Influence of hormone replacement therapy and aerobic exercise training on oxygen uptake kinetics in postmenopausal...

The purpose of this study was to determine the effects of aerobic exercise training on the adjustment of pulmonary oxygen (O2) uptake (VO2p) kinetics in postmenopausal women in 2 groups: those using hormone replacement therapy (HRT) (HRT group) (n = 7, aged 56 ± 4 years) and those not using HRT (nonHRT group) (n = 8, aged 60 ± 5 years). The influence of training (cycle-ergometer 3 times per week for 6 weeks) on step transitions to both moderate-intensity (80% of the gas exchange threshold) and heavy-intensity (Δ50) cycling exercise was studied. Breath-by-breath VO2p data were collected using a mass spectrometer. There were no differences in baseline characteristics between the HRT and nonHRT groups. Moderate-intensity exercise VO2p kinetics were significantly speeded (p < 0.05) with the τVO2p decreasing from 46 ± 8 s before training to 32 ± 4 s after training. Similarly, during the heavy-intensity exercise, on-transient phase 2 τVO2p was reduced from before training (48 ± 7 s) to after training (38 ± 6 s). The use of HRT did not influence the effect of the endurance exercise training on τVO2p during moderate or heavy exercise in healthy postmenopausal women. To provide insight into the mechanism of adjustment, knee extension exercise was studied, and the VO2p kinetics were significantly speeded (p < 0.05), with the τVO2p of the knee extension exercise decreasing from 62.2 ± 18.3 s before training to 48.0 ± 16.2 s after training. Thus, 6 weeks of exercise training resulted in appreciably faster cycling phase 2 VO2p kinetics during moderate and heavy exercise in older women, independent of HRT use.