The effects of a moderate physical activity program on heat tolerance in men
Moderate intensity training induces health benefits, however its influence on heat tolerance is unclear. Twelve inactive males (mean +- SD) (age = 24 +- 6 yrs, BMI = 25.3 +- 3.2 kg/m2, V02peak = 40.2 +- 8.1 ml/kg/min) performed work-heat tolerance and V02peak tests pre and post a moderate training intervention. All subjects were initially below the guidelines for physical activity set forth by the US Surgeon General, Health Canada, and CSEP. Eight randomly assigned subjects underwent the 12-week program, participating in activities such as cycling, walking, and recreational sports. Subjects were instructed to train at 50% V02Reserve, and gradually increased energy expenditure to reach a mean of 2158 kcal/week, which is beyond the above mentioned recommendations. Four control subjects remained sedentary. In the training group, V02peak increased 19% (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 sweat threshold. Health benefits associated with heat adaptations may require more vigorous exercise than recommended by current physical activity guidelines.