Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Health and Human Performance (Exercise Science Option)

Department or School/College

Department of Health and Human Performance

Committee Chair

Brent Ruby

Commitee Members

Charles Dumke, Stephen Lodmell


heat injury, heat related illness, heat stress, physiological strain index


University of Montana


Purpose: The purpose of this study was to determine heat acclimatization across a 4-month fire season in the western United States. Methods: Wildland firefighters (WLFF) (n =12) and non-WLFFs (n =14) completed a 60-min heat stress trial (treadmill walking at 50% peak VO2) in a climate controlled chamber (43.3°C, 33% RH) prior to and following the fire season (May through September). Peak VO2, body composition, core (Tc) and skin (Tsk) temperatures, heart rate (HR), physiological strain index (PSI), plasma volume change, sweat rate and perceived exertion (RPE) were measured during the heat stress trials. Results: Average peak VO2 was similar between groups (54.1 ± 1.3 and 57.3 ± 2.0, WLFFs and non-WLFFs respectively, p>0.05) and did not change over the season. During the heat trial, WLFFs demonstrated a season-by-time reduction in Tc at 45 and 60-min (38.3 ± 0.3°C vs. 38.1 ± 0.3°C and 38.5 ± 0.3°C vs. 38.2 ± 0.4°C at 45 and 60-min, pre- vs. post- season, respectively, p<0.05), and PSI for the last 30-min (5.6 ± 0.9 vs. 4.9 ± 1.0; 6.5 ± 0.9 vs. 5.8 ± 1.2; 7.1 ± 1.1 vs. 6.3 ± 1.3 at 30, 45, and 60- min, pre- vs. post- season, respectively, p<0.05), as well as a decrease in RPE (11.2 ± 2.1 vs. 10.2 ± 1.6, pre- vs. post- season, main effect for season, p<0.05). In contrast, there was no difference in Tc, PSI or RPE for non-WLFFs. Conclusion: WLFFs demonstrated less physiological strain with significant decreases in Tc and PSI despite no change in aerobic fitness (peak VO2), suggesting that heat acclimatization adaptations are accrued due to long-term environmental/occupational heat exposure.



© Copyright 2012 Brianna Lui