To investigate the effect of ambient humidity on thermoregulatory responses during exercise in men who clothed different types of sports wear, six healthy male performed a cycle exercise at almost 130 beats/min of heart rate (HR) for 50 min. We selected two environmental conditions of low humidity (LH, RH of 30%) and high humidity (HH, RH of 70%) at Ta of 26℃ with different T-shirts of two fiber types (cotton 100%: 100C, cotton 65% and polyester 35%: 65C35P). All subjects wore a running pant and T-shirt throughout each experiment. Although there were no significant differences in cardiovascular parameters between LH and HH conditions, skin temperature inside cloth tended to be higher with high humidity. There was also no marked difference in those parameters between two fiber types. Mean skin temperature (Tsk) and average skin temperatures of clothed sites (IC-Tsl from abdomen, chest, back and upper arm) in HH are significantly higher than those in LH (p<0.05). Also, sweating rate (SR) and skin blood flow (SkBF) on the clothed sites (back) and total body weight loss tended to be greater with a rise in humidity. The SR and SkBF at which RH inside cloth reached at 70% in HH100C were significantly lower than those in LH100C (p<0.05). Moreover, the time at which RH inside cloth reached at 70% was significantly different between the two fiber types with the same environmental condition (p<0.05). The difference in cloth types did not influence Tsk and IC-Tsl during exercise in LH while those parameters in HH was significantly higher in 100C than 65C35P (p<0.05). The SR, SkBF and time at which RH inside cloth reached at 70% were significantly lower only in 100C than 65C35P (p<0.05). These results suggest that high humidity induces markedly increase in Tsk and IC-Tsl relative to low humidity in both the fiber types of 100% cotton and 35% polyester with 65% cotton, and that the later fiber type diminishes thermoregulatory responses (skin temperatures) and changes in environmental conditions inside cloth in high ambient humidity but not in low one.

DESCENTE SPORTS SCIENCE Vol.25/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE