Influence of hormone replacement therapy and aerobic exercise training on oxygen uptake kinetics in postmenopausal women
2013
Stathokostas, Liza | Kowalchuk, John H. | Paterson, Donald H.
The purpose of this study was to determine the effects of aerobic exercise training on the adjustment of pulmonary oxygen (O₂) uptake (V˙O₂ₚ) 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 V˙O₂ₚ data were collected using a mass spectrometer. There were no differences in baseline characteristics between the HRT and nonHRT groups. Moderate-intensity exercise V˙O₂ₚ kinetics were significantly speeded (p < 0.05) with the τV˙O₂ₚ decreasing from 46 ± 8 s before training to 32 ± 4 s after training. Similarly, during the heavy-intensity exercise, on-transient phase 2 τV˙O₂ₚ 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 τV˙O₂ₚ during moderate or heavy exercise in healthy postmenopausal women. To provide insight into the mechanism of adjustment, knee extension exercise was studied, and the V˙O₂ₚ kinetics were significantly speeded (p < 0.05), with the τV˙O₂ₚ 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 V˙O₂ₚ kinetics during moderate and heavy exercise in older women, independent of HRT use.
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