High School Athletic Trainer Services for Knee Injuries.

CONTEXT: Participation in high school athletics carries a substantial risk of musculoskeletal injury, particularly to the knee. However, limited information is available on the care being provided by athletic trainers (ATs) for athletes with these injuries. DESIGN: Descriptive epidemiology study. SETTING: Data on athletic training facility visits and AT services were collected from 147 high schools in 26 states. PATIENTS OR OTHER PARTICIPANTS: High school student-athletes who participated in 13 boys' sports and 14 girls' sports and sustained a diagnosed knee injury during the 2011-2012 through 2013-2014 academic years. The ATs documented 6797 knee injuries, with 4242 sustained in boys' sports and 2555 sustained in girls' sports. MAIN OUTCOME MEASURE(S): The number of athletic training facility visits and individual AT services as well as the average, median, and interquartile range of athletic training facility visits (per injury) and AT services (per injury) were calculated by sport and for time-loss (TL; participation restricted for ≥24 hours) and non-time-loss (NTL; participation restricted for <24 hours) injuries. RESULTS: In total, 28 788 athletic training facility visits were reported, with an overall average of 4 athletic training facility visits per knee injury over the 3-year period. Most athletic training facility visits (72.6%) were associated with NTL injuries, but the majority of AT services (68.6%) were associated with TL injuries. A total of 81 245 AT services were provided for all knee injuries. Therapeutic activities or exercise were the most common type of AT service (52.5%). Overall, an average of 12 AT services were reported per knee injury. Compared with NTL injuries, TL injuries had a larger average number of AT services per injury (34 versus 9; P < .001). CONCLUSIONS: Knee injuries at the high school level are a considerable health care burden. This report demonstrates a high proportion of AT attention to the evaluation and treatment of these injuries. This study confirms the recommended management of knee injuries, with neuromuscular and therapeutic activities being the primary services after knee injury.

The epidemiology of back/neck/spine injuries in National Collegiate Athletic Association men's and women's ice hockey, 2009/2010 to 2014/2015.

This study describes the epidemiology of back/neck/spine injuries in National Collegiate Athletic Association (NCAA) men's and women's ice hockey. Data from 66 NCAA men's and 29 women's ice hockey programmes (total of 147 and 67 team-seasons, respectively) were analysed from the NCAA Injury Surveillance Program during the 2009/2010-2014/2015 academic years. In the study period, 226 and 97 back/neck/spine injuries were reported in men and women, respectively, for injury rates of 0.56 and 0.65/1000 athlete exposures. Injury rates were higher in competitions than practices in men (injury rate ratio [IRR] = 4.22; 95% confidence interval [CI]: 3.24-5.49) and women (IRR = 2.49; 95% CI: 1.67-3.70). Most injuries occurred in the lower back/lumbar spine (men: 52.2%; women: 48.5%). There were notably low rates of fractures and severe spinal injuries for both sexes. This study enhances our understanding of the incidence, mechanisms and factors influencing these injuries and can ultimately lead to more effective injury prevention.

Examining Play Counts and Measurements of Injury Incidence in Youth Football.

CONTEXT: Whereas researchers have provided estimates for the number of head impacts sustained within a youth football season, less is known about the number of plays across which such impact exposure occurs. OBJECTIVE: To estimate the number of plays in which youth football players participated during the 2013 season and to estimate injury incidence through play-based injury rates. DESIGN: Descriptive epidemiology study. SETTING: Youth football. PATIENTS OR OTHER PARTICIPANTS: Youth football players (N = 2098; age range, 5-15 years) from 105 teams in 12 recreational leagues across 6 states. MAIN OUTCOME MEASURE(S): We calculated the average number of athlete-plays per season and per game using independent-samples t tests to compare age groups (5-10 years old versus 11-15 years old) and squad sizes (<20 versus ≥20 players); game injury rates per 1000 athlete-exposures (AEs) and per 10 000 athlete-plays; and injury rate ratios (IRRs) with 95% confidence intervals (CIs) to compare age groups. RESULTS: On average, youth football players participated in 333.9 ± 178.5 plays per season and 43.9 ± 24.0 plays per game. Age groups (5- to 10-year-olds versus 11- to 15-year-olds) did not differ in the average number of plays per season (335.8 versus 332.3, respectively; t2086.4 = 0.45, P = .65) or per game (44.1 versus 43.7, respectively; t2092.3 = 0.38, P = .71). However, players from smaller teams participated in more plays per season (373.7 versus 308.0; t1611.4 = 8.15, P < .001) and per game (47.7 versus 41.4; t1523.5 = 5.67, P < .001). Older players had a greater game injury rate than younger players when injury rates were calculated per 1000 AEs (23.03 versus 17.86/1000 AEs; IRR = 1.29; 95% CI = 1.04, 1.60) or per 10 000 athlete-plays (5.30 versus 4.18/10 000 athlete-plays; IRR = 1.27; 95% CI = 1.02, 1.57). CONCLUSIONS: A larger squad size was associated with a lower average number of plays per season and per game. Increasing youth football squad sizes may help reduce head-impact exposure for individual players. The AE-based injury rates yielded effect estimates similar to those of play-based injury rates.

