Differences in Overuse Injuries in Gender-Comparable Sports: A Nationally Representative Sample of High School Athletes

Source of Data

We obtained data for this study from High School Reporting Information Online (RIO), the National High School Sports-Related Injury Surveillance Study. Methods of High School RIO data collection have been discussed in detail elsewhere.^15,16 Each year, 100 high schools are randomly chosen from 8 strata (based on geographic region and school size) to form a nationally representative sample of high schools. Each of these high schools must have at least 1 certified athletic trainer (AT) who is responsible for documenting details of injury events and submitting them to High School RIO, including information about injured athletes’ gender, class, sport, primary type of injury, body part injured, injury severity, injury setting (practice versus competition), postinjury assessment and care, recurrence of injury, and return-to-play timeline. All athletes participating in 9 common high school sports in the 100 high schools are included to form a nationally representative sample of high school athletes. A weighting algorithm is used to generate national estimates based on data collected from participating high schools.

Study Population and Gender-Comparable Sports

The study population consisted of high school athletes who sustained overuse injuries while participating in 3 girls’ sports (soccer, basketball, and softball) and 3 boys’ sports (soccer, basketball, and baseball) during the academic years of 2006–2007 through 2018–2019. Because the High School RIO database did not include “overuse/chronic” as a mechanism of injury during the 2005 to 2006 school year, we excluded data from that year. Data from 2019–2020 and 2020–2021 were also excluded because of the effects of the coronavirus disease 2019 pandemic on high school athletic activities during those academic years. High School RIO categorizes boys’ and girls’ sports but does not specify whether these categorizations are based on gender identity or biological sex.¹ Because state high school athletic associations determine the category for transgender athletes, the term gender was used in this study.⁸ Basketball, soccer, and baseball/softball are considered to be gender-comparable sports based on similar rules and play.

Definitions of Injury and Athlete Exposure

High School RIO defines an injury as one that (1) occurred because of participation in an organized practice or competition, (2) required medical attention by a certified AT or physician, and (3) resulted in restriction of the student-athlete’s participation for 1 or more days beyond the day of injury. Although heat illness, dental injury, fracture, or concussion with less than 1 day of time lost meet the High School RIO definition of injury, there was only 1 overuse injury case that met these criteria, and it was included in the study.¹⁵ Athletic trainers can update information on these injuries as new information is reported. In this study, we investigated overuse injuries, which are a subset of injuries in the High School RIO database. Athletic trainers record a diagnosis and a “basic mechanism” for each injury. The basic mechanism variable includes the category “chronic/overuse.” An overuse injury in this study was defined by using both the diagnosis and basic mechanism variables. Using the algorithm described by Ritzer et al,³ we defined an overuse injury as an injury that had (1) a diagnosis of blister, bursitis, inflammation, stress fracture, tendonitis, apophysitis, plantar fasciitis, shin splints, or spondylolysis or (2) a basic mechanism of “chronic/overuse.” Only overuse injuries associated with the 6 gender-comparable sports were included in the final analyses. Although this methodology has been used previously,³ there is potential for misclassification. For example, sprains and strains are diagnoses that are typically considered to be acute injuries; however, 7.5% of them were categorized by the AT as having a chronic/overuse basic mechanism and were therefore included in the analyses as overuse injuries.

An athlete exposure⁶ (AE) was defined in this study as 1 student-athlete participating in 1 school-sanctioned practice or competition of the 6 gender-comparable sports.¹⁵ To assess the effect of potential misclassification of sprains and strains as overuse injuries, we conducted a sensitivity analysis by recalculating the injury rate ratios (IRRs) and injury proportion ratios (IPRs) while excluding these cases from the dataset. This analysis aimed to determine whether our conclusions remained consistent after removing these types of injuries.

Some overuse injuries were grouped together because of similar diagnoses. For example, muscle strain (incomplete tear), muscle strain (unknown severity), and muscle strain were grouped into the category “muscle strain (any severity).” The same was done with “tendon strain (any severity)” and “ligament sprain (any severity).” The “other” injury diagnosis category included overuse diagnoses that were only recorded in a few sports, made up a smaller percentage of overuse injuries in a particular sport, or classified as an “other” injury with an overuse mechanism of action reported by the AT.

Additional Study Variables

Injured body regions were broadly categorized as (1) upper extremity, (2) lower extremity, and (3) other (including the High School RIO categories head/face, eye[s], neck/cervical spine, chest/thoracic spine/ribs, abdomen, lower back/lumbar spine/pelvis, clavicle/collar bone, male genitalia, and other). Injuries were categorized as (1) a new injury, (2) a recurrent injury, (3) other, and (4) unknown. The “unknown” category only included data from 2016–2017 through 2018–2019 for girls’ basketball, boys’ baseball, and girls’ softball due to a coding change made in High School RIO. Overuse injuries were analyzed by sport activity (what the athlete was doing when the injury was sustained) and position (what the athlete’s position was in the sport) using variable categories provided by High School RIO. The sport activity categories of general play, conditioning, pitching, and throwing are not defined by High School RIO; therefore, ATs determined for themselves how to define and use these categories. Outcome categories included (1) returned to play in less than 1 week, (2) returned to play in 1 to 3 weeks, (3) returned to play in greater than 3 weeks or medical disqualification, and (4) other (including athletes choosing not to continue the sport, athletes being released from the team, the season ending before athletes returned to activity, and other).

Statistical Analysis

IBM SPSS Statistics for Windows (version 28; IBM Corp) and SAS 9.4 (SAS Institute, Inc) were used to analyze data for this study. National estimates were calculated using sampling weights provided by High School RIO. Descriptive statistics included national estimates with 95% CIs. Injury rates were calculated as the number of unweighted injuries per 10 000 AEs. Injury rate ratios with 95% CIs were estimated using Poisson regression, with the rate of injuries among boys as the reference. Other analyses included calculation of IPRs. All analyses used weighted frequencies except IRRs. The level of significance was set at α = .05 for all analyses. This manuscript follows Strengthening the Reporting of Observational Studies in Epidemiology reporting guidelines for observational studies.

The following is an example of an IRR calculation:

The following is an example of an IPR calculation:

Ethical Considerations

This study was determined to be exempt from approval by the institutional review board of the authors’ institution.

Injury Frequency and National Estimates

From the 2006–2007 through the 2018–2019 school year, there were 21 412 injuries reported in the 6 sports analyzed in this study, representing a national estimate of 8 622 771 injuries, of which 88.4% were acute injuries, 10.5% were overuse injuries, and 1.0% were other injuries. Among overuse injuries, an estimated 398 419 injuries were reported among boys’ soccer, basketball, and baseball, representing 43.9% of overuse injuries nationally, and an estimated 509 876 injuries were reported among girls’ soccer, basketball, and softball, representing 56.1% of overuse injuries nationally (Table 1).

Table 1. Number of Reported and Estimated Overuse Injuries by Gender and by Academic Year, Sport, Class Year, and Event Type

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Among the 3 high school boys’ sports included in this study, soccer had the highest national estimated percentage of overuse injuries (52.5%), followed by baseball (28.2%) and basketball (19.4%). The 3 girls’ sports followed a similar trend, with soccer accounting for 53.2% of all girl’s overuse injuries, followed by softball (26.9%) and basketball (20.0%; Table 1).

Across class year, distributions of overuse injuries were different between girls’ and boys’ sports. Among boys’ sports, the estimated number of overuse injuries generally increased with increasing class year, whereas among girls’ sports, the estimated number of overuse injuries decreased with increasing class year (Figure A). Most overuse injuries for both boys (72.6%) and girls (73.4%) occurred during practice rather than competition (Table 1). This was true for all 6 sports (Figure B).

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Injury Rates and IRRs

Overall, girls (19.69 per 100 000 AEs) were more likely than boys (13.63 per 100 000 AEs) to sustain an overuse injury (IRR: 1.44; 95% CI = 1.33–1.57; Table 2). After excluding sprains and strains from the analyses, the relationship remained the same (IRR: 1.44; 95% CI = 1.30–1.60). When comparing overuse injury rates among sports, boys and girls both had higher rates for soccer, followed by baseball/softball and basketball. When comparing boys and girls by sport, girls had higher rates of overuse injuries than boys for basketball (IRR: 1.82; 95% CI = 1.56–2.14), followed by soccer (IRR: 1.37; 95% CI = 1.20–1.57) and baseball/softball (IRR: 1.21; 95% CI = 1.04–1.41). These relationships did not change after exclusion of sprains and strains from analyses (basketball [IRR: 1.74; 95% CI = 1.45–2.08], soccer [IRR: 1.37; 95% CI = 1.16–1.62], and baseball/softball [IRR: 1.25; 95% CI = 1.02–1.52]). Compared with boys, girls had higher overuse injury rates during practice (IRR: 1.50; 95% CI = 1.36–1.66), which was consistent across all sports. Likewise, the rate of overuse injuries during competition was higher among girls than boys (IRR: 1.30; 95% CI = 1.10–1.53), which was consistent for soccer and basketball but showed no difference in baseball/softball. After excluding sprains and strains from analyses, the rate of overuse injuries during practice (IRR: 1.49; 95% CI = 1.32–1.68) and competition (IRR: 1.30; 95% CI = 1.06–1.60) remained higher among girls than boys.

