High School Sport Specialization and Injury in Collegiate Club-Sport Athletes

This study was approved by the Institutional Review Board of the University of Wisconsin–Madison. We used a cross-sectional design with paper and online anonymous surveys. The surveys were administered from September 2019 to May 2020. In the fall of 2019, the primary investigator (K.M.B.) emailed club-sport presidents and organizers at the University of Wisconsin–Madison to ask permission to present the study to their respective sport club teams. All club sports at the University of Wisconsin–Madison were contacted except for e-sports, water ski and wakeboard, and fishing. The primary investigator was then invited to present the study and distribute the survey to sport club teams during practices or team meetings. The surveys were completed during this time and returned to the primary investigator. In the spring of 2020, because of COVID-19 restrictions, the survey was moved online using Qualtrics. The survey link was forwarded to the club-sport presidents and organizers, who then emailed it to their respective team participants. All participants were students at the same university. Of the sports clubs contacted, 31 of 48 (65%) were represented in our data set. Represented sports were aikijujitsu, archery, baseball, men's and women's basketball, boxing, cheer, dance elite, fencing, field hockey, figure skating, gymnastics, men's and women's ice hockey, Irish dancing, men's and women's lacrosse, women's rugby, women's soccer, softball, swim/dive, tennis, track, men's and women's volleyball, wrestling, taekwondo, triathlon, water polo, and men's and women's ultimate Frisbee. Because the survey was anonymous, the athletes were not required to sign a consent form. They were provided a written description of the study, and completing the survey was deemed consent.

The survey addressed the sport specialization classification for each high school year (9th–12th),¹⁷  high school sport(s) participation, and injuries sustained during the collegiate club-sport career. The original 3-point scale proposed by Jayanthi et al⁴  was adjusted based on research in which authors²²  identified misclassification by single-sport athletes and others¹⁷  who used the scale retrospectively to assess high school sport specialization in National Collegiate Athletic Association Division I collegiate athletes. For each grade, athletes were classified in the 3-point scale based on the answers to 3 questions: (1) “In high school, did you consider one of your sports more important than your other sports and if you only played one sport, select ‘yes'?” (2) “In high school, did you train more than 8 months a year in one sport?” (3) “In high school, did you quit a sport to focus more on a single sport OR have you only played a single sport?” Participants selected either yes (1 point) or no (0 points) for each question. Scores for each question were summed to determine the specialization category as low (0–1), moderate (2), or high (3) for the 9th, 10th, 11th, and 12th grades. Once an athlete selected yes to question 3, that question was marked as yes for subsequent high school grades.¹⁷  The number of years an individual was classified as highly specialized (range = 0–4 years) in high school was then calculated.

Multisport or single-sport participation was determined according to the number of sports an athlete identified participating in during his or her high school career. Those who selected 2 or more sports for the question “What sports did you participate in high school?” were categorized as multisport athletes. Conversely, athletes who selected only 1 sport for this question were categorized as single-sport athletes. Individuals who participated in the same sport in high school and college were considered athletes who continued their high school sport into college.

The Figure is an example of the survey format for collecting injury data. An injury must have been related to collegiate club-sport activities and could be classified as arising from a overuse, contact, or noncontact mechanism (Figure, column 4) that required the individual to seek treatment or diagnosis from an AT or physician (Figure, column 5). Injuries labeled as resulting from overuse were analyzed as overuse injuries and injuries that occurred from either contact or noncontact were designated acute injuries. Therefore, for analysis, injuries were classified into overuse or acute injuries to the upper extremity (UE), lower extremity (LE), or head/neck. The marked mechanism of injury was reviewed by 2 authors (K.M.B. and D.R.B.) who are ATs to verify that the mechanism of injury aligned with any further injury description given by the participant. Furthermore, athletes who wrote “concussion” in column 2 (Figure) of the head/neck injury section were classified as having sustained a concussion. An LE injury was considered an injury to the hip, upper leg, knee, lower leg, ankle, or foot (Figure, column 1). A UE injury was considered an injury to the shoulder, elbow, or wrist/hand (Figure, column 1). Back injuries were not included in this analysis because of the difficulty in classifying them as UE or LE without expanding the survey. Reported injuries could have occurred at any point during a participant's collegiate club-sport career (Figure). Participants were then dichotomized as either having or not having reported a UE overuse, UE acute, LE overuse, LE acute, head/neck overuse, head/neck acute, or head/neck concussion injury during their club-sport career. This was done because few participants had >1 UE overuse, UE acute, LE overuse, LE acute, head/neck overuse, head/neck acute, or head/neck concussion injury (Table 1). No more than 2 people in each category reported multiple UE overuse, UE acute, or LE acute injuries (Table 1). Fifteen reported >2 LE overuse injuries (Table 1). Furthermore, no one reported >1 head/neck injury (Table 1).

Data are presented as means and SDs for continuous variables and frequencies and percentages for categorical variables. Head/neck overuse injuries were not analyzed as only 2 injuries in the entire sample were reported (Table 1). We used a 2 × 2 χ² analysis to compare reported UE overuse (yes or no), UE acute (yes or no), LE overuse (yes or no), LE acute (yes or no), head or neck acute (yes or no), and concussion (yes or no) injuries between males and females. A 2 × 2 χ² analysis was used to compare reported UE overuse (yes or no), UE acute (yes or no), LE overuse (yes or no), LE acute (yes or no), head/neck acute (yes or no), and concussion (yes or no) injuries between multisport and single-sport high school athletes. The same 2 × 2 χ² analysis was used to compare each injury variable between those continuing and those not continuing their high school sport into college. The number of years in high school classified as highly specialized was aggregated into 3 categories: 0, 1 to 2, and 3 to 4 years of high specialization. We did this to avoid violating the assumption that each expected cell count must be >5 for χ² analysis.²³  A 2 × 3 χ² analysis was used to compare reported UE overuse (yes or no), UE acute (yes or no), LE overuse (yes or no), LE acute (yes or no), head/neck acute (yes or no), and concussion (yes or no) injuries among the 3 categories of years a participant was classified as highly specialized. Statistical significance was set a priori at P < .05 and all analyses were performed using SPSS (version 26.0; IBM Corp).

Demographic information is provided in Table 2. Men's and women's volleyball contributed the largest number of athletes (Table 2), but representation of club sports in this population was heterogeneous. Approximately 47% of collegiate club athletes were classified as highly specialized during their high school careers (Table 3). Reported levels of sport specialization increased as the high school grade increased.

Table 4 provides the numbers of athletes who reported at least 1 UE overuse, LE overuse, UE acute, or LE acute injury during their collegiate club sports career as well as the χ² analysis for each sport participation variable. High school single-sport or multisport participation was not associated with any reported injury mechanism or limb in collegiate club-sport athletes (Table 4). Similarly, the number of years an athlete was classified as highly specialized in high school was not associated with any reported injury mechanism or limb in collegiate club-sport athletes. Athletes who played a new collegiate club sport were more likely to report an acute LE injury than athletes who were continuing 1 of their high school sports into college (20% versus 8%, P = .006).

The number of athletes who reported a head/neck acute injury or concussion during their collegiate club sports career as well as the χ² analysis for each sport participation variable are shown in Table 5. All concussion injuries occurred from head/neck acute injuries. Head/neck acute injuries and concussion were not associated with either high school single-sport versus multisport participation or the number of years an athlete was classified as highly specialized. Athletes who played a new collegiate club sport were more likely to report a head/neck acute injury or a concussion compared with athletes who were continuing 1 of their high school sports into college (head/neck acute = 16% versus 3%, P < .001, and concussion = 13% versus 2%, respectively; P < .001).

Our findings did not support our hypothesis that high school sport specialization would be associated with reported injuries in collegiate club-sport athletes. A few factors may explain why sport specialization in high school was not associated with injuries in collegiate club-sport athletes. Though we were able to include many collegiate club sports in this study, it is important to recognize that these sports' playing styles, practices, season lengths, and competition levels vary widely. Therefore, it is possible that high school sport specialization is more detrimental for 1 sport than another. Post et al²⁴  reported that high school volleyball athletes who specialized were at an increased risk for overuse injuries compared with low-level specialized volleyball athletes, whereas the same relationship was not found in basketball or soccer high school athletes. Similarly, in a recent study of soccer players,²⁵  no link was evident between specialization and injury risk. Therefore, a sport-specific study in collegiate athletes may be beneficial to better understand the possible association of high school sport specialization with collegiate injuries and how this may vary among sports.

