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A Cluster of Exertional Rhabdomyolysis Affecting a Division I Football Team

Smoot, M. Kyle MD*,†; Amendola, Annunziato MD†,‡; Cramer, Elizabeth MD*; Doyle, Christopher MEd§; Kregel, Kevin C. PhD; Chiang, Hsiu-yin MS, PhD; Cavanaugh, Joseph E. PhD**; Herwaldt, Loreen A. MD‖,††,‡‡

Clinical Journal of Sport Medicine: September 2013 - Volume 23 - Issue 5 - p 365–372
doi: 10.1097/JSM.0b013e3182914fe2
Original Research
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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.

Supplemental Digital Content is Available in the Text.

*Department of Family Medicine, The University of Iowa Carver College of Medicine, Iowa City, Iowa;

Institute for Orthopaedics, Sports Medicine & Rehabilitation, The University of Iowa Carver College of Medicine, Iowa City, Iowa;

Department of Orthopaedics & Rehabilitation, The University of Iowa Carver College of Medicine, Iowa City, Iowa;

Departments of §Athletics; and

Health and Human Physiology, The University of Iowa, Iowa City, Iowa;

Department of Internal Medicine, The University of Iowa Carver College of Medicine, Iowa City, Iowa;

**Department of Biostatistics, The University of Iowa College of Public Health, Iowa City, Iowa;

††Program of Hospital Epidemiology, The University of Iowa Hospitals and Clinics, Iowa City, Iowa; and

‡‡Department of Epidemiology, The University of Iowa College of Public Health, Iowa City, Iowa.

Corresponding Author: M. Kyle Smoot, MD, Department of Family Medicine, The University of Iowa Carver College of Medicine, 01106 PFP, 200 Hawkins Dr, Iowa City, IA 52242-1097 (kyle-smoot@uiowa.edu).

The authors report no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.cjsportmed.com).

Received September 06, 2012

Accepted February 28, 2013

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