EFFECTS OF PREGNANCY AND CHRONIC EXERCISE ON RESPIRATORY RESPONSES TOGRADED-EXERCISE

Effects of cycle ergometer conditioning (heart rate 143 +/- 2 beats/mi n, 25 min/session, 3 sessions/wk) during the second and third trimeste rs of pregnancy were studied in 18 healthy previously sedentary women. A nonexercising control group (n = 9) was also studied. Graded exerci se tests were conducted for both groups at similar to 17, 27, and 37 w k of gestation and at 20 wk postpartum. Both groups exhibited augmente d ventilatory responses to exercise throughout pregnancy. Significant aerobic conditioning effects observed in the exercised group between e ntry and third trimester of pregnancy testing included a 17% increase in oxygen pulse at peak exercise, reduction in the respiratory exchang e ratio during standard submaximal exercise, and an increase in work r ate at the onset of blood lactate accumulation. Onset of blood lactate accumulation did not change significantly in the control group. Respi ratory exchange ratio at peak exercise was higher in postpartum tests compared with those conducted in late gestation in both groups. Peak p ostexercise lactate levels were also significantly lower in second and third trimesters of pregnancy testing compared with postpartum in the control group. This effect appeared to be prevented by physical condi tioning in the exercised group. The study results support the hypothes is that moderate aerobic conditioning increases maximal aerobic power and the capacity for sustained submaximal exercise. Chronic exercise a lso appeared to help to preserve anaerobic working capacity in late ge station.