Feasibility Of Heat Acclimation In Wildland Firefighters

PURPOSE: The purpose of this study was to determine the rationality of implementing pre-season heat acclimation (HA) for wildland firefighters (WFF) to reduce risk of EHI and associated monetary costs. METHODS: A mixed methods non-randomized controlled trial strategy was used. Physiological and perceptual measurements included rectal temperature (Tre), heart rate (HR), skin temperature (Tsk) thermal sensation (TS), thermal comfort (TC), and rating of perceived exertion (RPE). All variables were measured during Heat Tolerance Tests (HTT1 and HTT2; 120 min walking 3.1 mph in 40 °C, 40%rh environment separated by 10 days). Between HTTs the intervention group (ACC; n = 8) underwent a 6-exposure exercise heat acclimation. Semi-structured interviews prior to HTT1, following HTT2, and immediately after fire season were used to assess changes in self-efficacy (SE) regarding completion of future HA protocols. Three-way (Group (ACC vs. CON) x Time x HTT#) repeated measures ANOVAs were used to evaluate physiological and perceptual variables. Thematic analysis methods were utilized for qualitative data analysis. RESULTS: Between HTT1 and HTT2 significant main effects of time were observed for HR, and Tre (p < 0.000). A significant main effect of the HTT# was found for Tre, and TS (p < 0.017), and RPE (p = 0.019). A significant main effect of Group was seen for Tre for CON versus ACC (p = 0.031). A significant interaction between HTT#, Group, and Time was seen for Tre CON and ACC for finishers (p = 0.031) and for all participants up to 55 minutes (p = 0.024). Higher-order themes were identified within three sources of SE (mastery experiences, vicarious experience and physiological sensations) and feedback related to barriers and benefits of HA. Overall, SE was found to increase with both CON and ACC from the heat exposures of the HTTs. WFFs reported that they want to complete HA in the future. CONCLUSIONS: Tre was the only physiological marker improved during the HA. There was a psychological benefit with an increase in SE overall reported in the qualitative data for most participants. With these findings it is recommended that intentional heat exposures would be beneficial to WFF in pre-season training and future research should aim to identify a more physiologically beneficial HA protocol to meet WFF needs.