Injury prevention in male youth soccer: Current practices and perceptions of practitioners working at elite English academies

Best practices for the dissemination and implementation of neuromuscular training injury prevention warm-ups in youth team sport: a systematic review

OBJECTIVE

To evaluate best practices for neuromuscular training (NMT) injury prevention warm-up programme dissemination and implementation (D&I) in youth team sports, including characteristics, contextual predictors and D&I strategy effectiveness.

DESIGN

Systematic review.

DATA SOURCES

Seven databases were searched.

ELIGIBILITY

The literature search followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

INCLUSION CRITERIA

participation in a team sport, ≥70% youth participants (<19 years), D&I outcomes with/without NMT-related D&I strategies. The risk of bias was assessed using the Downs & Black checklist.

RESULTS

Of 8334 identified papers, 68 were included. Sport participants included boys, girls and coaches. Top sports were soccer, basketball and rugby. Study designs included randomised controlled trials (RCTs) (29.4%), cross-sectional (23.5%) and quasi-experimental studies (13.2%). The median Downs & Black score was 14/33. Injury prevention effectiveness (vs efficacy) was rarely (8.3%) prioritised across the RCTs evaluating NMT programmes. Two RCTs (2.9%) used Type 2/3 hybrid approaches to investigate D&I strategies. 19 studies (31.6%) used D&I frameworks/models. Top barriers were time restrictions, lack of buy-in/support and limited benefit awareness. Top facilitators were comprehensive workshops and resource accessibility. Common D&I strategies included Workshops with supplementary Resources (WR; n=24) and Workshops with Resources plus in-season Personnel support (WRP; n=14). WR (70%) and WRP (64%) were similar in potential D&I effect. WR and WRP had similar injury reduction (36-72%) with higher adherence showing greater effectiveness.

CONCLUSIONS

Workshops including supplementary resources supported the success of NMT programme implementation, however, few studies examined effectiveness. High-quality D&I studies are needed to optimise the translation of NMT programmes into routine practice in youth sport.

Longitudinal analysis of the incidence rate of injury in elite youth football: Trends over six years including the COVID-19 pandemic period

OBJECTIVES

We aimed to analyze injury trends and the possible effects of the coronavirus disease (COVID-19) pandemic on the incidence rates of injury in young elite football players.

DESIGN

A prospective cohort study design was adopted.

PARTICIPANTS

Our study included 832 male football players who suffered an injury during any of the six competitive seasons.

SETTING

An elite youth football academy.

MAIN OUTCOME MEASURE

Descriptive data and the incidence of injury were calculated. A generalized linear mixed model was used to assess differences in the occurrence of injury among the various age groups. Joinpoint regression was used to analyze injury trends.

RESULTS

Joinpoint regression models showed a statistically significant decrease in the incidence of injury in all age groups with an average annual percent change (AAPC) of 13.9 (95 %Confidence Interval [CI]:-23.2 - 3.4) and -13.5 (95 %CI:-24.5 to -0.9) for models with zero and one joinpoint, respectively. Football players in older age groups sustain a higher number of injuries, probably due to a higher number of matches and greater training intensity.

CONCLUSION

This study showed a downward trend in injuries in the participants prior to the pandemic, with an evident increase in the incidence rate of injury during the COVID-19 pandemic.

Profile of physiotherapists working with soccer teams in South Africa

Background

Soccer is one of the fastest growing sports in South Africa and the number of physiotherapists working with soccer teams has increased significantly. Despite increased appointments, very little is known regarding the demographic, education and work profiles of these physiotherapists.

Objective

To determine the profiles of physiotherapists working with soccer teams in South Africa.

Methods

A descriptive, cross-sectional study was used to collect data from physiotherapists employed with soccer teams. Physiotherapists who were employed on a part-time basis and not registered with the Health Professions Council of South Africa and who did not give consent were excluded. A total of 38 physiotherapists working with soccer teams participated in our study. A questionnaire was circulated, and participants were given 4 months to complete and submit it.

Results

Results showed that participants had a mean age of 31.35 years and were employed for a mean time of 3.41 years. Most participants were African (89.48%) and worked with amateur soccer teams (52.63%). The education results indicated that 66.67% of participants held bachelor's degrees. Postgraduate- and undergraduate education were used most frequently by participants to guide clinical decision-making. Job satisfaction was satisfactory, but they were not satisfied with their salaries.

Conclusion

Our study is the first to investigate the profiles of physiotherapists working with soccer teams in South Africa. Demographic, education and work profiles for physiotherapists working with soccer teams were compiled, and the lack of information regarding the profiles of these physiotherapists was identified.

Clinical implications

Extensive future research is needed to inform and train physiotherapists regarding the management of soccer teams.

Ankle proprioception in table tennis players: Expertise and sport-specific dual task effects

OBJECTIVES

To compare ankle proprioception between professional adolescent table tennis players at national and regional levels and age-matched non-athletes, and, in a nominally upper-limb sport, to explore the relationships between single- and dual-task ankle proprioception, years of training and sport-specific performance.

DESIGN

Cross-sectional observational study.

METHODS

Fifty-five participants (29 professional adolescent table tennis players and 26 non-athletic peers) volunteered. Ankle proprioception was first assessed using the active movement extent discrimination apparatus (AMEDA-single) for all; yet only the players were then re-assessed while executing a secondary ball-hitting task (AMEDA-dual). The mean Area Under the Receiver Operating Characteristic Curve was calculated as the proprioceptive score, and years of training and hitting rate were recorded.

RESULTS

National-level players had significantly better ankle proprioception as shown by higher AMEDA-single scores than the other groups (all p < 0.05). Ankle proprioceptive performance was significantly impaired while ball-hitting (F1,28 = 58.89, p ≤ 0.001, ηp2 = 0.69). National-level players outperformed the regional-level significantly on the AMEDA-dual task (F1,27 = 21.4, p ≤ 0.001, ηp2 = 0.44). Further, ankle proprioceptive performance was related to expertise, in that both AMEDA-single and AMEDA-dual proprioceptive scores were correlated with years of training and ball-hitting rate (r from 0.40 to 0.54, all p < 0.05).

CONCLUSIONS

Ankle proprioception is a promising measure that may be used to identify different ability levels among adolescent table tennis players. Superior ankle proprioception may arise from rigorous training and contribute to stroke accuracy. Dual-task proprioceptive assessment suggests how elite table tennis players perform differently from lower-ranked players in complex and changeable sports circumstances.

Can motor proficiency testing predict sports injuries and sports-induced bleeds in people with haemophilia?

INTRODUCTION

Predicting the risk of sports injuries and sports-induced bleeds (SIBs) in people with haemophilia (PWH) may support clinical counselling.

AIM

To assess the association between motor proficiency testing and sports injuries and SIBs and to identify a specific set of tests for predicting injury risk in PWH.

METHODS

In a single centre, prospective study male PWH aged 6-49 playing sports ≥1x/week were tested for running speed and agility, balance, strength and endurance. Test results below -2Z were considered poor. Sports injuries and SIBs were collected for 12 months while 7 days of physical activity (PA) for each season was registered with accelerometers. Injury risk was analysed according to test results and type of physical activity (%time walking, cycling, running). Predictive values for sports injuries and SIBs were determined.

RESULTS

Data from 125 PWH (mean [± SD] age: 25 [± 12], 90% haemophilia A; 48% severe, 95% on prophylaxis, median factor level: 2.5 [IQR 0-15]IU/dl) were included. Few participants (n = 19, 15%) had poor scores. Eighty-seven sports injuries and 26 SIBs were reported. Poor scoring participants reported 11/87 sports injuries and 5/26 SIBs. The current tests were poor predictors of sports injuries (Range PPV: 0%-40%), or SIBs (PPV: 0%-20%). PA type was not associated with season (activity seasonal p values > .20) and type of PA was not associated with sports injuries or SIBs (Spearman's rho < .15).

CONCLUSION

These motor proficiency- and endurance tests were unable to predict sports injuries or SIBs in PWH, potentially due to few PWH with poor results and low numbers of sports injuries and SIBs.

Substitutions in football - what coaches think and what coaches do

Substitutions are probably the most important opportunity for football coaches to actively influence a match in progress. The present article presents two studies investigating substitutions in football from two different methodological perspectives: Study I, a survey reporting the opinions of 73 licensed coaches, and Study II, data-based analysis of a total of 41,301 substitutions from 7,230 matches in seasons 2014/15 to 2018/19 of the top four European football leagues. The coaches stated to prefer offensive substitutions over defensive substitutions and additionally indicated that changing the current score was more likely to be a reason for substitution than keeping the score. The analysis of the data revealed that not offensive, but neutral substitutions, where the player is replaced by a player of the same playing position, were most frequent. However, offensive players participated significantly more frequently in substitutions. In addition, a high level of score dependence was found, as more than half of the defensive substitutions were made while winning and more than half of the offensive substitutions were made while losing. The present study sheds light on the substitution behaviour of coaches in football and intends to stimulate discussion on the optimal timing and the type of substitutions.

Incidence, burden, and pattern of injuries in Spanish male youth soccer players: A prospective cohort study

OBJECTIVES

To explore the incidence, burden, and pattern of injuries in Spanish male youth soccer players during a 9-month competitive season (from September to May-June).

DESIGN

Prospective cohort study.

PARTICIPANTS

314 young (10-19 years) soccer players.

MAIN OUTCOME MEASURES

Incidence, burden, location, type, severity, mechanism, and circumstance of injuries, as well as potential differences by tactical position, month of the year, age group, and maturity status.

RESULTS

A total of 146 time-loss injuries were sustained by 101 different players. This resulted in an overall injury incidence of 3.1 injuries per 1000 h, a training injury incidence of 1.8 injuries per 1000 h, and a match injury incidence of 11.2 injuries per 1000 h. The probability of injury over the season was 34%. Most of the injuries affected the lower extremity and were classified as muscle/tendon injuries, with hamstring muscle injuries representing the most burdensome diagnosis. The incidence of injuries increased with age and maturation, but a heightened risk of overuse injuries during periods around peak height velocity was also identified.

CONCLUSIONS

These findings suggest a need for implementing specific injury prevention measures. Due to the high burden shown, these measures should mainly focus on reducing the number and severity of hamstring muscle injuries.

