Epidemiology of injuries in professional football: a systematic review and meta-analysis

Smart sensor tights: Movement tracking of the lower limbs in football

This article presents a novel smart sensor garment with integrated miniaturized inertial measurements units (IMUs) that can be used to monitor lower body kinematics during daily training activities, without the need of extensive technical assistance throughout the measurements. The smart sensor tights enclose five ultra-light sensor modules that measure linear accelerations, angular velocities, and the earth magnetic field in three directions. The modules are located at the pelvis, thighs, and shanks. The garment enables continuous measurement in the field at high sample rates (250 Hz) and the sensors have a large measurement range (32 g, 4,000°/s). They are read out by a central processing unit through an SPI bus, and connected to a centralized battery in the waistband. A fully functioning prototype was built to perform validation studies in a lab setting and in a field setting. In the lab validation study, the IMU data (converted to limb orientation data) were compared with the kinematic data of an optoelectronic measurement system and good validity (CMCs >0.8) was shown. In the field tests, participants experienced the tights as comfortable to wear and they did not feel restricted in their movements. These results show the potential of using the smart sensor tights on a regular base to derive lower limb kinematics in the field.

Analysis of more than 20,000 injuries in European professional football by using a citizen science-based approach: An opportunity for epidemiological research?

OBJECTIVES

It has been claimed that analyses of large datasets from publicly accessible, open-collaborated ("citizen science-based") online databases may provide additional insight into the epidemiology of injuries in professional football. However, this approach comes with major limitations, raising critical questions about the current trend of utilizing citizen science-based data. Therefore, we aimed to determine if citizen science-based health data from a popular online database on professional football players can be used for epidemiological research, i.e. in providing results comparable to other data sources used in previously published studies.

DESIGN

Retrospective database analysis.

METHODS

Transfermarkt.com (Transfermarkt; Hamburg; Germany) is a publicly accessible online database on various data of professional football players. All information provided in the section "injury history" of football players from the top five European leagues over a period of ten seasons (2009/10-2018/19) was analyzed. Frequency, characteristics, and incidence of injuries were reported according to seasons and countries, and results compared with three previously published databases (a scientific injury surveillance, a media-based study, and an insurance database).

RESULTS

Overall, 21,598 injuries of 11,507 players were analyzed from the Transfermarkt.com database. Incidence was 0.63 injuries per player-season (95% confidence interval 0.62 to 0.64) but significant differences between subgroups (countries, years) were found. In comparison to other databases, citizen science-based data was associated with lower injury incidences and higher proportions of severe injuries.

CONCLUSIONS

With few exceptions (e.g., severe injuries), the use of citizen science-based health data on professional football players cannot be recommended at present for epidemiological research.

Injuries in elite-level women's football-a two-year prospective study in the Irish Women's National League

We investigated the pattern of injuries in elite-level women's football in Ireland, during a two-season prospective injury surveillance study in the Women's National League (WNL). Seven out of the eight clubs (271 players) in the WNL were followed prospectively during the 2018 and 2019 seasons. The injury incidence rate in matches (19.2/1000 h) was 7.5 times higher than in training (2.5/1000 h). Players, on average, sustained 0.69 injuries per season (266 injuries/383 player seasons), which equates to 15 time-loss injuries per season for a squad of 22 players. The majority of the injuries sustained by players were lower extremity injuries (85%), of which, 46% had a non-contact injury mechanism. Muscle, ligament, and contusion injuries were the most common injury types, while the ankle, knee, and thigh were the most commonly injured body sites. The most common injuries sustained over the two seasons were lateral ankle sprains (13.9%), hamstring strains (12.4%), knee meniscus/cartilage injuries (7.5%), adductor strains (6%), quadriceps strains (4.5%), and ankle contusions (4.5%). The injuries with the highest injury burden were ACL injuries (59 days lost/1000 h), knee meniscus/cartilage injuries (23/1000 h), lateral ankle sprains (21/1000 h), hamstring strains (12/1000 h), MCL sprains (11/1000 h), and quadriceps strains (11/1000 h). There were 8 ACL tears documented over the 2 seasons, which accounted for 28% of all time lost to injury with a mean days lost per injury of 247. We recommend that clubs in the WNL in Ireland should implement injury risk mitigation strategies, with a particular focus on injuries with a high injury burden.

Injury epidemiology in professional football in South America compared with Europe

Objective

To describe the injury epidemiology in professional football in South America and compare it with European professional football.

Methods

Data about football exposures and injury occurrences were registered in Six teams participating in Copa Libertadores in 2016. These teams’ exposure and injury data were compared with teams participating in the UEFA Elite Club Injury Study during the 2015/2016 and 2016/2017 seasons.

Results

A total of 271 injuries were reported in the South American cohort representing a training injury incidence of 3.2 (95% CI=2.7 to 3.7) injuries/1000 hours of training exposure and 20.9 (95% CI=17.3 to 25.1) injuries/1000 hours of match exposure. While no differences in muscle injury incidence were observed between South American and European teams, the ligament injury incidence in training among South American teams was significantly higher than European teams (0.6 vs 0.3, RR 1.87, 95% CI 1.21 to 2.87). In addition, a significantly higher proportion of all reported injuries among South American teams than European teams occurred in training.

Conclusions

A larger proportion of injuries occur in training in South American compared with European professional football. Specifically, ligament injuries in training were more frequent among South American teams.

Incidence of injuries in semi-professional soccer: a six-month retrospective study in the Italian fourth division

BACKGROUND

Soccer is one of the most popular sports in the world involving about 200 million athletes. Injury management in soccer is crucial for performance and for the costs related to rehabilitation and absence from official matches. While there is quite an exhaustive literature regarding injuries in professional soccer, for amateur soccer the incidence of injuries remains unknown. The purpose of this study was to analyse the prevalence of injuries in the fourth Italian soccer division during the competitive season.

METHODS

Medical staff completed an injury report every two months during the competitive season of the fourth Italian soccer division (14 teams, n = 278). The specific description of the problem, player field-position, number of training losses and number of match losses were collected for each player. The time periods were September/October (T1) November/December (T2), January/February (T3).

RESULTS

A significant association between injury type and the period of the season was observed: muscle and tendon injuries were the most prevalent injury type (48.9 %) in all three periods (χ2 (10) = 33.86, p < 0.001). Overall, 108 (39.7 %) injuries occurred at T1, 90 (33.1 %) at T2 and 74 (27.2 %) at T3 (χ2 (12) = 20.32, p = 0.071).

CONCLUSIONS

Coaches and athletic trainers should be aware of this greater injury risk when preparing a training program for the season, to implement injury prevention protocols for the most prevalent injury types.

Acute effects of an injury preventive warmup programme on unanticipated jump-landing-task performance in adult football players: A crossover trial

HIGHLIGHTS

Adapting movements rapidly to unanticipated external stimuli (e.g. unexpected landings) is crutial to prevent injuries in footballIt is unclear wether popular neuromuscular injury preventive warmup programmes (e.g. Prevent injury and Enhance Performance (PEP)) adaquatly prepare athletes for these situationsOur study shows that the PEP warm up programme has acute effects on anticipated landing stability, but no influence on unanticipated landings or decision making qualityClassic neuromuscular warm up programmes may not be the optimal choice to prepare athletes properly for the upcoming motor-cognitive demands in a football match.

Genetic variations associated with non-contact muscle injuries in sport: A systematic review

INTRODUCTION

Non-contact muscle injuries (NCMI) account for a large proportion of sport injuries, affecting athletes' performance and career, team results and financial aspects. Recently, genetic factors have been attributed a role in the susceptibility of an athlete to sustain NCMI. However, data in this field are only just starting to emerge.

OBJECTIVES

To review available knowledge of genetic variations associated with sport-related NCMI.

METHODS

The databases Pubmed, Scopus, and Web of Science were searched for relevant articles published until February 2021. The records selected for review were original articles published in peer-reviewed journals describing studies that have examined NCMI-related genetic variations in adult subjects (17-60 years) practicing any sport. The data extracted from the studies identified were as follows: general information, and data on genetic polymorphisms and NCMI risk, incidence and recovery time and/or severity.

RESULTS

Seventeen studies examining 47 genes and 59 polymorphisms were finally included. 29 polymorphisms affecting 25 genes were found significantly associated with NCMI risk, incidence, recovery time, and/or severity. These genes pertain to three functional categories: (i) muscle fiber structural/contractile properties, (ii) muscle repair and regeneration, or (iii) muscle fiber external matrix composition and maintenance.

CONCLUSION

Our review confirmed the important role of genetics in NCMI. Some gene variants have practical implications such as differences of several weeks in recovery time detected between genotypes. Knowledge in this field is still in its early stages. Future studies need to examine a wider diversity of sports and standardize their methods and outcome measures.

In-season training responses and perceived wellbeing and recovery status in professional soccer players

This study aimed to describe professional soccer players' training responses during a competitive season and to investigate the relationship between these responses with wellbeing and recovery indices. Thirteen professional soccer players from the same Spanish Second Division team were monitored during a sixteen-week in-season period. Players' external loads were analyzed using global positioning measurement units (GPS). Additionally, subjective reporting of sleep quality, sleep duration, fatigue, muscle soreness, and stress were assessed with a customized wellness questionnaire at the beginning of each training session. A two-step cluster analysis identified profiles of different training responses generally described as lower-demand sessions, intermediate-demand sessions, running-based sessions, and sprint-based sessions; which were discriminated by different total distance covered and high-intensity actions. Interestingly, no probabilistic interactions were found between these training responses with wellbeing and recovery markers (i.e., Bayes factor < 1 suggesting no evidence, for all the variables). These findings may raise concerns about using self-reporting tools, as they show that players' wellness data is probably not accounted for when coaching staff plan and optimize the training process. However, results should be interpreted with caution, due to representing a single team and coaching staff.

Incidence of injury in adult elite women's football: a systematic review and meta-analysis

AIM

To estimate the incidence of injury in adult elite women's football and to characterise the nature and anatomical location of injuries.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Combinations of the key terms were entered into the following electronic databases (PubMed, SPORTDiscus, Science Direct and Discover) from inception to May 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

(1) Used a prospective cohort design; (2) captured data on elite adult women players; (3) reported injury incidence by anatomical site; (4) captured data of at least one season or national team tournament; (5) included a definition of injury; and (6) written in English.

RESULTS

The search identified 1378 records. Twelve studies published between 1991 and 2018 were included in our review and sampled 129 teams. In domestic club football, injury incidence rate was estimated to be 5.7/1000 hours (total), 19.5/1000 hours (match) and 3.1/1000 hours (training). In tournament, football match incidence was estimated to be 55.7/1000 hours. The knee (22.8%; 368/1822) was the most common site of injury in domestic club football. The ankle (23.7%, 105/443) was the most common site of injury in tournament football. Ligament sprains were the most common type of injury (27.8%), followed by muscle strains (19.1%). Severn studies (58%) had a high risk of bias associated with exposure definition and measurement and considerable heterogeneity exists between the included studies (I2=49.7%-95%).