Epidemiology of Hip Flexor and Hip Adductor Strains in National Collegiate Athletic Association Athletes, 2009/2010-2014/2015.

BACKGROUND: Little research has examined the rates and patterns of hip flexor or hip adductor strains in student-athletes in the National Collegiate Athletic Association (NCAA). PURPOSE: To describe the epidemiology of hip flexor and adductor strains in NCAA athletes during the 2009/2010-2014/2015 academic years. STUDY DESIGN: Descriptive epidemiology study. METHODS: Rates and patterns of hip flexor and adductor strains in collegiate sports were examined in a convenience sample of NCAA varsity teams from 25 sports. Rates and distributions of strains by mechanism, recurrence, and participation restriction time were examined. Injury rate ratios (IRRs) and proportion ratios were calculated to compare rates within and between sports by event type, sex, mechanism, recurrence, and participation restriction time. RESULTS: A total of 770 hip flexor and 621 hip adductor strains were reported, resulting in overall injury rates of 1.60 and 1.29 per 10,000 athlete-exposures (AEs), respectively. In men, the rate of hip flexor strains was 1.81 per 10,000 AEs, and that for hip adductor strains was 1.71 per 10,000 AEs. In women, the rate of hip flexor strains was 1.59 per 10,000 AEs, and the rate of hip adductor strains was 1.15 per 10,000 AEs. The highest rates of strains were found in men's soccer and men's ice hockey (range, 2.47-3.77 per 10,000 AEs). Most hip flexor and hip adductor strains occurred in practice, but both had higher rates in competition. In sex-comparable sports, hip flexor strain rates did not differ between the sexes (IRR = 1.14; 95% CI, 0.96-1.36), but the rate of hip adductor strains was higher in men than women (IRR = 1.49; 95% CI, 1.22-1.81). Noncontact was the most common mechanism for both types of strains (hip flexor strains, 59.4%; hip adductor strains, 62.5%); 10.1% of hip flexor strains and 11.1% of hip adductor strains were recurrent. The highest rates of recurrence of both types of strain were found in men's and women's ice hockey (range, 16.0%-30.6%). Most hip flexor and hip adductor strains resulted in <1 week of participation restriction (hip flexor strains, 83.8%; hip adductor strains, 82.9%). CONCLUSION: The NCAA sports with the highest rates of hip flexor and hip adductor strains were men's soccer and men's ice hockey. In sex-comparable sports, men had a higher rate of hip adductor, but not hip flexor, strains. Recurrence rates were remarkably high in ice hockey. Male sports teams, especially soccer and ice hockey, should place an emphasis on prevention programs for hip adductor strains. Secondary prevention programs involving thorough rehabilitation and strict return-to-play criteria should be developed and implemented to curb the high recurrence rate of these injuries, particularly in ice hockey.

Epidemiology of Sport-Related Concussions in High School Athletes: National Athletic Treatment, Injury and Outcomes Network (NATION), 2011-2012 Through 2013-2014.

CONTEXT: Sports participation is one of the leading causes of concussions among nearly 8 million US high school student-athletes. OBJECTIVE: To describe the epidemiology of sport-related concussion (SRC) in 27 high school sports during the 2011-2012 through 2013-2014 academic years. DESIGN: Descriptive epidemiology study. SETTING: Aggregate injury and exposure data from 27 sports in 147 high schools in the National Athletic Treatment, Injury and Outcomes Network (NATION). PATIENTS OR OTHER PARTICIPANTS: Boy and girl high school athletes during the 2011-2012 through 2013-2014 academic years. MAIN OUTCOME MEASURE(S): Sport-related concussion counts, percentages, rates per 10 000 athlete-exposures (AEs), rate ratios (RRs), and injury proportion ratios (IPRs) were reported with 95% confidence intervals (CIs). Rate ratios and IPRs with 95% CIs not containing 1.0 were considered significant. RESULTS: Overall, 2004 SRCs were reported among 27 high school sports, for a rate of 3.89 per 10 000 AEs. Football had the highest SRC rate (9.21/10 000 AEs), followed by boys' lacrosse (6.65/10 000 AEs) and girls' soccer (6.11/10 000 AEs). The SRC rate was higher in competition than in practice (RR = 3.30; 95% CI = 3.02, 3.60). Among sex-comparable sports, the SRC rate was higher in girls than in boys (RR = 1.56; 95% CI = 1.34, 1.81); however, the proportion of SRCs due to player-to-player contact was higher in boys than in girls (IPR = 1.48; 95% CI = 1.27, 1.73). Common symptoms reported among all athletes with SRCs were headache (94.7%), dizziness (74.8%), and difficulty concentrating (61.0%). Only 0.8% of players with SRCs returned to play within 24 hours. The majority of athletes with SRCs (65.8%) returned to play between 7 and 28 days. More players had symptoms resolve after 7 days (48.8%) than less than a week (40.7%). CONCLUSIONS: Our findings provide updated high school SRC incidence estimates and further evidence of sex differences in reported SRCs. Few athletes with SRCs returned to play within 24 hours or a week. Most injured players returned after 7 days, despite a smaller proportion having symptoms resolve within a week.

Descriptive Epidemiology of Non-Time-Loss Injuries in Collegiate and High School Student-Athletes.

CONTEXT: Research on non-time-loss (NTL) injuries, which result in less than 24 hours of restriction from participation, is limited. OBJECTIVE: To describe the epidemiology of NTL injuries among collegiate and high school student-athletes. DESIGN: Descriptive epidemiology study. SETTING: Aggregate injury and exposure data collected from a convenience sample of National College Athletic Association varsity teams and 147 high schools in 26 states. PATIENTS OR OTHER PARTICIPANTS: Collegiate and high school student-athletes participating in men's and boys' baseball, basketball, football, lacrosse, soccer, and wrestling and women's and girls' basketball, field hockey, lacrosse, soccer, softball, and volleyball during the 2009-2010 through 2013-2014 and the 2011-2012 through 2013-2014 academic years, respectively, participated. Collegiate student-athletes participating in men's and women's ice hockey were also included. MAIN OUTCOME MEASURE(S): Injury data from the National Collegiate Athletic Association Injury Surveillance Program and the National Athletic Treatment, Injury and Outcomes Network were analyzed. Injury counts, rates per 1000 athlete-exposures (AEs), and rate ratios were reported with 95% confidence intervals (CIs). RESULTS: A total of 11 899 and 30 122 NTL injuries were reported in collegiate and high school student-athletes, respectively. The proportion of NTL injuries in high school student-athletes (80.3%) was 1.61 times greater than that of collegiate student-athletes (49.9%; 95% CI = 1.59, 1.63). The NTL injury rate in high school student-athletes (8.75/1000 athlete-exposures [AEs]) was 2.18 times greater than that of collegiate student-athletes (4.02/1000 AEs; 95% CI = 2.13, 2.22). Men's ice hockey (5.27/1000 AEs) and boys' football (11.94/1000 AEs) had the highest NTL injury rates among collegiate and high school athletes, respectively. Commonly injured body parts in collegiate and high school student-athletes were the hip/thigh/upper leg (17.5%) and hand/wrist (18.2%), respectively. At both levels, contusions, sprains, and strains were the most frequent diagnoses. Contact with another player was the most cited injury mechanism (college = 38.0%, high school = 46.3%). CONCLUSIONS: Non-time-loss injuries compose large proportions of collegiate and high school sports injuries. However, the NTL injury rate was higher in high school than in collegiate student-athletes. Tracking NTL injuries will help to better describe the breadth of injuries sustained by athletes and managed by athletic trainers.

Epidemiologic Measures for Quantifying the Incidence of Concussion in National Collegiate Athletic Association Sports.

