INFLUENCE OF VENOUS-BLOOD RETURNING FROM THE HAND ON FOREARM SKIN BLOOD-FLOW AND SWEATING RATE DURING EXERCISE IN HUMANS

1. The influence of venous blood returning from the hand on forearm heat loss was investigated in 5 healthy male subjects during exercise at an ambient temperature of 25-degrees-C. 2. To change the temperature of venous blood returning from the hand, one hand was immersed in temperature controlled-water at 35-degrees-C (W-side), while the other was kept at 20-degrees-C (C-side). 3. Forearm skin temperature (T(arm)) on the W-side promptly increased simultaneously with the onset of finger vasodilation, whereas T(arm) on the C-side profoundly decreased. 4. Nonevaporative heat loss estimated by, a thermogram from the forearm on the W-side was significantly greater than that on the C-side by ca 24 W/m2 at the end of a 30-min exercise period. 5. Forearm blood flow (Q(arm)) and sweating rate (m(sw)) significantly increased during a 30-min exercise period at an intensity of 40 or 60% V(Q2max). 6. Q(arm) and m(sw) on the W-side were significantly greater than those on the C-side for the last 8-18 min of exercise. 7. These results suggest that venous blood returning from the hand has a significant role in controlling evaporative and nonevaporative heat loss from the forearm,