Gas exchange kinetics following concentric-eccentric isokinetic arm and leg exercise.

PURPOSE: To evaluate the effects of exercise velocity (60, 150, 240deg∙s-1 ) and muscle mass (arm vs leg) on changes in gas exchange and arterio-venous oxygen content difference (avDO2 ) following high-intensity concentric-eccentric isokinetic exercise.

METHODS: Fourteen subjects (26.9±3.1years) performed a 3×20-repetition isokinetic exercise protocol. Recovery beat-to-beat cardiac output (CO) and breath-by-breath gas exchange were recorded to determine post-exercise half-time (t1/2 ) for oxygen uptake (V˙O2 pulm), carbon dioxide output (V˙CO2 pulm), and ventilation (V˙E ).

RESULTS: Significant differences of the t1/2 values were identified between 60 and 150deg∙s-1 . Significant differences in the t1/2 values were observed between V˙O2 pulm and V˙CO2 pulm and between V˙CO2 pulm and V˙E . The time to attain the first avDO2 -peak showed significant differences between arm and leg exercise.

CONCLUSIONS: The present study illustrates, that V˙O2 pulm kinetics are distorted due to non-linear CO dynamics. Therefore, it has to be taken into account, that V˙O2 pulm may not be a valuable surrogate for muscular oxygen uptake kinetics in the recovery phases.