CONTEXT: Injury rates compare the relative frequency of sport-related concussions across groups. However, they may not be intuitive to policy makers, parents, or coaches in understanding the likelihood of concussion. OBJECTIVE: To describe 4 measures of incidence (athlete-based rate, athlete-based risk, team-based rate, and team-based risk) during the 2011-2012 through 2014-2015 academic years. DESIGN: Descriptive epidemiology study. SETTING: Aggregate injury and exposure data collected from the National Collegiate Athletic Association Injury Surveillance Program in 13 sports (men's baseball, basketball, football, ice hockey, lacrosse, soccer, and wrestling and women's basketball, ice hockey, lacrosse, soccer, softball, and volleyball). PATIENTS OR OTHER PARTICIPANTS: Collegiate student-athletes. MAIN OUTCOME MEASURE(S): Sport-related concussion data from the National Collegiate Athletic Association Injury Surveillance Program during the 2011-2012 through 2014-2015 academic years were analyzed. We calculated concussion rates per 1000 athlete-exposures (AEs), concussion risk, average number of concussions per team, and percentage of teams with at least 1 concussion. RESULTS: During the 2011-2012 through 2014-2015 academic years, 1485 concussions were sustained by 1410 student-athletes across 13 sports. Concussion rates ranged from 0.09/1000 AEs in men's baseball to 0.89/1000 AEs in men's wrestling. Concussion risk ranged from 0.74% in men's baseball to 7.92% in men's wrestling. The average ± SD number of concussions per team ranged from 0.25 ± 0.43 in men's baseball to 5.63 ± 5.36 in men's football. The percentage of teams with a concussion ranged from 24.5% in men's baseball to 80.6% in men's football. CONCLUSIONS: Although men's wrestling had a higher concussion rate and risk, men's football had the largest average number of concussions per team and the largest percentage of teams with at least 1 concussion. The risk of concussion, average number of concussions per team, and percentage of teams with concussions may be more intuitive measures of incidence for decision makers. Calculating these additional measures is feasible within existing injury surveillance programs, and this method can be applied to other injury types.

A 6-year surveillance study of "Stingers" in NCAA American Football.

This study describes the epidemiology of "stinger" injuries in National Collegiate Athletic Association (NCAA) Men's Football. About 57 NCAA Men's Football programmes provided 153 team-seasons of injury data to the NCAA Injury Surveillance Programme (NCAA-ISP) during the 2009/2010-2014/2015 academic years. In the study period, 229 "stingers" were reported for an injury rate of 2.04/10,000 athlete-exposures (AE). Most "stingers" were reported during competitions (55.5%) and the preseason (80.3%) and resulted in time loss less than 24 hours (63.8%). One in five (18.8%) were recurrent. Most "stingers" were due to player contact (93.0%), particularly while tackling (36.7%) and blocking (25.8%) and occurred to defensive ends/linebackers (25.8%) and offensive linemen (23.6%). Although previous research reports a large prevalence of "stingers" among football players, the NCAA-ISP reported a relatively low injury rate. The transient nature of pain associated with "stingers" may have contributed to under-reporting, highlighting the need to deduce manners to increase reporting.

Epidemiology of 3825 injuries sustained in six seasons of National Collegiate Athletic Association men's and women's soccer (2009/2010-2014/2015).

AIM: To describe the epidemiology of National Collegiate Athletic Association (NCAA) men's and women's soccer injuries during the 2009/2010-2014/2015 academic years. METHODS: This descriptive epidemiology study used NCAA Injury Surveillance Program (NCAA-ISP) data during the 2009/2010-2014/2015 academic years, from 44 men's and 64 women's soccer programmes (104 and 167 team seasons of data, respectively). Non-time-loss injuries were defined as resulting in <24 h lost from sport. Injury counts, percentages and rates were calculated. Injury rate ratios (RRs) and injury proportion ratios (IPRs) with 95% CIs compared rates and distributions by sex. RESULTS: There were 1554 men's soccer and 2271 women's soccer injuries with injury rates of 8.07/1000 athlete exposures (AE) and 8.44/1000AE, respectively. Injury rates for men and women did not differ in competitions (17.53 vs 17.04/1000AE; RR=1.03; 95% CI 0.94 to 1.13) or practices (5.47 vs 5.69/1000AE; RR=0.96; 95% CI 0.88 to 1.05). In total, 47.2% (n=733) of men's soccer injuries and 47.5% (n=1079) of women's were non-time loss. Most injuries occurred to the lower extremity and were diagnosed as sprains. Women had higher concussion rates (0.59 vs 0.34/1000AE; RR=1.76; 95% CI 1.32 to 2.35) than men. CONCLUSIONS: Non-time-loss injuries accounted for nearly half of the injuries in men's and women's soccer. Sex differences were found in competition injuries, specifically for concussion. Further study into the incidence, treatment and outcome of non-time-loss injuries may identify a more accurate burden of these injuries.

Comparison of Indiana High School Football Injury Rates by Inclusion of the USA Football "Heads Up Football" Player Safety Coach.

BACKGROUND: In Indiana, high school football coaches are required to complete a coaching education course with material related to concussion awareness, equipment fitting, heat emergency preparedness, and proper technique. Some high schools have also opted to implement a player safety coach (PSC). The PSC, an integral component of USA Football's Heads Up Football (HUF) program, is a coach whose primary responsibility is to ensure that other coaches are implementing proper tackling and blocking techniques alongside other components of the HUF program. PURPOSE: To compare injury rates in Indiana high school football teams by their usage of a PSC or online coaching education only. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Athletic trainers (ATs) evaluated and tracked injuries at each practice and game during the 2015 high school football season. Players were drawn from 6 teams in Indiana. The PSC group, which used the PSC component, was comprised of 204 players from 3 teams. The "education only" group (EDU), which utilized coaching education only, was composed of 186 players from 3 teams. Injury rates and injury rate ratios (IRRs) were reported with 95% confidence intervals (CIs). RESULTS: During 25,938 athlete-exposures (AEs), a total of 149 injuries were reported, of which 54 (36.2%) and 95 (63.8%) originated from the PSC and EDU groups, respectively. The practice injury rate was lower in the PSC group than the EDU group (2.99 vs 4.83/1000 AEs; IRR, 0.62; 95% CI, 0.40-0.95). The game injury rate was also lower in the PSC group than the EDU group (11.37 vs 26.37/1000 AEs; IRR, 0.43; 95% CI, 0.25-0.74). When restricted to concussions only, the rate was lower in the PSC group (0.09 vs 0.73/1000 AEs; IRR, 0.12; 95% CI, 0.01-0.94), although only 1 concussion was reported in the PSC group. No differences were found in game concussion rates (0.60 vs 4.39/1000 AEs; IRR, 0.14; 95% CI, 0.02-1.11). CONCLUSION: Findings support the PSC as an effective method of injury mitigation in high school football. Future research should seek to replicate this study using larger samples from additional states.

The Epidemiology of Hip/Groin Injuries in National Collegiate Athletic Association Men's and Women's Ice Hockey: 2009-2010 Through 2014-2015 Academic Years.

BACKGROUND: There is limited research regarding the epidemiology of hip/groin injuries in ice hockey, the majority of which is restricted to time-loss injuries only. PURPOSE: To describe the epidemiology of hip/groin injuries in collegiate men's and women's ice hockey from 2009-2010 through 2014-2015. STUDY DESIGN: Descriptive epidemiology study. METHODS: Hip/groin injury data from the National Collegiate Athletic Association Injury Surveillance Program (NCAA-ISP) during the 2009-2010 through 2014-2015 seasons were analyzed. Injury rates, rate ratios (RRs), and injury proportion ratios (IPRs) were reported with 95% confidence intervals (CIs). RESULTS: During the 2009-2010 through 2014-2015 seasons, 421 and 114 hip/groin injuries were reported in men's and women's ice hockey, respectively, leading to injury rates of 1.03 and 0.78 per 1000 athlete-exposures (AEs), respectively. The hip/groin injury rate was greater in men than in women (RR, 1.32; 95% CI, 1.08-1.63). In addition, 55.6% and 71.1% of hip/groin injuries in men's and women's ice hockey, respectively, were non-time loss (NTL) injuries (ie, resulted in participation restriction time <24 hours); 7.6% and 0.9%, respectively, were severe (ie, resulted in participation restriction time >3 weeks). The proportion of hip/groin injuries that were NTL injuries was greater in women than in men (IPR, 1.28; 95% CI, 1.11-1.48). Conversely, the proportion of hip/groin injuries that were severe was greater in men than in women (IPR, 8.67; 95% CI, 1.20-62.73). The most common hip/groin injury diagnosis was strain (men, 67.2%; women, 76.3%). Also, 12 (2.9%) and 3 (2.6%) cases of hip impingement were noted in men's and women's ice hockey, respectively. CONCLUSION: Hip/groin injury rates were greater in men's than in women's ice hockey. Time loss varied between sexes, with men sustaining more injuries with time loss over 3 weeks. Despite increasing concerns of femoroacetabular impingement in ice hockey players, few cases of hip impingement were reported in this dataset.

