Background Recent injury data for collegiate-level swimming and diving are limited. This study describes the epidemiology of men's and women's swimming and diving injuries reported by the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP) during the 2009/2010 to 2013/2014 academic years.
Methods Injuries and athlete-exposure (AE) data reported within 9 men's and 13 women's swimming and diving programmes were analysed. Injury rates, injury rate ratios (IRR), and injury proportions by body site, diagnosis and mechanism were reported with 95% CIs.
Results The ISP captured 149 and 208 injuries for men's and women's swimming and diving, respectively, leading to injury rates of 1.54/1000 and 1.71/1000 AEs. Among females, divers had a higher injury rate (2.49/1000 AEs) than swimmers (1.63/1000 AEs; IRR=1.53; 95% CI 1.07 to 2.19). Injury rates for male divers (1.94/1000 AEs) and swimmers (1.48/1000 AEs) did not differ (IRR=1.33; 95% CI 0.85 to 2.31). Most injuries occurred to the shoulder, resulted in strains and were classified as overuse or non-contact. Female swimmers had a higher overuse injury rate (1.04/1000 AEs) than male swimmers (0.66/1000 AEs; IRR=1.58; 95% CI 1.14 to 2.19). Overuse injury rates for female divers (0.54/1000 AEs) and male divers (0.46/1000 AEs) did not differ (IRR=1.16; 95% CI 0.40 to 3.34). Injury rates in 2012/2013–2013/2014 were lower than those in 2009/2010–2011/2012 for women's swimming (IRR=0.70; 95% CI 0.52 to 0.95) and diving (IRR=0.56; 95% CI 0.30 to 1.08), respectively. No time trends existed for men's swimmers or divers.
Conclusions Shoulder, strain and overuse injuries were common in collegiate men's and women's swimming and diving. Female swimmers were more likely to suffer an overuse injury than male swimmers. In addition, divers may have higher injury rates than swimmers, although small reported numbers warrant additional research.
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The National Collegiate Athletic Association (NCAA) has sanctioned championship events in men's swimming and diving since 19371 and women's swimming and diving since 1982.2 In the 2013/2014 academic year, 9630 men and 12 333 women participated in NCAA swimming and diving.3 Swimming events range from 50 to 1500 m in freestyle, backstroke, breaststroke or butterfly. Divers compete in 1 m springboard, 3 m springboard and/or platform diving (Division I only). The repetitive nature of swim training and competition are major risk factors for overuse injury, particularly to the shoulder.4–6 Diving injury-related research exists7–12 but is limited to small samples.
We aim to help clinicians and researchers better understand the patterns, mechanisms and risk factors of injury in collegiate swimmers and divers. The NCAA Injury Surveillance Program (ISP) has monitored all injuries occurring in a sample of men's and women's swimming and diving varsity teams. This study utilises data from the NCAA ISP to describe the epidemiology of men's and women's swimming and diving injuries occurring within the NCAA competition level during the 2009/2010–2013/2014 academic years.
Data from the 2009/2010–2013/2014 academic years were obtained from the NCAA ISP, a prospective surveillance programme that is managed by the Datalys Center for Sports Injury Research and Prevention (hereafter known as the Datalys Center), an independent, non-profit research organisation. This study was approved by the Research Review Board of the NCAA, with student-athletes from participating teams providing consent at the beginning of each academic year.
Men's swimming and diving data originated from nine varsity programmes that contributed 23 team-seasons. Each team-season included an average 22.8 swimmers and 3.5 divers. Women's swimming and diving data originated from 13 varsity NCAA women's swimming and diving programmes that contributed 30 team-seasons. Each team-season included an average 22.4 swimmers and 3.2 divers.
The methodology of the NCAA ISP during the 2009/2010–2013/2014 academic years has been previously described.13 The ISP utilised a convenience sample of NCAA varsity sport teams with athletic trainers (ATs) reporting injury data. These ATs worked with these participating teams and attended school-sanctioned practices and competitions. When injuries occurred, the ATs reported them in real-time through the electronic health record application used by the team medical staff throughout the academic year. In addition to musculoskeletal injuries, the surveillance system captured other sports-related adverse health events such as illness, heat-related conditions, general medical conditions and skin infections. Only varsity-level practice and competition events and team conditioning sessions were included in the ISP data sets. Individual weight lifting and conditioning sessions were excluded.