SUMMARY/CONCLUSION

Ligament sprains occur more frequently in adult elite women football players. We advise caution in interpretating point estimates of the incidence of injury due to high statistical heterogeneity. Standardising injury reporting and the accurate recording of match and training exposure will overcome such limitations.

PROSPERO REGISTRATION NUMBER

CRD42019130407.su.

How injury prevention programs are being structured and implemented worldwide: An international survey of sports physical therapists

OBJECTIVE

To identify the role of sports physical therapists (PT) in the injury prevention process and to compare the structure of preventive programs and associated (organization) policies applied in athletic organizations and sports teams of varying gender and level world-wide.

DESIGN

cross-sectional study.

SETTING

LimeSurvey platform.

PARTICIPANTS

Sports PT working with athletes invited through the International Federation of Sports Physical Therapy.

MAIN OUTCOME MEASURES

Sports injury prevention program (IPP) structure and implementation.

RESULTS

414 participants fully participate in this survey study. Athlete's injury history (68.84%), the most common injuries within the sport modality (67.87%) and athlete's preseason screening results (64.01%) were most frequently used to customize IPPs. Warm-up (70.04%) and individually PT-guided exercise-therapy (70.04%) were the preferred methods to organize the prevention routine. The main barrier for IPP implementation was lack of time within the athlete's weekly training schedule (66.66%). The majority of the participants (72.84%) reported to evaluate the perception of IPP's effect by comparing current and preceding seasons' injury occurrences.

CONCLUSION

These survey results are the first identifying contemporary sports injury prevention organization and implementation policies on an international level. This information might support the sports PT community in improving and standardizing IPP (implementation) strategies worldwide.

Do exercise-based prevention programmes reduce non-contact musculoskeletal injuries in football (soccer)? A systematic review and meta-analysis with 13 355 athletes and more than 1 million exposure hours

OBJECTIVE

The aim of this systematic review was to investigate the effect of exercise-based programmes in the prevention of non-contact musculoskeletal injuries among football players in comparison to a control group.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

MEDLINE, EMBASE, CENTRAL, CINAHL, PEDro and SPORTDiscus databases were searched from the earliest record to January 2021.

ELIGIBILITY CRITERIA

Studies were eligible if they (1) included football players aged 13 years or older, (2) used exercise-based programmes as intervention, (3) presented the number of non-contact musculoskeletal injuries (ie, defined as any acute sudden onset musculoskeletal injury that occurred without physical contact) and exposure hours for each group, and (4) had a control group (eg, usual training, minimal intervention, education). All types of exercise-based prevention programmes were eligible for inclusion. Risk of bias for each included study and overall quality of evidence for the meta-analysis were assessed.

RESULTS

Ten original randomised controlled trials with 13 355 football players and 1 062 711 hours of exposure were selected. Pooled injury risk ratio showed very low-quality evidence that exercise-based prevention programmes reduced the risk of non-contact musculoskeletal injuries by 23% (0.77 (95% CI 0.61 to 0.97)) compared with a control group.

CONCLUSION

Exercise-based prevention programmes may reduce the risk of non-contact musculoskeletal injuries by 23% among football players. Future high-quality trials are still needed to clarify the role of exercise-based programmes in preventing non-contact musculoskeletal injuries among football players.

PROSPERO REGISTRATION NUMBER

CRD42020173017.

Limited implementation of the Nordic hamstring exercise in professional and semi-professional soccer

Background/Purpose:

In soccer players, non-contact injuries are most common, especially hamstring muscle injuries, which can be prevented by the Nordic hamstring exercise (NHE). This study assessed the professional and semi-professional soccer players and coaches’ awareness, implementation, and opinion of the NHE efficacy in reducing hamstring injuries.

Methods:

A questionnaire regarding the awareness, implementation, and opinions of the NHE’s efficacy in reducing hamstring muscle injuries was distributed.

Results:

The survey was completed by 812 (88.3% male and 11.7% female) players and coaches. Of these, 395 (48.6%) were aware of the NHE, and 355 (43.7%) implemented it in their current practice. Those implementing NHE had a positive opinion about its efficacy in reducing hamstring injuries.

Conclusion:

Further efforts and research are warranted to increase the international awareness and implementation of the NHE and educate soccer players and coaches about the importance of its implementation and effectiveness in preventing hamstring injury.

Exercise-Based Strategies to Prevent Muscle Injury in Elite Footballers: A Systematic Review and Best Evidence Synthesis

BACKGROUND

Exercise-based strategies are used to prevent muscle injuries in football and studies on different competitive-level populations may provide different results.

OBJECTIVES

To evaluate the effectiveness of exercise-based muscle injury prevention strategies in adult elite football.

METHODS

A systematic search was conducted in PubMed (MEDLINE), Web of Science, Cochrane Library, and SPORTDiscuss (EBSCO). We considered only elite adult (> 16 year-old) football players with no distinction for gender; the intervention to be any exercise/s performed with the target to prevent lower-limb muscle injuries; the comparison to be no injury prevention exercise undertaken; the outcome to be the number of injuries, injury incidence, and severity. We searched systematic reviews, randomized-controlled trials (RCTs), and non-randomized-controlled trials (NRCTs), limited for English language. Risk of bias was assessed using the Risk of Bias in Systematic Reviews tool, the Cochrane Collaboration's Tool for assessing risk of bias in RCTs, and the Risk of Bias in NRCTs of Interventions tool.

