RETURNElimination of Seasonal Variations in Thermoregulation during Exercise: Acute Effect of Pre-Warming in the Cold Season
Masafumi Torii and Hideaki Nakayama
Department of Hygiene, Faculty of Medicine, Tottori University, Yonago 683, Japan
We conducted the present experiment to assess whether thermoregulation in winter can be changed by means of thermal stimulation, warming in the nude for 30 min at 30°C, before exercise. Seasonal variations in sweating capacity and sensitivity, and in heat storage can be observed in humans undergoing exercise in winter without pre-warming (Experiment 1). When the subjects received the warming before exercise in winter, no such seasonal variation in their sweat rates during exercise was observed at 30 and 40°C (Experiment 2). In both cases, the sweat rate and the level of skin temperature, and the sweat rate and core temperature were dependent on the work load. In the cold season the sweating sensitivity and evaporative cooling can be enhanced by thermal stimulation. These values showed no significant differences between winter following pre-warming and summer (P > 0.05). Moreover, heat storage of the body and metabolic heat production in winter following pre-warming and in summer were not significantly different at the various work intensities (P > 0.05). The present result suggests that sweating may be facilitated by the heat dissipation activity not only of the hypothalamic mechanism receiving thermal information via the skin thermoreceptors but also of the peripheral sweat glands. These data may be of importance in evaluating the effectiveness of a physical training program.
Key words: evaporative heat loss; loss of seasonal variation in sweat rate; metabolic rate; pre-warming; submaximal bicycle exercise; thermal balance; thermoregulation