Latest research in football - week 37 - 2019

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

Following studies were retrieved for this week:

#1 A Single Session of Straight Line and Change-of-Direction Sprinting per Week Does Not Lead to Different Fitness Improvements in Elite Young Soccer Players
Reference: J Strength Cond Res. 2019 Sep 2. doi: 10.1519/JSC.0000000000003369. [Epub ahead of print]
Authors: Beato M, Bianchi M, Coratella G, Merlini M, Drust B
Summary: Effective prescription is especially important in elite soccer players, who have a very limited time to dedicate to specific physical development as a consequence of factors such as congested match schedules and travel. The aim of this study was to compare the effectiveness of one repeated-sprint training (RST) session per week over an 8-week period on physical performance. A second aim was to compare the effect of RST involving straight sprints (RST-SS) or changes of direction (RST-COD). This study used a randomized pre-post parallel group trial design. The elite soccer players were randomly assigned to either an RST-SS (10 players) or RST-COD (10 players). RST-SS was 3 sets of 7 × 30-m sprints with 20-second and 4-minute recovery between sprints and sets, respectively. RST-COD was 3 sets of 7 × 20 + 20 m (one COD of 180°) shuttle sprints with 20-second and 4-minute recovery between sprints and sets, respectively. The physical tests selected were long jump, repeated-sprint ability (RSA) best, RSA mean, 505 agility test, Yo-Yo recovery level 1, 10, 30, and 40 m sprints. RST-SS reported unclear variations in long jump, sprint 30 m, sprint 40 m, RSA best, and RSA mean, whereas RST-COD showed unclear and trivial variations in sprint 10 m, sprint 30 m, sprint 40 m, RSA best, and RSA mean. The between-group analysis did not report any statistical difference. In conclusion, a single session of RST-SS and RST-COD do not improve soccer-specific fitness indicators in elite youth players during the season.

#2 The Effects of Six-Weeks Change of Direction Speed and Technique Modification Training on Cutting Performance and Movement Quality in Male Youth Soccer Players
Reference: Sports (Basel). 2019 Sep 6;7(9). pii: E205. doi: 10.3390/sports7090205.
Authors: Dos'Santos T, McBurnie A, Comfort P, Jones PA
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Summary: Cutting manoeuvres are important actions associated with soccer performance and a key action associated with non-contact anterior cruciate ligament injury; thus, training interventions that can improve cutting performance and movement quality are of great interest. The aim of this study, therefore, was to determine the effects of a six-week change of dire[ction (COD) speed and technique modification training intervention on cutting performance and movement quality in male youth soccer players (U17s, n = 8) in comparison to a control group (CG) (U18s, n = 11) who continued 'normal' training. Cutting performance was assessed based on completion time and COD deficit, and the field-based cutting movement assessment score (CMAS) qualitative screening tool was used to assess cutting movement quality. Significant main effects for time (pre-to-post changes) (p ≤ 0.041, η2 = 0.224-0.839) and significant interaction effects of time and group were observed for cutting completion times, COD deficits, and CMASs. Improvements in completion time (p < 0.001, g = 1.63-1.90, -9% to -11% vs. -5% to 6%) and COD deficit (p ≤ 0.012, g = -1.63 to -2.43, -40-52% vs. -22% to -28%) for the COD intervention group (IG) were approximately two-times greater than the CG. Furthermore, lower CMASs (i.e., improved cutting movement quality) were only observed in the IG (p ≤ 0.025, g = -0.85 to -1.46, -23% to -34% vs. 6-19%) compared to the CG. The positive changes in CMASs were attributed to improved cutting technique and reduced incidences of high-risk deficits such as lateral trunk flexion, extended knee postures, knee valgus, hip internal rotation, and improved braking strategies. The results of this study indicate that COD speed and technique modification training, in addition to normal skills and strength training, improves cutting performance and movement quality in male youth soccer players. Practitioners working with male youth soccer players should implement COD speed and technique modification training to improve cutting performance and movement quality, which may decrease potential injury-risk.