FATIGUE OF KNEE EXTENSOR MUSCLES DOES NOT ALTER KNEE JOINT POSITION SENSE

The aim of this study is to investigate the effect of knee extensors fatigue on joint position sense. Fifteen healthy participants, all males, with no history of previous musculoskeletal lesions were recruited. Evaluation of the knee joint position sense and the muscle fatigue protocol had been performed using an isokinetic dynamometer. Fatigue was considered when the maximum torque was reduced by 50%. The joint position sense was analyzed by the absolute error and the variable error. The paired t-test was used to compare the mean in pre and during muscle fatigue conditions. The level of significance was 5%. Absolute and variable errors were not significantly affected by muscle fatigue. Knee joint position sense does not seem to be affected by fatigue of knee joint extensors.

Optimising long-term athletic development: An investigation of practitioners' knowledge, adherence, practices and challenges

Long-term athletic development practices have been recommended for the past two decades. However, limited research exists exploring the knowledge and skills required by practitioners to optimise long-term athletic development. Therefore, this study aimed to evaluate the knowledge, adherence, practices, and challenges of practitioners responsible for delivering long-term athletic development. A mixed methods survey was completed by 236 practitioners (e.g., sport coaches, physical education teachers) consisting of four parts; 1) demographics, 2) knowledge, 3) adherence, and 4) practices and challenges. Quantitative and qualitative data were analysed by Friedman’s analysis of variance and thematic analyses, respectively. Quantitative findings showed practitioners 1) recognised their responsibility for delivering long-term athletic development, 2) have a familiarity with existing developmental models, and 3) had high adherence, focused upon health and wellbeing, to delivering long-term athletic development. However, practices associated with growth and maturity, monitoring and assessment, and the systematic progression and individualisation of training had lower adherence. Qualitative analysis indicated that practitioner’s perceived definitions of athleticism and long-term athletic development were inconsistent, especially according to the psychological components (i.e., confidence). Practitioners’ descriptions of their long-term athletic development practices identified two higher order themes; 1) goals, in which long-term athletic development “is for life” and the importance of “an individual centered journey” highlighted as sub-themes; and 2) realities of delivering long-term athletic development, whereby variety in programme delivery, monitoring development and practical challenges were noted as key priorities. Eight practical challenges were identified including governance and priorities, resources, education, early specialization, high training volumes, staff communication, parents and youth motivation. This mixed method survey highlighted a multitude of knowledge, adherence, practices and challenges towards long-term athletic development. These novel findings can help inform policy to optimise long-term athletic development and to support the complex problem of developing a healthier, fitter and more physically active youth population.

Bilateral Strength Asymmetry in Elite Youth Soccer Players: Differences between Age Categories

The strength asymmetry of athletes as a negative health and performance factor is increasingly being researched in sports with a high load on the dominant limb when some specific unilateral movements, such as passing, jumping, and tackling, are required. This study aimed to determine the level of isokinetic strength bilateral asymmetry (BA) among knee extensors (KEs) and knee flexors (KFs) of elite youth soccer players. The sample (n = 87) consisted of three age categories of under 13 (U13), under 15 (U15), and under 17 (U17) years old. Isokinetic dynamometry was used to obtain the maximum peak torque of the KEs and KFs in the dominant and non-dominant lower limbs during concentric muscle contraction. The analysis revealed significantly lower values (p < 0.05) of BA in KEs in U17 than in younger categories, U13 and U15, and higher values (p < 0.05) of BA in KFs in the U15 category than in the U17category. The majority of the players in the U15 category (68%) reached KFs BA higher than 10% in comparison with U13 players (50%) and U17 players (28% of players) (p < 0.05). Our results showed a significant effect of age category on BA levels in young soccer players. High incidences of increased BA in the lower limbs occurred in the younger categories (U13, U15) and subsequently decreased in the later adolescent stages.

Shedding light on incidence and burden of physeal injuries in a youth elite football academy: A 4-season prospective study

INTRODUCTION

Physeal injuries have been overlooked in epidemiological research in youth sports. Our prospective study investigated the incidence, severity, and burden of physeal injuries in a youth elite football academy.

METHODS

In total, 551 youth male football players from under-9 to under-19 were included and observed over four consecutive seasons. Injuries involving the physis were diagnosed and recorded according to type, location, and diagnosis. Injury incidence (II), severity (days lost), and injury burden (IB) were calculated per squad per season (25 players/squad).

RESULTS

There were 307 physeal injuries: 262 apophyseal (85%), 26 physeal (9%), 2 epiphyseal (1%), and 17 other physeal injuries (5%) with 80% (n=245) causing time-loss. The overall mean incidence of time-loss physeal injuries was 6 injuries/squad-season, leading to a total of 157 days lost/squad-season. The U-16s had the highest burden with 444 days lost per squad-season [median: 20 (95% CI: 12-30) days; II: 10 (95% CI: 7.3.1-13.4)]. Apophyseal injuries of the hip-pelvis resulted in the greatest burden [median: 13 (95% CI: 10-17); II: 2.5 (95% CI: 2.1-3.0)]. Peak apophyseal injury incidence per body parts occurred in U-11 for foot-ankle (II: 2.4; 95% CI: 1.0-4.9), U-14 for knee (II: 4.5; 95% CI: 2.7-7.1), and U-17 for hip-pelvis (II: 6.4; 95% CI: 4.2-9.3).

