Oxygen Uptake And Leg Blood Flow Kinetics And The Influence Of Exercise Training In Older Women

Abstract

INTRODUCTION: Slow O2 uptake (VO2) kinetics are characteristic of the exercise response of older men, but VO2 kinetics are appreciably speeded with an exercise training program. For older women there is limited information on VO2 kinetics, and since adaptations to exercise training in older women appear to differ from those observed in men, with women not showing improvement in stroke volume (blood flow), it was of interest to determine whether VO2 kinetics were speeded in older women and if blood flow to the working limb was altered with training. PURPOSE: To examine phase 2 (pulmonary) VO2p kinetics and limb blood flow (LBF) during the on-transition to mo derate-intensity alternate-leg knee extension (KE) in older women, before and after a six week exercise training program. METHODS: Before and after training, 8 healthy sedentary older women (mean age, 59 yrs) performed step-transitions (3–4 repetitions) on a KE ergometer from passive exercise to a constant work rate corresponding to 70% of leg VO2peak. Training sessions consisted of cycle ergometer exercise, lasting 30 min/session, 3 sessions per week for 6 weeks. Breath-by-breath VO2p was measured by mass spectrometer and volume turbine. LBF was measured by Doppler ultrasound of the femoral artery (n=7). Data were interpolated, time-aligned, and ensemble-averaged into 10-s time bins. VO2p (phase 2) and LBF (from exercise onset) kinetics were estimated using a monoexponential model and nonlinear regression techniques. RESULTS: With training KE VO2peak was increased (p<0.05) by 14% (0.78 ± 0.03 l.min-1 to 0.89 ±0.05 l.min-1). The time constant for KE VO2p kinetics (?VO2) was reduced (p<0.05) from 62 ± 18s to 48 ± 16s post-training, while the ?LBF was reduced (p<0.05) from65 ± 17s to 48 ± 20s post-training. CONCLUSIONS: Slow VO2p kinetics of older women were appreciably speeded over the course of a six week exercise training programme, similar to that observed previously in older men. Additionally, in older women, LBF kinetics during the adaptation to moderate KE exercise were significantly speeded with exercise training suggesting that muscle O2 delivery was enhanced with training.