 6 months. Generalized estimating equations repeated-measures regressions determined whether personality predicted unintentional and intentional impacts. Personality traits were not associated with unintentional head impact(s) or frequency of intentional head impacts. These findings have important clinical implications, suggesting that personality is not driving the association between high levels of unintentional and intentional head impacts and worse neuropsychological functioning and concussive symptoms.


#11 Does Man Marking Influence Running Outputs and Intensity During Small-Sided Soccer Games?
Reference: J Strength Cond Res. 2018 Jun 20. doi: 10.1519/JSC.0000000000002668. [Epub ahead of print]
Authors: Aasgaard M, Kilding AE
Summary: Small-sided games (SSGs) are considered an effective training tool for physical development in soccer. Small-sided games can be modified in several ways to manipulate the physical demands to best match the game demands, player characteristics, and session objectives. The aim of this study was to compare the physiological, perceptual, and Global Positioning System (GPS)-derived time-motion characteristics of man marking (MM) vs. non-man marking (NMM) in 2v2, 3v3, and 4v4 SSGs. In an acute crossover design, 8 amateur soccer players (mean age ± SD: 23.6 ± 3.3 years) played 2v2, 3v3, and 4v4 SSGs consisting of 4 × 4-minute bouts, with 2-minute passive recovery. During all SSGs, players wore a heart rate (HR) monitor and GPS unit and reported their rating of perceived exertion (RPE). Average percent HR (%HRave) induced small to moderate effects with MM compared with NMM (%Δ = 1-2.7%; effect size [ES] = 0.22-0.65). Comparisons between MM formats indicated a decrease in %HRave with increased player numbers (%Δ = 1.6-3.5%; ES = 0.39-0.86). Perceptual load increased with MM compared with NMM (%Δ = 6.7-17.6%; ES = 0.66-2.09), whereas increases in player numbers (MM only) reduced RPE output (%Δ = 9.4-24.3%; ES = 1.14-3.61). Time-motion characteristics revealed substantially greater total distance covered in MM irrespective of player number (%Δ = 6.8-14.7%; ES = 1.34-2.82). There were very likely increases in distances covered at striding (13.1-17.8 km·h) (%Δ: 23.4-33.2; ES = 2.42-4.35) and high-intensity running (HIR) (17.9-21 km·h) (%Δ: 47.3-104; ES = 0.91-1.68) for MM compared with NMM irrespective of player number. In conclusion, MM substantially elevated perceptual load and distances from striding to HIR regardless of player number, whereas differences between NMM and MM for internal load remain unclear. Use of MM may allow coaches to condition for particularly demanding phases of the game and prescription of larger SSG formats to increase distance covered at higher velocities.

Wed

25

Jul

2018

Latest research in football - week 22 - 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 Prevention of Ankle Sprain Injuries in Youth Soccer and Basketball: Effectiveness of a Neuromuscular Training Program and Examining Risk Factors
Reference: Clin J Sport Med. 2017 Jun 29. doi: 10.1097/JSM.0000000000000462. [Epub ahead of print]
Authors: Owoeye OBA, Palacios-Derflingher LM, Emery CA
Summary: The primary objective of this study was to examine the effectiveness of a neuromuscular training (NMT) warm-up program in reducing the risk of ankle sprain injury (ASI) in youth soccer and basketball. The secondary objective included the evaluation of risk factors for ASI. Male and female youth (11-18 years) soccer and basketball players (n = 2265) in Alberta, Canada participated in this study. Ankle sprain injury was the primary outcome and was recorded using a validated prospective injury surveillance system consistent in all studies. The primary exposure of interest was NMT warm-up, which included aerobic, strength, agility, and balance components. Multivariable Poisson regression, controlling for clustering by team and offset for exposure hours, was used to estimate incidence rate ratios (IRRs) with 95% confidence intervals (CIs), with considerations for confounding and effect modification and evaluating all covariates as potential risk factors. A total of 188 ASIs were reported in 171 players. Neuromuscular training significantly reduced the risk of ASI [IRR = 0.68 (95% CI; 0.46-0.99)]. Independent risk factors for ASI included previous ASI [IRR = 1.98 (95% CI; 1.38-2.81)] and participation in basketball versus soccer [IRR = 1.83 (95% CI; 1.18-2.85)]. Sex, age, body mass index, and previous lower extremity injury (without previous ASI) did not predict ASI (P > 0.05). Exposure to an NMT program is significantly protective for ASI in youth soccer and basketball. Risk of ASI in youth basketball is greater than soccer, and players with a history of ASI are at greater risk


#2 Patellar tendon properties distinguish elite from non-elite soccer players and are related to peak horizontal but not vertical power
Reference: Eur J Appl Physiol. 2018 Jun 2. doi: 10.1007/s00421-018-3905-0. [Epub ahead of print]
Authors: Murtagh CF, Stubbs M, Vanrenterghem J, O'Boyle A, Morgans R, Drust B, Erskine RM
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00421-018-3905-0.pdf
Summary: The purpose was to investigate potential differences in patellar tendon properties between elite and non-elite soccer players, and to establish whether tendon properties were related to power assessed during unilateral jumps performed in different directions. Elite (n = 16; age 18.1 ± 1.0 years) and non-elite (n = 13; age 22.3 ± 2.7 years) soccer players performed vertical, horizontal-forward and medial unilateral countermovement jumps (CMJs) on a force plate. Patellar tendon (PT) cross-sectional area, elongation, strain, stiffness, and Young's modulus (measured at the highest common force interval) were assessed with ultrasonography and isokinetic dynamometry. Elite demonstrated greater PT elongation (6.83 ± 1.87 vs. 4.92 ± 1.88 mm, P = 0.011) and strain (11.73 ± 3.25 vs. 8.38 ± 3.06%, P = 0.009) than non-elite soccer players. Projectile range and peak horizontal power during horizontal-forward CMJ correlated positively with tendon elongation (r = 0.657 and 0.693, P < 0.001) but inversely with Young's modulus (r = - 0.376 and - 0.402; P = 0.044 and 0.031). Peak medial power during medial CMJ correlated positively with tendon elongation (r = 0.658, P < 0.001) but inversely with tendon stiffness (r = - 0.368, P = 0.050). Not only does a more compliant patellar tendon appear to be an indicator of elite soccer playing status but it may also facilitate unilateral horizontal-forward and medial, but not vertical CMJ performance. These findings should be considered when prescribing talent selection and development protocols related to direction-specific power in elite soccer players.


#3 Workload and non-contact injury incidence in elite football players competing in European leagues
Reference: Eur J Sport Sci. 2018 Jun 2:1-8. doi: 10.1080/17461391.2018.1477994. [Epub ahead of print]
Authors: Delecroix B, McCall A, Dawson B, Berthoin S, Dupont G
Summary: The aim of this study was to analyse the relationship between absolute and acute:chronic workload ratios and non-contact injury incidence in professional football players and to assess their predictive ability. Elite football players (n = 130) from five teams competing in European domestic and confederation level competitions were followed during one full competitive season. Non-contact injuries were recorded and using session rate of perceived exertion (s-RPE) internal absolute workload and acute:chronic (A:C) workload ratios (4-weeks, 3-weeks, 2-weeks and week-to-week) were calculated using a rolling days method. The relative risk (RR) of non-contact injury was increased (RR = 1.59, CI95%: 1.18-2.15) when a cumulative 4-week absolute workload was greater than 10629 arbitrary units (AU) in comparison with a workload between 3745 and 10628 AU. When the 3-week absolute workload was more than 8319 AU versus between 2822 and 8318 AU injury risk was also increased (RR= 1.46, CI95% 1.08-1.98). Injury incidence was higher when the 4-week A:C ratio was <0.85 versus >0.85 (RR = 1.31, CI95%: 1.02-1.70) and with a 3-week A:C ratio >1.30 versus <1.30 (RR = 1.37, CI95%: 1.05-1.77). Importantly, none of the A:C workload combinations showed high sensitivity or specificity. In elite European footballers, using internal workload (sRPE) revealed that cumulative workloads over 3 and 4 weeks were associated with injury incidence. Additionally, A:C workloads, using combinations of 2, 3 and 4 weeks as the C workloads were also associated with increased injury risk. No A:C workload combination was appropriate to predict injury.


#4 Hip and groin injury is the most common non-time-loss injury in female amateur football
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Jun 2. doi: 10.1007/s00167-018-4996-1. [Epub ahead of print]
Authors: Langhout R, Weir A, Litjes W, Gozeling M, Stubbe JH1, Kerkhoffs G, Tak I
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-018-4996-1.pdf
Summary: Hip and groin injuries in football are problematic due to their high incidence and risk of chronicity and recurrence. The use of only time-loss injury definitions may underestimate the burden of hip and groin injuries. Little is known about hip and groin injury epidemiology in female football. The first aim of this study was to examine the within-season (2014-2015) prevalence of total injury with and without time-loss in female amateur football players. The second aim was to study the within-season and preseason (2015-2016) prevalence of hip/groin injuries with and without time-loss. The third aim was to study the association between the duration of hip and groin injury in the 2014-2015 season and the severity of hip/groin problems during the 2015-2016 preseason. During the preseason, 434 Dutch female amateur football players completed an online questionnaire based on the previous season and current preseason. The hip and groin outcome score (HAGOS) was used to assess the severity of hip and groin injuries. The hip/groin (17%), knee (14%), and ankle (12%) were the most frequent non-time-loss injury locations. The ankle (22%), knee (18%), hamstring (11%), thigh (10%), and hip/groin (9%) were the most common time-loss injury locations. The previous season prevalence of total injury was 93%, of which non-time-loss injury was 63% and time-loss injury was 37%. The prevalence of hip/groin injury was 40%, non-time-loss hip/groin injury was 36% and time-loss hip/groin injury was 11%. The preseason prevalence of hip/groin injury was 27%, non-time-loss hip/groin injury was 25%, and time-loss hip/groin injury was 4%. Players with longstanding hip/groin injury (> 28 days) in the previous season had lower HAGOS scores at the next preseason than players with short-term (1-7 days) or no hip/groin injury (p < 0.001). From all players with hip/groin injury from the previous season, 52% also sustained hip/groin injury in the following preseason, of which 73% were recurrent and 27% were chronic hip/groin injuries. Injury risk, and especially non-time-loss hip and groin injury risk, is high in female amateur football. Three-quarters of the players with longstanding hip and groin injuries in the previous season have residual problems at the start of the following season.


#5 Distribution of Arsenic and Risk Assessment of Activities on Soccer Pitches Irrigated with Arsenic-Contaminated Water
Reference: Int J Environ Res Public Health. 2018 May 24;15(6). pii: E1060. doi: 10.3390/ijerph15061060.
Authors: Martinez-Villegas N, Hernandez A, Meza-Figueroa D, Sen Gupta B
Download link: www.mdpi.com/1660-4601/15/6/1060/pdf
Summary: The aim of this research was to estimate the risk of human exposure to arsenic due to sporting activities in a private soccer club in Mexico, where arsenic-contaminated water was regularly used for irrigation. For this purpose, the total concentration in the topsoil was considered for risk assessment. This was accomplished through three main objectives: (1) measuring arsenic concentrations in irrigation water and irrigated soils, (2) determining arsenic spatial distribution in shallow soils with Geographical Information Systems (GIS) using geostatistical analysis, and (3) collecting field and survey data to develop a risk assessment calculation for soccer activities in the soccer club. The results showed that the average arsenic concentrations in shallow soils (138.1 mg/kg) were 6.2 times higher than the Mexican threshold for domestic soils (22 mg/kg). Furthermore, dermal contact between exposed users and contaminated soils accounted for a maximum carcinogenic risk value of 1.8 &times; 10&minus;5, which is one order of magnitude higher than the recommended risk value, while arsenic concentrations in the irrigation water were higher (6 mg/L) than the WHO&rsquo;s permissible threshold in drinking water, explaining the contamination of soils after irrigation. To the best of our knowledge, this is the first risk study regarding dermal contact with arsenic following regular grass irrigation with contaminated water in soccer pitches.


#6 Modeling of relationships between physical and technical activities and match outcome in elite German soccer players
Reference: J Sports Med Phys Fitness. 2018 Jun 7. doi: 10.23736/S0022-4707.18.08506-7. [Epub ahead of print]
Authors: Konefal M, Chmura P, Kowalczuk E, Figueiredo AJ, Sarmento H, Rokita A, Chmura J, Andrzejewski M
Summary: The aim of this study was to determine what physical and technical activities of soccer players in different pitch positions affect significantly the match outcome of professional German soccer players; as well as to examine whether differences in physical and technical activities increase or reduce the probability of a match being won. The study sample comprised 4393 individual match observations of 350 soccer players competing in the Bundesliga during the 2014/2015 domestic season. Analysis was confined to outfield players (other than goalkeepers) who completed entire matches, and was carried out using the Impire AG motion analysis system. The selection of physical and technical activities to be used in predictive models was achieved using the lasso method. The odds ratio revealed that an mean running speed in the second half that was greater by 0.1 km/h was associated with a 27.0% improvement in the odds of a match being won (OR=1.27; 95% CI: 1.17 to 1.38) (forwards), 15.7% (OR=1.16; 95% CI: 1.09 to 1.23) (wide midfielders), and 10.0% (OR=1.10; 95% CI: 1.04 to 1.17) (central midfielders). Furthermore, in the case of wide midfielders, a significant variable was the distance covered at > 24 km/h, with an increase of 0.1 km associated with odds of winning the game improved by 31.7% (OR=1.32; 95% CI: 1.05 to 1.66). Match outcome is affected significantly where peak and mean running speeds in the second half of the match are greater, and where longer distances are covered at speeds in excess of 24 km/h.


#7 Professional soccer is associated with radiographic cam and pincer hip morphology
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Jun 6. doi: 10.1007/s00167-018-5008-1. [Epub ahead of print]
Authors: Falotico GG, Arliani GG, Yamada AF, Fernandes ADRC, Ejnisman B, Cohen M
Summary: Femoroacetabular impingement (FAI) syndrome is characterized by a triad: symptoms, clinical signs and imaging findings. Some individuals, especially athletes, have only imaging alterations. The objective of this study was to evaluate the prevalence of cam and pincer morphology in professional soccer players compared with a control group of non-athletes and to investigate the association between the age at which players start playing competitive soccer more than three times per week and duration of the soccer career with the prevalence of these radiographic findings. The prevalence of cam and pincer morphology in sixty professional adult male soccer players and thirty-two male controls was determined using pelvic anteroposterior radiography. Data were recorded for all hips and correlated with the age at which the players started competitive soccer practice and with the duration of their soccer career. The prevalence of morphological FAI in the soccer players was 92.5% versus 28.1% in the controls (p < 0.001). The duration of the soccer career was positively correlated with the alpha angle (p = 0.033) and negatively correlated with the retroversion index (p = 0.009). The age at which competitive play began was inversely correlated with the alpha angle (p < 0.001). The study showed a high prevalence of cam and pincer morphology in Brazilian professional soccer players compared with controls. The duration of the soccer career was associated with an increased alpha angle and a decreased retroversion index, and the age at which competitive soccer participation began was negatively associated with alpha angle values. Finally, this manuscript provides data about the association between greater exposure to soccer and cam and pincer morphological changes in the hip; specifically, cam morphology was more common in patients who began participating in sports at earlier ages. This information serves as an alert for coaches of youth teams to manage the training load in youth athletes.


#8 Injury rate and prevention in elite football: let us first search within our own hearts
Reference: Br J Sports Med. 2018 Jun 2. pii: bjsports-2018-099267. doi: 10.1136/bjsports-2018-099267. [Epub ahead of print]
Authors: Buchheit M, Eirale C, Simpson BM, Lacome M


#9 How the Experimental Setting Influences Representativeness: A Review of Gaze Behavior in Football Penalty Takers
Reference: Front Psychol. 2018 May 8;9:682. doi: 10.3389/fpsyg.2018.00682. eCollection 2018.
Authors: Kurz J, Munzert J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5952262/pdf/fpsyg-09-00682.pdf
Summary: This article reviews research on the gaze behavior of penalty takers in football. It focuses on how artificial versus representative experimental conditions affect gaze behavior in this far-aiming task. Findings reveal that-irrespective of the representativeness of the experimental conditions-different instructions regarding the aiming strategy and different threat conditions lead to different gaze patterns. Results also reveal that the goal size and the distance to the goal did not affect the gaze behavior. Moreover, it is particularly run-up conditions that lead to differences. These can be either artificial or more natural. During a natural run-up, penalty takers direct their gaze mainly toward the ball. When there is no run-up, they do not direct their gaze toward the ball. Hence, in order to deliver generalizable results with which to interpret gaze strategies, it seems important to use a run-up with a minimum length that is comparable to that in a real-life situation.


#10 Creatine kinase, neuromuscular fatigue, and the contact codes of football: A systematic review and meta-analysis of pre- and post-match differences
Reference: Eur J Sport Sci. 2018 Jun 5:1-11. doi: 10.1080/17461391.2018.1480661. [Epub ahead of print]
Authors: Hagstrom AD, Shorter KA
Summary: Physiological or performance tests are routinely utilised to assess athletes' recovery. At present, the ideal tool to assess recovery remains unknown. Therefore, the aim of this systematic review was to examine the change in creatine kinase (CK) and neuromuscular function as measured via a countermovement jump (CMJ) following a match in the contact codes of football. A comprehensive search of databases was undertaken with RevMan (V 5.3) used for statistical analysis. Our results demonstrated that CK pre- versus post-match (standardised mean difference (SMD) = 0.90, 95% CI = 0.50 to 1.31, p < .0001), CK pre- versus 24 h post-match (SMD = 1.50, 95% CI = 1.12 to 1.88, p < .00001), and CK pre- versus 48 h post-match all increased significantly (SMD = 0.90, 95% CI = 0.50 to 1.31, p < .0001), while CMJ peak power (PP) pre- versus post-match (SMD = -0.59, 95% CI = -1.12 to -0.06, p = .03), and pre- versus 24 h post-match (SMD = -0.80, 95% CI = -1.31 to -0.28, p = .002) decreased significantly. There was a significant relationship between the change in CK and the change in CMJ PP from immediately pre to immediately post (r = -0.924, p = .025), and between CMJ immediately following a match and 24 h CK change (r = -0.983, p = .017). In conclusion, CK levels increase and performance in the CMJ decreases following a match of a contact code of football. The identification of this relationship may allow coaching staff to implement a standalone measure of recovery.


#11 Lunacy revisited - the myth of the full moon: are football injuries related to the lunar cycle?
Reference: Chronobiol Int. 2018 Jun 6:1-6. doi: 10.1080/07420528.2018.1483943. [Epub ahead of print]
Authors: Yousfi N, Rekik RN, Eirale C, Whiteley R, Farooq A, Tabben M, Gillogly S, Bahr R, Chamari K
Summary: Previous literature suggests that human behaviour and physiology are somehow altered by the moon-cycle, with particular emphasis on poorer sleep quality and increased aggressive behaviour during full moon. The latter variables can negatively impact athletes' recovery and increase the likelihood of injury resulting from collision with another athlete. Therefore, the current study aimed to investigate the association between the lunar cycle and injury risk in professional football players (soccer). We monitored injuries and player exposure in the premier professional league in Qatar during four consecutive seasons (2013-2014 through 2016-2017). Acute (sudden-onset traumatic) injuries (n = 1184; 587 from contact with another player and 597 without player contact) recorded during matches and training were classified according to the lunar cycle characteristics on the date of injury: (i) moon illumination, (ii) lunar distance from earth and (iii) tidal coefficient, acquired from the lunar calendar and tide tables. We used a Poisson regression model to examine the relationship between injury risk and lunar cycle characteristics. We did not detect any association between injury risk and moon illumination, earth-to-moon distance or tidal coefficient, not for all acute injuries, nor for contact and non-contact injuries when examined separately. The findings suggest that the full moon or new moon or the gravitational pull have no effect on football injuries. Thus, organisers need not consult moon or tide tables when planning future event schedules.

Sun

08

Jul

2018

Latest research in football - week 21 - 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 Commotio Cordis in a Professional Soccer Player: Value of MRI in Unraveling Myocardial Damage
Reference: Circ Cardiovasc Imaging. 2018 Jun;11(6):e007848. doi: 10.1161/CIRCIMAGING.118.007848.
Authors: Zeldetz V, Greenberg S, Zeller L, Zahger D, Shalev A


#2 No Effect of Generalized Joint Hypermobility on Injury Risk in Elite Female Soccer Players: Response
Reference: Am J Sports Med. 2018 Jun;46(7):NP28-NP29. doi: 10.1177/0363546518773721.
Authors: Thijs KM, Blokland D, Backx FJG, Goedhart EA, Huisstede BMA.
Download link: http://journals.sagepub.com/doi/pdf/10.1177/0363546518773721


#3 Injuries in formal and informal non-professional soccer - an overview of injury context, causes, and characteristics
Reference: Eur J Sport Sci. 2018 May 29:1-9. doi: 10.1080/17461391.2018.1475507. [Epub ahead of print]
Authors: Gebert A, Gerber M, Puhse U, Gassmann P, Stamm H, Lamprecht M
Summary: The objective of this study is to analyse context, causes, and characteristics of injuries in non-professional soccer. Therefore, a retrospective telephone survey was carried out with persons who were injured while playing soccer and who reported this accident to the Swiss National Accident Insurance Fund (Suva). Based on these data, an analysis of 708 soccer injuries was performed. The findings show that 30.1% of the injuries occurred during informal soccer play, and 75.4% of the injured persons were soccer club members. 53.0% of all injuries were caused by contact and 29.5% by foul play. Foul play was not associated with injury severity. With respect to injury severity, twisting/turning and being tackled by an opponent were identified as the most influental injury causes. Moreover, the risk of being severely injured was particularly high players of the 30+/40+ amateur leagues. In conclusion, the findings highlight that 30+/40+ league players are a major target group for the prevention of severe soccer injuries. Soccer clubs may constitute an appropriate multiplier for implementing prevention strategies such as fair play education, healthy play behaviours, and prevention programmes. Finally, a better understanding of injury situations leading to severe injuries is needed to improve injury prevention.


#4 Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor
Reference: Int J Sports Physiol Perform. 2018 May 29:1-23. doi: 10.1123/ijspp.2018-0131. [Epub ahead of print]
Authors: McHugh MP, Clifford T, Abbott W, Kwiecien SY, Kremenic IJ, DeVita JJ, Howatson G
Summary: The purpose of this study was to assess the utility of an inertial sensor for assessing recovery in professional soccer players. In a randomized, crossover design, 11 professional soccer players wore shorts fitted with phase change material (PCM) cooling packs or uncooled packs (control) for 3 h after a 90 minute match. Countermovement jump (CMJ) performance was assessed simultaneously with an inertial sensor and an optoelectric system, pre match, and 12, 36 and 60 h post match. Inertial sensor metrics were flight height, jump height, low force, countermovement distance, force at low point, rate of eccentric force development, peak propulsive force, maximum power, and peak landing force. The only optoelectric metric was flight height. CMJ decrements, and effect of PCM cooling were assessed with repeated measures ANOVA. Jump heights were also compared between devices. For the inertial sensor data there were decrements in CMJ height on the days after matches (88±10% of baseline at 36 h P=0.012, effect size 1.2, for control condition) and accelerated recovery with PCM cooling (105±15% of baseline at 36 h, P=0.018 vs. control, effect size 1.1). Flight heights were strongly correlated between devices (r=0.905, P<0.001) but inertial sensor values were 1.8±1.8 cm lower (P=0.008). Low force during countermovement was increased (P=0.031) and landing force was decreased (P=0.043) after matches, but neither were affected by the PCM cooling intervention. Other CMJ metrics were unchanged after matches. This small portable inertial sensor provides a practical means of assessing recovery in soccer players.


#5 Neuromechanical response to passive cyclic loading of the ACL in non-professional soccer players: A pilot study
Reference: Phys Ther Sport. 2018 May 15;32:187-193. doi: 10.1016/j.ptsp.2018.05.013. [Epub ahead of print]
Authors: Nuccio S, Labanca L, Rocchi JE, Macaluso A, Sbriccoli P
Summary: The purpose was to investigate the effects of passive cyclic loading (CYC) on anterior tibial translation (ATT), knee extensor and flexor muscle strength and activation in soccer players. Functional Assessment Laboratory; Participants: Eight healthy competitive soccer players. The knee of the dominant limb was subjected to 10 min of CYC at 200 N force. ATT was measured before and after CYC. Percentage of variation was used to estimate ACL creep. Knee extension and flexion maximal voluntary contractions (MVCs) were assessed both before and after CYC. EMG amplitudes of both Biceps Femoris (BF) and Vastus Lateralis (VL) were recorded during both MVCs and CYC. There was a 20.7% increase in ATT after CYC application (p<0.001). Post-CYC agonist and antagonist BF activations were 37.7% and 18.4% lower than pre-CYC ones during MVCs (p<0.05). BF EMG activity in the last 30s of CYC was 19.9% higher than in the first 30s (p<0.05). The increased ATT and the variations in neuromuscular activation of the BF in response to loading may expose the knee at higher injury risk by increasing joint instability. Further studies are required to thoroughly investigate these aspects in both laboratory and real-field settings.


#6 Scheduling of Eccentric Lower-limb Injury Prevention Exercises during the Soccer micro-cycle: Which day of the week?
Reference: Scand J Med Sci Sports. 2018 May 24. doi: 10.1111/sms.13226. [Epub ahead of print]
Authors: Lovell R, Whalan M, Marshall PW, Sampson JA, Siegler JC, Buchheit M
Summary: Scheduling eccentric-based injury prevention programs (IPP) during the common 6-day micro-cycle in Soccer is challenged by recovery and tapering phases. This study profiled muscle damage, neuromuscular performance, and perceptual responses to a lower-limb eccentric-based IPP administered 1 (MD+1) versus 3 days (MD+3) post-match. 18 semi-professional players were monitored daily during 3 in-season 6-day micro-cycles, including weekly competitive fixtures. Capillary creatine kinase concentration (CK), posterior lower limb isometric peak force (PF), counter-movement jump (CMJ) performance, and muscle soreness were assessed 24 h prior to match-day (baseline), and every 24 h up to 120 h post-match. The IPP consisted of lunges, single stiff leg dead-lifts, single leg-squats and Nordic hamstring exercises. Performing the IPP on MD+1 attenuated the decline in CK normally observed following match-play (CON: 142%; MD+3: 166%; small differences). When IPP was delivered on MD+3, CK was higher versus CON and MD+1 trials on both MD+4 (MD+3: 260%; CON: 146%; MD+1: 151%; moderate differences) and MD+5 (MD+3: 209%; CON: 125%; MD+1: 127%; small differences). Soreness ratings were not exacerbated when the IPP was delivered on MD+1, but when prescribed on MD+3, hamstring soreness ratings remained higher on MD+4 and MD+5 (small differences). No between trial differences were observed for PF and CMJ. Administering the IPP in the middle of the micro-cycle (MD+3) increased measures of muscle damage and soreness, which remained elevated on the day prior to the next match (MD+5). Accordingly, IPP should be scheduled early in the micro-cycle, to avoid compromising preparation for the following match.


#7 Hamstring-to-Quadriceps Torque Ratios of Professional Male Soccer Players: A Systematic Review
Reference: J Strength Cond Res. 2018 May 23. doi: 10.1519/JSC.0000000000002609. [Epub ahead of print]
Authors: Baroni BM, Ruas CV, Ribeiro-Alvares JB, Pinto RS
Summary: The goal of this review was to determine the isokinetic hamstring-to-quadriceps (H/Q) torque ratios of professional male soccer players. Systematic searches were independently carried out by 2 researchers in 7 electronic databases. Only studies with teams from the first or second national leagues were included. From these studies, we extracted the players' H/Q conventional (concentric/concentric) and/or functional (eccentric/concentric) ratios. The initial search resulted in 2,128 articles that were filtered to 30 articles (1,727 players) meeting the inclusion criteria. The H/Q conventional ratio was assessed in 27 studies (1,274 players), whereas the H/Q functional ratio was assessed in 15 studies (1,082 players). The H/Q conventional ratio mean scores of professional male soccer players were close to 60% when tested at low to intermediate angular velocities (12°·s = 52 ± 7%; 30°·s = 52 ± 8%; 60°·s = 65 ± 12%; 90°·s = 57 ± 6%; 120°·s = 65 ± 16%; 180°·s = 67 ± 17%) and around 70-80% at fast angular velocities (240°·s = 80 ± 40%; 300°·s = 70 ± 15%; 360°·s = 80 ± 13%). The H/Q functional ratio mean scores of professional male soccer players were close to 80% at 60°·s (79 ± 19%), around 100-130% at intermediate to fast angular velocities (120°·s = 127 ± 42%; 180°·s = 96 ± 19%; 240°·s = 109 ± 22%; 300°·s = 123 ± 18%), and near or above 130% when angular testing velocities were mixed (eccentric hamstring < concentric quadriceps; 30/240°·s = 132 ± 26%; 60/180°·s = 129 ± 20%; 60/240°·s = 153 ± 30%). In conclusion, considering the tested isokinetic angular velocity, professional male soccer players do not meet the traditional reference landmarks used to assess the strength balance between quadriceps and hamstring muscles (i.e., 60 and 100% for H/Q conventional and functional ratios, respectively), which supports a need for specific reference values according to the angular velocity selected for testing H/Q torque ratios.


#8 Acupuncture techniques in professional football
Reference: Unfallchirurg. 2018 Jun;121(6):450-454. doi: 10.1007/s00113-018-0500-0. [Article in German]
Authors: Pfab F, Sommer B, Haser C
Summary: The number of scientific studies about acupuncture has increased significantly during recent years. Acupuncture can be used as an evidence-based adjunct therapy for a variety of indications in professional football. This review summarizes various acupuncture techniques and related techniques for utilization in the field of professional soccer. Besides knee, shoulder, spinal, elbow and postoperative pain, scientific meta-analyses also point towards the effectiveness of acupuncture in ankle sprains, allergic rhinoconjunctivitis and nausea. Dry needling is an emerging option for treatment of myofascial trigger points and could potentially result in improved prevention of muscular injuries and enhancement of muscular performance.


#9 Position specific player load during match-play in a professional football club
Reference: PLoS One. 2018 May 24;13(5):e0198115. doi: 10.1371/journal.pone.0198115. eCollection 2018.
Authors: Baptista I, Johansen D, Seabra A, Pettersen SA
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0198115&type=printable
Summary: There is a rapid growing body of knowledge regarding physical aspects of a football match due to studies using computer-assisted motion analysis. The present study used time-motion analysis and triaxial-accelerometers to obtain new insights about differences in physical profiles of elite football players across playing-positions. Player performance data in 23 official home matches from a professional football club, during two seasons were collected for analysis. Eighteen players from five different playing positions (central backs: n = 3; full-backs: n = 5; central midfielders: n = 6; wide midfielders: n = 3; and central forwards: n = 4), performing a total of 138 observations. A novel finding was that central backs and central midfielders had significantly lower work-rate in sprints, decelerations and accelerations than full-backs, wide midfielders and central forwards (p<0.001). Furthermore, wide midfielders and full-backs performed significantly more turns (>90°) than central backs. The most common distance covered in high-intensity runs (≥19.8 km·h-1) for central backs, central midfielders, wide midfielders and central forwards was 1-5 m, but for full-backs was 6-10 m. This may help coaches in developing individualized training programs to meet the demands of each position in match-play.


#10 Normative Quadriceps and Hamstring Muscle Strength Values for Female, Healthy, Elite Handball and Football Players
Reference: J Strength Cond Res. 2018 May 23. doi: 10.1519/JSC.0000000000002579. [Epub ahead of print]
Authors: Risberg MA, Steffen K, Nilstad A, Myklebust G, Kristianslund E, Moltubakk MM, Krosshaug T
Summary: This study presents normative values for isokinetic knee extension and flexion muscle strength tests in 350 elite, female, handball (n = 150) and football (n = 200) players. Isokinetic concentric muscle strength tests at 60°·sec were recorded bilaterally using a dynamometer. Peak torque (in Newton meter [N·m]), body mass normalized peak torque (N·m·kg), and hamstring to quadriceps ratio (H:Q ratio) for dominant and nondominant legs were recorded. The female elite players were 20.9 ± 4.0 years, started playing at the elite level at the age of 18.2 ± 2.7 years, with a mean of 9.7 ± 2.2 hours of weekly in-season training. Handball players demonstrated greater quadriceps muscle strength compared with football players (11.0%) (p < 0.001), also when normalized to body mass (4.1%) (p = 0.012), but not for weight-adjusted hamstring muscle strength. The H:Q ratio was higher on the dominant compared with the nondominant leg for handball players only (p = 0.012).The H:Q ratio was significantly lower for handball players (0.58) compared with football players (0.60) (p < 0.02). These normative values for isokinetic knee extension and flexion torques of healthy, elite, female handball and football players can be used to set rehabilitation goals for muscle strength after injury and enable comparison with uninjured legs. Significantly greater quadriceps muscle strength was found for handball players compared with football players, also when normalized to body mass.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 WAVE~Ripples for Change Obesity Two-Year Intervention in High School Soccer Players: Process Evaluation, Best Practices, and Youth Engagement
Reference: Nutrients. 2018 Jun 1;10(6). pii: E711. doi: 10.3390/nu10060711.
Authors: Meng Y, Wong SS, Manore MM, Patton-Lopez M
Download link: www.mdpi.com/2072-6643/10/6/711/pdf
Summary: This paper reports the process data on program fidelity, best practices for intervention implementation, youth and coach engagement, and youth application of knowledge and skills for the two-year WAVE~Ripples for Change (WAVE) obesity prevention intervention program focused on healthy eating, physical activity, and life skills with high school (HS) soccer players aged 14⁻19 years. Internal (staff: n = 7; volunteers: n = 27) and external (youth: n = 100; coaches: n = 9) stakeholders were interviewed/ surveyed. Staff rated program fidelity as high (94%), as did volunteers (85%). Best practices included coach encouragement for athlete participation, use of on-line consent for enrollment, building relationships with HS staff to complete assessments, sending text reminders, and providing incentives. Study results showed an enrollment rate of 72%, completion of baseline assessments of 89⁻98%, attendance of sports nutrition lessons in Year 1 and Year 2 of 90% and 39%, respectively, and team-building workshop (TBW) attendance of 25⁻31%. Activities exceeding youth expectations (>90%) included, (1) activities with their soccer team; (2) the TBW-cooking; and (3) sports nutrition lessons. The obesity prevention skills most applied by youth were obtained from the TBW-gardening and harvesting (49%), the TBW-cooking (43%), and sports nutrition lessons (44%). Coaches also rated the sports nutrition lessons highly and reported increased awareness for hydration/fueling during sport by the athletes. Using sport teams/clubs to engage youth in obesity prevention is a feasible model for future study.

Sun

08

Jul

2018

Latest research in football - week 20 - 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 Risk Factors for Groin Injury and Symptoms in Elite Level Soccer Players: A Cohort Study in the Dutch Professional Leagues
Reference: J Orthop Sports Phys Ther. 2018 May 23:1-30. doi: 10.2519/jospt.2018.7990. [Epub ahead of print]
Authors: Langhout R, Tak I, van Beijsterveldt AM, Ricken M, Weir A, Barendrecht M, Kerkhoffs G, Stubbe J
Summary: Groin injury and symptoms are common in soccer players. Their relationship with reduced hip range of motion (ROM) and previous injury is unclear. The purpose was to conduct a retrospective assessment of associations between previous injury and pre-season hip ROM and pre-season prevalence of severe groin symptoms; and prospective identification of risk factors for within-season groin injury. During 2015-2016, 190 players from 9 Dutch professional soccer clubs participated. Univariate and multivariate logistic regression were used to predict pre-season severe groin symptoms, identified using the Copenhagen Hip And Groin Outcome Score, from a history of previous groin injury, general injury (minimum 1 week duration) in previous season, and hip ROM. Cox regression was used to predict within-season groin injury. Point-prevalence of severe groin symptoms was 24% and within-season incidence of groin injury 11%. Total/training/match groin injury incidence was 0.5/0.2/2.6 injuries/1000 playing hours. A history of more than 1 previous groin injury was associated with current severe groin symptoms (Odds Ratio=3.0; 95% CI=1.0, 8.3; P=.038). General injury sustained in the previous season (ankle, knee, thigh, shoulder; median 9 weeks time-loss) was a risk factor for groin injury (Hazard Ratio=5.1; 95% CI=1.1, 14.6; P=.003). Severe injuries in the previous season to locations other than the groin increase the risk of groin injury the next season. A history of groin injury is associated with current severe groin symptoms. Pre-season hip ROM does not identify players at risk for groin injury.


#2 Talent identification for soccer: Physiological aspects
Reference: J Sci Med Sport. 2018 Jan 31. pii: S1440-2440(18)30027-6. doi: 10.1016/j.jsams.2018.01.009. [Epub ahead of print]
Authors: Dodd KD, Newans TJ
Summary: Soccer coaches are always looking to discover the next star player, without investing the necessary resources, time, and effort into a player's development. In the modern era, talent identification in soccer seems to be a comparative process rather than a developmental process. This article will look at the physiological profiles of soccer players in the modern era and how testing and talent identification processes should coincide with this data. An extensive literature search identifying the physiological attributes of soccer players that are required to compete at an elite level was conducted. An examination of the methods to test these attributes was also conducted. Studies were assigned into three areas to understand the physiological aspect of soccer: physiological testing methods, benchmark values, and correlations between different tests. A testing battery was established to test the key physiological attributes of prospective youth soccer players. Benchmark levels were also identified to allow coaches to understand areas of improvement. Using a physiological testing battery will allow teams to track their players' progress throughout their developmental years. This allows coaches to consistently identify a player's strengths and weaknesses, as well as allow players who may experience late maturation to still be identified.