CONCLUSION

Physeal injuries accounted for a quarter of all-time loss with the largest injury burden in U-16. Most physeal injuries involved the lower limb and affected the apophysis. Physeal and apophyseal injuries incidence, burden, and pattern vary substantially depending on age. Hip-pelvic apophyseal injuries accounted for the largest injury burden.

Biceps Femoris Activation during Hamstring Strength Exercises: A Systematic Review

BACKGROUND

The aim of the study was to systematically evaluate the biceps femoris long head activation across cross-sectional hamstring strength exercise studies.

METHODS

A systematic review design was followed. The search strategy conducted in PubMed, Cochrane Library, and Web of Sciences databases found a total of 3643 studies. Once inclusion and exclusion criteria were applied, 29 studies were finally included in this systematic review. A total of 507 participants and 114 different exercises were analyzed. Exercises were evaluated individually and grouped into several categories: Nordics, isokinetic exercises, lunges, squats, deadlifts, good mornings, hip thrusts, bridges, leg curls, swings, hip and back extensions, and others.

RESULTS

Results showed the isokinetic and Nordic exercises as the categories with highest biceps femoris activation (>60% of Maximal Voluntary Isometric Contraction). Nordic hamstring exercise ankle dorsiflexion was the exercise that achieved the highest biceps femoris long head activation (128.1% of its Maximal Voluntary Isometric Contraction).

CONCLUSIONS

The results from this systematic review suggest that isokinetic and Nordic exercises seem to be the best option to activate biceps femoris long head. Future studies evaluating the implementation of these exercises in prevention programs are needed.

Sports Injury Prevention is Complex: We Need to Invest in Better Processes, Not Singular Solutions

In recent years, an understanding has developed that sports injuries are the emergent outcomes of complex, dynamic systems. Thus, the influence of local contextual factors on injury outcomes is increasingly being acknowledged. These realisations place injury prevention research at a crossroads. Currently, injury prevention researchers develop universally applicable injury prevention solutions, but the adoption of these solutions in practice is low. This occurs because implementation contexts are both unique and dynamic in nature, and as a result singular, static solutions are often incompatible. In contrast, practitioners address injury prevention through iterative cycles of trial and error, aiming to optimise the injury prevention process within their own unique contexts. The purpose of this critical review is to draw attention to the misalignment between research and practice-based approaches to injury prevention. In light of this, we propose alternative research approaches that acknowledge the process-driven nature of injury prevention in practice. We propose that a core focus of sport injury prevention research should be to provide practitioners with useful and relevant information to support their decision making around their localised injury prevention practice. Through this approach, injury prevention research ceases to be about what works, and begins to engage with understanding what works in what contexts and why?

Influence of Size and Maturity on Injury in Young Elite Soccer Players

The involvement of pre-adolescents in soccer is becoming more and more frequent, and this growing participation generates some concerns about the potential factors for sports injuries. The purpose of this study was to investigate sports injuries in younger (U9–U11) and older (U12–U13) children playing soccer at an elite level, analyzing potential anthropometric and maturity risk factors. A total of 88 elite soccer players aged 9–13 years were investigated. Weight, stature, and sitting height were measured at the start and at the end of the competitive season, computing the relative growth velocities. Additional body composition parameters were taken during a second survey. Maturity offset was calculated using predictive equations based on anthropometric traits such as years from age at peak height velocity (YPHV). Injuries suffered during the competitive season were recorded. Maturity and some anthropometric characteristics were significantly different according to the presence or absence of injuries among the players. Multiple logistic regression revealed that YPHV, body mass index (BMI), and calf muscle area were the factors most significantly correlated with injuries. Players with increased BMI, with decreased calf muscle area, and who were closer to their peak height velocity, were at a higher risk of injury. Findings showed that a monitoring program of anthropometric characteristics taking into account the maturational stage needs to be developed to prevent injuries.

Motor performance is not related to injury risk in growing elite-level male youth football players. A causal inference approach to injury risk assessment

OBJECTIVE

To identify the causal relation between growth velocity and injury in elite-level youth football players, and to assess the mediating effects of motor performance in this causal pathway.

DESIGN

Prospective cohort study.

METHODS

We measured the body height of 378 male elite-level football players of the U13 to U15 age categories three to four months before and at the start of the competitive season. At the start of the season, players also performed a motor performance test battery, including motor coordination (Körperkoordinationstest für Kinder), muscular performance (standing broad jump, counter movement jump), flexibility (sit and reach), and endurance measures (YoYo intermittent recovery test). Injuries were continuously registered by the academies' medical staff during the first two months of the season. Based on the causal directed acyclic graph (DAG) that identified our assumptions about causal relations between growth velocity (standardized to cm/y), injuries, and motor performance, the causal effect of growth velocity on injury was obtained by conditioning on maturity offset. We determined the natural indirect effects of growth velocity on injury mediated through motor performance.

RESULTS

In total, 105 players sustained an injury. Odds ratios (OR) showed a 15% increase in injury risk per centimetre/year of growth velocity (1.15, 95%CI: 1.05-1.26). There was no causal effect of growth on injury through the motor performance mediated pathways (all ORs were close to 1.0 with narrow 95%CIs).