Table 2. Injury Rates and Injury Rate Ratios by Gender and by Academic Year, Sport, and Event Type

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Body Site, Time Loss, and Diagnosis

Although most overuse injuries in soccer (83.9% in boys’ soccer and 90.0% in girls’ soccer) and basketball (77.0% in boys’ basketball and 80.5% in girls’ basketball) occurred to a lower extremity, baseball and softball overuse injuries primarily involved an upper extremity (72.5% in boys’ baseball and 53.7% in girls’ softball; Figure C). Compared with girls, boys were equally likely to sustain an overuse injury to a lower extremity (versus another body site) in soccer or basketball; however, boys were at an increased risk of sustaining an overuse injury to an upper extremity (versus another body site) in baseball/softball (IPR: 1.35; 95% CI = 1.16–1.57) compared with girls. After excluding sprains and strains, these relationships remained the same for soccer, basketball, and baseball/softball.

Across all 6 sports studied, most high school athletes returned to their sport less than 1 week after an overuse injury diagnosis (Figure D). Comparing girls’ softball with boys’ baseball overuse injuries, the proportion of girls returning to play within less than 1 week of injury (60.4%) was higher than that for boys (43.7%; IPR: 1.38; 95% CI = 1.15–1.65; following exclusion of sprains and strains, IPR: 1.49; 95% CI = 1.17–1.89). In addition, the proportion of girls returning to play in greater than 3 weeks (3.4%) was lower than for boys (10.6%; IPR: 0.32; 95% CI = 0.15–0.70); however, statistical significance was lost following the exclusion of sprains and strains. No statistically significant gender differences in the time to return to play were found for soccer or basketball.

Tendonitis was the most common diagnosis in 4 of the 6 sports (girls’ soccer, 22.5%; boys’ basketball, 25.4%; girls’ basketball, 21.4%; and boys’ baseball, 32.9%), followed by muscle strain (girls’ soccer, 20.3%; boys’ basketball, 17.8%; girls’ basketball, 19.4%; and boys’ baseball, 20.4%). However, in boys’ soccer and girls’ softball, muscle strain was more common (25.3% and 34.9%, respectively) than tendonitis (19.2% and 29.7%, respectively; Table 3).

Table 3. Overuse Injury Diagnosis by Sport and Gender

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Sport Activity and Position

The sport activities associated with overuse injury were similar for boys’ and girls’ soccer, with most injuries associated with general play (boys, 60.1%; girls, 65.6%), followed by conditioning (boys, 16.3%; girls, 18.0%). Like soccer, the sport activities associated with overuse injury were similar for boys’ and girls’ basketball, with most injuries associated with general play (boys, 63.3%; girls, 66.2%), followed by conditioning (boys, 11.9%, girls, 14.9%). Pitching (43.5%) was the most common activity in boys’ baseball associated with overuse injury, and throwing (31.7%) was the most common activity in girls’ softball. The pitcher position had the greatest percentage of overuse injuries for both genders (boys, 48.0%; girls, 21.6%), followed by catchers (boys, 10.6%; girls, 13.8%).

Study Limitations

This study has some limitations. (1) The High School RIO sample was limited to high schools with ATs; therefore, our results may not be generalizable to high schools without ATs. (2) Some overuse injuries may not have been included in this study because they did not result in time loss from sport participation, thus potentially leading to an underreported number of injuries. There is also potential for misclassification of overuse injuries. (3) The definition of an overuse injury used in this study agrees with that in the study by Ritzer et al³ but may be subject to potential misclassification and/or differ from other studies, which can make comparisons of findings more difficult. (4) Because overuse injuries are gradual in onset, the characteristics described in this study for these injuries represent those that existed at the moment that the injury was recognized and documented. This “snapshot” of the injury provides useful information but cannot fully describe the dynamic nature of these injuries. (5) We were unable to adjust for some potential covariates, such as height, weight, type of shoes, and training load, because of database limitations. Therefore, our results may be biased due to uncontrolled confounding factors. (6) Although data for additional sports that are predisposed to overuse injuries, such as track and field sports and swimming, are included in High School RIO, they are not able to be extrapolated to national estimates and therefore were not included in this study. Therefore, our results may not be representative of overuse injuries in those sports. Despite these limitations, High School RIO is a high-quality database that has been the basis for more than 100 peer-reviewed publications.