Effect of partial body cooling on thermophysiological responses during cycling work in a hot environment

1. We measured rectal ( T re), tympanic ( T ty), and skin ( T sk) temperatures, skin blood flow (SkBF), local and whole-body sweat rate (SR), heart rate (HR), and thermal sensation in seven men during bicycle exercise for 40 min, with and without two types of cooling. 2. An increasing rate in T ty was suppressed by the ice cooling, but not in T re. By the fan cooling T ty was lowered 0.3 °C. Δ[ T re– T ty] was markedly higher with the fan cooling than with the ice cooling or control. 3. Local SR, SkBF and HR were significantly inhibited by both types of cooling, but whole-body SR was not lowered. However, enhancement of evaporative efficiency was observed with the fan cooling. There were improvements of thermal sensation during exercise after both types of cooling. 4. As apparent thermoregulatory responses-to-core temperature ( T core) relation, the relation differed between the control and both cooling trials. Δ [ T re– T ty]-to- and T re-to-local SR relation slopes were altered in both cooling trials as compared with the control. In all trials, the slope of SkBF– T ty relation was suddenly reduced at approximately 37.5 °C. 5. It is concluded that the present study confirms the effectiveness of partial cooling on the human body. We suggest that the beneficial effects of the cooling on the body should be taken into account when designing an adequate training program.