#3 Influence of Team's Rank on Soccer Referees' External and Internal Match Loads During Official Matches
Reference: J Strength Cond Res. 2018 Jun;32(6):1715-1722. doi: 10.1519/JSC.0000000000002040.
Authors: Castillo D, Castagna C, Camara J, Iturricastillo A, Yanci J
Summary: The aim was to examine the external and the internal match loads (ML) of field referees (FRs) attending teams of different ranking during championship matches. Twenty FR who officiated in 30 official soccer matches (30 observations) participated in our study. The criteria for allocating the soccer referees' ML results were based on the teams' final league positions as follows: matches performed by Top 10 teams (TOP10), matches performed by bottom 10 teams (BOT10), and matches played among TOP10 and BOT10 teams (MIXED). External (match activities, accelerations [Acc], and decelerations [Dec]) and internal MLs (Edwards' heart rate [HR]-derived training impulse [TRIMPEDW], HRmean expressed as a percentage of HRpeak [%HRpeak], and differentiated rating of perceived exertion [dRPE]) were recorded. The main results showed that FR, who officiated TOP10 matches, covered more distance at a low walking speed (<3.6 km·h) and performed a higher percentage of high-intensity accelerations and decelerations than those FR who officiated lower ranked teams' matches. Moreover, FR who officiated MIXED matches registered lower values of TRIMPEDW MLs and %HRpeak and declared higher respiratory (sRPEres ML) and muscular (sRPEmus ML) perceived MLs during the second half. Considering those FR who officiate matches between teams of a higher competitive level will need to produce higher match responses, especially regarding the percentage of distance covered at high intensity, accelerations, and decelerations; physical trainers of soccer referees at a high competitive level should implement these high-intensity short-term actions in specific training regimes.


#4 Association of Physical and Technical Activities With Partial Match Status in a Soccer Professional Team
Reference: J Strength Cond Res. 2018 Jun;32(6):1708-1714. doi: 10.1519/JSC.0000000000002033.
Authors: Moalla W, Fessi MS, Makni E, Dellal A, Filetti C, Di Salvo V, Chamari K
Summary: The purpose of this study was to examine the association between physical and technical activities and partial match status (winning, drawing, or losing) in a professional soccer team over 2 seasons. Physical and technical activities of 52 official matches were collected and analyzed at each 15-minute interval, for each half (45 minutes), and full match (90 minutes) using a multiple-camera computerized tracking system. The results indicated that according to full match outcome: winning status was characterized by players covering more total distance (p ≤ 0.05) and low-intensity running (<14.4 km·h) (p ≤ 0.05), whereas, losing status induced more sprinting (≥25.2 km·h) (p < 0.01) and high-intensity running (≥19.8 km·h) (p ≤ 0.05). However, according to partial match status (i.e., 15 minutes and half time), players covered more distance for all running intensities while winning (p < 0.01). Technical match performance scores were not influenced by match status. In conclusion, the present study showed that the physical activities including high-intensity running and total distance covered were related to the match status, whereas technical activities were not. The overall outcome shows that higher physical activity was associated with winning partial match periods. This approach highlights the importance of physical fitness in soccer and may help coaches to better modulate players' roles and team tactical organization throughout the match.


#5 Observation of Women Soccer Players' Physiology During a Single Season
Reference: J Strength Cond Res. 2018 Jun;32(6):1702-1707. doi: 10.1519/JSC.0000000000002025.
Authors: Paulsen KM, Butts CL, McDermott BP
Summary: The purpose of this study was to observe heart rate (HR) responses in match settings over the course of a conference season in National Collegiate Athletic Association Division I women's soccer. Twenty-one female collegiate soccer players were provided a HR monitor and instructed to wear it for the duration of match play. Player positions included 6 defenders (DEF), 6 midfielders (MID), and 9 forwards (FWD). Defenders were further identified as either center defenders (CD) or outside defenders (OD). A 1-way analysis of variance was used to determine if mean HR varied between FWD, MID, and DEF. An independent t-test was used to determine if there was a difference between CD and OD HRs. The FWD, MID, and DEF did have significantly different mean HR (p ≤ 0.05), but post-hoc analysis revealed no significant differences (p ≥ 0.05). However, CD demonstrated significantly lower HRs than OD (p = 0.009). Player position, specifically in the CD and OD role, impact the intensity of exercise in match settings and may be used to specify training and conditioning sessions.


#6 Alpha-Actinin-3 R577X Polymorphism Influences Muscle Damage and Hormonal Responses After a Soccer Game
Reference: J Strength Cond Res. 2018 May 17. doi: 10.1519/JSC.0000000000002575. [Epub ahead of print]
Authors: Coelho DB, Pimenta EM, Rosse IC, Veneroso C, Pussieldi GA, Becker LK, Oliveira EC, Carvalho MRS, Silami-Garcia E
Summary: Alpha-actinin-3 R577X polymorphism influences muscle damage and hormonal responses after a soccer game. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this study was to evaluate indicators of muscle damage and hormonal responses after soccer matches and its relation to alpha-actinin-3 (ACTN3) gene expression (XX vs. RR/RX), considering that the R allele produces alpha-actinin-3 and provides greater muscle strength and power. Thirty players (10 XX and 20 RR/RX) younger than 16 years were evaluated in this study. Blood samples were collected immediately before, after, 2, and 4 hours after the games to assess muscle damage (creatine kinase [CK] and alpha-actin) and hormonal responses (interleukin-6 [IL-6], cortisol, and testosterone). Postgame CK was higher as compared to the pregame values in both groups and it was also higher in the RR/RX (p < 0.05) than in the XX. The concentrations of alpha-actin and IL-6 were similar for both groups and did not change over time. Testosterone was increased after the game only in the RR/RX group (p < 0.05). Cortisol concentrations in group RR/RX were higher immediately after the game than before the game, and 2 and 4 hours after the game the concentration decreased (p < 0.05). The RR and RX individuals presented higher markers of muscle microtrauma and hormonal stress, probably because they performed more speed and power actions during the game, which is a self-regulated activity. From the different responses presented by RR/RX and XX genotypes, we conclude that the genotypic profile should be taken into account when planning training workloads and recovery of athletes.


#7 Psychosocial predictors and psychological prevention of soccer injuries: A systematic review and meta-analysis of the literature
Reference: Phys Ther Sport. 2018 May 15. pii: S1466-853X(17)30491-1. doi: 10.1016/j.ptsp.2018.05.006. [Epub ahead of print]
Authors: Slimani M, Bragazzi NL, Znazen H, Paravlic A, Azaiez F, Tod D
Summary: The purpose was To examine (a) the relationships between the psychosocial risk factors and injury rates and (b) the effects of psychological-based prevention interventions on the injury risk of soccer players. Scholarly electronic databases (PubMed/MEDLINE, Google Scholar, Scopus) were searched on 1 January 2017, complemented by manual searches of bibliographies. We identified 13 eligible studies, including a total of 1149 injured soccer players aged between 14 and 36 years. Psychosocial risk factors, psychological-based prevention interventions and injury risk in soccer players were set as main outcome measures. Personality traits, such as trait anxiety and perceived mastery climate, along with a history of stressors, like negative-life-event stress or high level of life stress, daily hassle, and previous injury, are the main predictors of injury rates among soccer players. Also, from injury prevention studies, it has been shown that psychological-based interventions reduce injury rates (effect size = 0.96; 95% CI 0.34-1.58; p = 0.002) in senior soccer players. Practitioners need to ensure injured soccer players are psychologically and socially ready to play. They should also employ psychological-based interventions (i.e., mindfulness, imagery, self-talk, stress management, relaxation, goal setting) when designing injury prevention programs.


#8 A review advocating caution with Major League Soccer expansion and investment in more rehabilitation professionals
Reference: Phys Ther Sport. 2018 May 9. pii: S1466-853X(18)30010-5. doi: 10.1016/j.ptsp.2018.05.008. [Epub ahead of print]
Authors: Mansfield CJ, Ferkovic-Mack C, Eibensteiner J, Zwolski C
Summary: Major League Soccer (MLS) has aggressively expanded from 10 teams to 23 teams. With the addition of more teams, the league will have to dictate a schedule that maximizes the league's popularity, while also maintaining the health of the players. A longer season and congested game schedule could increase the risk of injury for players. The purpose of this commentary is to make recommendations for the prevention of injuries among MLS players with respect to proposed league expansion. MLS has lengthened the regular season with each expansion in teams. An increase in season length was seen in conjunction with the MLS expansion from 14 to 19 teams during the 2008 through 2013 seasons. Data from the inaugural MLS season found injury rates were higher in games compared to practices and more injuries occurred later in the season. With the expansion of MLS, anterior cruciate ligament tears appeared to have increased each year. Current evidence suggests the implementation of a proper preseason in addition to the once-per-week game frequency would best promote player health and well-being. Players may benefit from in-season injury prevention training and weekly load monitoring.


#9 Strength recovery after anterior cruciate ligament reconstruction with quadriceps tendon versus hamstring tendon autografts in soccer players: A randomized controlled trial
Reference: Knee. 2018 May 15. pii: S0968-0160(18)30123-6. doi: 10.1016/j.knee.2018.03.011. [Epub ahead of print]
Authors: Martin-Alguacil JL, Arroyo-Morales M, Martin-Gomez JL, Monje-Cabrera IM, Abellan-Guillen JF, Esparza-Ros F, Lozano ML, Cantarero-Villanueva I
Summary: The comparison between HT and QT grafts in strength recovery and function after an ACLR is scarce in the literature. A total of 56 participants were enrolled in this randomized controlled trial and placed into two groups: HT or QT. The hamstring/quadriceps (H/Q) ratio was the primary end-point measured with a Genu-3 dynamometer. Peak torque, functional assessment (Lysholm knee scoring scale and Cincinnati Knee Rating System), and anteroposterior laxity (KT-2000™ arthrometer) were also assessed. An intention-to-treat analysis was performed. The results of the H/Q ratio analysis of the participants over time revealed significant differences at 60, 180, and 300°/s at three, six, and 12months of follow-up (60°/s: F=5.3, p=0.005; 180°/s: F=5.5, p=0.004; 300°/s: F=5.1, p=0.005). Furthermore, they revealed significant differences at 60°/s, 180°/s, and 300°/s in the participants over time for peak torque in the extensor muscle strength at three and six months of follow-up, with higher values in the hamstring tendon group but not at 12months of follow-up. There were no significant differences in functional endpoints or arthrometer assessments at 24months of follow-up. An ACLR with a QT graft showed similar functional results with a better isokinetic H/Q ratio compared to an ACLR with the HT at 12months of follow-up in soccer players. This higher H/Q ratio observed with the QT could be an advantage of this graft over the HT for an ACLR.


#10 No association between rate of torque development and onset of muscle activity with increased risk of hamstring injury in elite football
Reference: Scand J Med Sci Sports. 2018 May 23. doi: 10.1111/sms.13224. [Epub ahead of print]
Authors: van Dyk N, Bahr R, Burnett AF, Verhagen E, von Tiggelen D, Witvrouw E
Summary: Hamstring injuries remain a significant burden in sports that involve high speed running. In elite male football, hamstring injury has repeatedly been identified as the most common noncontact injury, representing 12% of all injuries. As the incidence remains high, investigations are aimed at better understanding how to improve prevention efforts. Intrinsic risk factors such as strength have been investigated extensively in a cohort of professional football players; however, other intrinsic measures of neuromuscular function have not been studied in this cohort. This study aims to investigate the association between timing of hamstring muscle activity onset and the rate of torque development during the early phase of isokinetic strength testing with risk of hamstring injury in professional football players in a prospective cohort study. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included rate of torque development and timing of muscle activity onset. A total of 367 unique players (60.6% of all QSL players) competed for 514 player seasons (103 players competed both seasons) and sustained 65 hamstring injuries. There was no difference in the onset of muscle activity between the biceps femoris and medial hamstrings comparing the injured to uninjured players. For both onset of muscle activity and rate of torque development, there were no significant differences between any of the variables (p>0.05), with small effect sizes detected across all the different variables (d<0.3). Rate of torque development and onset of muscle activity were not associated with a risk of future hamstring injury. The use of these measures as part of a periodic health evaluation to identify risk of hamstring injury is unsupported.


#11 A History of Anterior Cruciate Ligament Reconstruction at the National Football League Combine Results in Inferior Early National Football League Career Participation
Reference: Arthroscopy. 2018 May 19. pii: S0749-8063(18)30238-X. doi: 10.1016/j.arthro.2018.03.018. [Epub ahead of print]
Authors: Provencher MT, Bradley JP, Chahla J, Sanchez A, Beaulieu-Jones BR, Arner JW, Kennedy NI, Sanchez G, Kennedy MI, Moatshe G, Cinque ME, LaPrade RF
Summary: The purpose was to evaluate whether players with a history of an anterior cruciate ligament reconstruction (ACLR) before the National Football League (NFL) Combine played or started fewer games and/or participated in fewer eligible snaps compared with NFL Combine participants without a history of knee injury or surgery. We performed a retrospective review of all players who participated in the NFL Combine between 2009 and 2015 and who had a history of an ACLR. NFL Combine participants were included if they had a previous ACLR or combined anterior cruciate ligament (ACL) injury and nonoperatively managed medial collateral ligament injury. The number of games started, number of games played, draft number, overall draft pick, and snap percentage for each position were determined. The mean value of each outcome metric was compared between case and control players. We identified 110 players who had an ACL injury (n = 76) or a combined ACL and medial collateral ligament injury (n = 34). Players in the ACLR group had a significantly worse mean draft pick number (difference of 30.2, P = .002) and mean draft round (difference of 0.8, P = .019) versus controls. Compared with control players, players in the ACLR group started and played significantly fewer games in both season 1 (difference of 2.7 games started, P < .001; difference of 2.7 games played, P < .001) and season 2 (difference of 7.4 games started, P < .001; difference of 3.0 games played, P = .003) and had a significantly lower snap percentage in both season 1 (difference of 23.1%, P < .001) and season 2 (difference of 24.0%, P < .001). Athletes at the NFL Combine who previously underwent an ACLR had significantly lower early-career NFL player metrics, including fewer games started, fewer games played, and a lower snap percentage, than uninjured controls. Defensive linemen, defensive backs, and linebackers were the 3 most affected positions. Players with a prior ACLR and combined meniscal-chondral pathology had significantly lower numbers of games started and games played in seasons 1 and 2 and a significantly lower season 2 snap percentage.


#12 Strategies to improve impact efficiency in football kicking
Reference: Sports Biomech. 2018 May 22:1-14. doi: 10.1080/14763141.2018.1452970. [Epub ahead of print]
Authors: Peacock JCA, Ball K
Summary: In football, kicking with high ball velocity can increase scoring opportunities and reduce the likelihood of interception. Efficient energy transfer from foot to ball during impact is important to attain a high ball velocity. It is considered impact efficiency can be increased by reducing the change in ankle plantarflexion during foot-ball impact. However, conflicting evidence exists, questioning its effectiveness as a coaching cue. The aim of the present study was to systematically analyse joint stiffness, foot velocity and impact location with a mechanical kicking machine to determine if change in ankle plantarflexion during foot-ball impact and ball velocity are influenced. Sagittal plane data of the shank, foot and ball were measured using high-speed video (4,000 Hz). Increasing joint stiffness reduced change in ankle plantarflexion and increased ball velocity from a greater effective mass. Increasing foot velocity increased change in ankle plantarflexion and increased ball velocity. Distal impact locations increased change in ankle plantarflexion and reduced ball velocity as coefficient of restitution decreased. These results identify that change in ankle plantarflexion is a dependent variable during foot-ball impact and does not directly influence ball velocity. Coaches can assess ankle motion during impact to provide feedback to athletes on their impact efficiency.

Sat

30

Jun

2018

Latest research in football - week 19 - 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 geometry in young male and female football players: a peripheral quantitative computed tomography (pQCT) study
Reference: Arch Osteoporos. 2018 May 8;13(1):57. doi: 10.1007/s11657-018-0472-2.
Authors: Lozano-Berges G, Matute-Llorente ÁA, Gomez-Bruton A, Gonzalez-Aguero A, Vicente-Rodriguez G, Casajus JA
Summary: The present study shows that football practice during growth may improve bone geometry in male and female football players. However, only females had better bone strength in comparison with controls. The aim of this study was to compare bone geometry in adolescent football players and controls. A total of 107 football players (71 males/36 females; mean age 12.7 ± 0.6/12.7 ± 0.6 years) and 42 controls (20 males/22 females; mean age 13.1 ± 1.4/12.7 ± 1.3 years) participated in this study. Total and trabecular volumetric bone mineral content (Tt.BMC/Tb.BMC), cross-sectional area (Tt.Ar/Tb.Ar), and bone strength index (BSI) were measured at 4% site of the non-dominant tibia by peripheral quantitative computed tomography (pQCT). Moreover, Tt.BMC, cortical BMC (Ct.BMC), Tt.Ar, cortical Ar (Ct.Ar), cortical thickness (Ct.Th), periosteal circumference (PC), endosteal circumference (EC), fracture load in X-axis, and polar strength strain index (SSIp) were measured at 38% site of the tibia. Multivariate analyses of covariance were used to compare bone pQCT variables between football players and controls using the tibia length and maturity offset as covariates. Female football players demonstrated 13.8-16.4% higher BSI, Ct.Th, fracture load in X-axis, and SSIp than controls (p < .0036). Males showed no significant differences in bone strength when compared to controls (p > .0036). In relation to bone mineral content and area, male football players showed 8.8% higher Tt.Ar and Tb.Ar at the 4% site of the tibia when compared to controls; whereas 13.8-15.8% higher Tt.BMC, Ct.BMC, and Ct.Ar at the 38% site of the tibia were found in female football players than controls (p < .0036). In this study, female adolescent football players presented better bone geometry and strength values than controls. In contrast, only bone geometry was higher in male football players than controls.


#2 Physical preparation of the football player with an intramuscular hamstring tendon tear: clinical perspective with video demonstrations
Reference: Br J Sports Med. 2018 May 3. pii: bjsports-2017-098817. doi: 10.1136/bjsports-2017-098817. [Epub ahead of print]
Authors: Taberner M, Cohen DD
Download link: http://bjsm.bmj.com/content/bjsports/early/2018/05/02/bjsports-2017-098817.full.pdf



#3 "What is the score?" A review of football-based public mental health interventions
Reference: J Public Ment Health. 2017;16(4):144-158. doi: 10.1108/JPMH-03-2017-0011. Epub 2017 Dec 18.
Authors: Friedrich B, Mason OJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868541/pdf/jpublicmenthealth-16-0144.pdf
Summary: Football exercise as an intervention for people with severe mental health problems has seen an increasing interest in the past years. To date, there is, however, no comprehensive review of the empirical evidence regarding the effectiveness of these interventions. In this review, the authors have comprised the research findings from the peer-review literature as well as the theoretical approaches to football exercise as an adjunct treatment. This overview will be informative to everybody who is planning to develop a football intervention for this population as well as to the people who are preparing evaluation studies that measure the effectiveness of such interventions. The paper aims to discuss these issues. The authors identified research papers in the peer-review literature that feature empirical findings on "football interventions" that aim at improving mental and/or physical well-being in participants with mental health problems. The authors are using the term "football intervention" here in the sense that the participants actively took part in football exercise, so the authors excluded studies in which the participants only watched football or used football as a metaphor to discuss mental health problems. In a table, the authors indicate the definition of the target group, targeted outcomes, measured outcomes, form and frequency of the intervention as well as the research method(s). The authors identified 16 studies on 15 projects. The majority of studies were qualitative and had positive findings in which the participants reported increased well-being and connectedness, elevation of symptoms and improved physical well-being. The outcomes of the quantitative studies, however, were mixed with some results suggesting that not all intended goals were achieved. There seems to be a need for more quantitative studies to triangulate the qualitative findings. Interestingly, most interventions take place in the UK. Many studies fail to give detailed methodological information and often the aims of the interventions are vague or not stated at all. Due to the heterogeneity of the studies and relative scarcity of evaluation projects on football interventions for people with mental health problems, the authors could not conduct an in-depth systematic review. Furthermore, the information on methods was often unsatisfying and despite efforts to get more detailed input from the authors of cited papers, those gaps could not always be filled. Instead of coming up with a crystal-clear summary of whether and how football interventions work for everybody, topics were identified that need to be addressed in the planning of interventions, in evaluation studies, in implementation efforts and in the theoretical discourse. This paper constitutes a helpful overview for everybody who is interested in the theoretical background of football interventions for people with mental health problems, for people who are planning to develop respective interventions, for researchers who engage in evaluation projects that look into the effectiveness of football interventions (or similar exercise interventions) as well as for the people who are interested in how football interventions can be implemented. This paper is likely to make a contribution to the advancement of alternative exercise interventions that aim at improving mental, physical and social health in people with mental health problems. This paper will help putting the topic of football interventions (and similar, alternative exercise interventions) further up on the public health agenda by providing an overview of the empirical evidence at hand and by specifying advantages of the approach as well as pointing out actions that need to be taken to make football a recognised, evidence based and viable option for adjunct mental health treatment that is attractive to potential participants as well as funders as well as to the potential participants. There is no comprehensive summary to date that provides a (reasonably) systematic overview of empirical findings for football interventions for people with MH problems. Furthermore, the literature on the theoretical background of these interventions has been somewhat patchy and heterogonous. This paper aims at filling both these gaps and identifies the issues that need to be covered in the planning of respective interventions and evaluations. This paper will be useful to everybody who is developing football interventions (or similar alternative adjunct exercise interventions), who is conducting evaluation research in this area and who is interested in the implementation of football interventions.


