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 ± 0.2 m/s; P < 0.001) compared to NP (33.7 ± 4.9 min; 2.0 ± 0.2 m/s) and were further reduced in PGOB (19.6 ± 2.8 min; 1.4 ± 0.1 m/s; P < 0.001) indicating a performance limitation to exercise. Ventilation in response to exercise was increased in PG (49.4 ± 6.6 L/min) compared to NP (39.8 ± 5.4 L/min, at 100 W; p < 0.05) women, and was further augmented by obesity (56.7 ± 9.3 L/min, at 100 W; 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.