Epidemiology of injuries in male and female youth football players:A systematic review and meta-analysis

Background:To conduct a systematic review and meta-analysis of epidemiological data of injuries in male and female youth football players.Methods:Searches were performed in MEDLINE/PubMed,Web of Science,Cochrane Library,and SPORTDiscus databases.Studies were considered if they reported injury incidence rate in male and female youth(≤19 years old)football players.Two reviewers(FJRP and ALV)extracted data and assessed trial quality using the Strengthening the Reporting of Observational Studies in Epidemiology(STROBE)statement and the Newcastle Ottawa Scale.The Grading of Recommendations Assessment,Development,and Evaluation approach determined the quality of evidence.Studies were combined using a Poisson random effects regression model.Results:Forty-three studies were included.The overall incidence rate was 5.70 injuries/1000 h in males and 6.77 injuries/1000 h in females.Match injury incidence(14.43 injuries/1000 h in males and 14.97 injuries/1000 h in females)was significantly higher than training injury incidence(2.77 injuries/1000 h in males and 2.62 injuries/1000 h in females).The lower extremity had the highest incidence rate in both sexes.The most common type of injury was muscle/tendon for males and joint/ligament for females.Minimal injuries were the most common in both sexes.The incidence rate of injuries increased with advances in chronological age in males.Elite male players presented higher match injury incidence than sub-elite players.In females,there was a paucity of data for comparison across age groups and levels of play.Conclusion:The high injury incidence rates and sex differences identified for the most common location and type of injury reinforce the need for implementing different targeted injury-risk mitigation strategies in male and female youth football players.

Is it Possible to Protect the Adolescent Brain with Internal Mechanisms from Repetitive Head Impacts:Results from a PhaseⅡSingle Cohort,Longitudinal,Self-Control Study

Purpose To quantify the effects of an externally worn collar device for mitigating the influence of repetitive head impacts on alterations to diffusion tensor imaging(DTI)metrics of white matter.Methods Fifteen female high-school soccer athletes(age:14.00-16.98 yrs)completed pre-and post-season DTI over two consecutive years,including measures of diffusivity,changes in which may be associated with brain dysfunction.The collar was worn during year 1(Yr1)but not during year 2(Yr2).Athlete exposures(AEs)and head impact exposure were recorded over the competitive seasons.Results There were no significant differences in AEs or head impact exposures between Yr1 and Yr2(P>0.05).In Yr2,there was significant pre-to post-season mean diffusivity and/or axial diffusivity reduction in multiple WM regions(cor-rected P<0.05).Pre-to post-season mean diffusivity,axial diffusivity,and radial diffusivity decreases were 3.04%±2.53%,2.97%±2.19%,and 3.37%±3.34%,respectively,significantly greater than pre-to post-season changes in Yr1(mean dif-fusivity:-0.31%±1.78%,P=0.0014;axial diffusivity:-0.02%±2.25%,P=0.0014;radial diffusivity:-0.63%±2.10%,P=0.0030).Conclusions Mild bilateral compression to athletes'internal jugular vein through collar application may have increased intracranial blood volume and spatially redistributed head-impact-derived brain energy absorption.However,future research is needed to elucidate the potential clinical significance of WM changes of various degrees.Clinical trails registration NCT03014492.

Editorial

Welcome to the second edition of this two-part special issue of Journal of Science in Sport and Exercise(SSEJ)focussing on the topic of training young athletes.Part-two of the special issue continues to present a mix of review articles and empirical research that explore a diverse but intercon-nected range of topics.Throughout this special issue a multi-tude of perspectives and experimental designs are employed,bringing together inter and multidisciplinary research that consider a variety of interconnected themes related to train-ing different populations of young athletes.The collection of papers highlight how practitioners have the opportunity to positively impact on youth athletes in many different ways.

Editorial

Welcome to a special issue of Journal of Science in Sport and Exercise(SSEJ)focussing on the topic of training young athletes.Fostering a well-rounded development pathway for young athletes remains a“hot topic”within the fields of pediatric exercise science,sport science and medicine,and strength and conditioning.

The Influence of Biological Maturity on Dynamic Force-Time Variables and Vaulting Performance in Young Female Gymnasts

Purpose This cross-sectional study investigated dynamic force-time variables and vaulting performance in young female gymnasts of different maturity status.Methods 120 gymnasts aged 5-14 years were sub-divided into maturity groupings using percent of predicted adult height(%PAH)attained.Participants performed three jumping protocols,the squat jump(SJ),countermovement jump(CMJ)and drop jump(DJ),before completing straight jump vaults that were recorded using two-dimensional video.Results Jumping performance improved with biological maturity evidenced by the most mature gymnasts’producing sig-nificantly more absolute force(P<0.05;all d>0.78),impulse(P<0.05;all d>0.75)and power(P<0.05;all d>0.91)than the least mature group,resulting in the greater jump heights(P<0.05;all d>0.70).While,no significant differences were observed in relative peak force across multiple tests,measures of relative peak power did significantly increase with maturity.Based upon regression analyses,maturation was found to influence vertical take-off velocity during vaulting,explaining 41%of the variance in each jumping protocol.Across all tests,the DJ was found to have the highest predictive ability of vaulting vertical take-off velocity,explaining 55%of the total variance.Conclusion Biological maturation impacts jump height and underpinning mechanical variables in young female gymnasts.Vaulting vertical take-off velocity appears to be influenced by maturation and various dynamic force-time variables,par-ticularly those during DJ,which had the highest explained total variance.

Utility of Kinetic and Kinematic Jumping and Landing Variables as Predictors of Injury Risk: A Systematic Review

Purpose Jump-landing assessments provide a means to quantify an individual’s ability to attenuate ground reaction forces,generate lower limb explosive power and maintain joint alignment.In order to identify risk factors that can be targeted through appropriate training interventions,it is necessary to establish which(scalar)objective kinetic,kinematic,and performance measures are most associated with lower-extremity injury.Methods Online searches of MEDLINE,SCOPUS,EBSCOHost,SPORTDiscus and PubMed databases were completed for all articles published before March 2020 in accordance with PRISMA guidelines.Results 40 articles investigating nine jump-landing assessments were included in this review.The 79%of studies using drop jump(n=14)observed an association with future injury,while only 8%of countermovement jump studies(n=13)observed an association with injury risk.The 57%of studies using unilateral assessments found associations with risk of injury(n=14).Studies using performance measures(jump height/distance)as outcome measure were only associated with injury risk in 30%of cases.However,those using kinetic and/or kinematic analyses(knee abduction moment,knee valgus angle,knee separation distance,peak ground reaction force)found associations with injury in 89%of studies.Conclusion The landing element of jump-landing assessments appears to be superior for identifying individuals at greater risk of injury;likely due to a closer representation of the injury mechanism.Consequently,jump-landing assessments that involve attenuation of impact forces such as the drop jump appear most suited for this purpose but should involve assessment of frontal plane knee motion and ground reaction forces.