Effect of low-intensity training on transient kinetics of pulmonary oxygen uptake during moderate-intensity cycle...

It is unclear whether the slowed time constant of phase II in pulmonary oxygen uptake on-kinetics (V̇O2τ) in unfit and inactive men would be shortened by low exercise intensity (low-intensity) walking training. We therefore tested the hypothesis that the slowed V̇O2τ in sedentary population would speed up due to low-intensity walking training with high volume.

Ten unfit and inactive male subjects (aged 26 to 50 yrs) underwent a low-intensity (30-40% of V̇O2max), long-duration (>60 min) training in the form of walking exercise 3-4 times a week for 12 weeks. We prospectively collected data on anthropometric, maximal oxygen uptake (V̇O2max), time constant of heart rate (HRτ) and V̇O2τ before training (0 wk; Pre) and every six weeks (6 wk; Mid, 12 wk; Post) from the beginning of the training.

Anthropometric variables and V̇O2max showed no significant changes throughout the training program, whereas HRτ showed a tendency to be shortened with a progress of the training with no significant change. The slowed V̇O2τ at Pre (47.6±5.6 s) remained almost unchanged at Mid (48.8±4.9 s), but had a significant decrease at Post (40.5±7.9 s, P<0.05).

In this study acceleration of the slowed V̇O2τ due to low-intensity walking training is thought to occur presumably owing to an improved matching of oxygen delivery to oxygen utilization at the site of gas exchange in active muscle tissue. We concluded that low-intensity walking training at beginning stage of training could contribute to the acceleration of the slowed V̇O2τ in unfit and inactive subjects.