CONCLUSIONS

Growth velocity is causally related to injury risk in elite-level youth football players, but motor performance does not mediate this relation.

Eccentric Resistance Training in Youth: A Survey of Perceptions and Current Practices by Strength and Conditioning Coaches

BACKGROUND

Eccentric resistance training (ERT) in youth is advocated for aiding performance and injury risk. However, research investigating the applied practices of ERT in youth is in its infancy. In this study, we surveyed the perceptions and practices of practitioners utilizing ERT in youth to provide an understanding of its current application in practice.

METHODS

Sixty-four strength and conditioning coaches completed an online survey reporting their current use of ERT in youth using both open and closed questions.

RESULTS

Coaches deemed the inclusion of ERT important in youth with its inclusion based upon factors such as maturation status, training age and strength levels. Coaches also displayed an awareness of the physiological responses to eccentric exercise in youth compared to adults. ERT was primarily used for injury prevention, with the majority of coaches using body-weight and tempo exercises. Furthermore, utilizing eccentric hamstrings exercises was reported as highly important. The frequency of ERT tended to increase in older age groups and coaches mainly prescribed self-selected rest intervals. Finally, the need for further research into the training guidelines of ERT in youth was highlighted, in which coaches require more information on how maturation influences training adaptations and the fatigue-recovery responses.

CONCLUSION

Coaches emphasized the importance of including ERT for both performance and injury prevention factors in youth although further research is required to generate practical guidelines for coaches in order to support its inclusion within practice.

Effects of Different Inter-Set Rest Intervals during the Nordic Hamstring Exercise in Young Male Athletes

CONTEXT

The Nordic hamstring exercise (NHE) is known to reduce hamstrings injury (HIS) risk in athletes. In order to optimise the NHE it is important to understand how acute resistance training variables influence its performance.

OBJECTIVE

To examine the effects of different inter-set rest intervals (ISRI) on force indices during performance of the NHE. Design: Crossover Study.

SETTING

Laboratory based.

PATIENTS OR PARTICIPANTS

Ten (age = 20.7 ± 2.3 years; height = 179.4 ± 5.5 cm; body mass = 83.9 ± 12.4 kg) well-trained young male team-sport athletes.

INTERVENTION

Participants performed 2 x 6 repetitions of the NHE with either a SHORT (one-minute) or LONG (three-minute) ISRI. All sets were performed on the NordBord.

MAIN OUTCOMES MEASURE(S)

Peak force (N), average force (N), percent maintenance (%) and percent decline (%) were recorded for both dominant and non-dominant limbs as well as inter-limb force asymmetries (%) calculated.

RESULTS

Analyses revealed no statistically significant interactions or main effects (p > 0.05) between conditions and sets in all variables. However, analysis of individual repetitions showed significant reductions (p < 0.05, ES = 0.58-1.28) in peak force from repetition four onwards.

CONCLUSIONS

Our findings suggest that a one-minute ISRI is sufficient to maintain force production qualities and inter-limb asymmetries between sets during the NHE in well-trained athletes. However, practitioners should be aware of the potentially high decrements in peak force production that may occur within the set.

Monitoring Practices of Training Load and Biological Maturity in UK Soccer Academies

PURPOSE

Overuse injury risk increases during periods of accelerated growth, which can subsequently impact development in academy soccer, suggesting a need to quantify training exposure. Nonprescriptive development scheme legislation could lead to inconsistent approaches to monitoring maturity and training load. Therefore, this study aimed to communicate current practices of UK soccer academies toward biological maturity and training load.

METHODS

Forty-nine respondents completed an online survey representing support staff from male Premier League academies (n = 38) and female Regional Talent Clubs (n = 11). The survey included 16 questions covering maturity and training-load monitoring. Questions were multiple-choice or unipolar scaled (agreement 0-100) with a magnitude-based decision approach used for interpretation.

RESULTS

Injury prevention was deemed highest importance for maturity (83.0 [5.3], mean [SD]) and training-load monitoring (80.0 [2.8]). There were large differences in methods adopted for maturity estimation and moderate differences for training-load monitoring between academies. Predictions of maturity were deemed comparatively low in importance for bio-banded (biological classification) training (61.0 [3.3]) and low for bio-banded competition (56.0 [1.8]) across academies. Few respondents reported maturity (42%) and training load (16%) to parent/guardians, and only 9% of medical staff were routinely provided this data.

CONCLUSIONS

Although consistencies between academies exist, disparities in monitoring approaches are likely reflective of environment-specific resource and logistical constraints. Designating consistent and qualified responsibility to staff will help promote fidelity, feedback, and transparency to advise stakeholders of maturity-load relationships. Practitioners should consider biological categorization to manage load prescription to promote maturity-appropriate dose-responses and to help reduce the risk of noncontact injury.

Potential prognostic factors for hamstring muscle injury in elite male soccer players: A prospective study

Hamstring injuries remain the most common injury type across many professional sports. Despite a variety of intervention strategies, its incidence in soccer players playing in the UEFA Champions League has increased by 4% per year over the last decade. Test batteries trying to identify potential risk factors have produced inconclusive results. The purpose of the current study was to prospectively record hamstring injuries, to investigate the incidence and characteristics of the injuries, and to identify possible risk factors in elite male soccer players, playing in the Kosovo national premier league. A total of 143 soccer players from 11 teams in Kosovo were recruited. To identify possible prevalent musculoskeletal or medical conditions a widespread health and fitness assessment was performed including isokinetic strength testing, Nordic hamstring strength test, functional tests, and a comprehensive anamnesis surveying previous hamstring injuries. On average 27.9% of the players sustained at least one hamstring injury with three players suffering bilateral strains with the re-injury rate being 23%. Injured players were significantly older and heavier and had a higher body mass index compared to non-injured ones (p < 0.05). There was a lower passing rate in the Nordic hamstring strength test and a higher injury incidence among the previously injured players compared to non-injured ones (p < 0.05). Except for hamstring/quadriceps ratio and relative torque at 60°/sec (p < 0.05) for dominant and non-dominant leg, there were no other significant differences in isokinetic strength regardless of the angular velocity. No differences were observed for functional tests between cohorts. Regression analysis revealed that age, Nordic hamstring strength test, previous injury history, and isokinetic concentric torque at 240°/sec could determine hamstring injuries by 25.9%, with no other significant predicting risk factors. The battery of laboratory and field-based tests performed during preseason to determine performance related skills showed limited diagnostic conclusiveness, making it difficult to detect players at risk for future hamstring injuries.

Effects of whole body vibration with exercise therapy versus exercise therapy alone on flexibility, vertical jump height, agility and pain in athletes with patellofemoral pain: a randomized clinical trial

Background

Patellofemoral pain (PFP) is the most prevalent orthopedic problem in active young adults. Due to its multifactorial etiology, a variety of therapeutic measures have been adopted to treat PFP, including exercise therapy, electrotherapy, and manual therapy. It has also been suggested that whole body vibration (WBV) can improve neuromuscular function in persons with knee problems. The aim of the present study was to evaluate the effects of adding WBV to routine exercise programs on flexibility, vertical jump height, agility and pain in athletes with PFP.

Methods

Twenty-four male athletes with PFP were randomized into two groups of WBV + exercise (n = 12) or exercise only (n = 12). Participants received their interventions during 4 consecutive weeks (12 sessions). Pain intensity, flexibility and agility were assessed respectively as score on a numerical rating scale, the sit-and-reach test, and a modified T-test, and vertical jump height was measured to the nearest centimeter. The tests were done before and after the interventions, and the results were compared between the two groups. Independent t-tests and paired t-tests were used for between- and within-group comparisons, respectively.

Results

After the interventions, all variables for vertical jump height, flexibility, agility and pain intensity improved significantly in both groups (p < 0.05). The flexibility test showed significantly greater improvement in the WBV + exercise group (p<0.001), whereas for vertical jump height, agility and pain intensity, there were no statistically significant differences between groups (p>0.05).

Conclusions

The present findings showed that exercise therapy with and without WBV can significantly decrease pain and increase agility, vertical jump height and flexibility in athletes with PFP. Adding WBV to routine exercise therapy, however, can augment the effects of the latter on flexibility.

Trial registration

IRCT, IRCT20090831002391N39. Registered 7 February 2018, https://en.irct.ir/search/result?query=IRCT20090831002391N39.

Influence of Maturation Status on Eccentric Hamstring Strength Improvements in Youth Male Soccer Players After the Nordic Hamstring Exercise

PURPOSE

This study examined the effects of a 6-week Nordic hamstring exercise (NHE) program in youth male soccer players of less mature (pre-peak height velocity [PHV]) or more mature (mid/post-PHV) status.

METHODS

Forty-eight participants were separated into pre-PHV (11.0 [0.9] y) or mid/post-PHV (13.9 [1.1]) groups and further divided into experimental (EXP) and control groups with eccentric hamstring strength assessed (NordBord) both before and after the training program. Participants in the EXP groups completed a periodized NHE program performed once or twice weekly over a 6-week period.

RESULTS

The NHE program resulted in moderate and small increases in relative eccentric hamstring strength (in newtons per kilogram) in the pre-PHV EXP (d = 0.83 [0.03-1.68]) and mid-PHV EXP (d = 0.53 [-0.06 to 1.12]) groups, respectively. Moderate increases in the same measure were also seen in the between-groups analyses in the pre-PHV (d = 1.03 [0.23-1.84]) and mid-PHV (d = 0.87 [0.22-1.51]) groups, with a greater effect observed in the former.

CONCLUSION

The results from this study demonstrate that a 6-week NHE program can improve eccentric hamstring strength in male youth soccer players, with less-mature players achieving mostly greater benefits. The findings from this study can aid in the training prescription of NHE in youth male soccer players.

Comparison of Drop Jump and Tuck Jump Knee Joint Kinematics in Elite Male Youth Soccer Players: Implications for Injury Risk Screening

CONTEXT

Despite the popularity of jump-landing tasks being used to identify injury risk factors, minimal data currently exist examining differences in knee kinematics during commonly used bilateral jumping tasks. This is especially the case for rebounding-based protocols involving young athletes.

OBJECTIVE

To compare the frontal plane projection angles (FPPAs) during the drop vertical jump (DVJ) and tuck jump assessment (TJA) in a cohort of elite male youth soccer players of varying maturity status.