For each event, the AT completed a detailed event report on the injury or condition (eg, site, diagnosis) and the circumstances (eg, activity, mechanism, event type (ie, competition or practice)). For swimming events, the AT specified which stroke was being performed. The ATs were able to view and update previously submitted information as needed during the course of a season. In addition, ATs also provided the number of student-athletes participating in each practice and competition.
From the electronic health record application, common data elements that included injury and exposure information were stripped of any identifiers and personally identifiable information and retained only relevant variables and values.13 The frequency of export or submission of data varied slightly among vendors providing the electronic health record applications to team medical staff. This common data element standard allows ATs to document injuries as they normally would as part of their daily clinical practice, as opposed to having them separately report injuries for injury surveillance programme purposes. All electronic health record applications must have successfully completed a data-validation process to be certified.
Exported data passed through an automated verification process that conducted a series of consistency checks. Data were reviewed and flagged for invalid values. The AT and data quality assurance staff were notified and worked together to resolve the issue. Data that passed the verification process were then placed into the men's and women's swimming and diving aggregate data sets.
A reportable injury in the ISP was an injury that: occurred as a result of participation in an organised intercollegiate practice/competition and required attention from an AT or physician. Multiple injuries could be included as the result of one injury event.
A reportable athlete-exposure (AE) was defined as one student-athlete participating in one NCAA-sanctioned practice or competition in which he or she was exposed to the possibility of athletic injury, regardless of the time associated with that participation. Only athletes with actual playing time in a competition were included in competition exposures.
Body parts were categorised as: head/face, neck, shoulder/clavicle, arm/elbow, hand/wrist, trunk (including chest, abdomen, upper back and lower back), hip/groin, thigh/upper leg, knee, lower leg (including the Achilles), ankle, foot and other.
Injuries were also categorised by the number of days in which athletes were restricted from participation.
Non-time loss injuries were injuries that resulted in restriction of participation less than 24 h; however, this excluded concussions, fractures and dental injuries, which were considered time loss injuries, regardless of reported time loss. The inclusion of these injuries as time loss is typical in injury surveillance.14 ,15
Severe injuries were injuries that resulted in time loss over 3 weeks.16 Severe injuries may have also resulted in the student-athletes prematurely ending their season (ie, season-ending injury).
Classifying injuries and AEs by swimming versus diving
Student-athletes were grouped either swimmers or divers. If a student-athlete's injury record did not include the sport, we contacted school ATs to obtain such information. For AEs, we consulted historical team rosters for participating programmes to calculate the ratio of swimmers to divers. The AEs documented for that school for that year were then distributed based on these ratios. This distribution assumes that swimmers and divers participated in the same number of practices and competitions across a season. Thus, if a school's men's swimming and diving programme had 27 swimmers and 3 divers (ie, 9:1 ratio), and 200 competition AEs in the 2011/12 academic year, then we would assume that swimmers and divers had accounted for 180 and 20 of the competition AEs, respectively. ATs from participating programmes confirmed our methodology that swimmers and divers participated in approximately the same number of practices and competitions across a season.
Data were analysed to assess rates and patterns of college men's and women's swimming and diving injuries. Data were analysed using SAS-Enterprise Guide software (V.4.3; SAS Institute Inc, Cary, North Carolina, USA). Statistical analyses included calculation of injury rate ratios (IRRs), injury proportion ratios (IPRs) and χ2 tests. The overall injury rate was calculated as the ratio of injuries per 1000 total AEs. Injury rates were also calculated as the ratio of practice injuries per 1000 practice exposures and the ratio of competition injuries per 1000 competition exposures. The following is an example of an IRR comparing competition and practice injury rates:
The following is an example of an IPR comparing the proportion of shoulder injuries sustained in male and female divers:
All 95% CIs not containing 1.00 were considered statistically significant. Because of statistical power concerns in time trends, we grouped years as 2009/2010–2011/2012 and 2012/2013–2013/2014. Also, due to the small number of injuries, the majority of analyses utilise the overall count of injuries, as opposed to stratifying by competition and practice.