To the best of our knowledge, we are the first to report on the association of high school sport specialization and sport participation with collegiate club-sport injuries. Several groups^13,14,16,26  have examined the association of injuries with early sport specialization in Division I and professional athletes. Unlike our results, all of these authors^13,14,16,26  found an association with high school sport specialization and injuries in Division I and professional athletes. Confino et al¹⁴  and Rugg et al¹³  noted that single-sport athletes in high school had more publicly reported major injuries during their professional careers than professional athletes who were multisport athletes in high school. Buckley et al¹⁶  surveyed high school, collegiate, and professional athletes. Their goal was to cross-sectionally evaluate sport specialization habits in current high school, collegiate, and professional athletes and assess the association between reported injuries and sport specialization. Buckley et al¹⁶  found that current high school and collegiate players recalled more injuries that the athletes attributed to specializing in 1 sport compared with current professional athletes. Lastly, Ahlquist et al²⁶  determined that Division I athletes who specialized in a single sport before age 14 were more likely to report multiple collegiate sport-related injuries than athletes who specialized at a later age. These studies support the hypothesis that sport specialization may affect injury risks throughout an individual's sporting career. Several reasons are possible for our different results. Given the demands of professional sports, the long-term training load is likely higher in professional athletes compared with club-sport athletes. It is equally likely that long-term training volume and repetitive motions are significantly higher in professional athletes than in our club-sport athletes. Anecdotally, club-sport athletes practice a few times a week, have a shorter competition season, and have fewer organized team events outside the regular season than Division I collegiate or professional athletes. Club-sport athletes' lower volume and training load compared with those of Division I and professional athletes may negate the possible negative effects of high school sport specialization. This is supported by previous literature indicating that training volume was a more important predictor of injury than early sport specialization. For example, Sugimoto et al²⁷  observed that increases in training volume were associated with the injury risk in adolescent females. However, Sugimoto et al²⁷  did not find that single-sport athletes were more associated with injury than multisport athletes as they had hypothesized. Post et al⁸  reported similar findings; however, McGuine et al⁷  demonstrated that sport specialization was a risk factor independent of training volume. Therefore, future authors should prospectively study training volume, sport specialization, and sport-related injuries in high school athletes as they transition to collegiate sports to better illuminate how these variables may affect collegiate athletes' sport injury risk.

To the best of our knowledge, we are the first to report that collegiate club athletes who did not play their club sport in high school were more likely to report an LE acute injury, head/neck acute injury, or concussion compared with club athletes who were continuing their high school sport in college. Most club athletes who were participating in a new sport were involved in club sports such as rugby (10 of 67, 15%), ultimate Frisbee (21 of 67, 31%), or martial arts (8 of 67, 12%). It is possible that these athletes' high school sport specialization affected their injury risk in club-sport activities; however, our investigation lacked sufficient power to analyze this factor in this specific subset of individuals. A number of authors^10,12,28  demonstrated that adolescent multisport participation was associated with improved motor skills, movement patterns, endurance, and strength. When these athletes switch to a new sport, improvements (or lack of improvements) in these areas during adolescence may affect their risk of injury. Furthermore, switching sports after high school may protect an individual from overuse injuries but increase the risk for acute injuries. Evidence on the association of years of playing experience and sport-related injuries is limited and conflicting.^29,30  It has been proposed that athletes starting to compete in a new sport lack a transitional period to prepare for the movements and loads necessary in competition.²⁹  Thus, a lack of knowledge of the given sport and insufficient physical preparedness for that sport may lead to an increased risk of injury. Our results support this hypothesis, though future research is needed to bolster this theory. Athletic trainers working with collegiate club-sport programs or organizers of club-sport programs may benefit from identifying athletes new to their respective club sport and providing extra lessons and training sessions in that sport to reduce the risk of acute injuries in this population.

This study had several limitations. First, sport specialization was based on retrospective answers to questions regarding high school sport participation. Similarly, collegiate club-sport injuries were collected retrospectively; therefore, these data were subject to recall bias. However, we aimed to improve the accuracy of the injury data by restricting the analyses to injuries for which individuals could identify a specific mechanism of injury and that had been reported to a medical professional (AT or physician). The survey could have included more insight into training load and volume during athletes' high school athletic careers as well as the different sport organizations in which they participated (eg, Amateur Athletic Union, club volleyball). However, we left these questions out to avoid burdening participants with too lengthy a survey. These results may not be generalizable beyond this specific university or geographic location. Future authors who track sport participation and specialization through high school and into college may provide a better understanding of how high school sport specialization affects the injury risk for college-aged athletes at all levels.

High school sport specialization was not associated with injuries reported by collegiate club-sport athletes. This may have been due to reduced sport volume and training load for collegiate club-sport athletes compared with higher-level athletes or the heterogeneity of the analyzed sports. Collegiate athletes who were playing a club sport different from any of their high school sports were more likely to report an LE acute injury, head/neck acute injury, or concussion compared with those who were continuing to participate in their high school sport. This may have resulted from a lack of experience in the new sport, leading to more injuries. Athletic trainers and other professionals who work with collegiate club-sport programs may benefit their athletes by identifying individuals who are starting a new sport at the collegiate level.