Impact of pregnancy and obesity on cardiorespiratory responses during weight-bearing exercise.

The present study is the first to compare the cardiorespiratory responses during progressive weight-bearing treadmill exercise in normal-weight non-pregnant (NP, n=14), normal-weight pregnant (PG, n=20) and obese pregnant (PGOB, n=20) women. Exercise duration and peak treadmill speed were lower in PG (23.9+/-4.9 min; 1.6+/-0.2m/s; P<0.001) compared to NP (33.7+/-4.9 min; 2.0+/-0.2m/s) and were further reduced in PGOB (19.6+/-2.8 min; 1.4+/-0.1m/s; P<0.001) indicating a performance limitation to exercise. Ventilation in response to exercise was increased in PG (49.4+/-6.6L/min) compared to NP (39.8+/-5.4 L/min, at 100W; p<0.05) women, and was further augmented by obesity (56.7+/-9.3 L/min, at 100W; p<0.05 versus PG) secondary to an elevated metabolic cost of exercise as indicated by no further increase in .V(E)/.V(CO2) and .V(E)/.V(O2) in PGOB compared to PG women. The normal augmentation of heart rate observed in PG during exercise was not further increased by obesity at standardized sub-maximal work rates.