Overall frequencies and rates
Men's swimming and diving
The ATs reported 149 injuries during 2009/2010–2013/2014 in college men's swimming and diving, of which 124 (83.2%) and 25 (16.8%) occurred to swimmers and divers, respectively. A total of 133 (89.3%) occurred during practice; 16 occurred during competition (10.7%). Most injuries occurred in the regular season (61.7%); 36.2% and 2.0% occurred in the preseason and postseason, respectively. In addition, 77.2% were non-time loss and 2.7% were severe. Four injuries (2.7%) required surgery.
These 149 injuries occurred during 96 745 AEs, for an injury rate of 1.54/1000 AEs (95% CI 1.29 to 1.79; table 1). No difference existed between the injury rates for practice (1.50/1000 AEs) and competition (1.93/1000 AEs; IRR=0.78; 95% CI 0.46 to 1.30). When injury rates were stratified by athlete-type, injury rates for male divers (1.94/1000 AEs) and swimmers (1.48/1000 AEs) did not differ (IRR=1.33; 95% CI 0.85 to 2.31).
Women's swimming and diving
The ATs reported 208 injuries during 2009/2010–2013/2014 in college women's swimming and diving, of which 171 (82.2%) and 37 (17.8%) occurred to swimmers and divers, respectively. A total of 190 (82.2%) occurred during practice; 18 occurred during competition (17.8%). Most injuries occurred in the regular season (62.0%); 35.6% and 2.4% occurred in the preseason and postseason, respectively. In addition, 72.6% were non-time loss and 2.9% were severe. Four injuries (1.9%) required surgery.
These 208 injuries occurred during 121 719 AEs, for an injury rate of 1.71/1000 AEs (95% CI 1.48 to 1.94; table 1). No difference existed between the injury rates for practice (1.72/1000 AEs) and competition (1.61/1000 AEs; IRR=1.07; 95% CI 0.66 to 1.73). When injury rates were stratified by athlete-type, divers had a higher injury rate (2.49/1000 AEs) than swimmers (1.63/1000 AEs; IRR=1.53; 95% CI 1.07 to 2.19).
Comparison of overall rates
There were no sex differences in men's and women's swimming and diving injury rates overall (males vs females IRR=0.90; 95% CI 0.73 to 1.11), for practices (IRR=0.87; 95% CI 0.70 to 1.09), or for competitions (IRR=1.20; 95% CI 0.61 to 2.36). Injury rates did not differ between male and female swimmers (IRR=0.91; 95% CI 0.72 to 1.15) or divers (IRR=0.78; 95% CI 0.47 to 1.29).
In men's swimming and diving, there were no differences in injury rates for men's swimmers or divers between the two time periods (2009/2010–2011/2012 and 2012/2013–2013/2014; figure 1). In women's swimming, the injury rate was 30% lower in 2012/2013–2013/2014 compared with 2009/2010–2011/2012 to (2012/2013 IRR=0.70; 95% CI 0.52 to 0.95). In women's diving, there was also a 44% reduction in the later time period (IRR=0.56; 95% CI 0.30 to 1.08).
Body sites injured and diagnoses
Most injuries occurred to the shoulder in men's swimming (34.7%), men's diving (32.0%) and women's swimming (31.3%; table 2). However, in women's diving, the trunk comprised the largest proportion of injuries (37.8%). There were no sex differences in body part-specific injury rates among swimmers or divers. However, male divers sustained a greater proportion of shoulder injuries (32.0%) than female divers (5.4%; IPR=5.92; 95% CI 1.37 to 25.59).
The most common injury diagnosis was strains in men's swimming (21.8%), men's diving (20.0%), women's swimming (17.0%) and women's diving (16.2%; table 3). In addition, swimmers had large proportions of entrapment/impingement (men 14.5%; women 11.1%) and tendonitis (men 13.7%; women 15.8%). There were no sex differences in diagnosis-specific injury rates or proportions among swimmers or divers.
