Effects of maternal aerobic fitness on cardiorespiratory responses to exercise.
We hypothesized that aerobically fit women who continued to exercise throughout pregnancy would have enhanced cardiorespiratory responses to exercise. Physically active (N = 10) and sedentary (N = 6) subjects were compared during steady-state (15 min) semi-recumbent cycle exercise performed at a given heart rate (HR; 140 b.min-1) twice during pregnancy (25 wk, 36 wk) and 12 wk postpartum. Indirect calorimetry was used to measure volumes and fractional concentrations of expired gases. Cardiac output was estimated via CO2 rebreathing. Data were analyzed with repeated measures ANOVA. Caloric expenditure during exercise was significantly (P < 0.001) greater in the physically active (7.2 kcal.min-1) compared with sedentary (4.7 kcal.min-1) subjects. Alveolar ventilation and cardiac output responses to exercise were proportionally greater (P < 0.001) in the aerobically fit subjects. Ventilatory equivalents for O2 and physiological dead space/tidal volume ratios were significantly (P < 0.01) lower in the physically active subjects during exercise. In contrast, ratings of perceived exertion during exercise did not differ between subject groups. It appears that a physically active woman's enhanced cardiorespiratory responses to acute exercise are maintained during pregnancy if she continues her aerobic fitness program throughout gestation.
Pivarnik
J M
JM
Department of Pediatrics (Sections of Cardiology and Nutrition & GI), Baylor College of Medicine, Houston.
Ayres
N A
NA
Mauer
M B
MB
Cotton
D B
DB
Kirshon
B
B
Dildy
G A
GA
D000328:Adult; D000332:Aerobiosis; D002245:Carbon Dioxide / Q000378:metabolism; D002302:Cardiac Output / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology; D011247:Pregnancy / Q000502:physiology*; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000502:physiology; D012119:Respiration / Q000502:physiology*; D012126:Respiratory Dead Space / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D013990:Tidal Volume / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology
D002245:Carbon Dioxide