Upright exercise in a hot environment reduces venous return, which enhances cardiovascular drift and inhibits thermoregulatory peripheral vasodilation. In the present study, we quantified calf venous compliance and examined the systemic cardiovascular response to lower body negative pressure (LBNP). We also examined the effect of leg compression on the calf local blood flow response. The calculated calf venous compliance was 4.63±0.28 ml/100g tissue/100mmHg, and this value was not influenced by local calf skin heating. (LBNP) increased thoracic impedance (an index of central blood volume) and decreased cardiac stroke volume, which were accompanied with the increase in heart rate and decrease in forearm vascular conductance. The decrease in forearm conductance in response to LBNP was more pronounced during heat stress, suggesting that thermoregulatory peripheral vaodilation was inhibited by accumulation of blood in the lower extremities. These suggest that leg compression shoule be effective for maintenance of systemic circulation during gravitational stress by reducing blood pooling in the lower extremities. In contrast, local calf blood flow was reduced by leg compression because of reduced perfusion pressure. Further studies are required to determine the most effective compression in consideration of peripheral and systemic circulation.

DESCENTE SPORTS SCIENCE Vol.26/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE