Effects of Base Line Changes in Work Rate on Cardiorespiratory Dynamics in Incremental and Decremental Ramp Exercise

Abstract

The kinetics of ventilatory and gas exchange responses during the decremental (off) phase of trapezoidal and triangular ramp exercise in healthy subjects has been found to be significantly faster than those during the incremental (on) phase (1, 2). As an aid in exploring the mechanisms governing the on-off asymmetry of $\dot V{O_2}$ dynamics, a model analysis has been presented by Niizeki et al. (3). They suggested that the redistribution of blood flow during exercise would play a dominant role in producing the asymmetry of gas exchange response, assuming that the blood flow ratio of active muscles to total cardiac output increases linearly with the work intensity. Therefore, we tested the hypothesis that the asymmetrical response of gas exchange could be modulated by altering the absolute baseline of cardiac output. The dynamic properties of pulmonary gas exchange responses to trapezoidal ramp exercise in the upright position starting from two different baselines of 30- and 50-W were studied in five healthy men.