#3 Comparing Balance Control Between Soccer Players and Non-Athletes During a Dynamic Lower Limb Reaching Task
Reference: Res Q Exerc Sport. 2019 Sep 3:1-6. doi: 10.1080/02701367.2019.1649356. [Epub ahead of print]
Authors: Snyder N, Cinelli M
Summary: Balance control is an essential element of locomotion that enhances biomotor abilities and physical performance. Individuals with extensive soccer experience display superior static single leg balance control compared to athletes of other sports as well as non-athletes. However, during a match, players often encounter greater challenges to single leg balance that require rapid decision-making skills and dynamic stability. The purpose of this study was to determine if individuals with extensive soccer training demonstrate superior single-leg balance control compared to non-athletes during a dynamic lower limb reaching task. 22 varsity soccer players were matched with 21 non-athlete controls. Single-leg balance control was assessed during a Go/No-Go lower limb reaching task. Centre of pressure displacement (dCOP) was measured for both the dominant and non-dominant feet and compared between groups. Soccer players displayed reduced dCOP during All Go trials compared to non-athletes, particularly in the medial-lateral plane. Additionally, soccer players displayed reduced anterior-posterior dCOP during Go/No-Go trials compared to non-athletes, particularly on their dominant foot. Athletes with soccer-specific training demonstrate improved executive control and use of proprioceptive information, which results in an improved ability to maintain single-support balance and corral COP during a dynamic visuomotor lower limb-reaching task. As such, balance training may be a useful addition to athlete training regimes to improve sport-specific performance. Future research would compare these results to athletes of other sports to explore balance control during a visuomotor reaching task and how it may differ based on sport training history.

#4 Lactate Equivalent for Maximal Lactate Steady State Determination in Soccer
Reference: Res Q Exerc Sport. 2019 Sep 3:1-12. doi: 10.1080/02701367.2019.1643446. [Epub ahead of print]
Authors: Garcia-Tabar I, Rampinini E, Gorostiaga EM
Summary: The association between an overlooked classical Lactate Threshold (LT), named "Minimum Lactate Equivalent" (LEmin), with Maximal Lactate Steady State (MLSS) has been recently described with good MLSS prediction results in endurance-trained runners. This study aimed to determine the applicability of LEmin to predict MLSS in lower aerobic-conditioned individuals compared to well-established blood lactate-related thresholds (BLTs). Fifteen soccer players [velocity at MLSS (MLSSV) 13.2 ± 1.0 km·h-1; coefficient of variation (CV) 7.6%] conducted a submaximal discontinuous incremental running test to determine BLTs and 3-6 constant velocity running tests to determine MLSSV. LEmin did not differ from conventional LTs (p > .05) and was 24% lower than MLSS (p < .001; ES: 3.26). Among LTs, LEmin best predicted MLSSV (r = 0.83; p < .001; SEE = 0.59 km·h-1). There was no statistical difference between MLSS and estimated MLSS using LEmin prediction formula (p = .99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.58 km·h-1 and ±1.13 km·h-1, respectively. LEmin best predicted MLSSV (r = 0.92; p < .001; SEE = 0.54 km·h-1) in the pooled data of soccer players and endurance-trained runners of the previous study (n = 28; MLSSV range 11.2-16.5 km·h-1; CV 9.8%). Results support LEmin to be one of the best single predictors of MLSS. This study is the sole study providing specific operational regression equations to estimate the impractical gold standard MLSSV in soccer players by means of a BLT measured during a submaximal single-session test.

