Respiratory and Metabolic Responses to Endurance Cycle Exercise in Pregnant and Postpartum Women

This study was designed to determine whether endurance cycling responses in pregnancy differ from those postpartum. We studied 16 women longitudinally at ~ 32 wk pregnancy and ~ 10 wk postpartum. We measured heart rate (HR), O₂ uptake (VO₂), CO₂ output (VCO₂), minute ventilation VE and plasma concentrations of substrates and of catecholamines at rest, during maximal testing, and during ~ 35 - 40 min of cycling at ~70 - 75 % VO₂ peak. Endurance exercise time and power were 37.6 ± 1.0 min and 124 ± 8 W in pregnancy, similar to values observed postpartum. HR and respiratory responses near the end of endurance exercise were also unaffected by gestation, with pregnancy values of 173 ± 3 bpm, 1.87 ± 0.07 L/min VO₂, and 1.68 ± 0.07 L/min VCO₂, except that VE at 70.0 ± 3.5 L/min was 14 % higher than postpartum; plasma concentrations of free fatty acids (404 ± 62 mmol/L), glucose (3.34 ± 0.17 mmol/L), and lactic acid (4.51 ± 0.50 mmol/L) were lower than postpartum by 9, 24, and 19 %, respectively; catecholamine concentrations were not different from those determined postpartum. We conclude that pregnant women are equally capable as are postpartum women to perform ~ 40 min of cycling at 70 - 75 % VO₂ peak, and that the physiologic responses to endurance exercise are largely independent of gestation.

Key words

Pregnancy - endurance exercise - substrates - endocrine responses - ventilation