Effects of human pregnancy and aerobic conditioning on alveolar gas exchange during exercise

Abstract

This study examined the effects of aerobic conditioning during the second and third trimesters of human pregnancy on ventilatory responses to graded cycling. Previously sedentary pregnant women were assigned randomly to an exercise group (n = 14) or a nonexercising control group (n = 14). Data were collected at 15–17 weeks, 25–27 weeks and 34–36 weeks of pregnancy. Testing involved 20 W·min–1 increases in work rate to a heart rate of 170 beats·min–1 and (or) volitional fatigue. Breath-by-breath ventilatory and alveolar gas exchange measurements were compared at rest, a standard submaximal [Formula: see text]O2 and peak exercise. Within both groups, resting [Formula: see text]E, [Formula: see text]A, and VT/TI increased significantly with advancing gestation. Peak work rate, O2 pulse [Formula: see text]O2/HR, [Formula: see text]E, [Formula: see text]A respiratory rate, VT/TI, [Formula: see text]O2, [Formula: see text]CO2, and the ventilatory threshold (Tvent) were increased after physical conditioning. Chronic maternal exercise has no significant effect on pregnancy-induced changes in ventilation and (or) alveolar gas exchange at rest or during standard submaximal exercise. Training-induced increases in Tvent and peak oxygen pulse support the efficacy of prenatal fitness programs to improve maternal work capacity. Key words: human gestation, respiration, chronic exercise.