Nonshivering thermoregulatory responses in trained athletes: Effects of physical fitness and body fat

We studied the difference of thermoregulatory responses between trained male athletes (TR, n=9) and untrained men (UT, n=7) during 60 min of cold exposure (15°C) without shivering, and examined the effects of physical fitness and body fat on these responses. Mean skin temperature (T̄(sk)), esophageal temperature (T(es)), and skin conductance (K(b)) were similar between TR and UT, and heal production (M̄) for TR increased significantly during exposure at 15°C. The M̄ at 15°C correlated positively with maximal oxygen uptake and negatively with body fat (%BF), but not with T(es). The K(b) correlated negatively with T(es) and positively with T̄(sk). The %BF also correlated negatively with K(b) and T̄(sk) during exposure at 15°C, and the slope of %BF vs. T̄(sk) relationship was significantly steeper in TR than in UT. These results suggest that (1) body temperature is maintained by the reduction of skin conductance, and (2) heat insulation independent of body fat is enhanced in trained athletes during cold exposure without shivering.