Effects of low-intensity exercise on local skin and whole-body thermal sensation in hypothermic young males.

Thermal sensation, a key component of behavioral thermoregulation, is modulated by the changes in both skin and core temperatures. Although cutaneous thermal sensation to local cold is blunted during exercise as compared to rest in normothermic humans, it remains to be determined whether this holds true during core cooling. Furthermore, when local skin thermal sensation is diminished during exercise, it remains unclear whether whole-body thermal sensation is also attenuated. We therefore tested whether low-intensity exercise (VO: ~1300 ml min) attenuates local skin and/or whole-body thermal sensation in hypothermic young males. Eleven healthy young males (24 ± 2 years) were cooled through cold water immersion (18 °C) up to their lower abdomen while resting (rest trial) and during low-intensity cycling (30-60 W, 30 rpm) (exercise trial). Body temperature, cardiorespiratory variables, and whole-body (9-point scale: 0, unbearably cold; 4, neutral; 8, unbearably hot) and local skin thermal sensation were measured at baseline on land and before the esophageal temperature (T) began to decrease (defined as -0.0 T) and after 0.5 and 1.0 °C decrements in T from baseline during the immersion period. Local skin thermal sensation was measured using a thermostimulator with Peltier element that was attached to the chest. The temperature of the probe was initially equilibrated to the chest skin temperature, then gradually decreased at a constant rate (0.1 °C s ) until the participants felt coolness. The difference between the initial skin temperature and the local skin temperature that felt cool was assessed as an index of local skin thermal sensation. Throughout the immersions, esophageal and mean skin temperatures did not differ between the rest and exercise trials. Local skin thermal sensation also did not differ between the two trials or at any core temperature level. By contrast, the whole-body thermal sensation score was higher (participants felt less cold) in the exercise than in the rest trial at esophageal temperature of -1.0 °C (1.25 ± 0.46 vs. 0.63 ± 0.35 units, P = 0.035). These results suggest that local skin thermal sensation during low-intensity exercise is not affected by a decrease in core temperature. However, whole-body thermal sensation mediated by a decrease in core temperature (-1.0 °C) is blunted by low-intensity exercise during cold water immersion.