Vetilatory response of moderately obese women to submaximal exercise

To investigate the effect of moderate obesity on ventilatory responses to graded exercise, we compared the ventilatory responses of ten moderately obese (35 ± 5 percent body fat) and nine leaner women (22 ± 2 percent body fat) during walking on a treadmill with incremental increases in percent grade. Speed remained constant at 3.0 mph. In the obese women, V̇O₂ in l/min and ml/FFW/min, f(b) (b/min), V̇E (l/min), and HR were significantly greater (P < 0.05) at all four absolute workloads. At 10.0 and 12.5 percent grade, VO₂ (ml/kg/min) was smaller and V̇E/V̇O₂ was greater in the obese women. The difference in V̇E/V̇O₂ suggests a lower ventilatory threshold for the obese women. Percent V̇O₂max and R (V̇CO₂/ V̇O₂) were significantly different at 12.5 percent grade only. When VO₂ was divided by HR (oxygen pulse), the two groups were not significantly different at any of the four workloads tested. The groups were compared further at workloads representing approximately 55, 65, 75, and 85 percent of VO₂max. HR was not significantly different at any of the four relative exercise intensities. V̇E was significantly greater in the obese at 85 percent of maximum only (P < 0.05) and f(b) was significantly greater at 55, 75, and 85 percent of maximum. Whereas cardiorespiratory responses of moderately obese women are increased at absolute workloads when compared to that of leaner women, HR is similar at comparable intensities of exercise. V̇E is also similar at comparable intensities of exercise below ventilatory threshold but f(b) is greater. The effect of the higher f(b) on exercise tolerance is unknown. The higher f(b) may be related to a decreased chest wall compliance in the moderately obese women.