Relationship of peak exercise capacity with indexes of peripheral muscle vasodilation

Since leg muscles receive the majority of cardiac output and consume a large proportion of total oxygen consumption (VO2) during cycle exercise, maximum leg blood flow may be an important determinant of peak VO2 (VO2peak). We investigated the relationships between parameters of active hyperemia after thigh tourniquet occlusion (alone or with calf exercise) with whole body peak exercise capacity during maximum cycle exercise. Twenty-one healthy male subjects, aged 19-39 yr. performed maximum incremental cycle exercise. Calf blood flow, conductance (blood flow/mean blood pressure), vasodilatory capacity (peak/baseline conductance), and duration of vasodilation were then determined with venous occlusive plethysmography under two conditions: 1) after thigh tourniquet occlusion for 10 min; 2) after ischemic calf exercise (thigh tourniquet occlusion with calf exercise to exhaustion). Group mean VO2peak was 120 +/- 35% (standard deviation) predicted. There was a significant relationship between VO2peak/ lean body mass and peak calf conductance after maximum ischemic calf exercise (r = 0.556; P < 0.01). However, VO2peak/lean body mass was more closely correlated with the duration of vasodilation after thigh tourniquet occlusion with ischemic calf exercise (r = 0.861; P < 0.001). These results suggest that the duration of calf vasodilation after maximal ischemic calf exercise appears to be a better index of cycle exercise capacity in healthy subjects.