Background/Purpose:

The work-up of elevated muscle enzymes is a common reason for rheumatology consults. The differential diagnosis of rhabdomyolysis includes trauma, exertion, hereditary myopathies, drugs, toxins and infections. Especially exertional rhabdomyolysis can be underdiagnosed as its prevalence in civilians is unclear and its clinical course is mostly described by case reports. We studied the prevalence, nature, and consequences of exertional rhabdomyolysis in patients younger than 55 years. We especially focused on CrossFit- induced rhabdomyolysis as data of its involvement in rhabdomyolysis are controversial. CrossFit is a conditioning program involving high-intensity exercises performed in rapid repetition with minimal recovery time.

Methods: We conducted a retrospective chart review of all encounters with a diagnosis of rhabdomyolysis within all acute and ambulatory Sutter locations in Northern California between January 2004 and February 2016. Patients older than 55 years or with Medicare insurance were excluded. We reviewed the records and identified cases of rhabdomyolysis caused by exercise. Extracted data included age, gender, BMI, types of exercises performed, symptoms, sites of injury, location of presentation, creatinine and CPK levels at initial presentation and at follow-up, treatment administered, and hospitalization or discharge. Statistical analyses included Chi-square, Fisher’s exact tests, t-tests, and linear regression.

Results: We identified 1,277 patients with rhabdomyolysis. Exercise-induced rhabdomyolysis was diagnosed in 297 patients, with 42 of these cases caused by CrossFit. Mean age of all patients with exercise-induced rhabdomyolysis was 31 years (range: 12 to 53), with a gender composition of 70% males and 30% females. The majority of patients (51%) presented to the emergency department. Mean CPK at presentation was 36,120 U/L (range: 213 to 522,040), mean creatinine was 1.14 mg/dl (range: 0.37 to 29.00). Higher levels of CPK and creatinine were associated with hospitalization (p<0.0001 and p=0.004, respectively) and with longer hospital stays (p=0.025 and p<0.0001, respectively). Average hospital stay was 4 days (range 1-12 days). Patients with CrossFit relate rhabdomyolysis had lower creatinine levels at presentation (0.82 vs 1.19 mg/dl, p=0.008), were more likely to have IV fluids administered (86% vs 73%, p=0.048), and a shorter hospital stay (3.5 vs 4.4 days, p=0.029).

Conclusion:

This is the first large-scale study to investigate exercise- and CrossFit-induced rhabdomyolysis. The prevalence of exertional rhabdomyolysis is significant, with a notable proportion of these cases attributable to CrossFit. As patients with muscle pain and elevated muscle enzymes are referred to the rheumatologist it is important to know about this disease. There is often a delay in diagnosis and treatment, therefore education to physicians and athletes about exertional rhabdomyolysis for primary prevention and for early diagnosis is necessary.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/investigating-exercise-and-crossfit-induced-rhabdomyolysis-data-from-a-community-healthcare-system/