Comparison of the Kinetics of Pulmonary Oxygen Uptake and Middle Cerebral Artery Blood Flow Velocity During Cycling Exercise

Abstract

The present study investigated the changes of pulmonary oxygen uptake (VO₂) and the regional cerebral blood flow (rCBF) in constant load of exercise and compared the kinetics of the two parameters. Eight healthy young males performed two sets of constant workload of exercise bouts (10 min) by cycle ergometer with different intensities of moderate and heavy, corresponding to the level of 10–20% below lactate threshold (LT) and between LT and respiratory compensation point (RC), respectively. The kinetics of VO₂ and middle cerebral artery blood flow velocity (MCA V _mean) at the initial phase of the exercise was expressed by a monoexponential curve fitting model. The response of MCA V _mean during the transition from rest to exercise mimicked that of VO₂ and the time constant (τ) for VO₂ was related to τ for MCA V _mean in both the moderate- and heavy-intensity exercise. We speculate that an increase in both cardiac output and skeletal muscle metabolism, as the contributing factors for VO₂ during exercise, would be related to the neuronal activation in the corresponding areas of brain and CBF.