Alveolar Oxygen Uptake and Blood Flow Dynamics in Knee Extension Ergometry

Abstract:

The relationship was studied between the increase in oxygen uptake (VO₂) measured breath-by-breath at the mouth, and the increase in femoral artery blood flow measured continuously with pulsed and echo Doppler methods. Five men exercised at 50 W on a knee extension ergometer in both the supine and the upright posture. The kinetics of the responses were determined by curve fitting to obtain the mean response time (MRT = 63% of the time required to achieve steady state). In the upright position, the increase in blood flow (MRT = 12.4 ± 9.4 s, mean ± SD) was faster than the increase in VO₂ (29.6 ± 9.3 s). Likewise in the supine position, blood flow increased more rapidly (25.1 + 9.7 s vs. 36.7 ± 9.6 s). It should be noted that the increase in blood flow appeared to be faster than VO₂, yet when blood flow adapted more slowly in the supine posture, it had an impact on the adaptation of VO₂. This suggests that blood flow might have important effects on metabolism at the onset of submaximal exercise.

Keywords:

Oxygen Uptake - Exercise - Breath-by-Breath Gas Exchange - Pulsed Doppler - Echo Doppler

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