RESULTS

15 studies were included. Three systematic reviews showed inconsistent results, with one supporting (high risk of bias) and two showing insufficient evidence (low risk of bias) to support exercise-based strategies to prevent muscle injuries in elite players. Five RCTs and seven NRCTs support eccentric exercise, proprioception exercises, and a multi-dimensional component to an injury prevention program; however, all were deemed to be at high/critical risk of bias. Only one RCT was found at low risk of bias and supported eccentric exercise for preventing groin problems.

CONCLUSION

We found limited scientific evidence to support exercise-based strategies to prevent muscle injury in elite footballers.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42017077705.

Game Exposure, Player Characteristics, and Neuromuscular Performance Influence Injury Risk in Professional and Youth Field Hockey Players

BACKGROUND

Identifying factors that contribute to the occurrence of injury is an important step in designing training programs to minimize the risk of injury. However, despite high injury rates, variables contributing to injury in field hockey players remain relatively unexplored.

PURPOSE

To identify factors that may predict injury in professional and youth field hockey players.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHOD

Professional and youth hockey players completed preseason neuromuscular performance testing and were monitored for injuries, training, and game exposure throughout the subsequent 12-month indoor and outdoor hockey season. Least absolute shrinkage and selection operator analysis was conducted to identify injury risk factors. Receiver operating characteristic curves were then calculated to determine the individual predictive accuracy of the identified variables.

RESULTS

A total of 83 players (mean ± SD age, 20.7 ± 4.9 years; 34.9% female) with complete performance, injury, and exposure data were included for data analysis. Almost half of players (44.6%) sustained a time-loss injury during the season, and 73% of these injuries occurred in the lower limb. Playing more games and having an older age, asymmetrical and poor dynamic postural control, and better explosive performance were identified as jointly influencing the risk of injury. When considered individually, number of games played throughout the season was the most accurate predictor of injury risk (area under the curve [AUC] = 0.74; P < .001), while asymmetrical and poor dynamic postural control (AUCs = 0.61-0.65; P = .01-.04) and better explosive athletic performance (AUCs = 0.65-0.67; P < .01) were identified as moderate individual predictors of sustaining a general or lower limb injury.

CONCLUSION

A number of modifiable factors were individually and jointly associated with an increased injury risk in field hockey players, providing initial evidence for the design of targeted and sport-specific training programs to mitigate the risk of injury.

Anterior Cruciate Ligament Injuries in Australian Rules Football: Incidence, Prevention and Return to Play Outcomes

Australian Rules football is the most popular of the various codes of football played in Australia. During the game players perform frequent landing, cutting and pivoting manoeuvres that expose them to substantial risk for anterior cruciate ligament (ACL) injury. Recent years have seen the introduction of a professional women's league that has resulted in an exponential growth in the participation of women and girls in this sport. Unfortunately, there is a corresponding growth in ACL injury rates in female players. This review summarizes the incidence of ACL injury in both men's and women's Australian Rules football and reviews potential causative factors and risk reduction strategies. The final section takes an in depth look at return to sport outcomes after ACL reconstruction surgery in these populations. Whilst an ACL injury does not mean the end of a player's career in Australian football, it certainly presents a significant challenge in terms of return to preinjury levels of form and high rates of secondary and tertiary ACL injury are also a significant concern.

Head Impact Situations in Professional Football (Soccer)

To assess head impact incidents (HIIs) and to distinguish diagnosed head injuries from other incidents, a video observation analysis of match HIIs was conducted in the German Bundesliga (2017/18 season). Video recordings of each match were screened to identify the respective events. Head injury data were identified by a prospective injury registry. HII and head injury incidence rates (IR) were calculated with 95% CIs. The total number of HIIs was 1,362 corresponding to an IR of 134.9/1000 match hours (95% CI 127.9–142.2). In 123 HII (IR 12.2, 95% CI 10.2–14.5) the contact was classified as severe. Head contact with the opponent was the most frequent cause (85%). The most frequent mechanism was in 44% (combined) the arm and elbow-to-head, followed by head-to-head and hand-to-head contacts (each 13%). In 58%, the HIIs occurred during header duels. Twenty-nine head injuries were recorded (IR 2.9, 95% CI 2.0–4.1). Concussions/traumatic brain injuries accounted for 48%, head/facial fractures 24%, head/facial contusions 21%, and lacerations/abrasions 7%. The number of HIIs not classified as concussions/more severe trauma was high. Identification of HIIs and head injury severity should be improved during on-field assessment as many head injuries might go unrecognised based on the large number of HIIs.

Injury Rates in Major League Baseball During the 2020 COVID-19 Season

Background:

The 2020 Major League Baseball (MLB) season was drastically altered because of the COVID-19 pandemic. The changes included an extended layoff between March and July as well as a shortened preseason.

Purpose/Hypothesis:

To determine the incidence and epidemiology of MLB injuries in the abbreviated 2020 season compared with prior seasons. We hypothesized that there was an increase in the overall injury rate in the 2020 season compared with the 2018-2019 seasons and that it equally affected all body regions.

Study Design:

Descriptive epidemiology study.

Methods:

The MLB transactions database was queried to find players who had been placed on the injury list between 2018 and 2020. Injuries were categorized into upper extremity, lower extremity, spine/core, and other injuries. Incidence per 1000 athlete-exposures was calculated for the prior 2 seasons (2018-2019) and for the 2020 season separately. Incidence for each category was also calculated separately for pitchers and fielders. Incidence rate ratios (IRRs) and confidence intervals were used to compare injury rates in 2018-2019 versus 2020. The z test for proportions was used to determine significant differences between injury incidences.

