VENTILATORY 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, VO2 in l/min and ml/FFW/min, closed-integral-b (b/min), V(E) (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 V(E)/VO2 was greater in the obese women. The difference in V(E)/VO2 suggests a lower ventilatory threshold for the obese women. Percent VO2 max and R (VCO2/VO2) 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. V(E) was significantly greater in the obese at 85 percent of maximum only (P < 0.05) and closed-integral-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. V(E) is also similar at comparable intensities of exercise below ventilatory threshold but closed-integral-b is greater. The effect of the higher closed-integral-b on exercise tolerance is unknown. The higher closed-integral-b may be related to a decreased chest wall compliance in the moderately obese women.