Introduction Exertional rhabdomyolysis is a syndrome of muscle breakdown following exercise. This study describes laboratory and demographic trends of service members hospitalised for exertional rhabdomyolysis and examines the relationships with heat illness.
Methods We queried the US Armed Forces Health Surveillance Center’s Defence Medical Epidemiology Database for hospitalised cases of rhabdomyolysis associated with physical exertion from January 2010 July 2013. Descriptive statistics reported means and medians of initial, peak and minimal levels of creatine kinase (CK). Correlations explored the relationship between CK, creatinine, length of hospital stay (LOS) and demographic data.
Results We analysed 321 hospitalised cases of exertional rhabdomyolysis. 193 (60.1%) cases were associated with heat; 104 (32.4%) were not associated with heat; and 24 (7.5%) were classified as medical-associated exertional rhabdomyolysis. Initial, maximum and minimal CK levels were significantly lower in heat cases: CK=6528 U/L vs 19 247 U/L, p=0.001; 13 146 U/L vs 22 201 U/L, p=0.03; and 3618 U/L vs 10 321 U/L, p=0.023) respectively, compared with cases of rhabdomyolysis with exertion alone. Median LOS was 2 days (range=0–25). In the rhabdomyolysis with exertion alone group and the rhabdomyolysis with heat group, LOS was moderately correlated with maximal CK (Spearman’s ρ=0.52, p<0.001, and Spearman ρ=0.38, p<0.001, respectively). There was no significant difference in median LOS between the rhabdomyolysis with exertion alone and rhabdomyolysis associated with heat groups (2 vs 2, p value=0.96).
Conclusion Most hospitalisations for exertional rhabdomyolysis were associated with heat illness and presented with lower CK levels than cases without associated heat illness. These data add evidence that rhabdomyolysis with heat illness is a different entity than rhabdomyolysis with exertion alone. Differentiating exertional rhabdomyolysis with and without heat should inform future research on rhabdomyolysis prognosis and clinical management.
- SPORTS MEDICINE
- CLINICAL PHYSIOLOGY
- Musculoskeletal disorders
- ACCIDENT & EMERGENCY MEDICINE
Data availability statement
Data are available upon reasonable request.
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Contributors RCO conceived, planned and designed the study. RCO, DCB and CJM reviewed all International Classification of Diseases, Ninth Revision, codes and categorised the data. DCB completed the data analysis and initial draft of the manuscript. RCO, DCB and CJM wrote the manuscript, edited and gave the final approval of the manuscript. RCO is the guarantor and is responsible for the overall content.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Disclaimer The opinions and views are those of the authors and do not reflect the official policy or position of the Department of Veterans Affairs, the Department of the Army, the Department of Defense or the US government.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.