Methods and Descriptive Epidemiology of Services Provided by Athletic Trainers in High Schools: The National Athletic Treatment, Injury and Outcomes Network Study.

CONTEXT: Research is limited on the extent and nature of the care provided by athletic trainers (ATs) to student-athletes in the high school setting. OBJECTIVE: To describe the methods of the National Athletic Treatment, Injury and Outcomes Network (NATION) project and provide the descriptive epidemiology of AT services for injury care in 27 high school sports. DESIGN: Descriptive epidemiology study. SETTING: Athletic training room (ATR) visits and AT services data collected in 147 high schools from 26 states. PATIENTS OR OTHER PARTICIPANTS: High school student-athletes participating in 13 boys' sports and 14 girls' sports during the 2011-2012 through 2013-2014 academic years. MAIN OUTCOME MEASURE(S): The number of ATR visits and individual AT services, as well as the mean number of ATR visits (per injury) and AT services (per injury and ATR visit) were calculated by sport and for time-loss (TL) and non-time-loss (NTL) injuries. RESULTS: Over the 3-year period, 210 773 ATR visits and 557 381 AT services were reported for 50 604 injuries. Most ATR visits (70%) were for NTL injuries. Common AT services were therapeutic activities or exercise (45.4%), modalities (18.6%), and AT evaluation and reevaluation (15.9%), with an average of 4.17 ± 6.52 ATR visits and 11.01 ± 22.86 AT services per injury. Compared with NTL injuries, patients with TL injuries accrued more ATR visits (7.76 versus 3.47; P < .001) and AT services (18.60 versus 9.56; P < .001) per injury. An average of 2.24 ± 1.33 AT services were reported per ATR visit. Compared with TL injuries, NTL injuries had a larger average number of AT services per ATR visit (2.28 versus 2.05; P < .001). CONCLUSIONS: These findings highlight the broad spectrum of care provided by ATs to high school student-athletes and demonstrate that patients with NTL injuries require substantial amounts of AT services.

Epidemiology of Hamstring Strains in 25 NCAA Sports in the 2009-2010 to 2013-2014 Academic Years.

BACKGROUND: The epidemiology of hamstring strains among student-athletes has been extensively researched. However, there is a paucity of recent data describing patterns of hamstring strains. PURPOSE: To describe the epidemiology of hamstring strains in 25 National Collegiate Athletic Association (NCAA) championship sports. STUDY DESIGN: Descriptive epidemiology study. METHODS: Hamstring strains data were analyzed from the NCAA Injury Surveillance Program during the 2009-2010 to 2013-2014 academic years. Hamstring strain injury rates, rate ratios (RRs), and injury proportion ratios were reported with 95% CIs. RESULTS: During the study period, 1142 hamstring strains were reported, leading to an injury rate of 3.05 per 10,000 athlete-exposures (AEs). Most hamstring strains occurred during practices (68.2%). However, the competition rate (5.24 per 10,000 AEs) was larger than the practice rate (2.56 per 10,000 AEs; RR = 2.05; 95% CI, 1.81-2.32). A slight majority occurred during the regular season (52.9%). However, the preseason rate (5.00 per 10,000 AEs) was larger than the regular season/postseason rate (2.34 per 10,000 AEs; RR = 2.14; 95% CI, 1.90-2.40). Men's football, men's soccer, and women's soccer contributed the greatest proportion of hamstring strains (35.3%, 9.9%, and 8.3%, respectively). Most hamstring strains were due to noncontact (72.3%). Of all hamstring strains, 12.6% were recurrent, 37.7% resulted in a time loss of <24 hours, and 6.3% resulted in a time loss >3 weeks. Variations in hamstring strain patterns existed by sport. The hamstring strain rate was larger in men than in women in soccer (RR = 1.60; 95% CI, 1.22-2.11), baseball/softball (RR = 1.66; 95% CI, 1.07-2.59), and indoor track (RR = 1.88; 95% CI, 1.26-2.78). In addition, proportions of hamstring strains that were recurrent were higher among men in most sex-comparable sports, but this difference was not significant. CONCLUSION: Hamstring strain rates were higher in the preseason and in competition. Student-athletes should be acclimatized to the rigors of preseason participation. Meanwhile, further surveillance should investigate the effectiveness of prospective prevention programs in an effort to reduce the prevalence of initial and recurrent hamstring strain injuries.