Effect of obesity on ventilatory adjustment to exercise

¹ Department of Medicine, State University of New York, Upstate Medical Center, and Veterans Administration Hospital, Syracuse, New York

The ventilatory response to treadmill exercise was studied in normal and obese subjects, with an analysis of both the steady and unsteady states of exercise. Ventilation, oxygen consumption, carbon dioxide production, respiratory quotient, and alveolar and mixed expired gas concentrations were measured directly or computed. During the steady state of exercise obese subjects increased their ventilation sufficiently to maintain normal alveolar carbon dioxide tensions. During the first 2 min of exercise hypoventilation was more pronounced in obese subjects and in certain individuals resulted in mild reductions in alveolar oxygen tensions. Obese individuals exercised less efficiently than nonobese as manifested by excessive energy expenditure in relation to weight. Steady-state exercise Pa_CoCo2 values were higher in those subjects previously shown to be relatively insensitive to inhalation of 5% CO₂ but failed to correlate with the speed of ventilatory responsiveness.