Cardiorespiratory Dynamics in Men in Response to Passive Work

Abstract

Dynamic characteristics of ventilation, cardiac output, and gas exchange in response to passive limb movements were studied in four healthy men in an upright position. Passive exercise was performed on a motor-driven bicycle ergometer, of which pedaling rate was varied from control (30 rpm) to stimulus (90 rpm) level in a stepwise fashion. Stroke volume (SV), heart rate (HR), and cardiac output (Q̇) were determined continuously during the exercise by using an automated impedance cardiograph. Minute ventilation [formula omitted], respiratory frequency (f), tidal volume (Vt), oxygen consumption [formula omitted], carbon dioxide output [formula omitted], end-tidal pressure of oxygen and carbon dioxide ([formula omitted] and [formula omitted]), and the gas exchange ratio (R) were also determined at each breath. When the pedaling rate was increased, Q̇ and V̇E rose in excess of metabolic need with a half response time of about 10 sec, and remained elevated for the duration of the stimulus. [formula omitted] and [formula omitted] rose transiently, then recovered to the initial control level after a few min. [formula omitted] remained at the control level for about one min, then decreased by 1 Torr. [formula omitted] and R rose transiently. These results suggest that hyperpnea during passive exercise is not induced by chemical stimuli to known chemoreceptors, but is due to reflexes mediated either by moving limbs or the right heart. © 1985, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.