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
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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
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#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
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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
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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
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#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
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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
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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
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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
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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
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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.

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