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

PURPOSE: This study examined the hypothesis that walking training (WT) could accelerate the slowed time constant (τ) of phase II in pulmonary oxygen uptake ([Formula: see text]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[Formula: see text]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 [Formula: see text]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 ([Formula: see text]O2max ) 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[Formula: see text]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 [Formula: see text]O2 ratio (Δ[HHb]/Δ[Formula: see text]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[Formula: see text]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.