Table 4 summarises common injuries for men's and women's swimming and diving and the percentage of time loss injuries. For the three concussions in women's diving, two occurred from contact with the water and one occurred from contact with the diving board. In addition, zero cases of spondylolysis and four cases of lower back pain were reported.
Mechanism of injury and activity
The majority of injuries were classified as overuse (men's swimming 44.4%; men's diving 24.0%; women's swimming 63.7%; women's diving 21.6%) and non-contact (men's swimming 25.0%; men's diving 28.0%; women's swimming 17.0; women's diving 27.0%; table 5). Contact with water also accounted for large proportions of injuries in men's and women's diving (32.0% and 16.2%, respectively). Female swimmers had a higher rate of overuse injuries (1.04/1000 AEs) than male swimmers (0.66/1000 AEs; IRR=1.58; 95% CI 1.14 to 2.19). No sex differences in injury mechanism existed among divers. Among swimmers, the largest proportion of injuries occurred while swimming the medley (men 45.2%; women 45.6%). There were no sex differences in activity-specific injury rates or proportions among swimmers or divers.
Swimming and diving are treated as one NCAA team although they are two discrete sports. Our study utilised injury surveillance data to describe the epidemiology of men's and women's swimming and diving at the NCAA level over the past 5 years. The study extends the literature on men's and women's swimming and diving injuries, using quality data thoroughly checked for errors prior to landing in data sets.13 This study also captured both time loss and non-time loss injuries in an effort to optimally summarise the types of injuries managed and treated by team medical staff. Such data can help identify areas for prevention and healthcare related to injuries in swimming and diving. The importance of capturing time loss data has been previously explained.17
Comparison of rates with previous studies
Previous studies have utilised varying methods to report swimming injuries, leading to disparate rates. Mountjoy et al11 ,12 estimated that the injury rate per 100 swimmers at the 2009 and 2013 world championship events were 2.7 and 6.1, respectively. At the 2008 and 2012 Summer Olympics, Junge et al18 and Engebretsen et al19 found that 3.4% and 5.4% of swimmers were injured, respectively. Studies with college-level student-athletes are available, but considered injuries sustained outside of practice and competitions (eg, strength training, non-swimming-related activities). Across five seasons of men's and women's swimming at a Division I university, Wolf et al20 reported injury rates of 4.00 and 3.78 injuries per 1000 exposures in men's and women's swimming, respectively. Across seven seasons within a Division I women's swimming team, 2.12 injuries per 1000 exposures were reported.21 In these studies, activities outside of swimming contributed to 55–62% of injuries. A smaller study22 of 34 NCAA Division I male and female swimmers across one season restricted injuries to those sustained during school-sanctioned practices and competitions, yielding an overall rate of 5.55 injuries per 1000 AEs. Our study utilised data from 22 programmes and 53 seasons and yielded smaller swimming injury rates (men 1.48/1000 AEs; women 1.63/1000 AEs). The NCAA ISP currently does not collect injury data occurring during individual strength training and cross training sessions. Nevertheless, given the larger sample size and inclusion of all injuries from school-sanctioned practices and competitions (time loss and non-time loss), our rates may better estimate the true burden of injury during school-sanctioned practices and competitions than previously reported.
The low reported injury rate in swimmers may reflect swimming culture more so than truly reflect incidence of injury. In a sample of youth/adolescent swimmers, 95% believed that mild shoulder pain was normal and should be tolerated.23 However, only 14% reported an injury to team medical staff and 72% reporting using pain medication in order to participate.23 These findings suggest that swimmers may not associate shoulder pain with injury and rather than seeking care from team medical staff, may self-medicate with analgesics. Within the context of the NCAA ISP, it is only when an athlete discloses the pain, or when an AT notices the pain, that the injury would be reported. Using the injury surveillance method reported by the Oslo Sports Trauma Research Centre and being used at the Norwegian Olympic Training Centre (Oslo)24 may help to address this problem.
