Alveolar oxygen uptake and femoral artery blood flow dynamics in upright and supine leg exercise in humans

We tested the hypothesis that the slower increase in alveolar oxygen uptake (VO2) at the onset of supine, compared with upright, exercise would be accompanied by a slower rate of increase in leg blood flow (LBF). Seven healthy subjects performed transitions from rest to 40-W knee extension exercise in the upright and supine positions. LBF was measured continuously with pulsed and echo Doppler methods, and VO2 was measured breath by breath at …