#4 The effects of short term detraining and retraining on physical fitness in elite soccer players
Reference: PLoS One. 2018 May 10;13(5):e0196212. doi: 10.1371/journal.pone.0196212. eCollection 2018.
Authors: Joo CH
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196212&type=printable
Summary: The aim of this study was to examine the effects of aerobic high-intensity training with reduced volume and training cessation on body composition and physical fitness after the end of season and the time required to recapture physical fitness with intensified retraining following two weeks of detraining in elite soccer players. Twenty male semi-professional soccer players participated in this study. The soccer players were assigned to either a group that completed high-intensity aerobic training (HAT, n = 10) or to a detraining and retraining group (DHAT, n = 10) for a 5-week period immediately after the end of the season. The first 2 weeks of the period, members of the HAT group performed high-intensity aerobic exercise (80-90% of HRmax, 12 min × 3, three times per week), whereas members of the DHAT group abstained from any physical activity. During the subsequent 3 weeks, members of both the HAT and DHAT groups completed high-intensity aerobic exercise. Exercise performance testing and body composition analysis were performed before; after 2 weeks of detraining; and at 1, 2 and 3 weeks of retraining. Intensified high-intensity training for 5 weeks maintained the performance in the Yo-Yo Intermittent Recovery level 2 test (Yo-Yo IR2) and repeated sprints at any time point (P > 0.05). However 2 weeks of detraining resulted in significant decreases in the performance on the Yo-Yo IR2 (P < 0.01) and repeated sprints test (P < 0.05). Performance on the Yo-Yo IR2 enhanced after 2 weeks of retraining and was maintained up to 3 weeks after retraining, with no significant differences between conditions (P > 0.05). In addition, repeated sprint performance markedly decreased after the detraining period (P < 0.05) and was continuously lower compared to the baseline at 2 weeks after retraining (P < 0.05). Furthermore, this value reached baseline level at the end of the experimental period (P > 0.05). There were no significant differences between conditions in body composition, performance of agility, or sprint ability throughout the 5-week experimental period (P > 0.05). The present data suggest that short-term detraining after the competitive season can markedly decrease performances in the Yo-Yo IR2 test and repeated sprints. To return to a previous level of ability on the Yo-Yo IR2 and/or sprint test with retraining through high-intensity aerobic training after a period of detraining, a similar or longer period of retraining is required. However, the high-intensity training with reduced amount of training after competitive season can prevent reductions in physical fitness.


#5 Angle-Specific Isokinetic Metrics Highlight Strength Training Needs of Elite Youth Soccer Players
Reference: J Strength Cond Res. 2018 May 2. doi: 10.1519/JSC.0000000000002612. [Epub ahead of print]
Authors: Eustace SJ, Page RM, Greig M
Summary: The purpose of this study was to assess traditional and angle-specific isokinetic strength of eccentric knee flexors (eccKFs) and concentric knee extensors (conKEs) between senior professional and youth soccer players. Thirty-four male soccer players (17 senior and 17 youth) were recruited for bilateral assessments at 180, 270, and 60°·s. Peak torque (PT), dynamic control ratio (DCR), angle of peak torque (APT), functional range (FR), angle-specific torque (AST), and angle-specific DCR (DCRAST) were compared. The eccentric knee flexor (eccKF) and conKE PT (p = 0.782) and DCR (p = 0.508) were not different between groups across all angular velocities. Significant differences were identified for eccKF APT (p = 0.018) and FR (p = 0.006), DCRAST at 270°·s (p = 0.031), and in AST data recorded across angular velocities for eccKF and conKE (p = 0.003). Traditional strength measures were not sensitive to playing age, with implications for misinterpretation in training prescription. By contrast, AST data did differentiate between ages. Strength deficits that highlight the muscle contraction type, angular velocity, and joint angle can be manipulated within an individualized training intervention. Given the relevance to injury etiology, this study highlights potential implications for improved assessment strategies to inform training prescription for performance and injury prevention. Given the high number of injuries in adolescent soccer players, and in line with previous recommendations, practitioners should consider using more informed and specific strength and conditioning practices at younger ages.


#6 Dose-Response Relationship between Training Load and Changes in Aerobic Fitness in Professional Youth Soccer Players
Reference: Int J Sports Physiol Perform. 2018 May 10:1-22. doi: 10.1123/ijspp.2017-0843. [Epub ahead of print]
Authors: Fitzpatrick JF, Hicks KM, Hayes PR
Summary: The aim of this study was to compare the dose-response relationship between, traditional arbitrary speed thresholds versus an individualised approach, with changes in aerobic fitness in professional youth soccer players. Fourteen youth soccer players, completed a 1500 metre time trial to estimate maximal aerobic speed (km.h-1, (MAS)) at the start and the end of a six week period. Training load was monitored on a daily basis during this study. External load measures were; total distance covered (TD), total acceleration and deceleration distance > 2m.s-2 (A/D Load). Arbitrary high speed running measures were; metres covered and time spent > 17 km.h-1 (m>HSD, t>HSD) and 21 km.h-1 (m>VHSD, t>VHSD). Individualised high speed running measures were; metres covered and time spent > MAS km.h-1 (m>MAS, t>MAS) and 30% anaerobic speed reserve (m>30ASR, t>30ASR). In addition, internal load measures were also collected; heart rate exertion (HRE) and rating of perceived exertion (RPE). Linear regression analysis was used to establish the dose-response relationship between mean weekly training load and changes in aerobic fitness. Substantial very large associations were found between t>MAS and changes in aerobic fitness (R2 = 0.59). Substantial large associations were found for t>30ASR (R2 = 0.38) and m>MAS (R2 = 0.25). Unsubstantial associations were found for all other variables. An individualised approach to monitoring training load, in particular t>MAS, may be a more appropriate method than using traditional arbitrary speed thresholds when monitoring the dose-response relationship between training load and changes in aerobic fitness.


#7 Monitoring of Post-match Fatigue in Professional Soccer: Welcome to the Real World
Reference: Sports Med. 2018 May 8. doi: 10.1007/s40279-018-0935-z. [Epub ahead of print]
Authors: Carling C, Lacome M, McCall A, Dupont G, Le Gall F, Simpson B, Buchheit M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0935-z.pdf
Summary: Participation in soccer match-play leads to acute and transient subjective, biochemical, metabolic and physical disturbances in players over subsequent hours and days. Inadequate time for rest and regeneration between matches can expose players to the risk of training and competing whilst not entirely recovered. In professional soccer, contemporary competitive schedules can require teams to compete in excess of 60 matches over the course of the season with periods of fixture congestion occurring, prompting much attention from researchers and practitioners to the monitoring of fatigue and readiness to play. A comprehensive body of research has investigated post-match acute and residual fatigue responses. Yet the relevance of the research for professional soccer contexts is debatable, notably in relation to the study populations and designs employed. Monitoring can indeed be invasive, expensive, time inefficient, and difficult to perform routinely and simultaneously in a large squad of regularly competing players. Uncertainty also exists regarding the meaningfulness and interpretation of changes in fatigue response values and their functional relevance, and practical applicability in the field. The real-world need and cost-benefit of monitoring must be carefully weighed up. In relation to professional soccer contexts, this opinion paper intends to (1) debate the need for post-match fatigue monitoring; (2) critique the real-world relevance of the current research literature; (3) discuss the practical burden relating to measurement tools and protocols, and the collection, interpretation and application of data in the field; and (4) propose future research perspectives.


#8 Comparison of technical and physical activities between 8 vs. 8 and 11 vs. 11 games in young Korean soccer players
Reference: J Exerc Rehabil. 2018 Apr 26;14(2):253-258. doi: 10.12965/jer.1836034.017. eCollection 2018 Apr.
Authors: Oh SH, Joo CH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931162/pdf/jer-14-2-253.pdf
Summary: The aims of this study were to examine the differences in technical aspects and physical demands between small-size games (SSG; 8 vs. 8) and regular-size games (RSG; 11 vs. 11) in young Korean soccer players. Seventy-nine young soccer players from 6 teams (U-12) volunteered to participate in the study. The players completed 4 games (2 SSG, 62×51 m, and 2 RSG, 80×54 m) in 2 days. Each game was filmed to evaluate technical actions. Physical demand variables were measured using global positioning system technology. SSG showed significantly greater numbers of technical plays among 17 variables when compared to RSG (P<0.05). The players covered significantly greater total distance during low-, moderate-, and high-speed running and sprinting in SSG than in RSG (P<0.05). Higher numbers of high-intensity activities (repeated high-intensity efforts, explosive efforts, decelera-tions, accelerations, and sprinting) were observed in SSG compared to RSG (P<0.05). Mean heart rate was also higher in SSG than in RSG (P<0.05). Despite the greater physical demands during SSG, the exercise intensity was similar to that reported in previous studies. Therefore, the SSG format applied in the present study can be a suitable official game format for Korean young soccer players, resulting in significantly greater exposure to technical plays without excessive physical demands.


#9 Hamstring and Ankle Flexibility Deficits Are Weak Risk Factors for Hamstring Injury in Professional Soccer Players: A Prospective Cohort Study of 438 Players Including 78 Injuries
Reference: Am J Sports Med. 2018 May 1:363546518773057. doi: 10.1177/0363546518773057. [Epub ahead of print]
Authors: van Dyk N, Farooq A, Bahr R, Witvrouw E
Summary: Hamstring injuries remain a significant injury burden in sports such as soccer that involve high-speed running. It has repeatedly been identified as the most common noncontact injury in elite male soccer, representing 12% of all injuries. As the incidence of hamstring injuries remains high, investigations are aimed at better understanding how to prevent hamstring injuries. Stretching to improve flexibility is commonly used in elite-level sports, but risk factor studies have reported contradicting results, leading to unclear conclusions regarding flexibility as a risk factor for hamstring injuries. The purpose was to investigate the association of lower limb flexibility with the risk of hamstring injuries in professional soccer players. All teams (n = 18) eligible to compete in the premier soccer league in Qatar (Qatar Stars League [QSL]) underwent a comprehensive musculoskeletal assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included passive knee extension and ankle dorsiflexion range of motion. A clustered multivariate Cox regression analysis was used to identify associations with the risk of hamstring injuries. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity. A total of 438 unique players (72.4% of all QSL players) competed for 601 player-seasons (148 players competed both seasons) and sustained 78 hamstring injuries. Passive knee extension range of motion (hazard ratio [HR], 0.97 [95% CI, 0.95-0.99]; P = .008) and ankle dorsiflexion range of motion (HR, 0.93 [95% CI, 0.88-0.99]; P = .02) were independently associated with the injury risk. The absolute differences between the injured and uninjured players were 1.8° and 1.4 cm, respectively, with small effect sizes ( d < 0.2). The ROC curve analyses showed an area under the curve of 0.52 for passive knee extension and 0.61 for ankle dorsiflexion, indicating failed to poor combined sensitivity and specificity of the 2 strength variables identified in the multivariate Cox regression analysis. This study identified deficits in passive hamstring and ankle dorsiflexion range of motion as weak risk factors for a hamstring injury. These findings have little clinical value in predicting the risk of future hamstring injuries, and test results must therefore be interpreted cautiously in athletic screening.


#10 Maturity Status Strongly Influences the Relative Age Effect in International Elite Under-9 Soccer
Reference: J Sports Sci Med. 2018 May 14;17(2):216-222. eCollection 2018 Jun.
Authors: Muller L, Gehmaier J, Gonaus C, Raschner C, Muller E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950738/pdf/jssm-17-216.pdf
Summary: The aim of the study was to assess the role of the relative age effect (RAE) and to investigate the influence of the biological maturity status on the RAE in international under-9 soccer. The birth dates of 222 male participants of the U9 Eurochampionship Soccer Tournament in Vienna in 2016 were analyzed and divided into four relative age quarters (Q1-Q4) and the biological maturity status was assessed with the age at peak height velocity (APHV) method. Based on the mean±standard deviation of the APHV, the athletes were divided into three groups of maturity: early, normal and late maturing. Chi-Square-tests were used to assess the difference between the observed and the expected even relative age quarter distribution and to evaluate the difference between the observed distribution of early, normal and late maturing athletes and the expected normal distribution. A univariate analysis of variance was performed to assess differences in the APHV between the relative age quarters. A RAE was present (χ2 = 23.87; p < 0.001; ω = 0.33). A significant difference was found in APHV between the four relative age quarters (F = 9.906; p < 0.001); relatively older athletes were significantly less mature. A significant difference was found between the distribution of early, normal and late maturing athletes and the expected normal distribution for athletes of Q1 (high percentage of late maturing athletes: 27%; χ2 = 17.69; p < 0.001; ω = 0.46) and of Q4 (high percentage of early maturing soccer players: 31%; χ2 = 12.08; p = 0.002; ω = 0.58). These findings demonstrated that the selection process in international soccer, with athletes younger than 9 years, seems to be associated with the biological maturity status and the relative age. Relatively younger soccer players seem to have a better chance for selection for international tournaments, if they enter puberty at an earlier age, whereas relatively older athletes seem to have an increased likelihood for selection independent of their biological maturity status.


#11 Relation Between Iliopsoas Cross-sectional Area and Kicked Ball Speed in Soccer Players
Reference: Int J Sports Med. 2018 May 14. doi: 10.1055/a-0592-7370. [Epub ahead of print]
Authors: Wakahara T, Chiba M
Summary: This study aimed to investigate the relationship between the maximal anatomical cross-sectional area (ACSA) of the iliopsoas muscle and ball speed in side-foot and instep kicks. The ACSA of the psoas major and iliacus was measured in 29 male collegiate soccer players by using magnetic resonance imaging. They performed maximal side-foot and instep kicks to a stationary ball. The kicked ball speed was measured with a high-speed camera. Ball speed in the side-foot and instep kicks was significantly correlated with body height (side-foot kick: r=0.650, P<0.001; instep kick: r=0.583, P<0.001). After adjustment for body height, the maximal ACSA of the psoas major was significantly correlated with ball speed in the side-foot kick (r=0.441, P=0.017), but not in the instep kick. The maximal ACSA of the iliacus was not correlated with ball speed in side-foot or instep kicks, even after adjustment for body height. Our results suggest that: 1) body height is a significant determinant of the ball speed in side-foot and instep kicks, and 2) for a given body height, the maximal ACSA of the dominant psoas major is a factor that affects the ball speed in side-foot kick.

Wed

20

Jun

2018

Latest research in football - week 18 - 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 Effects of a lighter, smaller football on acute match injuries in adolescent female football: a pilot cluster-randomized controlled trial
Reference: J Sports Med Phys Fitness. 2018 May;58(5):644-650. doi: 10.23736/S0022-4707.17.07903-8.
Authors: Zebis MK, Thorborg K, Andersen LL, Moller M, Christensen KB, Clausen MB, Holmich P, Wedderkopp N, Andersen TB, Krustrup P
Summary: The high injury incidence during match-play in female adolescent football is a major concern. In football, males and females play matches with the same football size. No studies have investigated the effect of football size on injury incidence in female adolescent football. Thus, the aim of the present study was to investigate the effects of introducing a lighter, smaller football on the injury pattern in female adolescent football. We conducted a pilot cluster randomized controlled trial including 26 football teams representing 346 adolescent female football players (age 15-18 years). The teams were randomized to a new lighter, smaller football (INT, N.=12 teams) or a traditional FIFA size 5 football (CON, N.=14 teams) during a full match-season. Acute time-loss injuries and football-exposure during match-play were reported weekly by text-message questions and verified subsequently by telephone interview. In total, 46 acute time-loss injuries were registered (5 severe injuries), yielding an incidence rate of 15.2 injuries per 1000 hours of match-play (95% CI: 8.5-27.2) in INT and 18.6 injuries per 1000 hours of match-play (95% CI: 14.0-24.8) in CON. The estimated 22% greater injury incidence rate risk (IRR: 1.22 [95% CI: 0.64-2.35]) in the CON group was not significant. With an IRR of 1.22, a future RCT main study would need to observe 793 acute time-loss injuries during match-play, in order to have a power of 80%. A large-scaled RCT is required to definitively test for beneficial or harmful effects of a lighter, smaller football in adolescent female football.


#2 Football training improves metabolic and cardiovascular health status in 55- to 70-year-old women and men with prediabetes
Reference: Scand J Med Sci Sports. 2018 May 2. doi: 10.1111/sms.13081. [Epub ahead of print]
Authors: Skoradal MB, Weihe P, Patursson P, Mortensen J, Connolly L, Krustrup P, Mohr M
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13081
Summary: We examined the effects of 16 weeks of football training and dietary advice on blood glucose control and health status in 55- to 70-year-old women and men with prediabetes. Fifty participants with prediabetes (age; 61 ± 6 years, BMI; 29.6 ± 4.7; VO2max 22.3 ± 5.7 mL·min-1 ·kg-1 ) were randomized into a football and dietary advice group (F+D; n = 27) and a dietary advice group (D; n = 23). F+D performed football training (twice weekly 30- to 60-minutes sessions) and received dietary advice, while D only received dietary advice. An oral glucose tolerance test (OGTT) was completed pre and post the 16-week period. Body composition, blood pressure, and maximal oxygen uptake (VO2max ) were additionally measured. Both groups demonstrated a decrement (P < .05) in fasting blood glucose (-0.4 ± 0.5 mmol·L-1 ) and lowered blood glucose throughout OGTT. F+D displayed lower values than D (P < .05) after 60 minutes (9.0 ± 2.7 vs 10.6 ± 2.9 mmol·L-1 ) and 120 minutes (5.7 ± 1.6 vs 7.5 ± 2.4 mmol·L-1 ). VO2max increased by 14% in F+D, with a higher (P < .05) change score than in D (2%). Mean arterial pressure declined more (P < .05) in F+D than in D (-8 ± 9 vs -4 ± 11 mm Hg). Fat loss was greater (P < .05) in F+D than in D (-3.4 ± 2.8 vs -1.2 ± 2.0 kg), and the increase in lean body mass was also greater (P < .05) in F+D than in D (0.7 ± 1.5 vs -0.3 ± 1.6 kg). In conclusion, football training combined with dietary advice has broad-spectrum effects on metabolic and cardiovascular health profile with greater overall effects than professional dietary advice per se for 55- to 70-year-old women and men with prediabetes.