Results:

In 2020, the overall incidence rate per 1000 athlete-exposures was almost twice the rate compared with the 2 seasons before COVID-19 (8.66 vs 5.13; IRR, 1.69 [95% CI, 1.53-1.87]; P < .001). Injury incidence increased similarly in 2020 for both pitchers (IRR, 1.68 [95% CI, 1.47-1.91]; P < .001) and fielders (IRR, 1.68 [95% CI, 1.45-1.96]; P < .001). Increases in injury incidence were seen in the upper extremity, spine/core, and other injury categories; however, the incidence of the lower extremity did not change significantly.

Conclusion:

There was a significant increase in injury incidence for both pitchers and fielders in 2020. Injury rates increased in anatomic zones of the upper extremity and spine/core but were not significantly changed in the lower extremity. The overall increase in injury rate suggests that irregular or insufficient sport-specific preparation prior to the start of the season placed athletes at a greater risk of injury when play resumed.

Injuries in functional fitness: an updated systematic review

INTRODUCTION

This study aimed to analyze injuries of functional fitness participants through a systematic review.

EVIDENCE ACQUISITION

A systematic search of the literature was conducted in CINAHL, EMBASE, PEDro, PubMed, SCOPUS, SPORTDiscus, and Web of Science, supplemented by searching in the grey literature, from 2017 to November 2020. This systematic review followed the PRISMA guidelines and was documented in the PROSPERO registry (CRD42020201259). Two reviewers independently extracted data including methodological (age, sex, time of practice, location, period, time frame, and completion rate) and injury (definition, diagnosis, prevalence, incidence, severity, mechanism, type, location, risk factors, and treatment) variables, as well as assessing study quality and risk of bias.

EVIDENCE SYNTHESIS

Twenty-six studies were included (10967, range 6-3049, participants). Injury was defined fairly differently across studies. The majority of studies used a retrospective study design and the main variables reported were prevalence, body location, and associated factors of injuries. The mean prevalence of musculoskeletal injuries was 32.8%, ranging from 2.4 to 60.6%, and the injury incidence per 1000 hours ranged from 0.21 to 67 36. The most affected body location in the studies was the shoulder, followed by lumbar spine, and knee. Muscle, joint, and ligament/tendon injuries were the most frequently reported. The majority of studies were of moderate methodological quality. All studies were considered as high risk of bias.

CONCLUSIONS

This review broadened the scope of 75 previous reviews on injuries in functional fitness. There have been few investigations regarding severity, mechanism, and treatment of injuries, so further research is warranted.

Implementing Strength Training Strategies for Injury Prevention in Soccer: Scientific Rationale and Methodological Recommendations

Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg, a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors’ opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players.

A Field-Based Approach to Determine Soft Tissue Injury Risk in Elite Futsal Using Novel Machine Learning Techniques

Lower extremity non-contact soft tissue (LE-ST) injuries are prevalent in elite futsal. The purpose of this study was to develop robust screening models based on pre-season measures obtained from questionnaires and field-based tests to prospectively predict LE-ST injuries after having applied a range of supervised Machine Learning techniques. One hundred and thirty-nine elite futsal players underwent a pre-season screening evaluation that included individual characteristics; measures related to sleep quality, athlete burnout, psychological characteristics related to sport performance and self-reported perception of chronic ankle instability. A number of neuromuscular performance measures obtained through three field-based tests [isometric hip strength, dynamic postural control (Y-Balance) and lower extremity joints range of motion (ROM-Sport battery)] were also recorded. Injury incidence was monitored over one competitive season. There were 25 LE-ST injuries. Only those groups of measures from two of the field-based tests (ROM-Sport battery and Y-Balance), as independent data sets, were able to build robust models [area under the receiver operating characteristic curve (AUC) score ≥0.7] to identify elite futsal players at risk of sustaining a LE-ST injury. Unlike the measures obtained from the five questionnaires selected, the neuromuscular performance measures did build robust prediction models (AUC score ≥0.7). The inclusion in the same data set of the measures recorded from all the questionnaires and field-based tests did not result in models with significantly higher performance scores. The model generated by the UnderBagging technique with a cost-sensitive SMO as the base classifier and using only four ROM measures reported the best prediction performance scores (AUC = 0.767, true positive rate = 65.9% and true negative rate = 62%). The models developed might help coaches, physical trainers and medical practitioners in the decision-making process for injury prevention in futsal.

Assessment of External Load During Matches in Two Consecutive Seasons Using the Mediacoach® Video Analysis System in a Spanish Professional Soccer Team: Implications for Injury Prevention

(1) Background: Knowledge of competition loads is a relevant aspect of injury prevention. We aimed to describe the training and match injury incidence and physical demand variables observed during a competition using a multi-camera video analysis system (Mediacoach^®) (LaLiga^TM, Madrid, Spain) in a professional Spanish soccer team during two consecutive seasons. (2) Methods: 30 players (age: 26.07 ± 3.78 years) participated in the study. Physical variables of 74 matches were collected retrospectively. Injury characteristics of both seasons were also collected. Differences in these variables between the two seasons and by player position and correlations between variables were explored. (3) Results: There were statistically significant differences between the two seasons in the total distance traveled and the distance traveled at a high-intensity sprint (p < 0.05). During the two seasons, there was an average of 4.7 ± 2.2 injuries. The total distance traveled was different according to the playing position, and statistically significant correlations were found in the total distance and sprint at a high intensity for certain positions with different injury severity (4) Conclusions: The match performance data recorded by the Mediacoach^® system may provide relevant information by player position to technical and medical staff for injury prevention.

