Date of Award


Degree Type


Degree Name

Master of Science


Health and Human Performance


Exercise Science

First Advisor/Chairperson

Dr. Scott Drum

Second Advisor

Dr. Randall Jensen

Third Advisor

Dr. Maggy Moore


Rhabdomyolysis is the breakdown of muscle tissue causing myoglobin, creatine kinase, and other intracellular proteins and electrolytes to leak into circulation, disrupting cell homeostasis. Exertional rhabdomyolysis (ER) occurs after extremely rigorous physical training that could include high amounts of strenuous eccentric exercise. There has been an increase in reports for mild to severe ER as well as other musculoskeletal injuries as the popularity of extreme conditioning programs (e.g., CrossFit®) increases. Therefore, the main purposes of this investigation were to identify: primary risk factors associated with ER during CrossFit®, CrossFit® workouts that might induce a higher risk for the development of ER, and ratings of perceived exertion (RPE) for CrossFit® vs. American College of Sports Medicine (ACSM) training guidelines. A questionnaire was completed by 101 CrossFit® participants and 56 ACSM participants (n = 157). CrossFit® and ACSM groups reported significantly different RPEs of 7.29 ± 1.74 and 5.52 ± 1.35 (p ≤ 0.001), and performed significantly different hard days per week of 3.99 ± 1.07 and 3.55 ± 1.39 (p = 0.044), respectively. The top five perceived hardest workouts based on frequency were Fran (47), Murph (27), Fight Gone Bad (10), Helen (9) and Filthy 50 (9). One occurrence of ER was reported out of 101 CrossFit® participants. Therefore, the overall risk of developing ER may be minimal, especially if a participant understands their body’s limitations in regard to the intensity of CrossFit®.