Objective: To identify risk factors for exertional rhabdomyolysis (ER) among collegiate football athletes. We hypothesized that a back squat workout triggered ER in some players, and that the risk of ER was altered by players' characteristics or other exposures.
Design: Case report and case-control study.
Setting: National Collegiate Athletic Association Division I Football Program and an academic medical center.
Participants: National Collegiate Athletic Association Division I football players.
Independent variables: Characteristics, performance during the implicated workout, and exposures of players.
Main outcome measures: Exertional rhabdomyolysis was the primary outcome; the hypotheses were formulated before data were collected.
Results: Initial serum creatine kinase and creatinine values ranged from 96,987 to 331,044 U/L and from 1.0 to 3.4 mg/dL, respectively. The risk of ER increased as the time and number of sets needed to complete 100 back squats increased [odds ratio (OR), 1.11; 95% confidence interval (CI), 1.03-1.19; P = 0.0051 and OR, 1.33; 95% CI, 1.09-1.63; P = 0.0056, respectively]. Affected players were significantly more likely than unaffected players to report that they went to muscle failure (P = 0.006), did not think they could complete the workout (P = 0.02), and performed extra squats (P = 0.02) during the back squat assignment. For athletes playing skilled or semiskilled positions, the risk of ER increased as the percent body weight lifted increased [OR (corresponding to a 10% increase), 1.77; 95% CI, 1.06-2.94; P = 0.0292]. Drinking protein shakes after the implicated workout was associated with a decreased risk (OR, 0.70; 95% CI, 0.51-0.96; P = 0.0284); the odds decreased about 30% per shake.
Conclusions: Percent body weight lifted, the number of sets, and time needed to complete 100 back squats were significantly associated with increased risk of ER. Affected athletes were more likely to report going to muscle failure, thinking they could complete the workout, and performing extra squats during the back squat assignment. Consuming protein shakes after the implicated workout was associated with a decreased risk. Clinicians, athletes, and athletic program staff must know risk factors for ER and early symptoms of ER.