Injury Profile in Women's Football: A Systematic Review and Meta-Analysis

BACKGROUND

Football is the most popular sport among women; however, little is known about the injury profile in this population. This information would help design tailored injury risk mitigation strategies that may make football safer for women.

OBJECTIVE

The aim of this study was to perform a systematic review and meta-analysis of epidemiological data of injuries in women´s football.

METHODS

A systematic review following PRISMA guidelines was performed up to January 2020 in PubMed, Web of Science, Sportdiscus and the Cochrane Library databases. Twenty-two studies reporting the incidence of injuries in women football were analysed. Two reviewers independently extracted data (intraclass correlation coefficient [ICC] for inter-reviewer reliability = 0.87) and assessed study quality using the STROBE statement, GRADE approach, Newcastle Ottawa Scale and Downs and Black assessment tools. Studies were combined in pooled analyses (injury incidence and injury proportion) using a Poisson random effects regression model.

RESULTS

The overall incidence of injuries in female football players was 6.1 injuries/1000 h of exposure. Match injury incidence (19.2 injuries/1000 h of exposure) was almost six times higher than training injury incidence rate (3.5 injuries/1000 h of exposure). Lower extremity injuries had the highest incidence rates (4.8 injuries/1000 h of exposure). The most common types of injuries were muscle/tendon (1.8 injuries/1000 h of exposure) and joint (non-bone) and ligament (1.5 injuries/1000 h of exposure), which were frequently associated with traumatic incidents. Slight/minimal injuries (1-3 days of time loss) were the most common. The incidence rate of injuries during matches in the top five world ranking leagues was higher than the rest of the leagues (19.3 vs 10.7 injuries/1000 h of exposure, respectively). The weighted injury proportion was 1.1 (95% confidence interval = 0.6-1.7) whereby on average players sustained more than one injury per season.

CONCLUSIONS

Female football players are exposed to a substantial risk of sustaining injuries, especially during matches that require the highest level of performance. To markedly reduce overall injury burden, efforts should focus on introducing and evaluating preventative measures that target match specific dynamics to make football players more capable of responding to the challenges that they have to deal with during match play.

REGISTRATION

This systematic review was registered in the PROSPERO international prospective register of systematic reviews (ID = CRD42019118152).

The Association Between Training Load and Injury Risk in Elite Youth Soccer Players: a Systematic Review and Best Evidence Synthesis

BACKGROUND

Injury risk in elite youth soccer players is high. Implementing an optimal training load is of utmost importance to reduce the risk of injuries.

OBJECTIVE

To conduct a systematic review and best evidence synthesis to explore the effects of internal and external training load on injury risk in elite youth soccer players.

METHODS

MEDLINE, Embase, Web of Science, CENTRAL, and CINAHL were searched up until 17 January 2020. Each article had to meet all of the following criteria: (1) the study population consisted of male elite youth soccer players aged between 12 and 21 years; (2) a longitudinal, prospective study design was used; (3) soccer-related injuries were registered (i.e., self-reported or by medical staff); (4) external and/or internal load parameters were described; and (5) the article was published in an English peer-reviewed scientific journal. The quality of the included articles was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). A best evidence synthesis was performed to rank the level of evidence.

RESULTS

Five studies (2 high quality, 3 low quality) were included. Best evidence synthesis highlighted that there was moderate evidence for (1) no association between 2-, 3-, and 4-week cumulative loads for total distance covered; (2) no association between 1-week workloads (sRPE × duration); and (3) no association between A:C workload ratios (4 weeks) and injury risk. For all other comparisons, only insufficient or conflicting evidence was found.

CONCLUSION

There is a paucity of evidence for an association between internal and external training load parameters and injury risk in elite youth soccer players.

Football-related injuries are the major reason for the career end of professional male football players

PURPOSE

Little is known about the consequences of injuries on professional male football players' career and retirement period. The aim of this study is to investigate the impact of injuries that male professional football players endure during their career, reasons for the end of their career and the post-career phase of retirement.

METHODS

In a retrospective cross-sectional cohort study, retired male professional football players of the German Bundesliga were investigated by a standardised questionnaire to analyse the history of injuries sustained during their professional football career, the reasons for ending their career, their current health status and their suggestions for future prevention strategies.

RESULTS

Most of the 116 analysed players (n = 73 (62.9%)) stated an injury as the reason for ending their professional career. Relevant injuries were mainly located in the lower extremities (n = 587 (61.3%)) with a focus on the knee (p < 0.001) and ankle (p < 0.001). A significant majority of the participants who had retired due to injury described degenerative symptoms, such as pain or instability, and were diagnosed with osteoarthritis after retirement (p < 0.001). These players had also often been affected by symptoms of depression during their career, which had decreased significantly after retirement. Moreover, players who had not retired due to injury had significantly better overall health status and quality of life after retirement.

CONCLUSION

Football-related injuries have a significant impact on the career end of professional male football players and their health status after retirement. Future prevention strategies need to particularly address injuries to the knees and ankles and to implement measures for preventing osteoarthritis after retirement.

LEVEL OF EVIDENCE

Level III.

