Changes in pulmonary oxygen uptake and muscle deoxygenation kinetics during cycling exercise in older women performing walking training for 12 weeks

Abstract

Purpose

This study examined the hypothesis that walking training (WT) could accelerate the slowed time constant (τ) of phase II in pulmonary oxygen uptake ( \(\dot {V}\) O₂) on-kinetics in older women. Also, we aimed to demonstrate that O₂ delivery and O₂ utilization were better matched at the site of gas exchange in exercising muscles when τ \(\dot {V}\) O₂ was shortened.

Methods

20 recreationally active older women underwent WT sessions of approximately 60 min, 3–4 times a week for 12 weeks. We assessed \(\dot {V}\) O₂, heart rate (HR) and deoxygenated-hemoglobin concentration ([HHb]) kinetics during a constant-load exercise test before training (0 week—Pre), and at 6 and 12 weeks (6 weeks—Mid, 12 weeks—Post) throughout the training period.

Results

Maximal oxygen uptake ( \(\dot {V}\) O_2max) was unchanged throughout the training program. τHR tended to decline at Mid (58.6 ± 22.0 s), and was significantly shorter at Post (51.7 ± 21.7 s, p = 0.01) compared to Pre (67.1 ± 23.8 s). τ \(\dot {V}\) O₂ significantly decreased from 38.9 ± 8.6 s for Pre, to 31.5 ± 7.9 s for Mid (p = 0.02), and 32.3 ± 10.5 s for Post (p = 0.03). The normalized [HHb] to \(\dot {V}\) O₂ ratio (Δ[HHb]/Δ \(\dot {V}\) O₂) at Pre (1.32 ± 0.93) gradually approached the perfectly matched value (= 1.0) at Mid (1.15 ± 0.61) and Post (1.07 ± 0.52).

Conclusions

The restoration to baseline (≒ 30 s) of the slower τ \(\dot {V}\) O₂ due to WT, which may reflect better matching of O₂ delivery and O₂ utilization at the site of gas exchange, suggests that a longer period of WT could be a useful tool for improving exercise tolerance in older individuals.

from Physiology via xlomafota13 on Inoreader https://ift.tt/2xjKlmy
via IFTTT