BACKGROUND: Ongoing monitoring of concussion rates and distributions is important in assessing temporal patterns. Examinations of high school sport-related concussions need to be updated. This study describes the epidemiology of concussions in 20 high school sports during the 2013-2014 to 2017-2018 school years. METHODS:In this descriptive epidemiology study, a convenience sample of high school athletic trainers provided injury and athlete exposure (AE) data to the National High School Sports-Related Injury Surveillance Study (High School Reporting Information Online). Concussion rates per 10 000 AEs with 95% confidence intervals (CIs) and distributions were calculated. Injury rate ratios and injury proportion ratios examined sex differences in sex-comparable sports (soccer, basketball, baseball and softball, cross country, track, and swimming). We also assessed temporal trends across the study period.RESULTS: Overall, 9542 concussions were reported for an overall rate of 4.17 per 10 000 AEs (95% CI: 4.09 to 4.26). Football had the highest concussion rate (10.40 per 10 000 AEs). Across the study period, football competition-related concussion rates increased (33.19 to 39.07 per 10 000 AEs); practice-related concussion rates decreased (5.47 to 4.44 per 10 000 AEs). In all sports, recurrent concussion rates decreased (0.47 to 0.28 per 10 000 AEs). Among sex-comparable sports, concussion rates were higher in girls than in boys (3.35 vs 1.51 per 10 000 AEs; injury rate ratio = 2.22; 95% CI: 2.07 to 2.39). Also, among sex-comparable sports, girls had larger proportions of concussions that were recurrent than boys did (9.3% vs 6.4%; injury proportion ratio = 1.44; 95% CI: 1.11 to 1.88).CONCLUSIONS: Rates of football practice-related concussions and recurrent concussions across all sports decreased. Changes in concussion rates may be associated with changes in concussion incidence, diagnosis, and management. Future research should continue to monitor trends and examine the effect of prevention strategies.WHAT'S KNOWN ON THIS SUBJECT: Previous estimates of concussion incidence in high school sports are available but dated. Ongoing monitoring of injury incidence provides the opportunity for clinicians and researchers to understand how concussion rates and distributions may have changed over time.

IMPORTANCE Soccer, originally introduced as a safer sport for children and adolescents, has seen a rapid increase in popularity in the United States over the past 3 decades. Recently, concerns have been raised regarding the safety of soccer ball heading (when an athlete attempts to play the ball in the air with his or her head) given the rise in concussion rates, with some calling for a ban on heading among soccer players younger than 14 years. OBJECTIVES To evaluate trends over time in boys' and girls' soccer concussions, to identify injury mechanisms commonly leading to concussions, to delineate soccer-specific activities during which most concussions occur, to detail heading-related soccer concussion mechanisms, and to compare concussion symptom patterns by injury mechanism. DESIGN, SETTING, AND PARTICIPANTS Retrospective analysis of longitudinal surveillance data collected from 2005-2006 through 2013-2014 in a large, nationally representative sample of US high schools. Participants were boys and girls who were high school soccer players. EXPOSURES Concussions sustained during high school-sanctioned soccer games and practices. MAIN OUTCOMES AND MEASURES Mechanism and sport-specific activity of concussion.RESULTS Overall, 627 concussions were sustained during 1 393 753 athlete exposures (AEs) among girls (4.50 concussions per 10 000 AEs), and 442 concussions were sustained during 1 592 238 AEs among boys (2.78 concussions per 10 000 AEs). For boys (68.8%) and girls (51.3%), contact with another player was the most common concussion mechanism. Heading was the most common soccer-specific activity, responsible for 30.6% of boys' concussions and 25.3% of girls' concussions. Contact with another player was the most common mechanism of injury in heading-related concussions among boys (78.1%) and girls (61.9%). There were few differences in concussion symptom patterns by injury mechanism. CONCLUSIONS AND RELEVANCEAlthough heading is the most common activity associated with concussions, the most frequent mechanism was athlete-athlete contact. Such information is needed to drive evidence-based, targeted prevention efforts to effectively reduce soccer-related concussions. Although banning heading from youth soccer would likely prevent some concussions, reducing athlete-athlete contact across all phases of play would likely be a more effective way to prevent concussions as well as other injuries.

Shoulder and elbow injury rates and patterns in high school baseball players differed between field positions (pitchers vs position players) and by type of exposure (practice vs competition). This study suggests several areas of emphasis for targeted injury prevention interventions, most notably limiting fatigue and preventing overuse injuries.

Background:The risk of heat-related illness and death may continue to increase in many locations as a consequence of climate change, but information on the effectiveness of policies to protect populations from the adverse effects of excessive heat is limited. In 2009, the National Athletic Trainers’ Association Inter-Association Task Force (NATA-IATF) released guidelines to reduce exertional heat illness (EHI) among U.S. high school athletes participating in preseason sports activities, including preseason practice sessions for American football. A subset of state high school athletic associations have implemented state-mandated guidelines consistent with the 2009 NATA-IATF recommendations, but their effectiveness for reducing preseason EHI is unknown.Objectives:This study examines the association between the enactment of state high school athletic association–mandated NATA-IATF guidelines and the rate of EHI among high school students during preseason American football practice sessions.Methods:We performed a quasi-experimental interrupted time-series study of EHI during high school American football practices in the 2005/2006–2016/2017 school years. We estimated state-level EHI rates using High School Reporting Information Online injury and athlete-exposure data, and used generalized estimating equations Poisson regression models to estimate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) comparing state-years with and without mandated NATA-IATF guidelines. State-level covariates included state-year–specific average August temperatures, yearly deviations from each state’s August average temperature across the study period, and school year.Results:Data were available for 455 state-years from 48 states, including 32 state-years (7.0%) from 8 states when mandated guidelines consistent with the NATA-IATF recommendations were implemented. During an estimated 2,697,089 athlete-exposures, 190 EHIs were reported. Estimated preseason EHI rates were lower during state-years with versus without mandated guidelines (adjusted IRR=0.45, 95% CI: 0.23, 0.87).Conclusions:Our findings suggest that high school athletes would benefit from enactment of the 2009 NATA-IATF guidelines. Similar analyses of the effectiveness of other public health policies to reduce adverse health effects from ambient heat are warranted. https://doi.org/10.1289/EHP4163

Twenty subjects participated in four experiments designed to compare time to task failure and motor-unit recruitment threshold during contractions sustained at 15% of maximum as the elbow flexor muscles either supported an inertial load (position task) or exerted an equivalent constant torque against a rigid restraint (force task). Subcutaneous branched bipolar electrodes were used to record single motor unit activity from the biceps brachii muscle during ramp contractions performed before and at 50 and 90% of the time to failure for the position task during both fatiguing contractions. The time to task failure was briefer for the position task than for the force task (P=0.0002). Thirty and 29 motor units were isolated during the force and position tasks, respectively. The recruitment threshold declined by 48 and 30% (P=0.0001) during the position task for motor units with an initial recruitment threshold below and above the target force, respectively, whereas no significant change in recruitment threshold was observed during the force task. Changes in recruitment threshold were associated with a decrease in the mean discharge rate (-16%), an increase in discharge rate variability (+40%), and a prolongation of the first two interspike intervals (+29 and +13%). These data indicate that there were faster changes in motor unit recruitment and rate coding during the position task than the force task despite a similar net muscle torque during both tasks. Moreover, the results suggest that the differential synaptic input observed during the position task influences most of the motor unit pool.

Context The advent of Web-based sports injury surveillance via programs such as the High School Reporting Information Online system and the National Collegiate Athletic Association Injury Surveillance Program has aided the acquisition of girls' and women's basketball injury data. Objective To describe the epidemiology of injuries sustained in high school girls' basketball in the 2005–2006 through 2013–2014 academic years and collegiate women's basketball in the 2004–2005 through 2013–2014 academic years using Web-based sports injury surveillance. Design Descriptive epidemiology study. Setting Online injury surveillance from basketball teams in high school girls (annual average = 100) and collegiate women (annual average = 57). Patients or Other Participants Girls' and women's basketball players who participated in practices and competitions during the 2005–2006 through 2013–2014 academic years in high school or the 2004–2005 through 2013–2014 academic years in college. Main Outcome Measure(s) Certified athletic trainers collected time-loss (≥24 hours) injury and exposure data. Injury rates per 1000 athlete-exposures (AEs) were calculated. Injury rate ratios (IRRs) with 95% confidence intervals (CIs) were used to compare injury rates by school size or division, time in season, event type, and competition level. Results The High School Reporting Information Online system documented 2930 time-loss injuries during 1 609 733 AEs; the National Collegiate Athletic Association Injury Surveillance Program documented 3887 time-loss injuries during 783 600 AEs. The injury rate was higher in college than in high school (4.96 versus 1.82/1000 AEs; IRR = 2.73; 95% CI = 2.60, 2.86). The injury rate was higher in competitions than in practices for both high school (IRR = 3.03; 95% CI = 2.82, 3.26) and collegiate (IRR = 1.99; 95% CI = 1.86, 2.12) players. The most common injuries at both levels were ligament sprains, concussions, and muscle/tendon strains; the majority of injuries affected the ankle, knee, and head/face. These injuries were often caused by contact with another player or a noncontact mechanism. Conclusions Injury rates were higher in collegiate than in high school athletes and in competitions than in practices. Similarities in distributions of injuries by body parts, specific diagnoses, and mechanisms of injury suggest that both levels may benefit from similar injury-prevention strategies.

