In the comparison of the foot immersion vs control interventions during exposure to hot, humid conditions, the whole-body sweat rate was significantly lower (114 g/h vs 179 g/h, respectively; difference, −66 g/h [95% CI, −109 to −23 g/h]; P = .003) and the thermal discomfort level was lower (45 mm vs 66 mm; difference, −21 mm [95% CI, −39 to −3 mm]; P = .02); however, heart rate was not (75/min vs 80/min; difference, −5/min [95% CI, −11/min to 1/min]; P = .14). The findings for whole-body sweat rate and heart rate were similar under very hot, dry conditions, but thermal discomfort was not significant (Table ).In the comparison of the self-dousing vs control interventions during exposure to hot, humid conditions, heart rate was significantly lower (75/min vs 80/min, respectively; difference, −5/min [95% CI, −10/min to 0/min]; P = .04) as well as the whole-body sweat rate (93 g/h vs 179 g/h; difference, −87 g/h [95% CI, −144 to −29 g/h]; P = .004) and thermal discomfort level (38 mm vs 66 mm; difference, −27 mm [95% CI, −49 to −6 mm]; P = .01). Results were similar under very hot, dry conditions.In the comparison of the self-dousing vs foot immersion intervention during exposure to very hot, dry conditions, the whole-body sweat rate and thermal discomfort level were lower with self-dousing; however, no differences between interventions were observed under hot, humid conditions. No differences in core temperature or effects of intervention order for any outcome were found.The reductions in heart rate with the foot immersion and self-dousing interventions attained clinical significance in hot, humid conditions as did the reductions in whole-body sweat rate with self-dousing in very hot, dry conditions. Discussion | In this preliminary study, foot immersion lowered sweating during exposure to both environmental conditions and lowered thermal discomfort only in hot, humid conditions. The self-dousing intervention lowered heart rate, sweating, and thermal discomfort under both environmental conditions and was more effective than the foot immersion intervention at reducing sweating and thermal discomfort in very hot, dry conditions. Core temperature was unaltered. However, morbidity and mortality from dehydration and cardiovascular failure during heat waves typically surpass those from hyperthermia alone. 5 Limitations include testing of only a small number of healthy volunteers. Responses must be evaluated among older adults and among those who have health conditions, are taking medications, or both, which could potentially disrupt thermoregulation. 6