Epidemiology of Injuries in Ultimate (Frisbee): A Systematic Review

Ultimate is a high-intensity, non-contact team sport played with a flying disc (e.g., frisbee). Despite the growing popularity of ultimate worldwide, there is limited information about the epidemiology of injury in the sport. The purpose of this review is to provide a comprehensive overview and synthesis of the literature on the epidemiology of injury in ultimate. A comprehensive search of the literature was conducted in five electronic databases (i.e., MEDLINE, Embase, AMED, SPORTDiscus, and AusportMed). All databases were searched from inception to 1 July 2020. A total of eleven studies were included and qualitatively synthesized. Injury incidence rate estimates ranged from 0.4 to 84.9 injuries per 1000 athlete-exposures. The lifetime prevalence of any injury and concussion were 100% and 26%, respectively. The most commonly injured body region was the lower limb, with the knee and thigh being the most frequently injured anatomical locations. The most frequent injury types were muscle injuries and superficial contusions. The most common injury situation was direct contact with another player. There is a substantial risk of injury in ultimate, in particular muscle strains and joint sprains to the knee and shoulder areas. Development and implementation of effective, sport-specific injury prevention initiatives, including improved injury risk management and sport safety culture, should be a priority to reduce the burden of injury in ultimate.

Cardiovascular fitness and health effects of various types of team sports for adult and elderly inactive individuals - a brief narrative review

Recreational team sports offer an alternative form of exercise to inactive individuals across the lifespan and sexes. Soccer is the most investigated recreational team sport reporting a wide range of health benefits, including cardiovascular (CV) health. The quest for novel paradigms to promote exercise in the general population, recently extended its interest to other team sports besides soccer. The available research supports the importance of recreational team handball, floorball, basketball, touch rugby, futsal and volleyball as training paradigms to improve CV fitness and other health-related variables in inactive individuals across ages and sexes. In most cases, recreational team sports programs assume the form of small-sided games, eliciting mean heart rates of 72-85% of the individual maximal. The majority of the training interventions were carried out for 12weeks with a reported mean attendance of 2 times 40-60min per week. Maximal oxygen uptake improvements were different in magnitude across the recreational team sports, with recreational team handball providing significant and clinically relevant increases (>3.5ml·kg^-1·min^-1). Game format, training exposure and pre-intervention health and fitness status are issues that need further investigation with the aim to optimize recreational team sports exercise programs implementation. Furthermore, the nature and effects of grassroots team sports should be further studied in order to provide as many as possible effective training tools for former practitioners and for the general population that has none or little experience of sport. Given the potential positive impact of recreational team sports practice on world population's health, large-scale randomized controlled trials are warranted.

Is It High Time to Increase Elite Soccer Substitutions Permanently?

Rules determine how team sport matches occur. Match-induced fatigue is specific to each sport, and may be associated with injury incidence. For example, the injury rate in soccer is distinctly higher during matches than in training sessions. Understanding the differences between team sports rules might be useful for enhancing rules (e.g., safer sport). Therefore, this study aimed to evaluate the impact of the rule-induced physical demands between soccer, futsal, basketball, and handball, focusing on substitution rules. Data from the elite team sports' rules (e.g., absolute and relative court dimensions; the number of players, substitutions allowed, total game time, time-outs) were collected, including the changes due to the coronavirus disease (COVID-19) pandemic in soccer substitutions, and comparisons were performed. The data showed that soccer has higher rule-induced physical demands: e.g., substantially lower substitution rate, higher dimensions in absolute (eight to fifteen times), and relative (four to eight times) values. Simulations also showed that soccer has extremely large differences, even considering COVID-19 substitution changes (from three to up to five). We conclude that elite soccer has remarkably higher overall rule-induced physical demands than elite futsal, basketball and handball, and increasing soccer substitutions permanently (e.g., unlimited) might mitigate overall soccer demands.

The prevalence of non-contact muscle injuries of the lower limb in professional soccer players who perform Salah regularly: a retrospective cohort study

Background

The present study assessed the prevalence of non-contact muscle injuries of the lower limbs, including hamstring injuries, in professional Russian soccer players who regularly perform Salah, an obligatory Muslim prayer performed 5 times a day.

Methods

Using a retrospective cohort study design, 68 professional male soccer players (excluding goalkeepers), 34 of whom were Muslims regularly performing Salah (exposure group) and 34 were randomly chosen non-Muslim players (control group), were included in the study. The groups were similar in their playing leagues, field positions, age (27 ± 3.1 vs 28 ± 4.2 years), and body mass index (22 ± 1.2 vs 23 ± 0.92 kg/m²).

Results

The incidence of hamstring injury was significantly lower in the exposure group (2 vs 14, p = 0.0085). A declining trend for the number of muscle injuries (either hamstring or not) was observed in the exposure group (11 vs 27, p = 0.0562). Two players in the exposure group and 11 in the control group (p = 0.0115, OR 0.1307, 95% CI 0.0276 to 0.5698) suffered a hamstring injury, with no statistically significant difference in the occurrence of other injuries. The total amount of the training and play days missed because of hamstring and other muscle injuries was significantly lower in the exposure group (24 vs 213 days, p = 0.0043, and 200 vs 344 days, p = 0.0066, respectively).

Conclusion

The prevalence of non-contact muscle injuries, including hamstring injuries, was lower in professional Russian soccer players who regularly performed Salah.

Reducing Injuries in Soccer (Football): an Umbrella Review of Best Evidence Across the Epidemiological Framework for Prevention

Soccer is the most popular sport in the world. Expectedly, the incidence of soccer-related injuries is high and these injuries exert a significant burden on individuals and families, including health and financial burdens, and on the socioeconomic and healthcare systems. Using established injury prevention frameworks, we present a concise synthesis of the most recent scientific evidence regarding injury rates, characteristics, mechanisms, risk and protective factors, interventions for prevention, and implementation of interventions in soccer. In this umbrella review, we elucidate the most recent available evidence gleaned primarily from systematic reviews and meta-analyses. Further, we express the exigent need to move current soccer injury prevention research evidence into action for improved player outcomes and widespread impact through increased attention to dissemination and implementation research. Additionally, we highlight the importance of an enabling context and effective implementation strategies for the successful integration of evidence-based injury prevention programs into real-world soccer settings. This narrative umbrella review provides guidance to inform future research, practice, and policy towards reducing injuries among soccer players.

