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 similar to 32 wk pregnancy and similar to 10 wk postpartum, We measured heart Fate (HR), O-2 uptake ((V) over dot O-2), CO2 output ((V) over dot CO2), minute ventilation (V) over dot E and plasma concentrations of substrates and of catecholamines at rest, during maximal testing, and during similar to 35-40 min of cycling at similar to 70-75% (V) over dot O-2peak. 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+/-3bpm, 1.87+/-0.07 L/min (V) over dot O-2 and 1.68+/-0.07 L/min (V) over dot CO2 except that (V) over dot E at 70.0+/-3.5 L/min was 14% higher than postpartum; plasma concentrations of free fatty acids (404+/-62 mu mol/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 similar to 40 min of cycling at 70-75% (V) over dot O-2 peak, and that the physiologic responses to endurance exercise are largely independent of gestation.