This study was to see the significance for physical fitness and sports medicine of cutaneous arteriovenous anastomoses (AVA) in human extremities from a viewpoint of thermal physiology. To investigate the effects of stopping blood flow to the hand by wrist occlusion on forearm skin temperature and sweat rate during exercise, the experiment has been performed. The results from this experiment showed that the hand vasodilation (mainly AVA) induced not only increased hand blood flow, but also increases in forearm skin temperature and forearm sweat rate through the rising venous blood flow returning from the hand. The similar responses were ovserved in the lower extremities. An additional experiment was carried out to observe the effects of both wrist occlusion on esophageal temperature (Tes) and mean blood pressure (MBP) during thermal load. Suppressed hand blood flow in wrist occlusion (OCCL), induced compensatory increases of skin blood flow and sweat rate in the chest when compared with control (CONT) without wrist occlusion. Tes was higher in OCCL and MAP was lower in OCCL than those in CONT. These results suggest that increased hand blood flow (mainly AVA) contributes to the efficacious heat loss without any fall of MAP during thermal load.
　Effects of local cold and heat stimulations on finger blood flow were tested. When finger was exposed to the cold water at 5 °C, finger blood flow measured by laser-Doppler flowmeter showed increase in AVA (CIVD : Cold-induced vasodilation). When finger was exposed to the warm water at above 39°C, finger blood flow showed decrease in AVA (HIVC : Heat-induced vasoconstriction).
　These results suggested that AVA vessels played an important role of defense responses against various thermal stresses, and showed the significance for physical fitness and sports medicine of cutaneous AVA vessel in human extremities.

DESCENTE SPORTS SCIENCE Vol.18/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE