OCCLUSION AND HEAD-UP TILT

The potential role of lower limb blood pooling in reducing venous return to the heart during orthostasis and elevated venous pressure is investigated. This study compares lower limb capacitance, microvascular filtration, and peripheral resistance between a group of highly trained endurance athletes and a group of their sedentary peers. Seven endurance trained males were selected between the ages of 23-33 [(29.1 ± 4.1 yr), mean ± SD]. The subjects ’ weekly cycling mileage ranged from 80 to 150 miles per week with an average of 125 ± 8.5 miles/week. Nine healthy, age-matched sedentary subjects (25.8 ± 4.8 yr.) were selected for the control group, based upon their reporting they had not participated in repeated lower-body or cardiovascular exercise in the months prior to their study. Results show that both subject groups had similar calf venous capacitances, rates of capillary fluid filtration, and local flow shunting (vascular resistance change) in response to venous thigh occlusion and 70 ° head-up tilt (HUT). The only significant difference found between groups was the cyclist group’s smaller rise in heart rate in response to HUT. The findings of this study suggest that cyclists are no