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Updated: Nov 11, 2025

Induction and Assessment of Exertional Skeletal Muscle Damage in Humans
Published on: December 11, 2016
Muscle Damage and Overreaching During Wildland Firefighter Critical Training
Katherine S Christison1, Shae C Gurney, Joseph A Sol
1School of Integrative Physiology and Athletic Training, University of Montana, Missoula, Montana (Ms Christison, Mr Gurney, Mr Sol, Ms Williamson-Reisdorph, Ms Quindry, Dr Quindry, Dr Dumke); United States Department of Agriculture, Forest Service, National Technology and Development Program, Missoula, Montana (Mr Sol).
Objective:
To document the effects of wildland firefighter (WLFF) critical training (CT) on physiologic markers of muscle damage and acute overreaching.
Methods:
Eighteen male and three female WLFFs were studied during an 11-day CT. Upper-body (US), lower-body (LS) muscle soreness and body weight (BW) were collected daily. Blood was collected on days 1, 4, 8, and 11 to measure creatine kinase (CK), lactate dehydrogenase (LDH), cortisol, and testosterone. Skinfolds were taken on days 1 and 11 to estimate body fat (BF) and lean body weight (LBW).
Results:
CT resulted in a significant depression in BF and elevation in LBW, while main effects of time were seen in US, LS, CK, LDH, cortisol, and testosterone/cortisol ratio (P < 0.05).
Conclusion:
These data suggest WLFFs undergo significant physiological stressors resulting in muscle soreness, damage, and possible overreaching during CT.
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