#3 Longitudinal motor performance development in early adolescence and its relationship to adult success: An 8-year prospective study of highly talented soccer players
Reference: PLoS One. 2018 May 3;13(5):e0196324. doi: 10.1371/journal.pone.0196324. eCollection 2018.
Authors: Leyhr D, Kelava A, Raabe J, Honer O
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196324&type=printable
Summary: Several talent identification and development (TID) programs in soccer have implemented diagnostics to measure players' motor performance. Yet, there is a lack of research investigating the relationship between motor development in adolescence and future, adult performance. This longitudinal study analyzed the three-year development of highly talented young soccer players' speed abilities and technical skills and examined the relevance of this development to their adult success. The current research sample consisted of N = 1,134 players born between 1993 and 1995 who were selected for the German Soccer Association's TID program and participated in nationwide motor diagnostics (sprinting, agility, dribbling, ball control, shooting) four times between the Under 12 (U12) and Under 15 (U15) age class. Relative age (RA) was assessed for all players, and a total motor score was calculated based on performances in the individual tests. In order to investigate players' future success, participants were divided into two groups according to their adult performance level (APL) in the 2014/2015 season: Elite (1st-5th German division; N = 145, 12.8%) and non-elite players (lower divisions; N = 989, 87.2%). Using multilevel regression analyses each motor performance was predicted by Time, Time2 (level-1 predictors), APL, and RA (level-2 covariates) with simultaneous consideration for interaction effects between the respective variables. Time and Time2 were significant predictors for each test performance. A predictive value for RA was confirmed for sprinting and the total motor score. A significant relationship between APL and the motor score as well as between APL and agility, dribbling, ball control, and shooting emerged. Interaction effects distinctly failed to reach significance. The study found a non-linear improvement in players' performance for all considered motor performance factors over a three-year period from early to middle adolescence. While their predictive value for future success was confirmed by a significant relationship between APL and most of the considered factors, there was no significant interaction between APL and Time. These findings indicate that future elite players had already been better at the beginning of the TID program and maintained this high level throughout their promotion from U12 to U15.


#4 Heading Frequency Is More Strongly Related to Cognitive Performance Than Unintentional Head Impacts in Amateur Soccer Players
Reference: Front Neurol. 2018 Apr 24;9:240. doi: 10.3389/fneur.2018.00240. eCollection 2018.
Authors: Stewart WF, Kim N, Ifrah C, Sliwinski M, Zimmerman ME, Kim M, Lipton RB, Lipton ML
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5928847/pdf/fneur-09-00240.pdf
Summary: Compared to heading, unintentional head impacts (e.g., elbow to head, head to head, head to goalpost) in soccer are more strongly related to risk of moderate to very severe Central Nervous System (CNS) symptoms. But, most head impacts associated with CNS symptoms that occur in soccer are mild and are more strongly related to heading. We tested for a differential relation of heading and unintentional head impacts with neuropsychological (NP) test performance. Active adult amateur soccer players were recruited in New York City and the surrounding areas for this repeated measures longitudinal study of individuals who were enrolled if they had 5+ years of soccer play and were active playing soccer 6+ months/year. All participants completed a baseline validated questionnaire ("HeadCount-2w"), reporting 2-week recall of soccer activity, heading and unintentional head impacts. In addition, participants also completed NP tests of verbal learning, verbal memory, psychomotor speed, attention, and working memory. Most participants also completed one or more identical follow-up protocols (i.e., HeadCount-2w and NP tests) at 3- to 6-month intervals over a 2-year period. Repeated measures General Estimating Equations (GEE) linear models were used to determine if variation in NP tests at each visit was related to variation in either heading or unintentional head impacts in the 2-week period before testing. 308 players (78% male) completed 741 HeadCount-2w. Mean (median) heading/2-weeks was 50 (17) for men and 26 (7) for women. Heading was significantly associated with poorer performance on psychomotor speed (p < 0.001) and attention (p = 0.02) tasks and was borderline significant with poorer performance on the working memory (p  = 0.06) task. Unintentional head impacts were not significantly associated with any NP test. Results did not differ after excluding 22 HeadCount-2w with reported concussive or borderline concussive symptoms. Poorer NP test performance was consistently related to frequent heading during soccer practice and competition in the 2 weeks before testing. In contrast, unintentional head impacts incurred during soccer were not related to cognitive performance.


#5 Soccer Injury Movement Screen (SIMS) Composite Score Is Not Associated With Injury Among Semi-Professional Soccer Players
Reference: J Orthop Sports Phys Ther. 2018 May 8:1-29. doi: 10.2519/jospt.2018.8037. [Epub ahead of print]
Authors: McCunn R, Funten KA, Whalan M, Sampson JA, Meyer T
Summary: The association between movement quality and injury is equivocal. No soccer-specific movement assessment has been prospectively investigated in relation to injury risk. The aim was to investigate the association between a soccer-specific movement quality assessment and injury risk among semi-professional soccer players. Semi-professional soccer players (n=306) from 12 clubs completed the Soccer Injury Movement Screen (SIMS) during the pre-season period. Individual training/match exposure and non-contact time loss injuries were recorded prospectively for the entirety of the 2016 season. Relative risks (RR) were calculated, and presented with 90% confidence intervals (CI), for the SIMS composite and individual sub-test scores from generalized linear models with Poisson distribution offset for exposure. When considering non-contact time loss lower extremity injuries (primary level of analysis), there was a most likely trivial association with the SIMS composite score. Similarly, SIMS composite score demonstrated most likely to likely trivial associations to all injury categories included in the secondary level of analysis (non-contact time loss hip/groin, thigh, knee and ankle injuries). When considering hamstring strains and ankle sprains specifically (tertiary level of analysis) the SIMS composite score, again, demonstrated very likely trivial associations. A total of 262 non-contact time loss injuries were recorded. The overall (training and match exposure combined) incidence of non-contact time loss injury was 12/1000 hours. The SIMS composite score demonstrated no association to any of the investigated categories of soccer-related injury. The SIMS composite score should not be used to group players into 'high' or 'low' risk groups.


#6 Accuracy of Anthropometric Equations for Estimating Body Fat in Professional Male Soccer Players Compared with DXA
Reference: J Sports Med (Hindawi Publ Corp). 2018 Mar 14;2018:6843792. doi: 10.1155/2018/6843792. eCollection 2018.
Authors: Lopez-Taylor JR1, Gonzalez-Mendoza RG1, Gaytan-Gonzalez A, Jimenez-Alvarado JA, Villegas-Balcazar M, Jauregui-Ulloa EE, Torres-Naranjo F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872598/pdf/JSM2018-6843792.pdf
Summary: There are several published anthropometric equations to estimate body fat percentage (BF%), and this may prompt uncertainty about their application. The purpose was to analyze the accuracy of several anthropometric equations (developed in athletic [AT] and nonathletic [NAT] populations) that estimate BF% comparing them with DXA. We evaluated 131 professional male soccer players (body mass: 73.2 ± 8.0 kg; height: 177.5 ± 5.8 cm; DXA BF% [median, 25th-75th percentile]: 14.0, 11.9-16.4%) aged 18 to 37 years. All subjects were evaluated with anthropometric measurements and a whole body DXA scan. BF% was estimated through 14 AT and 17 NAT anthropometric equations and compared with the measured DXA BF%. Mean differences and 95% limits of agreement were calculated for those anthropometric equations without significant differences with DXA. Five AT and seven NAT anthropometric equations did not differ significantly with DXA. From these, Oliver's and Civar's (AT) and Ball's and Wilmore's (NAT) equations showed the highest agreement with DXA. Their 95% limits of agreement ranged from -3.9 to 2.3%, -4.8 to 1.8%, -3.4 to 3.1%, and -3.9 to 3.0%, respectively.Oliver's, Ball's, Civar's, and Wilmore's equations were the best to estimate BF% accurately compared with DXA in professional male soccer players.


#7 Planning Training Workload in Football Using Small-Sided Games' Density
Reference: J Strength Cond Res. 2018 May 8. doi: 10.1519/JSC.0000000000002598. [Epub ahead of print]
Authors: Sangnier S, Cotte T, Brachet O, Coquart J, Tourny C
Summary: To develop the physical qualities, the small-sided games' (SSGs) density may be essential in soccer. Small-sided games are games in which the pitch size, players' number, and rules are different to those for traditional soccer matches. The purpose was to assess the relation between training workload and SSGs' density. The 33 densities data (41 practice games and 3 full games) were analyzed through global positioning system (GPS) data collected from 25 professional soccer players (80.7 ± 7.0 kg; 1.83 ± 0.05 m; 26.4 ± 4.9 years). From total distance, distance metabolic power, sprint distance, and acceleration distance, the data GPS were divided into 4 categories: endurance, power, speed, and strength. Statistical analysis compared the relation between GPS values and SSGs' densities, and 3 methods were applied to assess models (R-squared, root-mean-square error, and Akaike information criterion). The results suggest that all the GPS data match the player's essential athletic skills. They were all correlated with the game's density. Acceleration distance, deceleration distance, metabolic power, and total distance followed a logarithmic regression model, whereas distance and number of sprints follow a linear regression model. The research reveals options to monitor the training workload. Coaches could anticipate the load resulting from the SSGs and adjust the field size to the players' number. Taking into account the field size during SSGs enables coaches to target the most favorable density for developing expected physical qualities. Calibrating intensity during SSGs would allow coaches to assess each athletic skill in the same conditions of intensity as in the competition.


#8 Physical performance tests - a relationship of risk factors for muscle injuries in elite level male football players
Reference: J Exerc Rehabil. 2018 Apr 26;14(2):282-288. doi: 10.12965/jer.1836028.014. eCollection 2018 Apr.
Authors: Svensson K, Alricsson M, Olausson M, Werner S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931166/pdf/jer-14-2-282.pdf
Summary: The purpose of the present study was to investigate whether there is a relationship between the outcome of preseason physical performance tests and the risk of sustaining lower extremity muscle injuries within the same season, in male football players at elite level. This is a cohort study of a male football team (63 players) from the first league in Sweden. The football players are prospectively followed, in terms of muscle injuries of the lower extremity during five seasons between 2010 and 2014. All muscle injuries were evaluated and diagnosed with ultraso-nography. The following physical performance tests were included: squats, chin-ups, YoYo intermittent recovery level 2, counter movement jump, squat jump, standing long jump, sprint, one leg squat test, and a functional movement screen. A total of 86 muscle injuries occurred during the study period. No significant correlation was found between the results of the physical performance tests and muscle injuries of the lower extremity. None of the evaluated tests predicted the risk of sus-taining muscle injuries of the lower extremity. We conclude that muscle injury risk factors are more complex than solely related to the results of the preseason physical performance tests.


#9 Perceived motivational factors for female football players during rehabilitation after sports injury - a qualitative interview study
Reference: J Exerc Rehabil. 2018 Apr 26;14(2):199-206. doi: 10.12965/jer.1836030.015. eCollection 2018 Apr.
Authors: Hildingsson M, Fitzgerald UT, Alricsson M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931154/pdf/jer-14-2-199.pdf
Summary: Compliance with a rehabilitation program is significant among athletes following a sports injury. It is also one of the main factors that influence the rehabilitation process; moreover, the outcome is also influenced by the athlete's motivation. It is primarily an autonomous motivation, resulting in rehabilitation adherence. The aim of this study was to investigate the perceived motivation of female football players during rehabilitation after a sports injury and the extent to which these motivating factors were autonomous. Qualitative interviews, based on a semistructured interview guide with injured female football players undergoing rehabilitation, were analyzed using content analysis. The motivational factors that were described were their set goals, social support as well as external and internal pressures during rehabilitation. The perceived autonomy varied somewhat but overall, they experienced external motivation; therefore, the behavior was not entirely self-determined. Results are expected to provide a better understanding of women football players' motivation in relation to their rehabilitation; hence, physiotherapists and coaches who are part of the rehabilitation process can contribute by increasing the autonomous motivation, thus, improving the compliance and outcome of the rehabilitation.


#10 Sub-Elite Football Players With Hip-Related Groin Pain and Positive Flexion Adduction Internal Rotation Test Exhibit Distinct Biomechanical Differences Compared With the Asymptomatic Side
Reference: J Orthop Sports Phys Ther. 2018 May 8:1-26. doi: 10.2519/jospt.2018.7910. [Epub ahead of print]
Authors: King MG, Semciw AI, Hart HF, Schache AG, Middleton KJ, Heerey JJ, Agricola R, Crossley KM
Summary: Study Design Observational cross-sectional study. Background Hip-related groin pain is common in sub-elite football players and may be associated with altered hip biomechanics. Objectives To compare the hip biomechanics, bony hip morphology associated with femoroacetabular impingement (FAI) syndrome, and hip strength and range of motion between the symptomatic and asymptomatic limb of sub-elite football players with unilateral hip-related groin pain and a positive flexion adduction internal rotation test. Methods Fifteen sub-elite football (soccer) players with unilateral hip-related groin pain and a positive flexion adduction internal rotation test were recruited. Three-dimensional motion analysis and ground reaction force data were recorded for walking and a single leg drop jump (SLDJ) task. Participants also underwent a standard anterior-posterior hip radiograph and hip strength and range of movement assessment. Between-limb differences were assessed using paired t-tests or Wilcoxon sign-rank tests. Results The symptomatic limb displayed a smaller peak hip extension angle (P=.01) and a lower peak hip adduction moment (P=.03) compared with the asymptomatic limb during the stance phase of walking. Additionally, during the SLDJ, the symptomatic limb demonstrated less total sagittal plane range of motion (P=.04). The symptomatic limb also demonstrated less external rotation range of motion (P=.03) however, no differences were found between limbs for bony hip morphology associated with FAI syndrome or hip strength. Conclusion This study found between limb asymmetries in low- and high-impact functional tasks such as walking and a SLDJ in football players with unilateral hip-related groin pain. Despite unilateral pain, bony morphology associated with FAI syndrome did not differ between limbs

Tue

29

May

2018

Football is...(#62)

The role of anthropometry for certain positions - debatable?

Mon

28

May

2018

Latest research in football - week 17 - 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 Assessing Repeated-Sprint Ability in Division I Collegiate Women Soccer Players
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002527. [Epub ahead of print]
Authors: Lockie RG, Liu TM, Stage AA, Lazar A, Giuliano DV, Hurley JM, Torne IA, Beiley MD, Birmingham-Babauta SA, Stokes JJ, Risso FG, Davis DL, Moreno MR, Orjalo AJ
Summary: Repeated-sprint ability (RSA) is a key component of soccer, and is the capacity to repeatedly produce near-maximal to maximal sprints with short recovery periods. Repeated-sprint ability has received little analysis in collegiate women soccer players. The purpose of this study was to investigate relationships between RSA and tests of soccer-specific performance. Nineteen players from the same Division I collegiate women's soccer team were recruited. The RSA test consisted of six 20-m sprints completed on 15-second cycles. The measurements taken were total time (TT) and percent decrement (PD; percent change from first to last sprint). Subjects also completed tests of: lower-body strength (1 repetition maximum [1RM] back squat); jump performance (vertical and standing long jumps); linear (0-5, 0-10, and 0-30 m sprint intervals) and change-of-direction (505 from each leg) speed; and soccer-specific fitness (Yo-Yo intermittent recovery test level 1 [YYIRT1]). Pearson's correlations (p ≤ 0.05) were used to calculate relationships between RSA TT and PD with the performance tests. Total time exhibited significant relationships with the 0-10 (r = 0.50) and 0-30 m (r = 0.71) sprint intervals, and the left-leg 505 (r = 0.57). However, lower-body strength measured by the 1RM back squat and jump performance did not relate to TT. Percent decrement correlated only with the left-leg 505 (r = 0.53) and no other performance test. This included the YYIRT1, although both PD and YYIRT1 performance are limited by fatigue. The results from this study indicated that faster linear sprinting speed could positively influence RSA in Division I collegiate women soccer players.


#2 EEG alpha activity during imagining creative moves in soccer decision-making situations
Reference: Neuropsychologia. 2018 Apr 24. pii: S0028-3932(18)30166-0. doi: 10.1016/j.neuropsychologia.2018.04.025. [Epub ahead of print]
Authors: Fink A, Rominger C, Benedek M, Perchtold CM, Papousek I, Weiss EM, Seidel A, Memmert D
Summary: This study investigated task-related changes of EEG alpha power while participants were imagining creative moves in soccer decision-making situations. After presenting brief video clips of a soccer scene, participants had to imagine themselves as the acting player and to think either of a creative/original or an obvious/conventional move (control condition) that might lead to a goal. Performance of the soccer task generally elicited comparatively strong alpha power decreases at parietal and occipital sites, indicating high visuospatial processing demands. This power decrease was less pronounced in the creative vs. control condition, reflecting a more internally oriented state of information processing characterized by more imaginative mental simulation rather than stimulus-driven bottom-up processing. In addition, more creative task performance in the soccer task was associated with stronger alpha desynchronization at left cortical sites, most prominently over motor related areas. This finding suggests that individuals who generated more creative moves were more intensively engaged in processes related to movement imagery. Unlike the domain-specific creativity measure, individual's trait creative potential, as assessed by a psychometric creativity test, was globally positively associated with alpha power at all cortical sites. In investigating creative processes implicated in complex creative behavior involving more ecologically valid demands, this study showed that thinking creatively in soccer decision-making situations recruits specific brain networks supporting processes related to visuospatial attention and movement imagery, while the relative increase in alpha power in more creative conditions and in individuals with higher creative potential might reflect a pattern relevant across different creativity domains.


#3 Inter-season variability in isokinetic strength and poor correlation with nordic hamstring eccentric strength in football players
Reference: Scand J Med Sci Sports. 2018 Apr 25. doi: 10.1111/sms.13201. [Epub ahead of print]
Authors: van Dyk N, Witvrouw E, Bahr R
Summary: In elite sport, the use of strength testing to establish muscle function and performance is common. Traditionally, isokinetic strength tests have been used, measuring torque during concentric and eccentric muscle action. A device that measures eccentric hamstring muscle strength while performing the Nordic hamstring exercise is now also frequently used. The study aims to investigate the variability of isokinetic muscle strength over time, e.g. between seasons, and the relationship between isokinetic testing and the new Nordic hamstring exercise device. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Qatar. Isokinetic strength was investigated for measurement error, and correlated to Nordic hamstring exercise strength. Of the 529 players included, 288 players had repeated tests with one/two seasons between test occasions. Variability (measurement error) between test occasions was substantial, as demonstrated by the measurement error (approximately 25Nm, 15%), whether separated by one or two seasons. Considering hamstring injuries, the same pattern was observed among injured (n=60) and uninjured (n=228) players. A poor correlation (r=0.35) was observed between peak isokinetic hamstring eccentric torque and Nordic hamstring exercise peak force. The strength imbalance between limbs calculated for both test modes were not correlated (r=0.037). There is substantial intraindividual variability in all isokinetic test measures, whether separated by one or two seasons, irrespective of injury. Also, eccentric hamstring strength and limb-to-limb imbalance were poorly correlated between the isokinetic and Nordic hamstring exercise tests. This article is protected by copyright. All rights reserved.


