Effects of a heat acclimation program on physiologic and psychological responses to work and heat while wearing fire ensemble

Heat acclimation program effects on rectal temperature and heart rate during walks in the heat wearing structural fire protective ensemble (FE) were examined. On six consecutive days, male subjects (N = 7) walked 30 minutes on a treadmill (46--53% V˙O2peak) within a 40 +/- 2°C, 20--22% r.h. environment, wearing FE. Rectal (Trec) mean skin (Tsk), and rectal-skin temperature gradient (T rec-Tsk), heart rate (HR), oxygen uptake (VO2), minute ventilation (VE), rating of perceived exertion (RPE), rating of thermal discomfort (RTD), sweat rate and Na+ and K+ were assessed daily. Significance (p < 0.05) was determined by one way repeated measures ANOVA. Average heart rate, and daily sweat Na+ and K+ concentrations were the only variables observed to decrease significantly during the six days. These changes however were small and represent a questionable practical benefit. Therefore, a six day heat acclimation program during summer months provides no benefit to work in the heat while wearing FE.