We examined the effect of age and training status on the oxygen uptake (V˙ O2) kinetics of untrained and recreationally trained women. Young (20-35yr), middle-age (40-55yr) and older (58-71yr) recreationally trained (YTR, n = 10; MTR, n = 12; OTR, n = 9) and untrained (YUT, n = 12; MUT, n = 10; OUT, n = 9) women participated in this crossectional study. Breath-by-breath V˙ O2 and near-infrared-spectroscopy-derived (NIRS) muscle deoxygenation [HHb] were monitored continuously during increasing and constant walking exercises. On-transition V˙ O2 and [HHb] responses to moderate intensity walking were modeled as mono-exponential. The data were normalized for each subject (0%-100 %), and [HHb]/ V˙ O2 ratio was calculated as the average [HHb]/ V˙ O2 during the 20- to 120-s period after the onset of moderate intensity walking exercise. The time constant of V˙ O2 (τ V˙ O2) was longer in OUT(23.8 ± 2.4), MUT(25.4 ± 5.1), YUT(23.1 ± 3.4) than in YTR(16.2 ± 2.0), MTR(16.7 ± 3.9), OTR(16.3 ± 2.8) women (p < 0.05). The [HHb]/ V˙ O2 ratio in OUT (1.31 ± 0.18) was higher than in YTR(1.08 ± 0.05), MTR(1.13 ± 0.09), YUT(1.12 ± 0.09) (p < 0.05). It is concluded that recreationally trained women had faster V˙ O2 kinetics along with better matching of O2 delivery and utilization at the site of gas exchange in the exercising muscles.
Keywords: Aging; Muscle deoxygenation; Oxygen uptake kinetic; Recreationally trained; Women.
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