#4 Variability of activity profile during medium-sided games in professional soccer
Reference: J Sports Med Phys Fitness. 2018 Apr 24. doi: 10.23736/S0022-4707.18.08376-7. [Epub ahead of print]
Authors: Rago V, Silva JR, Mohr M, Barreira D, Krustrup P, Rebelo AN
Summary: In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason. Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers). Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3 %). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59). During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.


#5 Landing Kinematics in Elite Male Youth Soccer Players of Different Chronologic Age and Stage of Maturation
Reference: J Athl Train. 2018 Apr 25. doi: 10.4085/1062-6050-493-16. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MBA, Myer GD, Lloyd RS
Summary: Despite the high frequency of knee injuries in athletes, few researchers have studied the effects of chronologic age and stage of maturation on knee-joint kinematics in male youth soccer players. The aim was to use a coach-friendly screening tool to examine knee-valgus scores for players of different ages and at different stages of maturation. A total of 400 elite male youth soccer players aged 10 to 18 years categorized by chronologic age and stage of maturation based on their years from peak height velocity (PHV) participated in the study. Knee valgus was evaluated during the tuck-jump assessment via 2-dimensional analysis. Frontal-plane projection angles were subjectively classified as minor (<10°), moderate (10°-20°), or severe (>20°), and using these classifications, we scored knee valgus in the tuck jump as 0 ( no valgus), 1 ( minor), 2 ( moderate), or 3 ( severe). A trend toward higher valgus scores was observed in the younger age groups and the pre-PHV group. The lowest frequency of no valgus occurred in the U18 and post-PHV groups. The highest percentages of severe scores were in the U13 and pre-PHV groups for the right limb. Knee-valgus scores were lower for both lower extremities in the U18 group than in all other age groups ( P < .001) except the U16 group. Scores were lower for the post-PHV than the pre-PHV group for the right limb ( P < .001) and both pre-PHV and circa-PHV groups for the left limb ( P < .001). Noteworthy interlimb asymmetries were evident in the U14, U15, and circa-PHV groups. Reductions in knee valgus with incremental age and during the later stages of maturation indicated that this risk factor was more prevalent in younger players. Interlimb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.


#6 Team Dynamics, Running, and Skill-Related Performances of Brazilian U11 to Professional Soccer Players During Official Matches
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002577. [Epub ahead of print]
Authors: Palucci Vieira LH, Aquino R, Moura FA, Barros RML, Arpini VM, Oliveira LP, Bedo BLS, Santiago PRP
Summary: Analyses of movements during soccer competition have been used previously to help develop conditioning programs. However, this has not been extensively studied in youth populations. Therefore, the purposes of this study were to examine (1) dynamics of collective tactical movements, (2) running, and (3) skill-related performances during soccer matches disputed by children to senior players. A total of 120 Brazilian players in the age groups U11, U13, U15, U17, U20, and professional (PRO) were monitored during official competition matches (N = 12). Using semiautomatic video-based tracking (30 Hz), match running variables including total distance traveled, average speed, maximum sprint speed, and high-intensity activities were evaluated. Tactical metrics were computed as team surface area, spread, and median frequency. Through notational analysis, technical skills such as involvements with the ball, passes, ball touches, duels, and goal attempts were also recorded. One-way analysis of variance and magnitude-based inferences were used to detect differences between ages. Although the average speed, team surface area, and spread tended to present stabilized increases from the U15 (e.g., U15 > U13 > U11), maximal sprinting speed (PRO > U17 > U15, U13, U11) and percentage at very high-intensity activities (U20 > PRO, U17 > U15 > U13 > U11) demonstrated continuous gains. Median frequencies were higher in the younger groups (U13, U15, U17 > U20, PRO), although the percentage of successful passes was higher in the older groups (PRO > U17, U15 > U13, U11). We concluded that Brazilian U11 to PRO players present different performance profiles for running, collective movement dynamics, and technical skills, and that the rate of development regarding these components varies. Coaches should be aware of these differences to select and adapt training content for each age group.


#7 New Tool to Control and Monitor Weighted Vest Training Load for Sprinting and Jumping in Soccer
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002580. [Epub ahead of print]
Authors: Carlos-Vivas J, Freitas TT, Cuesta M, Perez-Gomez J, De Hoyo M, Alcaraz PE
Summary: The purpose of this study was to develop 2 regression equations that accurately describe the relationship between weighted vest loads and performance indicators in sprinting (i.e., maximum velocity, Vmax) and jumping (i.e., maximum height, Hmax). Also, this study aimed to investigate the effects of increasing the load on spatio-temporal variables and power development in soccer players and to determine the "optimal load" for sprinting and jumping. Twenty-five semiprofessional soccer players performed the sprint test, whereas a total of 46 completed the vertical jump test. Two different regression equations were developed for calculating the load for each exercise. The following equations were obtained: % body mass (BM) = -2.0762·%Vmax + 207.99 for the sprint and % BM = -0.7156·%Hmax + 71.588 for the vertical jump. For both sprinting and jumping, when the load increased, Vmax and Hmax decreased. The "optimal load" for resisted training using weighted vest was unclear for sprinting and close to BM for vertical jump. This study presents a new tool to individualize the training load for resisted sprinting and jumping using weighted vest in soccer players and to develop the whole force-velocity spectrum according to the objectives of the different periods of the season.


#8 Injury prevention and return to play strategies in elite football: no consent between players and team coaches
Reference: Arch Orthop Trauma Surg. 2018 Apr 20. doi: 10.1007/s00402-018-2937-6. [Epub ahead of print]
Authors: Loose O, Achenbach L, Fellner B, Lehmann J, Jansen P, Nerlich M, Angele P, Krutsch W
Summary: Injuries are a common problem in football. To improve prevention strategies, the players' (p) and coaches' (c) views need to be disclosed as they have a strong impact on return to play decisions. The aim of this study is to reveal current opinions with regard to injury prevention and return to play strategies to introduce new strategies in elite football. In a retrospective data analysis of elite salaried football players (n = 486) and team coaches (n = 88), a detailed investigation by means of a standardized questionnaire was carried out. In a preseason period of the 2015/16 season and as part of a large interventional research project in elite salaried German football, a request about players' and team coaches' knowledge and opinions was performed. Topics such as injury prevention, return to play after injuries, the importance of screening tests, general problems of injuries in football, or the decision-making in terms of prevention and return to play in elite football were investigated. The study revealed a high interest in injury prevention and screening tests among players and coaches (p 82.5%; c 99.1%). The participants of the study reported warm-up exercises (p 76.4%; c 74.7%), regeneration training (p 54.1%; c 56.3%), and core stability (p 53.8; c 70.1%) as the most important prevention methods, but the additional investigation of the teams' current daily training routine showed that the transfer is incomplete. Coaches are more familiar with scientific published warm-up programs like FIFA 11 + than players (42.5 vs. 12.6; p < 0.001). Knee injuries (p 90.7%; c 93.1%) and ACL injuries in particular were reported as the most severe and common problem in elite football. Players and coaches expressed different attitudes concerning return to play decisions. While players want to decide themselves (81.4%), team coaches consult medical advice ahead of the decision of return to play after injuries (83.5%; p < 0.001). Decisions against the doctor's recommendation are often made by both groups (p 64.4% vs. c 87.1%; p < 0.001). The basic knowledge of prevention and injuries is sufficient in elite football, but the transfer from theoretical knowledge to practical routine is suboptimal. The study also shows possibilities to improve the prevention process and communication between players, coaches, doctors, and physiotherapists, while there is no consent between players and coaches regarding return to play decision.


#9 Dynamics of submaximal effort soccer instep kicking
Reference: J Sports Sci. 2018 May 1:1-8. doi: 10.1080/02640414.2018.1470216. [Epub ahead of print]
Authors: Nunome H, Inoue K, Watanabe K, Iga T, Akima H
Summary: During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact.


#10 Periodic Health Examination and Injury Prediction in Professional Football (Soccer): Theoretically, the Prognosis is Good
Reference: Sports Med. 2018 Apr 27. doi: 10.1007/s40279-018-0928-y. [Epub ahead of print]
Authors: Hughes T, Sergeant JC, van der Windt DA, Riley R, Callaghan
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0928-y.pdf
Summary: In professional soccer and other elite sports, medical and performance screening of athletes (also termed periodic health examination or PHE) is common practice. The purposes of this are: (1) to assist in identifying prevalent conditions that may be a threat to safe participation, (2) to assist in setting benchmark targets for rehabilitation or performance purposes and (3) to assist clinicians in determining which athletes may be at risk of future injury and selecting appropriate injury prevention strategies to reduce the perceived risk. However, when using PHE as an injury prevention tool, are clinicians seeking to identify potential causes of injury or to predict future injury? This Current Opinion aims to examine the conceptual differences between aetiology and prediction of injury while relating these areas to the capabilities of PHE in practice. We also introduce the concept of prognosis-a broader approach that is closely related to prediction-and why this may have greater applicability to PHE of professional athletes.

Thu

24

May

2018

Latest research in football - week 16 - 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 Association between Cumberland Ankle Instability Tool score and postural stability in collegiate soccer players with and without functional ankle instability
Reference: Phys Ther Sport. 2018 Mar 23;32:29-33. doi: 10.1016/j.ptsp.2018.03.002. [Epub ahead of print]
Authors: Kunugi S, Masunari A, Yoshida N, Miyakawa S
Summary: The purpose of this study was to investigate the association between Cumberland Ankle Instability Tool (CAIT) scores and postural stability during a diagonal landing, and to investigate whether postural stability is altered in collegiate soccer players with and without functional ankle instability (FAI). Ninety-one soccer players were classified into a FAI group (history of at least two ankle sprains and a CAIT-Japanese version score ≤25, n = 28), a copers group (history of one ankle sprain and a CAIT-Japanese version score ≥26, n = 32), or a control group (no history of ankle sprain, n = 31). Time to anteroposterior stabilisation (TTSAP) and mediolateral stabilisation (TTSML) were measured during the diagonal single-leg landing. The CAIT scores were correlated with TTSAP (P < 0.05, rs = -0.214) and TTSML (P < 0.01, rs = -0.566). TTSAP was longer in the FAI group than in the control group, and TTSML was longer in the FAI group than in the other groups. Our findings indicate the presence of an association between the CAIT-J score and TTSML, as well as postural stability deficits in collegiate soccer players with FAI during diagonal landings.


#2 Isolated Subscapularis Tendon Tear in a Skeletally Immature Soccer Player
Reference: Joints. 2017 Dec 11;6(1):68-70. doi: 10.1055/s-0037-1608952. eCollection 2018 Mar.
Authors: Avanzi P, Dei Giudici L, Giovarruscio R, Gigante A, Zorzi C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5906114/pdf/10-1055-s-0037-1608952.pdf
Summary: Subscapularis injury in adolescents, usually associated to an avulsion fracture of the lesser humeral tuberosity, accounts for less than 2% of all fractures of the proximal humerus. Isolated tears of the subscapularis tendon without a history of dislocation and associated avulsion fractures are an even rarer occurrence, and treatment is controversial. This article describes a rare case of a 12-year-old suffering from an isolated subscapularis tear and discusses its management. The patient was evaluated at presentation, and at 1 to 2.5 months after he underwent a cuff tear arthroscopic repair with a single "all suture" anchor loaded with two wires, active/passive range of motion (A/PROM), Constant-Murley score, and American Shoulder and Elbow Surgeons (ASES) score were noted. Patient reported an excellent outcome, recovered the whole ROM, was pain free, and returned to the previous level of activity. Isolated avulsion of the subscapularis tendon requires a high index of suspicion for a proper diagnosis as early treatment is required for a good recovery. Arthroscopy reserves more advantages in proper hands, restoring the previous levels of function and activity. An increase in attention for this condition is mandatory in a society where many adolescents are getting more and more active in high levels of sport activities.


#3 The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie A
Reference: PLoS One. 2018 Apr 19;13(4):e0196253. doi: 10.1371/journal.pone.0196253. eCollection 2018.
Authors: Brustio PR, Lupo C, Ungureanu AN, Frati R, Rainoldi A, Boccia G
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196253&type=printable
Summary: The relative age effect (RAE; i.e., an asymmetry in the birth distribution) is a bias observed in sport competitions that may favour relatively older athletes in talent identification. Therefore, the aim of this study was to investigate the presence of RAE in elite soccer players competing in the Italian championships, even considering the discriminations of younger and older Serie A players (in relation to the median age of the sample), and different positional roles (i.e., goalkeeper, defender, midfielder, forward) for each observed category. A total of 2051 players competing into the 2017-2018 Italian under-15 (n = 265), under-16 (n = 362), under-17 (n = 403), Primavera (n = 421) and Serie A (n = 600) championships were analysed. The birth-date distributions, grouped in four quartiles (i.e., January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4), were compared to a uniform distribution using Chi-squared analysis. The week of birth was analysed using Poisson regression. The results showed a large over-representation of players born in Q1 in all soccer player categories. However, the effect size of this trend resulted smaller as age increased. Individuals born in Q1 have about two-folds more chances to become a Serie A player compared to those born in Q4. The Poisson regression analysis showed that RAE was greater for defenders than for forwards among all categories. Therefore, a strongly biased selection emerged among elite soccer players competing in Italian championships, highlighting how young individuals born in the first three months have many more chances to become elite players compared to the others.


#4 Ratios of torques of antagonist muscle groups in female soccer players
Reference: Acta Bioeng Biomech. 2018;20(1):153-158.
Authors: Struzik A, Siemienski A, Bober T, Pietraszewski B
Summary: An increase in the value of the hamstring-to-quadriceps (H/Q) ratio with an increase in angular velocity may effectively prevent injuries of the back of the thigh. Previous studies have found that the conventional H/Q ratio was unaltered along with an increasing angular velocity in females. Therefore, this study aimed to investigate the relationships between the conventional H/Q ratio and angular velocity in a group of female soccer players. The study was carried out on a group of 16 female soccer players (age: 20.7 ± 3.9 years, body height: 166.1 ± 5.8 cm, body mass: 58.4 ± 6.2 kg, training experience: 8.8 ± 4.1 years). Measurements of peak torque of extensors and flexors of the knee joint under static conditions and under isokinetic conditions (at angular velocities of 30°/s, 60°/s, 90°/s and 120°/s) were carried out using a Biodex dynamometer. There was a statistically significant increase in the conventional H/Q ratio with an increase in angular velocity. These differences occurred between measurements at angular velocities of 0°/s and 30°/s, and 30°/s and 60°/s. As previously found for males, an increase in conventional H/Q ratio with increased angular velocity was also present in this group of female players. This phenomenon should reduce the number of injuries of the muscles of back of the thigh. Coaches should pay attention to increasing the level of strength in the group of knee joint flexor muscles so as to make the value of the H/Q ratio appropriately high and increasing with increasing angular velocity.


#5 Investigation of knee control as a lower extremity injury risk factor: A prospective study in youth football
Reference: Scand J Med Sci Sports. 2018 Apr 19. doi: 10.1111/sms.13197. [Epub ahead of print]
Authors: Raisanen AM, Arkkila H, Vasankari T, Steffen K, Parkkari J, Kannus P, Forsman H, Pasanen K
Summary: This prospective study in youth football examined the relationship between frontal plane knee projection angle (FPKPA) during the single-leg squat and sustaining an acute lower extremity injury or acute non-contact lower extremity injury. Secondly, side-to-side asymmetry in FPKPA and sex as injury risk factors were explored. In addition, we investigated the influence of age, sex and leg dominance on the FPKPA. A total of 558 youth football players (U11 to U14), participated in the single-leg squat test and prospective injury registration. FPKPA was not found as a risk factor for injuries at this age. There was no difference in the mean FPKPA between sexes. However, FPKPA was associated with age; oldest subjects displayed the smallest FPKPA. Among boys, the frontal plane knee control improved by age. Among girls, the relationship between age and FPKPA was not as clear but the oldest girls displayed the smallest mean FPKPA in the study (12.2°+ 8.3°). The FPKPA was greater on the dominant kicking leg compared to the non-dominant support leg (P<0.001 for boys, P=0.001 for girls). However, side-to-side asymmetry in FPKPA was not associated with future injuries. In conclusion, frontal plane knee control in the single-leg squat was not associated with lower extremity injuries among young football players. As the single-leg squat to 90° knee flexion was too demanding for many subjects, easier single-leg squat test procedure or a different movement control test, such as a double-legged squat, could be more suitable for the young football players.


#6 Is the message getting through? Awareness and use of the 11+ injury prevention programme in amateur level football clubs
Reference: PLoS One. 2018 Apr 19;13(4):e0195998. doi: 10.1371/journal.pone.0195998. eCollection 2018.
Authors: Wilke J, Niederer D, Vogt L, Banzer W
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0195998&type=printable
Summary: A large body of evidence suggests that the 11+ warm-up programme is effective in preventing football-related musculoskeletal injuries. However, despite considerable efforts to promote and disseminate the programme, it is unclear as to whether team head coaches are familiar with the 11+ and how they rate its feasibility. The present study aimed to gather information on awareness and usage among German amateur level football coaches. A questionnaire was administered to 7893 individuals who were in charge of youth and adult non-professional teams. Descriptive and inferential statistics were used to analyse the obtained data. A total of 1223 coaches (16%) returned the questionnaire. There was no risk of a non-response bias (p>.05). At the time of the survey, nearly half of the participants (42.6%) knew the 11+. Among the coaches who were familiar with the programme, three of four reported applying it regularly (at least once per week). Holding a license (φ = .28, p < .0001), high competitive level (Cramer-V = .13, p = .007), and coaching a youth team (φ = .1, p = .001) were associated with usage of 11+. Feasibility and suitability of the 11+ were rated similarly by aware and unaware coaches. Although a substantial share of German amateur level coaches is familiar with the 11+, more than half of the surveyed participants did not know the programme. As the non-usage does not appear to stem from a lack of rated feasibility and suitability, existing communication strategies might need to be revised.


#7 Muscle injuries in professional football : Treatment and rehabilitation
Reference: Unfallchirurg. 2018 Apr 17. doi: 10.1007/s00113-018-0501-z. [Epub ahead of print]  [Article in German]
Authors: Riepenhof H, Del Vescovo R, Droste JN, McAleer S, Pietsch A
Summary: Muscle injuries are common in professional sports, especially in football. Recent epidemiological studies showed that muscle injuries account for more than 30% of professional football injuries (1.8-2.2/1000 h exposure); however, even though there are significant differences within a European comparison, a single professional football team diagnosed on average 12 muscle injuries per season, corresponding to more than 300 availability days lost. The aim of this work is to present the diagnosis, general treatment and comprehensive management of muscle injuries in professional football. The present work is based on current scientific findings, experiences of the authors and examples from routine practice in the management of muscle injuries in a professional sports environment. The authors present a model of gradual progression for the treatment of muscular injuries and their rehabilitation. Due to the time-pressured nature of the professional sports environment, often promoted by coaches and media, this model could help lead players to recover as quickly as possible and return to competitive sports without relapse or sequel injury. This model integrates the player into the treatment plan. The progression sequences in the rehabilitation should be made clear to players and other parties involved, which are crucial for optimal healing. Even if absolute certainty cannot be achieved, i.e. the occurrence of re-injury or secondary injury, this model attempts to minimize the level of risk involved for the returning athlete. Since it is hardly possible to act strictly in line with more conservative guidelines due to the particular circumstances of the professional sport environment, the experiences of the authors are presented in the sense of best practice in order to support future decision-making processes.