METHODS

A total of 57 male youth soccer players from an English championship soccer club participated in this study. Participants performed 3 trials of the DVJ and TJA, during which movement was recorded with 2-dimensional video cameras. FPPA for both right (FPPA-r) and left (FPPA-l) legs, with values <180° indicative of medial knee displacement.

RESULTS

On a whole-group level, FPPA-r (172.7° [7.4°] vs 177.2° [11.7°]; P < .05; effect size [ES] = 0.46) and FPPA-l (173.4° [7.3°] vs 179.2° [11.0°]; P < .05; ES = 0.62) were significantly greater for both limbs in the TJA compared with the DVJ; however, these differences were less consistent when grouped by maturity status. FPPA-r during the TJA was significantly and moderately greater in the circa-peak height velocity (PHV) group compared with the post-PHV cohorts (169.4° [6.4°] vs 175.3° [7.8°]; P < .05; ES = 0.49). Whole-group data showed moderate relationships for FPPA-r and FPPA-l between the TJA and DVJ; however, stronger relationships were shown in circa- and post-PHV players compared with the pre-PHV cohort.

CONCLUSIONS

Considering that the TJA exposed players to a larger FPPA and was sensitive to between-group differences in FPPA-r, the TJA could be viewed as a more suitable screen for identifying FPPA in young male soccer players.

The influence of a soccer season on non-contact injury and isokinetic peak torque of the quadriceps and hamstrings in professional youth soccer players

Isokinetic strength screening is utilized in professional soccer. However, there has been little research on the interaction between seasonal changes in players' peak torque (PT) and injury incidence. Twenty-five (age 16.5±0.68 years) professional youth soccer players participated in the study. Bilateral isokinetic concentric (CON) and eccentric (ECC) testing of Quadriceps (Q) and Hamstrings (H) were conducted at three time-points across the season. Absolute CON and ECC PT were measured at 60 degree/sec and in a supine 170-degree position. Testing data was normalized to body mass. A mixed design (2 by 3) repeated measures ANOVA with injury as a co-variate was conducted to evaluate the effect of season and/or limb dominance on PT and injury incidence. With regard to the seasonal variation and injury incidence, an interaction was identified with respect to non-dominant limb (NDL) QCON (p = 0.01) and to a lesser extent the dominant limb (DL) QCON (p = 0.05). The seasonal variation of the PT of the NDL QCON was different between the injured and non-injured individuals. Non-injured individuals, QCON strength increased over the course of the season. While for the Injured players, QCON declined from pre-season to mid-season then increased but never recovered to starting pre-season values.

Perceptions of the technical staff of professional teams regarding injury prevention in Spanish national futsal leagues: a cross-sectional study

Futsal is a sport with increasing popularity and level of performance, both in male and female categories. Also, there are several injuries along a season, so it is needed to know how to reduce this burden. The purpose of this study was to describe the perceptions of technical staff on injury risk factors, risk testing and preventive measures, and the strategies used by them within professional male and female futsal teams. A cross-sectional study was designed during the 2017–2018 season. A total of 32 futsal teams involved in male and female Spanish national futsal leagues completed, through an online survey platform, a questionnaire about injury risk factors, risk testing and preventive measures. Findings showed that: (a) most teams reported enough human resources, but insufficient material and time resources, (b) the main risk factors detected were previous injuries, strength deficits and dehydration, (c) functional movement patterns, flexibility tests and self-report questionnaires were the most applied tests for detecting injury risks in their players and (d) most of the main preventive measures used by technical staff matched with the best valued by them. Technical staff defined properly the main risk factors in futsal performance, as well as they applied preventive strategies with scientific support. The information provided in this research could be of interest for sport scientists and technical staff when designing more accurate and efficient injury prevention programs in futsal.

Effect of Drop Height on Vertical Jumping Performance in Pre-, Circa-, and Post-Pubertal Boys and Girls

PURPOSE

To examine the effect of drop height on vertical jumping performance in children with respect to sex and maturity status.

METHODS

Thirty-seven pre-pubertal, 71 circa-pubertal, and 69 post-pubertal boys and girls performed, in a randomized order, 2 squat jumps, 2 countermovement jumps, and 2 drop jumps (DJ) from heights of 20, 30, 40, 50, 60, and 70 cm. The trial with the best jump height in each test was used for analysis.

RESULTS

No significant sex × maturity status × jump type interaction for jump height was observed. However, on average, the children jumped higher in the countermovement jump than in squat jump and DJs (+1.2 and +1.6 cm, P < .001, respectively), with no significant differences between DJs and squat jumps or between DJs when increasing drop heights. Regarding DJs, 59.3% of the participants jumped higher from drop heights of 20 to 40 cm.

CONCLUSIONS

Children, independent of sex and maturity status, performed best in the countermovement jump, and no performance gain was obtained by dropping from heights of 20 to 70 cm. During maturation, the use of drop heights between 20 and 40 cm may be considered in plyometric training, but the optimum height must be obtained individually.

The 11+ Kids warm-up programme to prevent injuries in young Iranian male high-level football (soccer) players: A cluster-randomised controlled trial

OBJECTIVE

To assess the effectiveness of the 11+ Kids warm-up programme regarding injury reduction in male high-level children's football players.

