Latest research in football - week 6 - 2016

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 Physical and Physiological Characteristics of Various-Sided Games in Elite Female Soccer
Reference: Int J Sports Physiol Perform. 2016 Feb 9. [Epub ahead of print]
Authors: Mara JK, Thompson KG, Pumpa KL
Summary: The purpose of the study was to investigate the physical and physiological response to different formats of various-sided games. Eighteen elite female soccer players wore 15Hz global positioning system (GPS) devices and heart-rate monitors during various-sided games (small: 4v4 and 5v5, medium: 6v6 and 7v7, large: 8v8 and 9v9). Players covered more relative sprinting distance during large-sided games when compared with small- (p < 0.001, d = 0.69) and medium- (p < 0.001, d = 0.54) sided games. In addition, a greater proportion of total acceleration efforts that had a commencement velocity < 1 m/s were observed in small-sided games (44.7% ± 5.5) when compared to large-sided games (36.7% ± 10.6) (p = 0.018, d = 0.94). This was accompanied by a greater proportion of acceleration efforts with a final velocity equivalent to the sprint threshold in large-sided games (15.4% ± 7.7), than small-sided games (5.2% ± 2.5) (p < 0.001, d = 1.78). The proportion of time spent in heart rate zone 4 (> 85% HRmax) was greatest during small-sided games (69.8% ± 2.5) compared with medium- (62.1% ± 2.8, d = 2.90) and large- sided games (54.9% ± 3.1) (p < 0.001, d = 5.29). The results from this study demonstrate that coaches can use small-sided games as an aerobic conditioning stimulus and to develop players' explosiveness and repeat sprint ability over short durations. Large-sided games can be used to maintain aerobic capacity and develop maximum speed over longer distances.

#2 Two-Weeks of Repeated-Sprint Training in Soccer: To Turn or Not to Turn?
Reference: Int J Sports Physiol Perform. 2016 Feb 9. [Epub ahead of print]
Authors: Taylor JM, Macpherson T, McLaren SJ, Spears I, Weston M.
Summary: The purpose of the study was to compare the effects of two repeated-sprint training programs on fitness in soccer. Fifteen semi-professional soccer players (age 24 ± 4 y; body mass 77 ± 8 kg) completed 6 repeated-sprint training sessions over a two week period. Players were assigned to a straight-line (STR) (n = 8; 3-4 sets of 7 × 30-m) or change of direction (CoD) (n = 7; 3-4 sets of 7 × 20-m) repeated-sprint training group. Performance measures included 5, 10 and 20-m sprints, countermovement jump, Illinois agility and Yo-Yo intermittent recovery level 1 (YYIRTL1) performance. Internal (heart rate) and external (GPS-derived measures) training loads were monitored throughout. Data were analysed using magnitude-based inferences. Internal and external loads were higher in STR than CoD with large differences in maximum velocity (28.7%; ±90% confidence limits 3.3%), moderate differences in mean heart rates (7.0%; ±1.4%) and PlayerLoad™ (17.6%; ±8.6%), and small differences in peak heart rates (3.0%; ±1.6%). Large improvements in 5-m (STR: 9.6%; ±7.0% and CoD: 9.4%; ±3.3%), 10-m (STR: 6.6%; ±4.6% and CoD: 6.7%; ±2.2%) and 20-m (STR: 3.6; ±4.0% and CoD: 4.0; ±1.7%) sprints were observed. Large and moderate improvements in YYIRTL1 performance were observed following STR (24.0%; ±9.3%) and CoD (31.0%; ±7.5%), respectively. Between-group differences in outcome measures were unclear. Two weeks of repeated-sprint training stimulates improvements in acceleration, speed and high-intensity running performance in soccer players. Despite STR inducing higher internal and external training loads, training adaptations were unclear between training modes, indicating a need for further research.

#3 Technical and physical determinants of soccer match-play performance in elite youth soccer players
Reference: J Sports Med Phys Fitness. 2016 Feb 11. [Epub ahead of print]
Authors: Rowat O, Fenner J, Unnithan V
Summary: The purpose of the study was to evaluate whether physical performance characteristics could be a better predictor than technical skills in determining the technical level of county soccer players in a match situation. With institutional ethics approval, 25 male youth soccer players aged 16-18.5 years from a professional soccer academy in South East Asia were selected and height and body mass were recorded. Players were tested for sexual maturity (pubertal development scale [PDS] self-assessment), aerobic capacity (yo-yo intermittent recovery test level 1 [YYIRT1]), repeated sprint ability (7 x 35 m sprints) acceleration (15 m sprint) and four soccer skills tests (dribble with pass, dribbling speed, passing and shooting accuracy). Players' technical ability during match play was assessed in small-sided games of soccer (5 v 5) using a novel game technical scoring chart (scoring chart completed by coaches to assess technical performance in a match situation) developed from criteria (e.g., first touch, dribbling and two footedness) used by youth soccer coaches for talent identification. A Spearman's rank correlation showed the YYIRT1 test and 15 m sprint test were limited in predicting technical match performance (r=0.03, p=0.88, r=-0.23, p=0.32 respectively). A Pearson product moment correlation showed that the repeated sprint test was also limited in predicting technical match performance (r=-0.34, p=0.14). A dribbling skill with a pass was found to be the best determinant of a player's technical ability in a match (r=-0.57, p=0.00). Talent identification and selection programmes in Asian youth soccer should include a dribbling skill performed with a pass.

#4 The Vertical Drop Jump Is a Poor Screening Test for ACL Injuries in Female Elite Soccer and Handball Players: A Prospective Cohort Study of 710 Athletes
Reference: Am J Sports Med. 2016 Feb 11. pii: 0363546515625048. [Epub ahead of print]
Authors: Krosshaug T, Steffen K, Kristianslund E, Nilstad A, Mok KM, Myklebust G, Andersen TE, Holme I, Engebretsen L, Bahr R
Summary: The evidence linking knee kinematics and kinetics during a vertical drop jump (VDJ) to anterior cruciate ligament (ACL) injury risk is restricted to a single small sample. Still, the VDJ test continues to be advocated for clinical screening purposes. The purpose of the study was to test whether 5 selected kinematic and kinetic variables were associated with future ACL injuries in a large cohort of Norwegian female elite soccer and handball players. Furthermore, the authors wanted to assess whether the VDJ test can be recommended as a screening test to identify players with increased risk. Elite female soccer and handball players participated in preseason screening tests from 2007 through 2014. The tests included marker-based 3-dimensional motion analysis of a drop-jump landing. The authors followed a predefined statistical protocol in which they included the following candidate risk factors in 5 separate logistic regression analyses, with new ACL injury as the outcome: (1) knee valgus angle at initial contact, (2) peak knee abduction moment, (3) peak knee flexion angle, (4) peak vertical ground-reaction force, and (5) medial knee displacement. A total of 782 players were tested (age, 21 ± 4 years; height, 170 ± 7 cm; body mass, 67 ± 8 kg), of which 710 were included in the analyses. The authors registered 42 new noncontact ACL injuries, including 12 in previously ACL-injured players. Previous ACL injury (relative risk, 3.8; 95% CI, 2.1-7.1) and medial knee displacement (odds ratio, 1.40; 95% CI, 1.12-1.74 per 1-SD change) were associated with increased risk for injury. However, there was an association with medial knee displacement among the 643 players with no history of previous injury. A receiver operating characteristic curve analysis of medial knee displacement showed an area under the curve of 0.6, indicating a poor-to-failed combined sensitivity and specificity of the test, even when including previously injured players. Of the 5 risk factors considered, medial knee displacement was the only factor associated with increased risk for ACL. However, receiver operating characteristic curve analysis indicated a poor combined sensitivity and specificity when medial knee displacement was used as a screening test for predicting ACL injury. For players with no previous injury, none of the VDJ variables were associated with increased injury risk. VDJ tests cannot predict ACL injuries in female elite soccer and handball players.

#5 Beach Soccer Injuries During the Japanese National Championships
Reference: Orthop J Sports Med. 2016 Jan 29;4(1):2325967115625636. doi: 10.1177/2325967115625636. eCollection 2016.
Authors: Shimakawa T, Shimakawa Y, Kawasoe Y, Yoshimura K, Chinen Y, Eimon K, Chibana W, Shirota S, Kadekawa K, Bahr R, Uezato T, Ikeda H
Summary: The frequency and severity of injury in beach soccer are unknown. Consequently, the purpose of the study was to estimate the incidence rates, characteristics, and risk factors for injuries associated with beach soccer. The same sports physician examined and recorded injuries incurred during the Japanese National Beach Soccer Championships in 2013 and 2014. Posttournament follow-up was made for all injuries. Match exposure for each player was recorded through video review to examine individual risk factors. A total of 58 injuries were recorded during 54 matches. The overall injury rate was 179.0 (95% CI, 138.4-231.6), and the time-loss injury rate was 28.2 (95% CI, 14.7-54.1) per 1000 player-hours. The foot/toe (34.9%) was the most frequently injured area, followed by the lower leg (22.2%) and thigh (11.1%). There was only 1 ankle injury (1.6%). The most frequent injury type was contusions (60.3%), followed by lacerations/abrasions (14.3%) and sprains/ligament injuries (6.3%). Only 4 injuries resulted in ≥30 days of time-loss (7.4%). After adjusting for age, a previous history of severe injury and longer experience of beach soccer were significantly associated with injury risk. The time-loss injury rate in this study was comparable to the rates reported during the matches of soccer or futsal tournaments. However, a greater incidence of foot/toe injury and lacerations/abrasions as well as a lower incidence of ankle injury distinguished beach soccer from soccer and futsal, possibly related to the specific playing conditions of being barefoot on a sand surface.

#6 Failure of Internal Fixation for Painful Bipartite Navicular in Two Adolescent Soccer Players: A Report of Two Cases
Reference: J Foot Ankle Surg. 2016 Feb 6. pii: S1067-2516(16)00016-8. doi: 10.1053/j.jfas.2016.01.015. [Epub ahead of print]
Authors: Yamaguchi S, Niki H, Akagi R, Yamamoto Y, Sasho T
Summary: Bipartite navicular bone is an uncommon condition that can cause midfoot pain in children and adolescents. No treatment methods, other than conservative management, have been reported. We report the cases of 2 adolescent soccer players who underwent internal fixation of the painful bipartite fragments, resulting in nonunion. After failure of conservative management, the patients underwent surgery. Curettage of the junction between the 2 bone fragments was performed, and autologous cancellous bone was grafted. Next, the fragments were fixed with variable-threaded screws. Bone union of the bipartite fragments was once achieved on computed tomography in both cases at 3 and 5 months after surgery, respectively. However, separation of the fragment occurred in both cases after the patients had returned to sports. Although the patients were able to return to sports activities, they still had mild midfoot pain 3 and 2 years after surgery, respectively. Internal fixation using screws and an autologous bone graft for painful bipartite navicular bone in adolescent athletes is not recommended, and other surgeries should be considered to achieve bony union.

#6 Neuromuscular Risk Factors for Knee and Ankle Ligament Injuries in Male Youth Soccer Players
Reference: Sports Med. 2016 Feb 8. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MB, Myer GD, Lloyd RS
Summary: Injuries reported in male youth soccer players most commonly occur in the lower extremities, and include a high proportion of ligament sprains at the ankle and knee with a lower proportion of overuse injuries. There is currently a paucity of available literature that examines age- and sex-specific injury risk factors for such injuries within youth soccer players. Epidemiological data have reported movements that lead to non-contact ligament injury include running, twisting and turning, over-reaching and landing. Altered neuromuscular control during these actions has been suggested as a key mechanism in females and adult populations; however, data available in male soccer players is sparse. The focus of this article is to review the available literature and elucidate prevalent risk factors pertaining to male youth soccer players which may contribute to their relative risk of injury.

#7 The within-participant correlation between perception of effort and heart rate-based estimations of training load in elite soccer players
Reference: J Sports Sci. 2016 Feb 6:1-5. [Epub ahead of print]
Authors: Kelly DM, Strudwick AJ, Atkinson G, Drust B, Gregson W
Summary: The measurement of relative physiological stress during training is important because this is the stimulus for the long-term adaptive response. Measurements of perceived exertion (RPE) have been reported to correlate with the heart rate during field-based training sessions. Nevertheless, there are few studies on how well RPE tracks with the heart rate over repeated training sessions in elite soccer players. Therefore, we aimed to quantify the within-participant correlations between variability in session-RPE (sRPE) and the heart rate in elite male soccer players, and to determine whether the playing position moderated these correlations. The field-based training of four central defenders, four wide defenders, six central midfielders, two wide midfielders and three attackers from an elite English Premier League squad were monitored over an entire in-season competitive period, giving a total of 1010 individual training sessions for study. Correlations between session-RPE and heart rates were quantified using a within-participant model. The correlation between changes in sRPE and heart rates was r = 0.75 (95% CI: 0.71-0.78). This correlation remained high across the various player positions (wide-defender, r = 0.81; central-defender, r = 0.74; wide midfielder, r = 0.70; central midfielder, r = 0.70; attacker, r = 0.84; P < 0.001). The correlation between changes in RPE and heart rates, measured during a season-long period of field-based training, is high in a sample of elite soccer players.

#8 Musculoskeletal Asymmetry in Football Athletes: A Product of Limb Function over Time
Reference: Med Sci Sports Exerc. 2016 Feb 11. [Epub ahead of print]
Authors: Hart NH, Nimphius S, Weber J, Spiteri T, Rantalainen T, Dobbin M, Newton RU.
Summary: Asymmetrical loading patterns are commonplace in football sports. Our aims were to examine the influence of training age and limb function on lower-body musculoskeletal morphology. Fifty-five elite football athletes were stratified into less experienced (≤3 years; n = 27) and more experienced (>3 years; n = 28) groups by training age. All athletes underwent whole-body DXA scans and lower-body pQCT tibial scans on the kicking and support limbs. Significant interactions between training age and limb function were evident across all skeletal parameters ([F(16, 91) = 0.182, p = 0.031; Wilks' Λ = 0.969]). Asymmetries between limbs were significantly larger in the more experienced players than less experienced players for tibial mass (p ≤ 0.044; d ≥ 0.50), total cross-sectional area (p ≤ 0.039; d ≥ 0.53) and stress-strain indices (p ≤ 0.050; d ≥ 0.42). No significant asymmetry was evident for total volumetric density. More experienced players also exhibited greater lower-body tibial mass (p ≤ 0.001; d ≥ 1.22), volumetric density (p ≤ 0.009; d ≥ 0.79), cross-sectional area (p ≤ 0.387; d ≥ 0.21), stress-strain indices (p ≤ 0.012; d ≥ 0.69), fracture loads (p ≤ 0.018; d ≥ 0.57), muscle mass and cross-sectional area (p ≤ 0.016; d ≥ 0.68) than less experienced players. Asymmetries were evident in athletes as a product of limb function over time. Chronic exposure to routine high-impact, gravitational loads afforded to the support limb preferentially improved bone mass and structure (cross-sectional area and cortex thickness) as potent contributors to bone strength relative to the high-magnitude, muscular loads predominantly afforded to the kicking limb.

#9 'Coz football is what we all have': masculinities, practice, performance and effervescence in a gender-sensitised weight-loss and healthy living programme for men
Reference: Sociol Health Illn. 2016 Feb 11. doi: 10.1111/1467-9566.12402. [Epub ahead of print]
Authors: Bunn C, Wyke S, Gray CM, Maclean A, Hunt K
Summary: In this paper we use a social practice approach to explore men's experience of Football Fans in Training (FFIT), a group-based weight management programme for men that harnesses men's symbolic attachment to professional football clubs to engage them in lifestyle change. FFIT is delivered by community coaches in clubs' stadia and is gender-sensitised in relation to context, content and style of delivery. Using a 'toolkit' of concepts from the work of Bourdieu, Goffman and Durkheim we analysed data from 13 focus group discussions with participants, and fieldwork notes from programme observations to investigate the appeal and success of FFIT, and how it worked to support change. Our analysis builds on our work on the importance of shared symbolic commitment to the football club and being with 'men like me' to understand how the interaction context facilitated 'effervescent' experiences. These experiences encouraged men to make changes to their diet and physical activity, talk about them, practice performing them and implement them in their lives. Thus a social practice approach illuminated the social processes through which lifestyle change was achieved, and we argue that it can deepen and enrich both intervention design and evaluation.

#10 The application of a multi-dimensional assessment approach to talent identification in Australian football
Reference: J Sports Sci. 2016 Feb 10:1-6. [Epub ahead of print]
Authors: Woods CT, Raynor AJ, Bruce L, McDonald Z, Robertson S
Summary: This study investigated whether a multi-dimensional assessment could assist with talent identification in junior Australian football (AF). Participants were recruited from an elite under 18 (U18) AF competition and classified into two groups; talent identified (State U18 Academy representatives; n = 42; 17.6 ± 0.4 y) and non-talent identified (non-State U18 Academy representatives; n = 42; 17.4 ± 0.5 y). Both groups completed a multi-dimensional assessment, which consisted of physical (standing height, dynamic vertical jump height and 20 m multistage fitness test), technical (kicking and handballing tests) and perceptual-cognitive (video decision-making task) performance outcome tests. A multivariate analysis of variance tested the main effect of status on the test criterions, whilst a receiver operating characteristic curve assessed the discrimination provided from the full assessment. The talent identified players outperformed their non-talent identified peers in each test (P < 0.05). The receiver operating characteristic curve reflected near perfect discrimination (AUC = 95.4%), correctly classifying 95% and 86% of the talent identified and non-talent identified participants, respectively. When compared to single assessment approaches, this multi-dimensional assessment reflects a more comprehensive means of talent identification in AF. This study further highlights the importance of assessing multi-dimensional performance qualities when identifying talented team sports.

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