#8 Post-Game High Protein Intake May Improve Recovery of Football-Specific Performance during a Congested Game Fixture: Results from the PRO-FOOTBALL Study
Reference: Nutrients. 2018 Apr 16;10(4). pii: E494. doi: 10.3390/nu10040494.
Authors: Poulios A, Fatouros IG, Mohr M, Draganidis DK, Deli C, Papanikolaou K, Sovatzidis A, Nakopoulou T, Ermidis G, Tzatzakis T, Laschou VC, Georgakouli K, Koulouris A, Tsimeas P, Chatzinikolaou A, Karagounis LG, Batsilas D, Krustrup P, Jamurtas AZ
Download link: www.mdpi.com/2072-6643/10/4/494/pdf
Summary: The effects of protein supplementation on performance recovery and inflammatory responses during a simulated one-week in-season microcycle with two games (G1, G2) performed three days apart were examined. Twenty football players participated in two trials, receiving either milk protein concentrate (1.15 and 0.26 g/kg on game and training days, respectively) (PRO) or an energy-matched placebo (1.37 and 0.31 g/kg of carbohydrate on game and training days, respectively) (PLA) according to a randomized, repeated-measures, crossover, double-blind design. Each trial included two games and four daily practices. Speed, jump height, isokinetic peak torque, and muscle soreness of knee flexors (KF) and extensors (KE) were measured before G1 and daily thereafter for six days. Blood was drawn before G1 and daily thereafter. Football-specific locomotor activity and heart rate were monitored using GPS technology during games and practices. The two games resulted in reduced speed (by 3-17%), strength of knee flexors (by 12-23%), and jumping performance (by 3-10%) throughout recovery, in both trials. Average heart rate and total distance covered during games remained unchanged in PRO but not in PLA. Moreover, PRO resulted in a change of smaller magnitude in high-intensity running at the end of G2 (75-90 min vs. 0-15 min) compared to PLA (P = 0.012). KE concentric strength demonstrated a more prolonged decline in PLA (days 1 and 2 after G1, P = 0.014-0.018; days 1, 2 and 3 after G2, P = 0.016-0.037) compared to PRO (days 1 after G1, P = 0.013; days 1 and 2 after G2, P = 0.014-0.033) following both games. KF eccentric strength decreased throughout recovery after G1 (PLA: P=0.001-0.047-PRO: P =0.004-0.22) in both trials, whereas after G2 it declined throughout recovery in PLA (P = 0.000-0.013) but only during the first two days (P = 0.000-0.014) in PRO. No treatment effect was observed for delayed onset of muscle soreness, leukocyte counts, and creatine kinase activity. PRO resulted in a faster recovery of protein and lipid peroxidation markers after both games. Reduced glutathione demonstrated a more short-lived reduction after G2 in PRO compared to PLA. In summary, these results provide evidence that protein feeding may more efficiently restore football-specific performance and strength and provide antioxidant protection during a congested game fixture.


#9 Hip and groin time-loss injuries decreased slightly but injury burden remained constant in men's professional football: the 15-year prospective UEFA Elite Club Injury Study
Reference: Br J Sports Med. 2018 Apr 24. pii: bjsports-2017-097796. doi: 10.1136/bjsports-2017-097796. [Epub ahead of print]
Authors: Werner J, Hagglund M, Ekstrand J, Walden M
Summary: Hip and groin injuries are common in men's professional football, but the time-trend of these injuries is not known. The aim of the study was to investigate hip and groin injury rates, especially time-trends, in men's professional football over 15 consecutive seasons. 47 European teams were followed prospectively for a varying number of seasons between 2001/2002 and 2015/2016, totalling 268 team seasons. Time-loss injuries and individual player exposure during training and matches were recorded. Injury rate was defined as the number of injuries/1000 hours and injury burden as the number of lay-off days/1000  hours. Time-trends for total hip and groin injuries and adductor-related injury rates were analysed using Poisson regression, and injury burden was analysed using a negative binomial regression model. Hip and groin injuries contributed 1812 out of 12 736 injuries (14%), with adductor-related injury as the most common of hip and groin injuries (n=1139, 63%). The rates of hip and groin injury and adductor-related injury were 1.0/1000 hours and 0.6/1000 hours, and these rates decreased significantly with on average 2% (Exp(b)=0.98, 95% CI 0.97 to 0.99, P=0.003) and 3% (Exp(b)=0.97, 95% CI 0.95 to 0.99, P<0.001) per season (year on year), respectively. The seasonal trend of hip and groin injury burden did not improve (Exp(b)=0.99, 95% CI 0.97 to 1.01, P=0.40). Hip and groin injuries constitute a considerable part of all time-loss injuries in men's professional football. Although there was a promising slight decreasing trend in the rates of hip and groin injury (as a category) and adductor-related injury (as a specific diagnosis), the injury burden remained at a consistent level over the study period.


#10 Body composition and somatotypes of male Zimbabwean Premier League football referees
Reference: J Sports Med Phys Fitness. 2018 Apr 20. doi: 10.23736/S0022-4707.18.08326-3. [Epub ahead of print]
Authors: Banda M, Grobbelaar HW, Terblanche E
Summary: Elite athletes need to optimise their body composition to deliver world class performances and this argument could be extended to elite referees as well. Unfortunately, there is a scarcity of body composition information among football referees. The aim of the study was to determine and compare the body composition and somatotypes of male football referees and assistant referees who officiated in the 2013 Zimbabwe Premier Football League. Forty-one participants (21 referees, 20 assistant referees; 8 FIFA, 33 ZIFA licenced referees) with a mean age of 34.89 ± 5.13 years took part. They had on average 10.85 ± 3.85 years of refereeing experience. The ISAK restricted anthropometric profile was used to measure body mass, height, skinfolds, girths and bone breadths, from which body mass index (BMI), waist-to-hip ratio (WHR), percentage body fat and somatotype were calculated. The referees were significantly taller than the assistant referees. The FIFA referees had moderately more desirable anthropometric profiles than the ZIFA referees. With a mean somatotype of 2.62-4.65-2.65, the total sample could be classified as balanced mesomorphs. They had lower BMI and body fat percentages than that observed among referees from other nationalities in the available literature. The results add to the paucity of information on the body composition of football officials. Referees aiming to excel at higher levels need to obtain and maintain an ideal body composition since elite level football is intense and requires high fitness levels.

Thu

17

May

2018

Latest research in football - week 14 - 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 Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players
Reference: Hum Mov Sci. 2018 Apr 3;59:81-87. doi: 10.1016/j.humov.2018.03.016. [Epub ahead of print]
Authors: Coratella G, Beato M, Schena F
Summary: The aim of this study was to investigate the relationship between in quadriceps and hamstrings inter-limb strength asymmetry and change of direction, sprinting and jumping abilities in U21 elite soccer players. Twenty-seven soccer players volunteered for this study. Isokinetic quadriceps and hamstrings peak torque was measured at high and low angular velocities, both in concentric and eccentric modalities. Performance in agility T-test, 20 + 20 m shuttle-test, 10 m and 30 m sprint, squat jump (SJ) and counter-movement jump (CMJ), were measured. Overall, time on agility T-test and 20 + 20 m shuttle-test was moderately and positively correlated with the quadriceps and hamstrings inter-limb eccentric peak torque asymmetry, both at high and low angular velocities. In addition, time on 10 m and 30 m sprints was moderately and positively correlated with the hamstrings inter-limb high-velocity concentric peak torque asymmetry. SJ and CMJ showed trivial to small correlations with hamstrings and quadriceps inter-limb peak torque asymmetry. The present results provide further information insight the role of lower-limb muscle strength balance in COD, sprinting and jumping performance.


#2 "Good, better, creative": the influence of creativity on goal scoring in elite soccer
Reference: J Sports Sci. 2018 Apr 6:1-5. doi: 10.1080/02640414.2018.1459153. [Epub ahead of print]
Authors: Kempe M, Memmert D
Summary: This study investigated the level of creativity of goals scored in football. Therefore, all goals in the Football FIFA World Cup 2010 and 2014, as well as the Football UEFA Euro 2016 were qualitatively examined. Three Football experts evaluated the last eight actions before each goal using a creativity scale ranging from 0 to 10 (0 = not creative, 10 = highly creative) of all goals scored via open play (311 goals in 153 matches). Level of creativity was revealed using an Analysis of Variance and the frquency of high highly creative goals using a Kruskall- Wallis Test. The results showed that the closer the actions to a goal, the more creative they were evaluated. Teams that advanced to the later rounds of the tournament demonstrated greater creativity than teams that failed to do so. High creativity in the last two actions before the actual shot on goal proved to be the best predictor for game success. In conclusion, this study is the first one to show that creativity seems to be a factor for success in high level football. Thereby it provides an empirical basis for the ongoing debate on the importance of creativity training in football.


#3 Mental Fatigue and Soccer: Current Knowledge and Future Directions
Reference: Sports Med. 2018 Apr 5. doi: 10.1007/s40279-018-0908-2. [Epub ahead of print]
Authors: Smith MR, Thompson C, Marcora SM, Skorski S, Meyer T, Coutts AJ
Summary: Fatigue is a complex state with multiple physiological and psychological origins. However, fatigue in soccer has traditionally been investigated from a physiological perspective, with little emphasis on the cognitive demands of competition. These cognitive demands may induce mental fatigue, which could contribute to the fatigue-related performance decrements observed during and after soccer matches. Recent research investigating the relationship between mental fatigue and soccer-specific performance supports this suggestion. This leading article provides an overview of the research in this emerging field, outlining the impact of mental fatigue on soccer-specific physical, technical, decision-making, and tactical performances. The second half of this review provides directions for future research in response to the limitations of the existing research. Emphasis is placed on translating the current body of knowledge into practical applications and developing a greater understanding of the mechanisms underpinning the negative impact of mental fatigue on soccer performance. A conceptual model is presented to help direct this future research.


#4 Specific Changes in Young Soccer Player's Fitness After Traditional Bilateral vs. Unilateral Combined Strength and Plyometric Training
Reference: Front Physiol. 2018 Mar 22;9:265. doi: 10.3389/fphys.2018.00265. eCollection 2018.
Authors: Ramirez-Campillo R, Sanchez-Sanchez J, Gonzalo-Skok O, Rodriguez-Fernandez A, Carretero M, Nakamura FY
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874317/pdf/fphys-09-00265.pdf
Summary: The aim of this study was to compare changes in young soccer player's fitness after traditional bilateral vs. unilateral combined plyometric and strength training. Male athletes were randomly divided in two groups; both received the same training, including strength training for knee extensors and flexors, in addition to horizontal plyometric training drills. The only difference between groups was the mode of drills technique: unilateral (UG; n = 9; age, 17.3 ± 1.1 years) vs. bilateral (TG; n = 9; age, 17.6 ± 0.5 years). One repetition maximum bilateral strength of knee muscle extensors (1RM_KE) and flexors (1RM_KF), change of direction ability (COD), horizontal and vertical jump ability with one (unilateral) and two (bilateral) legs, and limb symmetry index were measured before and after an 8-week in-season intervention period. Some regular soccer drills were replaced by combination of plyometric and strength training drills. Magnitude-based inference statistics were used for between-group and within-group comparisons. Beneficial effects (p < 0.05) in 1RM_KE, COD, and several test of jumping performance were found in both groups in comparison to pre-test values. The limb symmetry index was not affected in either group. The beneficial changes in 1RM_KE (8.1%; p = 0.074) and 1RM_KF (6.7%; p = 0.004), COD (3.1%; p = 0.149), and bilateral jump performance (from 2.7% [p = 0.535] to 10.5% [p = 0.002]) were possible to most likely beneficial in the TG than in the UG. However, unilateral jump performance measures achieved likely to most likely beneficial changes in the UG compared to the TG (from 4.5% [p = 0.090] to 8.6% [p = 0.018]). The improvements in jumping ability were specific to the type of jump performed, with greater improvements in unilateral jump performance in the UG and bilateral jump performance in the TG. Therefore, bilateral strength and plyometric training should be complemented with unilateral drills, in order to maximize adaptations.


#5 Switching between pitch surfaces: practical applications and future perspectives for soccer training
Reference: J Sports Med Phys Fitness. 2018 Apr 4. doi: 10.23736/S0022-4707.18.08278-6. [Epub ahead of print]
Authors: Rago V, Silva JR, Brito J, Barreira D, Mohr M, Krustrup P, Rebelo AN
Summary: Soccer training and completion is conventionally practiced on natural grass (NG) or artificial turf (AT). Recently, AT pitches for training / competition, and of unstable surfaces for injury prevention training has increased. Therefore, soccer players are frequently exposed to variations in pitch surface during either training or competition. These ground changes may impact physical and physiological responses, adaptations as well as the injury. The aim of this review was to summarize the acute physical and physiological responses, chronic adaptations, and injury risk associated with exercising on different pitch surfaces in soccer. Eligible studies were published in English, had pitch surface as an independent variable, and had physical, physiological or epidemiological information as outcome variables. Specific data extracted from the articles included the training response, training adaptations or injury outcomes according to different pitch surfaces. A total of 224 studies were retrieved from a literature search. Twenty articles met the inclusion criteria: 9 for acute physical and physiological responses, 2 for training adaptations and 9 for injury assessment. The literature lacks consistent evidence regarding the effects of pitch surface on performance and health outcomes in soccer players. However, it seems that occasionally switching training surfaces seems a valuable strategy for focusing on specific musculoskeletal queries and enhancing players' fitness. For instance, sand training may be occasionally proposed as complementary training strategy, given the recruitment of additional musculature probably not involved on firmer surfaces, but the possible training-induced adaptations of non-conventional soccer surfaces (e.g., sand) might potentially result into a negative transfer on AT or NG. Since the specific physical demands of soccer can differ between surfaces, coaches should resort to the use of non-traditional surfaces with parsimony, emphasizing the specific surface-related motor tasks, normally observed on natural grass or artificial turf. Further studies are required to better understand the physiological effects induced by systematic surface-specific training, or switching between pitch surfaces.


#6 Shoulder and elbow injuries in soccer goalkeepers versus field players in the National Collegiate Athletic Association, 2009-2010 through 2013-2014
Reference: Phys Sportsmed. 2018 Apr 4. doi: 10.1080/00913847.2018.1462083. [Epub ahead of print]
Authors: Goodman AD, Etzel C, Raducha JE, Owens BD
Summary: Examination of the incidence of shoulder and elbow injuries in the collegiate soccer player population is limited, as is comparison between goalkeepers and field players. We hypothesized that goalkeepers would have a higher incidence of shoulder and elbow injuries than field players. Furthermore, we sought to determine the incidence of shoulder and elbow injuries among National Collegiate Athletic Association (NCAA) soccer players, and to determine injury risk factors. The NCAA Injury Surveillance Program database was analyzed for injuries to NCAA men's and women's soccer players during the 2009-2010 through 2013-2014 academic years. The incidence of injury was calculated per 10,000 athletic exposures (AE) for goalkeepers versus field players, activity, and injury characteristics, and compared using univariate analysis and risk-ratios to determine injury risk factors. While the overall incidence of shoulder and elbow injuries in soccer players was 2.7/10,000AE [95% CI 2.62-2.78], the incidence among goalkeepers was 4.6-fold higher (8.3 vs. 1.8/10,000AE, p<0.0001). Goalkeepers had significantly higher incidences of injury in practice (21.3-fold) and in the preseason (16.1-fold) than field players. Women goalkeepers were disproportionately affected, with injury incidences 7.7-fold higher than women field players, and 1.9-fold higher than male goalkeepers. Acromioclavicular joint injuries, rotator cuff tears/sprains, and elbow and shoulder instability constituted the majority of the goalkeeper injuries. Shoulder and elbow injuries in NCAA soccer players are significantly more common in goalkeepers than field players. Incidence varies widely by position and injury, with a number of associated risk factors. Soccer players sustaining these injuries, along with their coaches and medical providers, may benefit from this injury data to best manage expectations and outcomes. Soccer governing bodies may use this to track injury incidence and response to preventative measures.


#7 The effects of maturation on jumping ability and sprint adaptations to plyometric training in youth soccer players
Reference: J Sports Sci. 2018 Apr 3:1-7. doi: 10.1080/02640414.2018.1459151. [Epub ahead of print]
Authors: Asadi A, Ramirez-Campillo R, Arazi H, Saez de Villarreal E
Summary: The aim of this study was to investigate the effects of maturation on power and sprint performance adaptations following 6 weeks of plyometric training in youth soccer players during pre-season. Sixty male soccer players were categorized into 3 maturity groups (Pre, Mid and Post peak height velocity [PHV]) and then randomly assigned to plyometric group and control group. Vertical jump, standing long jump, and 20-m sprint (with and without ball) tests were collected before- and after-intervention. After the intervention, the Pre, Mid and Post-PHV groups showed significant (P ≤ 0.05) and small to moderate effect size (ES) improvement in vertical jump (ES = 0.48; 0.57; 0.73), peak power output (E = 0.60; 0.64; 0.76), standing long jump (ES = 0.62; 0.65; 0.7), 20-m sprint (ES = -0.58; -0.66), and 20-m sprint with ball (ES = -0.44; -0.8; -0.55) performances. The Post-PHV soccer players indicated greater gains than Pre-PHV in vertical jump and sprint performance after training (P ≤ 0.05). Short-term plyometric training had positive effects on sprinting and jumping-power which are important determinants of match-winning actions in soccer. These results indicate that a sixty foot contact, twice per week program, seems effective in improving power and sprint performance in youth soccer players.


#8 Passing Decisions in Football: Introducing an Empirical Approach to Estimating the Effects of Perceptual Information and Associative Knowledge
Reference: Front Psychol. 2018 Mar 22;9:361. doi: 10.3389/fpsyg.2018.00361. eCollection 2018.
Authors: Steiner S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874613/pdf/fpsyg-09-00361.pdf
Summary: The importance of various information sources in decision-making in interactive team sports is debated. While some highlight the role of the perceptual information provided by the current game context, others point to the role of knowledge-based information that athletes have regarding their team environment. Recently, an integrative perspective considering the simultaneous involvement of both of these information sources in decision-making in interactive team sports has been presented. In a theoretical example concerning passing decisions, the simultaneous involvement of perceptual and knowledge-based information has been illustrated. However, no precast method of determining the contribution of these two information sources empirically has been provided. The aim of this article is to bridge this gap and present a statistical approach to estimating the effects of perceptual information and associative knowledge on passing decisions. To this end, a sample dataset of scenario-based passing decisions is analyzed. This article shows how the effects of perceivable team positionings and athletes' knowledge about their fellow team members on passing decisions can be estimated. Ways of transfering this approach to real-world situations and implications for future research using more representative designs are presented.