DESIGN

Cluster-randomised controlled trial.

METHOD

Male youth football teams of Iran's high-level football schools were invited to participate. Inclusion criteria were: teams are competing in the highest league of their province; players are between 7 and 14 years old; regular training takes place at least twice per week. Teams were excluded if they used an injury prevention measure. Participating clubs were randomised to an intervention (INT, N = 20 teams) and a control group (CON, N = 22 teams), stratified by the number of teams and the age group. The groups were blinded against each other. The follow-up period was one season (9 months). INT replaced their warm-up by 11+ Kids. CON performed a standard warm-up programme. The primary outcome was the injury incidence density (injuries per 1000 h of football exposure), compared between groups by incidence rate ratios (RR).

RESULTS

In total, 64,047 h of football exposure of 962 players (INT = 443 players, 31,934 h of football, CON = 519 players, 32,113 h of football) were recorded. During the study, 90 (INT = 30; CON = 60) injuries occurred. The overall injury incidence density in INT was reduced by 50% compared to CON (RR 0.50; 95%-CI 0.32, 0.78). No injuries occurred during the execution of the intervention exercises.

CONCLUSIONS

The 11+ Kids reduces injuries in high-level children's football players, thus supporting player health and potentially performance and player development.

Eccentric Resistance Training in Youth: Perspectives for Long-Term Athletic Development

The purpose of this narrative review is to discuss the role of eccentric resistance training in youth and how this training modality can be utilized within long-term physical development. Current literature on responses to eccentric exercise in youth has demonstrated that potential concerns, such as fatigue and muscle damage, compared to adults are not supported. Considering the importance of resistance training for youth athletes and the benefits of eccentric training in enhancing strength, power, speed, and resistance to injury, its inclusion throughout youth may be warranted. In this review we provide a brief overview of the physiological responses to exercise in youth with specific reference to the different responses to eccentric resistance training between children, adolescents, and adults. Thereafter, we discuss the importance of ensuring that force absorption qualities are trained throughout youth and how these may be influenced by growth and maturation. In particular, we propose practical methods on how eccentric resistance training methods can be implemented in youth via the inclusion of efficient landing mechanics, eccentric hamstrings strengthening and flywheel inertia training. This article proposes that the use of eccentric resistance training in youth should be considered a necessity to help develop both physical qualities that underpin sporting performance, as well as reducing injury risk. However, as with any other training modality implemented within youth, careful consideration should be given in accordance with an individual's maturity status, training history and technical competency as well as being underpinned by current long-term physical development guidelines.

The Importance of Fundamental Motor Skills in Identifying Differences in Performance Levels of U10 Soccer Players

This study examined the differences in fundamental motor skills (FMSs) and specific conditioning capacities (SCCs) between a coach’s classification of first team (FT) and second team (ST) U10 soccer players and examined the most important qualities based on how the coach differentiates them. The FT (n = 12; M_age = 9.72 ± 0.41) and ST (n = 11; M_age = 9.57 ± 0.41) soccer players were assessed using the Test of Gross Motor Development-2, standing long jump, sit and reach, diverse sprints, and the 20 m multistage fitness test (MSFT). The coach’s subjective evaluation of players was obtained using a questionnaire. No significant differences existed between the FT and ST in any variables (p > 0.05). However, large and moderate effect sizes were present in favour of the FT group in locomotor skills (d = 0.82 (0.08, 1.51)), gross motor quotient (d = 0.73 (0.00, 1.41)), height (d = 0.61 (−0.12, 1.29)), MSFT (d = 0.58 (−0.14, 1.25)), and maximum oxygen uptake (VO_2max) (d = 0.55 (−0.17, 1.22)). Furthermore, the coach perceived the FT group as having greater technical and tactical qualities relative to ST players. This suggests that it might be more relevant for players of this age to develop good FMS connected to technical skills, before focusing on SCC. Therefore, it might be beneficial for soccer coaches to emphasize the development of FMSs due to their potential to identify talented young soccer players and because they underpin the technical soccer skills that are required for future soccer success.

The elite player performance plan: the impact of a new national youth development strategy on injury characteristics in a premier league football academy

The objective of this study was to investigate the injury incidence and patterns in elite youth football at a category 1 Premier League Academy before and after the introduction of a new development strategy, the Elite Player Performance Plan (EPPP). A prospective study was performed over six consecutive seasons encompassing three years before and after the introduction of the EPPP. The findings revealed a most likely moderate increase in total exposure per player per season when the post-EPPP football exposure (640.86 ± 83.25 hours per player per year) was compared with the pre-EPPP football exposure (539.08 ± 71.59). The total injury incidence pre-EPPP was 3.0/1000 hours compared to 2.1/1000 hours post-EPPP (rate ratio 1.43). 6% of all injuries were re-injuries (20.24 ± 33.43 days) but did not result in a substantially longer absence (16.56 ± 15.77 days). The injury burden decreased for the U12-U15 from pre- to post-EPPP, whereas the injury burden increased for the U16-U18 (respectively 125 and 47% higher). These findings suggest that following the introduction of the EPPP there has been a reduction in injuries in the younger age groups U12-U15 but in the older age groups U16-U18 there has been an increase in the severity of the injuries sustained at this club.