Context The advent of Web-based sports injury surveillance via programs such as the High School Reporting Information Online system and the National Collegiate Athletic Association Injury Surveillance Program has aided the acquisition of boys' and men's basketball injury data. Objective To describe the epidemiology of injuries sustained in high school boys' basketball in the 2005–2006 through 2013–2014 academic years and collegiate men's basketball in the 2004–2005 through 2013–2014 academic years using Web-based sports injury surveillance. Design Descriptive epidemiology study. Setting Online injury surveillance from basketball teams of high school boys (annual average = 100) and collegiate men (annual average = 55). Patients or Other Participants Boys' and men's basketball players who participated in practices and competitions during the 2005–2006 through 2013–2014 academic years in high school or the 2004–2005 through 2013–2014 academic years in college. Main Outcome Measures Athletic trainers collected time-loss (≥24 hours) injury and exposure data. Injury rates per 1000 athlete-exposures (AEs) were calculated. Injury rate ratios (IRRs) with 95% confidence intervals (CIs) compared injury rates by school size or division, time in season, event type, and competition level. Results The High School Reporting Information Online system documented 3056 time-loss injuries during 1 977 480 AEs; the National Collegiate Athletic Association Injury Surveillance Program documented 4607 time-loss injuries during 868 631 AEs. The injury rate was higher for college than for high school (5.30 versus 1.55/1000 AE; IRR = 3.43; 95% CI = 3.28, 3.59). The injury rate was higher for competitions than for practices in both high school (IRR = 2.38; 95% CI = 2.22, 2.56) and college (IRR = 2.02; 95% CI = 1.90, 2.14). The most common injuries at both levels were ligament sprains, muscle/tendon strains, and concussions; most injuries affected the ankle, knee, and head/face. Injuries were most often caused by contact with another player or noncontact mechanisms. Conclusions Injury rates were greater among collegiate players compared with high school players and were greater during competitions than practices at both levels. Distributions of injuries by body part, diagnoses, and mechanisms of injury were similar, suggesting that athletes at both levels may benefit from similar injury-prevention strategies.

Context:  The advent of Web-based sports injury surveillance via programs such as the High School Reporting Information Online system and the National Collegiate Athletic Association Injury Surveillance Program has aided in the acquisition of girls' and women's volleyball injury data. Objective:  To describe the epidemiology of injuries sustained in high school girls' volleyball in the 2005–2006 through 2013–2014 academic years and collegiate women's volleyball in the 2004–2005 through 2013–2014 academic years using Web-based sports injury surveillance. Design:  Descriptive epidemiology study. Setting:  Online injury surveillance from high school girls' (annual average = 100) and collegiate women's (annual average = 50) volleyball teams. Patients or Other Participants:  Girls' and women's volleyball players who participated in practices and competitions during the 2005–2006 through 2013–2014 academic years in high school and the 2004–2005 through 2013–2014 academic years in college. Main Outcome Measure(s):  Athletic trainers collected time-loss (≥24 hours) injury and exposure data. Injury rates per 1000 athlete-exposures (AEs), injury rate ratios (IRRs) with 95% confidence intervals (CIs), and injury proportions by body site and diagnosis were calculated. Results:  The High School Reporting Information Online system documented 1634 time-loss injuries during 1 471 872 AEs; the National Collegiate Athletic Association Injury Surveillance Program documented 2149 time-loss injuries during 563 845 AEs. The injury rate was higher in college than in high school (3.81/1000 versus 1.11/1000 AEs; IRR = 3.43; 95% CI = 3.22, 3.66), and higher in high schools with ≤1000 students than in those with >1000 students (IRR = 1.35; 95% CI = 1.23, 1.49). Injury rates did not vary by collegiate division. The injury rate was higher during competitions than practices for high school (IRR = 1.23; 95% CI = 1.12, 1.36) but not for college (IRR = 1.01; 95% CI = 0.92, 1.10). Ankle sprains were common in both the high school and collegiate setting. However, liberos had a high incidence of concussion. Conclusions:  Injury rates were higher among collegiate than high school players. However, injury rates differed by event type in high school, unlike college. Concussion injury patterns among liberos varied from those for other positions. These findings highlight the need for injury-prevention interventions specific to setting and position.