#5 Creative and Intuitive Decision-Making Processes: A Comparison of Brazilian and German Soccer Coaches and Players
Reference: Res Q Exerc Sport. 2019 Sep 3:1-15. doi: 10.1080/02701367.2019.1642994. [Epub ahead of print]
Authors: Klatt S, Noël B, Musculus L, Werner K, Laborde S, Lopes MC, Greco PJ, Memmert D, Raab M
Summary:  The concepts of creativity and intuition have been well studied in isolation, but less is known about their distinctive contributions to option generation in decision making. We examined the relation between creative and intuitive decision making in two studies-one involving coaches and one involving soccer players-using video footage of real soccer matches. Additionally, we analyzed whether this relation is culture generic or culture specific by conducting matched cross-cultural studies in a European and a South American country. In Study 1, results indicate a conceptual overlap of creativity and intuition for Brazilian and German soccer coaches. Furthermore, coaches did not differ in their evaluation of creative and intuitive actions of players of both cultures. In Study 2, we found that for both subsamples the total number of generated options was positively correlated with the quality of the first and the final option and that the quality of players' first (intuitive) option was higher than that of options generated later. Moreover, results indicate a positive correlation between a player's creativity score and the quality of the first generated option for the whole sample. Overall, our findings provide meaningful information regarding athletes' and coaches' option-generation processes in decision making in complex team sports.

#6 Should you let your child play football? What about soccer or hockey?
Reference: Appl Neuropsychol Child. 2019 Sep 2:1-6. doi: 10.1080/21622965.2019.1654385. [Epub ahead of print]
Authors: Ferraro FR, Cuccolo K, Wise RA
Summary: College students (n = 120) answered 18 yes-no questions that varied the child's gender (male, female), grade (grade school, high school, college), and sport (football, soccer, hockey). The format of the 18 yes or no questions was "If you had a child in (grade school, high school, college) would you let (him, her) play (football, soccer, hockey)"? Similar to a previous study, a large percentage (78.8%) of the respondents answered yes to the questions about football, indicating that they would permit their children to play football despite the risk of concussion (96% yes for male children, 67% yes for female children). Although the number of respondents who would allow their male child to play soccer (98% for male children, 99% for female children) or hockey (92% for male children, 89% for female children) was similar to the percentage of respondents that would allow their male child to play football, significantly more respondents would allow their female child to play soccer or hockey than football. This result is potentially problematic because soccer and hockey have high rates of concussion, especially for females, which suggests that the respondents may have been unaware of this fact.

#7 Psychological characteristics in women football players: Skills, mental toughness, and anxiety
Reference: Scand J Psychol. 2019 Sep 6. doi: 10.1111/sjop.12571. [Epub ahead of print]
Authors: Kristjánsdóttir H, Jóhannsdóttir KR, Pic M, Saavedra JM
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Summary: Women's football has been far less studied than men's. This work's objectives were to: (1) analyze the differences in psychological skills, mental toughness (MT), and anxiety in women football players according to their level (national team, first division, and second division); and (2) predict those three levels (using a multivariate model) according to the players' psychological skills, mental toughness, and anxiety. One hundred and forty-two Icelandic women football players (23.5 ± 3.5 years) participated in the study. They were classified into three groups according to their level: national team, and first and second divisions. Three questionnaires were used: the Test of Performance Strategies Questionnaire, the Sport Mental Toughness Questionnaire, and the Sport Anxiety Scale-2 questionnaire. A one-way ANOVA with Bonferroni post hoc correction was used to examine differences between teams. Applying a classification tree analysis, the participants were classified into three groups according to their level. There were few differences between the three groups in psychological skills, but in mental toughness and anxiety the national team had the highest and lowest values respectively, and the first and second division players differed in relaxation in competition (TOPS), total score and confidence (SMTQ), and worry (SAS-2). The classification tree correctly classified 54.9% of the sample with the variables total score (SMTQ) and activation in practice (TOPS). Therefore, given the relevance that psychological attributes appear to have for women football players' performance, it would seem indispensable to incorporate the figure of the sports psychologist into national and club teams.

#8 Different Marks in the Pitch Constraint Youth Players' Performances During Football Small-sided Games
Reference: Res Q Exerc Sport. 2019 Sep 3:1-9. doi: 10.1080/02701367.2019.1645938. [Epub ahead of print]
Authors: Coutinho D, Gonçalves B, Travassos B, Folgado H, Figueira B, Sampaio J

Summary: This study aimed to compare players' performances when manipulating the external markings of the pitch during football small-sided games. Ten under-15 players performed a 5-a-side (plus goalkeepers) under three conditions: (i) Lines, the game was played in a pitch in which the external boundaries were painted with full lines; (ii) Dashed, the game was played in a pitch in which the external boundaries were painted with dashed lines; (iii) Corners, the game was played in a pitch were the external boundaries were delimited by one marker at each pitch corner. Players' positional data was used to compute tactical and time-motion variables. Also, technical analysis was comprised using video footage. Results showed similar tactical, physical and technical performances between the Lines and Dashed conditions. In contrast, the Lines condition showed small higher effects than Corners scenario in the time spent synchronized in longitudinal and lateral displacements, game pace, total distance covered, distance covered while jogging, number successful dribbles and shots on target. The Lines scenario has also revealed a lower effective playing space, distance covered at walking and running and a lower number of passes (small effects) compared to Corners. These results highlight that these changes in informational perception constraints modify players movement behavior. Accordingly, pitches with more visible boundaries were likely to decrease team dispersion, which may optimize team synchrony and technical performances, while decreasing the distance covered at higher speeds. Coaches may use this information to modify the types of pitch external boundaries markings, exposing the players to different environmental information.

#9 Return to play after surgery for isolated unstable syndesmotic ankle injuries (West Point grade IIB and III) in 110 male professional football players: a retrospective cohort study
Reference: Br J Sports Med. 2019 Aug 31. pii: bjsports-2018-100298. doi: 10.1136/bjsports-2018-100298. [Epub ahead of print]
Authors: D'Hooghe P, Grassi A, Alkhelaifi K, Calder J, Baltes TP, Zaffagnini S, Ekstrand J
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Summary: The purpose was to evaluate time to return to play following surgical stabilisation of isolated unstable syndesmosis injuries in a cohort of professional male football players. All professional football players undergoing surgery for isolated unstable syndesmosis injury (West Point grade ≥IIB) at a specialised Orthopaedic and Sports Medicine Hospital were followed up until return to play (minimum ≥6 months). Players with a stable syndesmosis, injuries older than 6 weeks, concomitant medial or lateral malleolar fracture or previous ankle surgery were excluded. During rehabilitation, time required to return to sports-specific rehabilitation, team training and first match play, were recorded. Between January 2012 and December 2017, a total of 110 male professional football players were included. The mean time required to begin on field rehabilitation was 37±12 days, while the mean time to return to team training was 72±28 days. The first official match was played on average 103±28 days postoperatively. Multivariable analysis revealed that the severity of injury, the concomitant presence of talar cartilage injury and the age of the player were significantly associated (p<0.00001) with time to return to on field rehabilitation, team training and match play. In this cohort of professional football players, surgical stabilisation of isolated unstable syndesmosis injuries (West Point grade ≥IIB) allowed for relatively quick return to play. High grade injury (West Point grade III), concomitant cartilage injury and greater age were associated with longer return to play times.

#10 Blood Biomarkers of Recovery Efficiency in Soccer Players
Reference: Int J Environ Res Public Health. 2019 Sep 6;16(18). pii: E3279. doi: 10.3390/ijerph16183279.
Authors: Nowakowska A, Kostrzewa-Nowak D, Buryta R, Nowak R
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Summary: Physical exercise strongly affects human metabolism and causes biochemical changes. This study aimed to investigate the relationship between routine plasma biomarker levels and recovery efficiency in soccer players during an entire competitive match season. The players participating in the study were divided into a midfielder/defender group (seven midfielders and seven defenders) and a goalie/substitute group (six persons-goalkeepers and players with a short cumulative match-time). The fasting capillary blood samples were taken 17-24 h after each competitive match. The blood plasma was used to determine the creatinine, urea, alkaline phosphatase, creatine kinase, lactate dehydrogenase, aspartate and alanine aminotransferase, iron and magnesium levels of the athletes. The levels of (AST) (aspartate aminotransferase), (ALT) (alanine aminotransferase) and (Cr) creatinine were higher in the midfielder/defender group than in the control group, but only AST and Cr significantly varied over time (AST decreased, and Cr increased with time). The (LDH) (lactate dehydrogenase) activity and urea level were significantly lower in the midfielder/defender group than in the goalie/substitute group, and it significantly varied over time (LDH decreased, and urea increased with time). No differences in the (CK) creatine kinase and (ALP) alkaline phosphatase activities between the groups was found, although CK increased significantly with time in the midfielder/defender group (particularly midfielders in the spring round). In midfielders, the AST activity and the iron level were significantly lower in the spring than in the autumn round. On the contrary, ALT, CK, urea and magnesium levels were significantly higher in the spring than in autumn round. A long-term measurement of biochemical parameters in elite soccer players indicated that AST, CK, LDH and creatinine levels, when analyzed together, could constitute a useful set of markers for monitoring recovery periods.

#11 Effect of Pre-training and Post-training Nordic Exercise on Hamstring Injury Prevention, Recurrence, and Severity in Soccer Players
Reference:  Ann Rehabil Med. 2019 Aug;43(4):465-473. doi: 10.5535/arm.2019.43.4.465. Epub 2019 Aug 31.
Authors: Elerian AE, El-Sayyad MM, Dorgham HAA
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Summary: The purpose was to investigate the effect of adding Nordic exercise as post-training in decreasing hamstring initial, recurrent injuries rates, and their severity. In this randomly controlled trial study, 34 professional football players aged 21 to 35 years were randomly assigned into two groups (17 players each) from Sporting clubs at Alexandria, Egypt. For group one, Nordic hamstring exercise (NHE) was performed pre-training and post-training. For group two, NHE was only performed pre-training. The control group was the same team during the previous season. Length of the trial was 12 weeks. The Australian football association injury form was used to collect incidence of injuries for each subject in both groups. Pooled results based on total injuries showed that group one had significantly less hamstring initial injuries (92% less) than the previous season, while group two had 80% less initial injuries and 85% less recurrent injuries than previous season. Regarding the severity of injuries in term of mean number of absent days, it was 1 day for group one and 2.7 days for group two while it was 7.95 days for the previous season during total risk time of 116.3±13.2 and 117.6±5.7 exposure hours for group one and group two, respectively. The use of NHE as a prevention protocol was effective in reducing all hamstring injuries with the use of NHE during pre-training and post-training having the greatest effect.

#12 Pressure pain sensitivity over nerve trunk areas and physical performance in amateur male soccer players with and without chronic ankle instability
Reference: Phys Ther Sport. 2019 Sep 4;40:91-98. doi: 10.1016/j.ptsp.2019.09.002. [Epub ahead of print]
Authors: Navarro-Santana MJ, Albert-Lucena D, Gómez-Chiguano GF, Plaza-Manzano G, Fernández-de-Las-Peñas C, Cleland J, Pérez-Silvestre Á, Asín-Izquierdo I
Summary: Chronic ankle instability (CAI) is reported after ankle sprain. Our aim was to assess differences in mechanical pain sensitivity of lower extremity nerve trunks and physical performance between amateur soccer players with and without CAI. Fifty-five male soccer players, 28 with and 27 without CAI participated in this stud. The perceived instability was assessed with the Cumberland Ankle Instability Tool (CAIT). Pressure pain thresholds (PPTs) on the common peroneal and tibialis nerve trunks, vertical jump, lateral step-down test and joint position sense of the knee were assessed by a blinded assessor.Soccer players with CAI showed lower PPTs over the common peroneal nerve than those without CAI (between-groups mean difference: 1.0 ± 0.8 kg/cm2, P < 0.001). No differences for PPT over the tibialis posterior (P = 0.078) or any physical performance outcome (knee joint positioning sense [P = 0.798], lateral step-down test [P = 0.580] and vertical jump variables [all, P > 0.310]) were found. PPT over the common peroneal nerve exhibited a significant moderate correlation with the CAIT score (r = 0.528, P < 0.001).Amateur soccer players with CAI have higher pressure pain sensitivity over the common peroneal nerve but exhibit similar physical performance to amateur soccer players without CAI.

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