Kinetics of oxygen uptake and cardiac output at onset of arm exercise

Abstract Pulmonary oxygen uptake (V O 2 ) kinetics at onset of exercise is reported to be slower for arm than for leg exercise. This could be attributed to reduced cardiac output (Q) or reduced arteriovenous O 2 content difference or both. To test this, V O 2 , mean tissue oxygen consumption (V O 2T ), and Q kinetics in arm cranking were compared with corresponding values found in leg cycling. The increase in V O 2 during phase 1 (abrupt increase after onset of exercise) was less in arm than in leg exercise, suggesting that immediate Q adjustments to arm exercise were less pronounced. Mean response times (MRT, the relative rates at which a steady state was attained) for V O 2 , V O 2T , and Q were prolonged during arm exercise. The MRT of V O 2 in arm exercise at a given blood lactate increase was higher than in leg exercise. The delayed V O 2 kinetics in arm exercise might be due to delayed Q kinetics and higher anaerobic glycolysis occurring early during arm exercise.