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