Injury Profile of Male and Female Senior and Youth Handball Players: A Systematic Review

Handball is a team sport in which players are exposed to high physical conditioning requirements and several contacts and collisions, so they must face various musculoskeletal injuries throughout their career. The aim of this study was to summarize the characteristics of handball injuries both in training and in competition contexts, differentiating by gender and age. A systematic review was conducted and a total of 15 studies (33 cohorts) met the inclusion criteria. Higher injury incidence was reported during matches compared to training sessions in all groups (i.e., male and female senior and youth players), with male senior players presenting the greatest values. Lower extremities were more frequently injured, being contusions and sprains the most common type of injuries. Females reported more serious injuries than males, who presented a higher percentage of acute injuries caused by direct contact, while in female players these injuries were not caused by direct contact actions. Wings and backs presented the highest injury incidence; additionally, players registered higher match incidence during international championships compared to national leagues. Due to the differences in the injury profile of handball players, specific preventive strategies should be implemented for each group to optimize the injury prevention process.

Genetic association research in football: A systematic review

Genetic variation is responsible for a large amount of the inter-individual performance disparities seen in sport. As such, in the last ten years genetic association studies have become more common; with one of the most frequently researched sports being football. However, the progress and methodological rigour of genetic association research in football is yet to be evaluated. Therefore, the aim of this paper was to identify and evaluate all genetic association studies involving football players and outline where and how future research should be directed. Firstly, a systematic search was conducted in the Pubmed and SPORTDiscus databases, which identified 80 eligible studies. Progression analysis revealed that 103 distinct genes have been investigated across multiple disciplines; however, research has predominately focused on the association of the ACTN3 or ACE gene. Furthermore, 55% of the total studies have been published within the last four years; showcasing that genetic association research in football is increasing at a substantial rate. However, there are several methodological inconsistencies which hinder research implications, such as; inadequate description or omission of ethnicity and on-field positions. Furthermore, there is a limited amount of research on several key areas crucial to footballing performance, in particular; psychological related traits. Moving forward, improved research designs, larger sample sizes, and the utilisation of genome-wide and polygenic profiling approaches are recommended. Finally, we introduce the Football Gene Project, which aims to address several of these limitations and ultimately facilitate greater individualised athlete development within football.

Making football safer for women: a systematic review and meta-analysis of injury prevention programmes in 11 773 female football (soccer) players

Objective

To evaluate the effects of injury prevention programmes on injury incidence in any women’s football code; explore relationships between training components and injury risk; and report injury incidence for women’s football.

Design

Systematic review and meta-analysis.

Data sources

Nine databases searched in August 2019.

Eligibility criteria

Randomised controlled trials evaluating any injury prevention programme (eg, exercise, education, braces) were included. Study inclusion criteria were: ≥20 female football players in each study arm (any age, football code or participation level) and injury incidence reporting.

Results

Twelve studies, all in soccer, met inclusion criteria, with nine involving adolescent teams (aged <18 years). All studies (except one) had a high risk of bias. Eleven studies examined exercise-based programmes, with most (9/11) including multiple (≥2) training components (eg, strength, plyometric, balance exercises). Multicomponent exercise programmes reduced overall (any reported) injuries (incidence rate ratio (IRR) 0.73, 95% CI 0.59 to 0.91) and ACL injuries (IRR 0.55, 95% CI 0.32 to 0.92). For exercise-based strategies (single-component and multicomponent), hamstring injuries were also reduced (IRR 0.40, 95% CI 0.17 to 0.95). While exercise-based strategies resulted in less knee, ankle and hip/groin injuries, and the use of multiple training components was associated with greater reductions in overall and knee injuries, further studies would be required to increase the precision of these results. The incidence of overall injuries in women’s football was 3.4 per 1000 exposure hours; with ankle injuries most common.

Conclusion

In women’s football, there is low-level evidence that multicomponent, exercise-based programmes reduce overall and ACL injuries by 27% and 45%, respectively.

PROSPERO registration number

CRD42018093527.

Psychometric Analysis and Effectiveness of the Psychological Readiness of Injured Athlete to Return to Sport (PRIA-RS) Questionnaire on Injured Soccer Players

The decision-making process about when an athlete may safely return to training and competition after an injury is a difficult decision. Safe return to training and competition is characterised by physical and psychological readiness to return to the sport. The objectives of this study are (1) to assess the measurement properties of the Psychological Readiness of Injured Athlete to Return to Sport questionnaire (PRIA-RS), and (2) to analyse the effectiveness which the PRIA-RS questionnaire possesses when applied during four consecutive seasons on professional soccer players. One hundred and nine male soccer players from the Albacete Soccer Club (Spain) were involved during four consecutive seasons for the current study: 2012–2013, 2013–2014, 2014–2015 and 2015–2016. Psychometric analysis (validity, reliability, internal consistency and effectiveness) and external psychometric analysis (evaluating measures of patient-reported outcomes (EMPRO)) were confirmed and supported. The main results of the study reveal that the psychometric properties of this questionnaire are optimum for their application in a professional sports context.