#9 Concurrent validation of an inertial measurement system to quantify kicking biomechanics in four football codes
Reference: J Biomech. 2018 Mar 21. pii: S0021-9290(18)30212-4. doi: 10.1016/j.jbiomech.2018.03.031. [Epub ahead of print]
Authors: Blair S, Duthie G, Robertson S, Hopkins W, Ball K
Summary: Wearable inertial measurement systems (IMS) allow for three-dimensional analysis of human movements in a sport-specific setting. This study examined the concurrent validity of a IMS (Xsens MVN system) for measuring lower extremity and pelvis kinematics in comparison to a Vicon motion analysis system (MAS) during kicking. Thirty footballers from Australian football (n = 10), soccer (n = 10), rugby league and rugby union (n = 10) clubs completed 20 kicks across four conditions. Concurrent validity was assessed using a linear mixed-modelling approach, which allowed the partition of between and within-subject variance from the device measurement error. Results were expressed in raw and standardised units for assessments of differences in means and measurement error, and interpreted via non-clinical magnitude-based inferences. Trivial to small differences were found in linear velocities (foot and pelvis), angular velocities (knee, shank and thigh), sagittal joint (knee and hip) and segment angle (shank and pelvis) means (mean difference: 0.2-5.8%) between the IMS and MAS in Australian football, soccer and the rugby codes. Trivial to small measurement errors (from 0.1 to 5.8%) were found between the IMS and MAS in all kinematic parameters. The IMS demonstrated acceptable levels of concurrent validity compared to a MAS when measuring kicking biomechanics across the four football codes. Wearable IMS offers various benefits over MAS, such as, out-of-laboratory testing, larger measurement range and quick data output, to help improve the ecological validity of biomechanical testing and the timing of feedback. The results advocate the use of IMS to quantify biomechanics of high-velocity movements in sport-specific settings.

Wed

16

May

2018

Football is...(#61)

Long throw-ins might create goal scoring opportunities

Mon

14

May

2018

Latest research in football - week 12 - 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 Evaluation of Seasonal Changes in Fitness, Anthropometrics, and Body Composition in Collegiate Division Ii Female Soccer Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002578. [Epub ahead of print]
Authors: Peart AN, Nicks CR, Mangum M, Tyo BM
Summary: The purpose of this study was to investigate anthropometrics, body composition, aerobic and anaerobic fitness of collegiate Division II female soccer players throughout a calendar year. Eighteen (20 ± 0.9y) NCAA division II female soccer players from the same team participated in the study. Anthropometrics and body composition variables were assessed in addition to the Counter Movement Jump (CMJ), Wingate Anaerobic Test (WAT), and peak oxygen uptake (VO2peak). Data were collected over five time points: end of competitive seasons (ECS1 and ECS2), beginning of off-season (BOS), end of off-season (EOS), and pre-season (PS). Repeated-measures analysis of variance (ANOVA) were conducted to compare test scores among all five data collection points. Where appropriate, Bonferroni post-hoc tests were used to determine which points were significantly different. Hip circumference (HC) decreased significantly (p < 0.001) from EOS (98.47 ± 6.5 cm) to PS (94.46 ± 6.8 cm). Fat mass (FM) (12.73 ± 5.4 kg) was significantly different in ECS2 compared to BOS and EOS means (p ≤ 0.05) and percentage of body fat (%BF) (20.08 ± 5.44) significantly different in ECS2 compared to ECS1, BOS, and EOS means (p ≤ 0.05), while fat-free mass (FFM) was maintained from ECS1 to ECS2. CMJ, WAT, and VO2peak performance did not significantly change from ECS1 to ECS2. Anthropometrics and body composition results are similar to previous studies measuring Division II to professional female soccer players. CMJ results remained consistent and are comparable to results on Division I female soccer players. Coaches and researchers can use these data to help design and evaluate training programs throughout a calendar year.


#2 The Effect of Match-Factors on the Running Performance of Elite Female Soccer Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002584. [Epub ahead of print]
Authors: Trewin J, Meylan C, Varley MC, Cronin J, Ling D
Summary: The purpose of this study was to examine the effects of match-factors on the match-running of elite female soccer players. Players from the same women's national team (n = 45) were monitored during 47 international fixtures (files = 606) across four years (2012-2015) using 10-Hz global positioning system devices. A mixed model was used to analyse the effects of altitude, temperature, match-outcome, opposition ranking and congested schedules. At altitude (>500 m) a small increase in the number of accelerations (ES = 0.40) and a small decrease in total distance (ES = -0.54) was observed, whereas at higher temperatures there were decreases in all metrics (ES = -0.83 to -0.16). Playing a lower-ranked team in a draw resulted in a moderate increase in high-speed running (ES = 0.89), with small to moderate decreases in total distance and low-speed running noted in a loss or a win. Winning against higher-ranked opponents indicated moderately higher total distance and low-speed running (ES = 0.75), compared to a draw. Whilst the number of accelerations were higher in a draw against lower-ranked opponents, compared to a win and a loss (ES = 0.95 and 0.89 respectively). Practitioners should consider the effect of match-factors on match-running in elite female soccer.


#3 Sequencing Effects of Plyometric Training Applied Before or After Regular Soccer Training on Measures of Physical Fitness in Young Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002525. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Gentil P, Loturco I, Sanchez-Sanchez J, Izquierdo M, Moran J, Nakamura FY, Chaabene H, Granacher U
Summary: The objective was to compare the effects of short-term (i.e., 7 week) plyometric training applied before (PJT-B) or after (PJT-A) soccer practice on components of physical fitness in young soccer players, a single-blind randomized controlled trial was conducted. Post-pubertal boys aged 17.0±0.5 years were allocated to three groups: PJT-B (n=12), PJT-A (n=14), and control (CON; n=12). The outcome measures included tests to evaluate 20-m speed, standing long jump [SLJ], squat jump [SJ], countermovement jump [CMJ], and drop jump [DJ], 20-m multistage shuttle running speed [MSSRT], and Illinois change of direction speed [ICODT]. While the CON performed soccer-specific training, the PJT-A and PJT-B groups conducted the same soccer-specific sessions but replaced ∼11% of their time with plyometric training. The PJT-B group performed plyometric exercises after a warm-up program, and the PJT-A group conducted plyometric exercises ∼10 minutes after the completion of soccer training. Analyses of variance (ANOVAs) were used to detect differences between groups in all variables for pre- and post-training tests. Main effects of time (all p<.01; d=0.19-0.79) and group x time interactions (all p<.05; d=0.17-0.76) were observed for all examined variables. Post hoc analyses revealed significant increases in the PJT-B group (SLJ: 9.4%, d=1.7; CMJ: 11.2%, d=0.75; 20-m MSSRT: 9.0%, d=0.77) and the PJT-A group (SLJ: 3.1%, d=0.7; CMJ: 4.9%, d=0.27; 20-m MSSRT: 9.0%, d=0.76). Post hoc analyses also revealed significant increases in the PJT-B group (20-m speed: -7.4%, d=0.75; 20-cm DJ reactive strength index: 19.1%, d=1.4; SJ: 6.3%, d=0.44; ICODT results: -4.2%, d=1.1). In general, our study revealed that plyometric training is effective in improving measures of physical fitness in young male soccer players when combined with regular soccer training. More specifically, larger training induced effects on physical fitness were registered if plyometric training was conducted prior to soccer specific training.


#4 Postactivation Potentiation Following Acute Bouts of Plyometric versus Heavy-Resistance Exercise in Collegiate Soccer Players
Reference: Biomed Res Int. 2018 Feb 7;2018:3719039. doi: 10.1155/2018/3719039. eCollection 2018.
Authors: Sharma SK, Raza S, Moiz JA, Verma S, Naqvi IH, Anwer S, Alghadir AH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5820625/pdf/BMRI2018-3719039.pdf
Summary: Postactivation potentiation is referred to as an acute and temporary enhancement of muscle performance resulting from previous muscle contraction. The purpose of this study was to compare the acute effect of plyometric exercise (PLY) and heavy-resistance exercise (RES) on the blood lactate level (BLa) and physical performance. Fourteen male collegiate soccer players were randomized to perform either RES or PLY first and then crossed over to perform the opposite intervention. PLY consisted of 40 jumps, whereas RES comprised ten single repetitions at 90% of one repetition maximum. BLa and physical performance (countermovement jump height and 20-m sprint) were measured before and at 1 and 10 min following the exercise. No significant difference was observed in the BLa for both exercises (PLY and RES). Relative to baseline, countermovement jump (CMJ) height was significantly better for the PLY group after 1 min (P = 0.004) and after 10 min (P = 0.001) compared to that of the RES group. The 20-m sprint time was significantly better for PLY at 10 min (P = 0.003) compared to that of RES. The present study concluded that, compared to RES, PLY causes greater potentiation, which leads to improved physical performance.


#5 Aerobic fitness in professional soccer players after anterior cruciate ligament reconstruction
Reference: PLoS One. 2018 Mar 22;13(3):e0194432. doi: 10.1371/journal.pone.0194432. eCollection 2018.
Authors: Almeida AM, Santos Silva PR, Pedrinelli A, Hernandez AJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864031/pdf/pone.0194432.pdf
Summary: Although anterior cruciate ligament (ACL) reconstruction is considered a successful procedure in restoring knee stability, few studies have addressed the issue of aerobic capacity after ACL surgery. Soccer players need technical, tactical and physical skills to succeed, such as good knee function and aerobic capacity. Our purpose is to evaluate aerobic fitness in ACL injured professional football players and six months after ACL reconstruction compared to a control group. Twenty athletes with ACL injury were evaluated and underwent ACL reconstruction with hamstrings autograft, and were compared to twenty healthy professional soccer players. The methods used to evaluate aerobic fitness were maximum oxygen uptake (VO2max) and ventilatory thresholds with a treadmill protocol, before and six months after surgery, compared to a control group. Knee function questionnaires, isokinetic strength testing and body composition evaluation were also performed. Median ACL-injured patients age was 21 years old, and controls 20.5 years old. (n.s.). Preoperative VO2max in the ACL injured group was 45.2 ± 4.3 mL/kg/min, postoperative 48.9 ± 3.8 mL/kg/min and controls 56.9 ± 4.2 mL/kg/min. (p< .001 in all comparisons). Body composition evaluation was similar in all situations. Knee function questionnaires and quadriceps peak torque deficit improved after surgery but were significantly lower compared to controls. Aerobic fitness is significantly reduced in professional soccer players with ACL injury, and six months of rehabilitation was not enough to restore aerobic function after ACL reconstruction, compared to non-injured players of the same level.


#6 Validation of Field Methods to Assess Body Fat Percentage in Elite Youth Soccer Players
Reference: Int J Sports Med. 2018 Mar 21. doi: 10.1055/s-0044-101145. [Epub ahead of print]
Authors: Munguia-Izquierdo D, Suarez-Arrones L, Di Salvo V, Paredes-Hernandez V, Alcazar J, Ara I, Kreider R, Mendez-Villanueva A
Summary: This study determined the most effective field method for quantifying body fat percentage in male elite youth soccer players and developed prediction equations based on anthropometric variables. Forty-four male elite-standard youth soccer players aged 16.3-18.0 years underwent body fat percentage assessments, including bioelectrical impedance analysis and the calculation of various skinfold-based prediction equations. Dual X-ray absorptiometry provided a criterion measure of body fat percentage. Correlation coefficients, bias, limits of agreement, and differences were used as validity measures, and regression analyses were used to develop soccer-specific prediction equations. The equations from Sarria et al. (1998) and Durnin & Rahaman (1967) reached very large correlations and the lowest biases, and they reached neither the practically worthwhile difference nor the substantial difference between methods. The new youth soccer-specific skinfold equation included a combination of triceps and supraspinale skinfolds. None of the practical methods compared in this study are adequate for estimating body fat percentage in male elite youth soccer players, except for the equations from Sarria et al. (1998) and Durnin & Rahaman (1967). The new youth soccer-specific equation calculated in this investigation is the only field method specifically developed and validated in elite male players, and it shows potentially good predictive power.


#7 Cardiac deformation parameters and rotational mechanics by cardiac magnetic resonance feature tracking in pre-adolescent male soccer players
Reference: Cardiol Young. 2018 Mar 21:1-3. doi: 10.1017/S1047951118000343. [Epub ahead of print]
Authors: Malek LA, Barczuk-Falęcka M, Brzewski M
Summary: The purpose of the study was to analyse whether prolonged and regular physical training in children leads to changes in myocardial systolic deformation and rotational mechanics. For that purpose, cardiac MRI feature tracking was performed retrospectively in 35 pre-adolescent male soccer players and 20 matched controls. There were no changes in global strain, but left ventricular twist and apical rotation were greater in soccer players, which adds to the features of paediatric athlete's heart.


#8 Effect of Core Muscle Strengthening Exercises (Including Plank and Side Plank) on Injury Rate in Male Adult Soccer Players: A Systematic Review
Reference: Sportverletz Sportschaden. 2018 Mar;32(1):35-46. doi: 10.1055/a-0575-2324. Epub 2018 Mar 20. [Article in German; Abstract available in German from the publisher]
Authors: Blasimann A, Eberle S, Scuderi MM
Summary: Soccer is seen as highly intensive sport with an increased injury rate. Male adults are the players with the highest injury incidence. Accordingly, the importance of core muscle strengthening to prevent injury has increased in the past few years. Up to date, core muscle strengthening plays an important role in different prevention programs, such as the "FIFA 11 +". The aim of this systematic review was to investigate the effect of core muscle strengthening on injury rate in male adult soccer players, including at least the known and easy exercises "plank" and "side plank", on injury rate in male adult soccer players. The databases PubMed, PEDro, Cochrane Library, SPORTDiscus and Cinahl were searched systematically. Included studies had to comprise exercises for core muscles as an intervention (as a part of a prevention program) for adult male soccer players. The control group had to continue their usual exercise routine. The exercises "plank" and "side plank" were mandatory elements of the training program. The number of injuries and/or the injury rate (per 1000 hours) were defined as outcomes. The quality of the included studies was assessed with the PEDro scale and the Risk of Bias tool. Seven studies with 2491 participants in total could be included. Two studies found a significant decrease in the injury rate in the intervention group (p < 0.05, p < 0.001 respectively). In two studies, no significance level was reported, but the training showed preventive effects in the intervention group. In the other three studies, no significant changes in the injury rate were found (p > 0.05). The seven included studies differed greatly with respect to the applied methods, the chosen interventions and the obtained results. Furthermore, core muscles were never trained separately but were always part of a program containing other preventive elements. Therefore, it was difficult to compare the studies. However, prevention programs including strengthening exercises for core muscles tend to positively affect the injury rate. Based on the literature found, the research question cannot definitively be answered. In the future, further studies are needed which investigate the effect of isolated core muscle training on the injury rate of soccer players.


#9 In-season monitoring of hip and groin strength, health and function in elite youth soccer: Implementing an early detection and management strategy over two consecutive seasons
Reference: J Sci Med Sport. 2018 Mar 14. pii: S1440-2440(18)30071-9. doi: 10.1016/j.jsams.2018.03.004. [Epub ahead of print]
Authors: Wollin M, Thorborg K, Welvaert M, Pizzari T
Summary: The primary purpose of this study was to describe an early detection and management strategy when monitoring in-season hip and groin strength, health and function in soccer. Secondly to compare pre-season to in-season test results. Twenty-seven elite male youth soccer players (age: 15.07±0.73years) volunteered to participate in the study. Monitoring tests included: adductor strength, adductor/abductor strength ratio and hip and groin outcome scores (HAGOS). Data were recorded at pre-season and at 22 monthly intervals in-season. Thresholds for alerts to initiate further investigations were defined as any of the following: adductor strength reductions >15%, adductor/abductor strength ratio <0.90, and HAGOS subscale scores <75 out of 100 in any of the six subscales. Overall, 105 alerts were detected involving 70% of players. Strength related alerts comprised 40% and remaining 60% of alerts were related to HAGOS. Hip adductor strength and adductor/abductor strength ratio were lowest at pre-season testing and had increased significantly by month two (p<0.01, mean difference 0.26, CI95%: 0.12, 0.41N/kg and p<0.01, mean difference 0.09, CI95%: 0.04, 0.13 respectively). HAGOS subscale scores were lowest at baseline with all, except Physical Activity, showing significant improvements at time-point one (p<0.01). Most (87%) time-loss were classified minimal or mild. In-season monitoring aimed at early detection and management of hip and groin strength, health and function appears promising. Hip and groin strength, health and function improved quickly from pre-season to in-season in a high-risk population for ongoing hip and groin problems.


#10 Exploring the effects of mental and muscular fatigue in soccer players' performance
Reference: Hum Mov Sci. 2018 Apr;58:287-296. doi: 10.1016/j.humov.2018.03.004. Epub 2018 Mar 15.
Authors: Coutinho D, Goncalves B, Wong DP, Travassos B, Coutts AJ, Sampaio J
Summary: This study examined the effects of induced mental and muscular fatigue on soccer players' physical activity profile and collective behavior during small-sided games (SSG). Ten youth soccer players performed a 5vs5 SSG under three conditions: a) control, playing without any previous activity; b) muscular fatigue, playing after performing a repeated change-of-direction task; c) mental fatigue, playing after completing a 30 min Stroop color-word task. Players' positional data was used to compute time-motion and tactical-related variables. The muscular fatigue condition resulted in lower distances covered in high speeds (∼27%, 0.3; ±0.5) than the control condition. From the tactical perspective, the muscular fatigue condition resulted in lower distance between dyads and players spent ∼7% more time synchronized in longitudinal displacements than the control condition (0.3; ±0.3). Additionally, players spent ∼14% more time synchronized with muscular fatigue than with mental fatigue (0.7; ±0.3). The mental fatigue condition resulted in a very likely more predictable pattern in the distance between dyads than in muscular fatigue condition (0.4; ±0.2). Also, the mental fatigue possibly decreased the teams' stretch index when compared with control (0.2; ±0.3) and likely increased compared with muscular fatigue (0.5; ±0.5). The better levels of longitudinal synchronization after muscular fatigue, might suggest the usage of tactical-related tasks after intense exercise bouts. The lower physical performance and time spent longitudinally synchronized after mental fatigue, should alert to consider this variable before matches or training activities that aim to improve collective behavior.


#11 Is Bony Hip Morphology Associated With Range of Motion and Strength in Asymptomatic Male Soccer Players?
Reference: J Orthop Sports Phys Ther. 2018 Mar 16:1-29. doi: 10.2519/jospt.2018.7848. [Epub ahead of print]
Authors: Mosler AB, Agricola R, Thorborg K, Weir A, Whiteley RJ, Crossley KM, Holmich P
Summary: Study Design Cross-sectional cohort study. Background Athletes with femoroacetabular impingement (FAI) syndrome have cam and/or pincer morphology, pain on orthopaedic testing, and often have reduced hip range of motion (ROM) and strength. However, cam and pincer morphology are also common in asymptomatic hips. Therefore, it is currently unknown whether the ROM and strength deficits observed in athletes with FAI syndrome result from the variance in their bony hip morphology or hip condition. Objectives To investigate the relationship between musculoskeletal screening findings and bony hip morphology in asymptomatic male soccer players. Methods Male professional soccer players in Qatar were screened specifically for hip/groin pain in 2 consecutive seasons. The screening battery included: pain provocation, ROM and strength tests, and hip radiographs. Univariate and multivariate regression analyses using generalised estimating equations evaluated the relationship between musculoskeletal screening findings and each bony hip morphological variant (cam, large cam, pincer, and acetabular dysplasia). Results Asymptomatic hips with cam and large cam morphology were associated with lower ROM in internal rotation and bent knee fall out, and a higher likelihood of pain on provocation testing. Pincer morphology was associated with lower abduction ROM and higher abduction strength. Acetabular dysplasia was associated with higher abduction ROM. Each association was weak and demonstrated poor or failed discriminatory power. Conclusion Bony hip morphology is associated with hip joint ROM and abduction strength, but musculoskeletal screening tests have a poor abi