Twenty male athletes were grouped into high (H-G) and low (L-G), based on their maximal oxygen intake, were examined for cold-induced vasodilation (CIVD) and autonomic thermoregulatory response during exercise in cold environment. The subjects sit for 30 minutes and exercised using the ergometer at 70% of maximum oxygen uptake for 30 minutes in a climatic chamber (mean room temperature;10 ℃, mean relative humidity ; 60%, mean air stream 0.5m/sec). Their rectal temperature (Tre) skin temperature (forehead, chest, abdomen, back, upper arm, forearm, thigh, dosum of manus), metabolic rate and CIVD were measured.
　On the H-G group, there was a small decrease in rectal temperature, whereas in L-G, an increase was noted before exercise in a cold. Mean skin temperature (T ̅sk) decreased in both groups immediately after cold exposure. L-G showed a lower T ̅sk during exercise. In both groups, metabolic heat production (M ; W / m²) increased after cold exposure, and the increase was much larger during exercise. The value of M was always highest in H-G. CIVD indicators, which were : mean skin temperature (MST), temperature first rise (TFR) and resistance index (RI), were significantly higher in H-G than in L-G. Time of temperature rise (TTR) in H-G was also faster. The body fat (BF%) was significantly negatively correlate with Vo₂max, Tre, T ̅sk and M ; thus, it may be inferred that high physical fitness for endurance is less affected by body fat. High tolerance to cold can be explained by increases M and skin vessel constriction.
　Endurance training may improves thermal sensibilities and metabolic heat production. The relationship between the peripheral vessel vasomotor reaction and the autonomic thermoregulatory response during exercise in the cold environment become clearer.

DESCENTE SPORTS SCIENCE Vol.20/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE