K. Christison, S. Gurney, C. Williamson-Reisdorph, T. Quindry, J. Sol, K. Tiemessen, C. Palmer, M. Bundle, J. Quindry, FACSM, C. Dumke, FACSM

University of Montana, Missoula, MT

Wildland firefighters (WLFF) undergo a critical training (CT) period immediately prior to the firefighting season. The intensive nature of preparatory CT exercise regimen could lead to muscle damage, as previously reported cases of rhabdomyolysis in WLFF have been documented. PURPOSE: To establish the effects of a two-week critical training period on acute markers of muscle damage in WLFF. METHODS: Eighteen male (29.4±1.1 years, 182.1±1.6 cm) and three female (26.7±2.6 years, 169.5±4.2 cm) Type I Interagency Hotshot (IHC) WLFF were studied during a 13-day critical training period. Daily body weight (BW), upper body (US), and lower body (LS) muscle soreness scales were collected. Venous blood was collected from the antecubital region on Days 1, 4, 8, and 11 to measure creatine kinase (CK) and lactate dehydrogenase (LDH). Skin fold measurements were taken on Day 1 and Day 11 to calculate body fat (BF). Fitness was assessed by the BLM fitness challenge (pushups, pullups, situps, 1.5-mile run). One- way repeated measures ANOVA were used to analyze CK, LDH, US, and LS. Paired samples t-tests were used to identify differences in BW and BF. Data presented as mean±SEM. RESULTS: No differences in body weight were observed between Day 1 and 11 (p=0.065). BF significantly decreased from Day 1 and 1 (15.3±1.4% vs. 14.1±1.3%, p=0.002). US and LS showed a main effect of time, elevated from baseline for subsequent days, with a peak on Day 3 (US: 3.8±0.5 cm, p<0.001; LS: 4.3±0.3 cm, p<0.001). CK showed a significant effect of time, elevated from baseline, with a peak on Day 4 (73.4±14.4 U·L-1 vs. 132.8±15.4 U·L-1, p=0.001). LDH showed a significant effect of time, where Day 11 significantly increased from Day 1 (159.4±5.5 IU·L-1 vs.164.4±6.9 IU·L-1, p=0.04). Fitness was negatively correlated with the change in muscle soreness from baseline to peak (r=-0.72, p=0.013). CONCLUSION: These data suggest that WLFF undergo significant physiological stressors that result in muscle soreness and damage during CT. Fitness appears to attenuate the soreness induced by CT. Careful preparation and monitoring of the training stimulus is key to avoid clinical ramifications.

Funded by the USFS 16-CR-11138200-005.

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