The effects of a moderate physical activity program on thermoregulatory responses in a warm environment in men.

Moderate intensity training induces health benefits, but its influence on thermoregulatory responses during exercise in a warm environment is unclear. Twelve inactive men (mean age 24.0 +/- 6.5 yrs) underwent exercise heat tests, and peak VO2 tests, before and after a moderate training program (n= 8) or no training intervention (n = 4). Assignment to groups was random. All subjects were initially below the guidelines for physical activity set forth by Health Canada, the Canadian Society for Exercise Physiology (CSEP), and the U.S. Surgeon General. Those in the 12-week training program participated in activities such as cycling, walking, and recreational sports. Subjects were instructed to train at 50% VO2 reserve, and to gradually increase energy expenditure beyond the above mentioned recommendations. In the training group, peak VO2 increased 13%, p < 0.01, and resting peripheral blood flow during heat stress increased, p < 0.01, indicating some initial thermoregulatory benefits. No significant differences were observed in esophageal temperature or sweating threshold. Health benefits associated with thermoregulatory adaptations to exercise in a warm environment may require more vigorous exercise than recommended by current physical activity guidelines.