The urgent need for greater disclosure of non-time loss injuries is further highlighted by our study and previous studies4–6 ,22 ,25 ,26 finding large proportions of shoulder and overuse injuries. In addition, female swimmers were more likely to suffer an overuse injury than male swimmers. Previous research has suggested that anatomical, physiological and psychological differences between male and female athletes may contribute to increased risk of overuse injury in females.27 Despite the possible sex differences in overuse injuries, the cause of overuse injuries among swimmers of both sexes should be further explored. In particular, future studies should examine the adverse effects of rapid increases in the frequency and intensity of training, and the protective effects of adequate recovery time. Because swimming heavily relies on the upper extremity to propel the body forward,28 such research should also examine whether proper form also mitigates shoulder injuries.29
Research related to divers is limited. At the 2008 and 2012 Summer Olympics, Junge et al18 and Engebretsen et al19 found that 2.1% and 8.1% of divers were injured, respectively. In our study, divers had a higher injury rate than swimmers, although the finding was only significant in females. Diving injuries were mostly strains and to the shoulder and trunk. This was similar to findings in junior elite Japanese divers,30 Junior Olympic divers,31 but dissimilar to emergency department data,32 although such data may exclude less severe injuries. In addition, although previous research33 ,34 has highlighted the cases of spondylolysis, lower back pain and concussions among divers, ISP data reported zero, four and three cases, respectively. Our sample of 25 male and 37 female diving injuries may not represent the true incidence of these injuries among all NCAA swimming and diving programmes.
Our findings may not be generalisable to other swimming and diving programmes within the NCAA or from other levels of competition. The NCAA ISP also does not collect data related to activities outside of school-sanctioned practices and competitions, as did previous studies.20 ,21 Because AEs were unit-based rather than time-based, event-based or distance-based, we were unable to report injury rates by the number of minutes/hours of practice/competition, the number of specific events in which athletes participated per competition or the number of metres swum. This recording method reduces reporting burden for participating ATs and provides consistency for comparisons across various sports injury surveillance research outcomes. Because the NCAA places swimmers and divers on the same team, we had to estimate the distribution of AEs between swimmers and divers. As a result, caution must be taken when interpreting rate-based results specific to swimmers and divers. We utilised historical rosters that identified swimmers and divers on university websites as well as guidance from ATs on how to distribute AEs between both types of student-athletes. However, these assumptions may not be valid among other collegiate programmes.
What are the new findings?
The study adds to the literature on men's and women's swimming and diving injuries, using data that have been thoroughly checked for errors prior to landing in data sets.
Divers had a higher injury rate than swimmers, although the finding was only significant in females.
Female swimmers were more likely to suffer an overuse injury than male swimmers.
How might it impact on clinical practice in the near future?
By capturing both time loss and non-time loss injuries, current findings may better summarise the types of injuries that are sustained by student-athletes and managed and treated by team medical staff.
The large proportions of overuse injuries reported in swimming and diving highlight the need to emphasise proper technique and avoid rapid increases in the frequency of training to avoid overuse shoulder injuries.
The authors thank the many ATs who have volunteered their time and efforts to submit data to the NCAA Injury Surveillance Program. Their efforts are greatly appreciated and have had a tremendously positive effect on the safety of collegiate athletes.
Contributors ZYK led the creation and analysis of the study, and drafting of the manuscript. CMB and EEH assisted with the analysis of the study, interpretation of findings and assisted in drafting the manuscript. The remaining authors, EMS, RH and TPD, assisted with the creation of the study, and drafting of the manuscript. All authors approve the final manuscript as presented.
Funding The NCAA Injury Surveillance Program data were provided by the Datalys Center for Sports Injury Research and Prevention. The Injury Surveillance Program was funded by the NCAA. CMB was supported by the National Institute Of Mental Health of the National Institutes of Health under Award Number T32MH019733. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Competing interests None.
Ethics approval NCAA Research Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data from the NCAA Injury Surveillance Program are available for use by external researchers via a request at http://www.disc.datalyscenter.org/.
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