Fitness Level and Not Aging per se, Determines the Oxygen Uptake Kinetics Response (original) (raw)

2018, Frontiers in Physiology

Although aging has been associated to slowerVO 2 kinetics, some evidence indicates that fitness status and not aging per se might modulate this response. The main goal of this study was to examine theVO 2 , deoxygenated hemoglobin+myoglobin (deoxy-[Hb+Mb]) kinetics, and the NIRS-derived vascular reperfusion responses in older compared to young men of different training levels (i.e., inactive, recreationally active, and endurance trained). Ten young inactive [YI; 26 ± 5 yrs.; peakVO 2 (VO 2peak), 2.96 ± 0.55 L•min −1 ], 10 young recreationally active (YR; 26 ± 6 yrs.; 3.92 ± 0.33 L•min −1), 10 young endurance trained (YT; 30 ± 4 yrs.; 4.42 ± 0.32 L•min −1), 7 older inactive (OI; 69 ± 4 yrs.; 2.50 ± 0.31 L•min −1), 10 older recreationally active (OR; 69 ± 5 yrs.; 2.71 ± 0.42 L•min −1), and 10 older endurance trained (OT; 66 ± 3 yrs.; 3.20 ± 0.35 L•min −1) men completed transitions of moderate intensity cycling exercise (MODS) to determineVO 2 and deoxy-[Hb+Mb] kinetics, and the deoxy-[Hb+Mb]/VO 2 ratio. The time constant ofVO 2 (τVO 2) was greater in YI (38.8 ± 10.4 s) and OI (44.1 ± 10.8 s) compared with YR (26.8 ± 7.5 s) and OR (26.6 ± 6.5 s), as well as compared to YT (14.8 ± 3.4 s), and OT (17.7 ± 2.7 s) (p < 0.05). τVO 2 was greater in YR and OR compared with YT and OT (p < 0.05). The deoxy-[Hb+Mb]/VO 2 ratio was greater in YI (1.23 ± 0.05) and OI (1.29 ± 0.08) compared with YR (1.11 ± 0.03) and OR (1.13 ± 0.06), as well as compared to YT (1.01 ± 0.03), and OT (1.06 ± 0.03) (p < 0.05). Similarly, the deoxy-[Hb+Mb]/VO 2 ratio was greater in YR and OR compared with YT and OT (p < 0.05). There was a main effect of training (p = 0.033), whereby inactive (p = 0.018) and recreationally active men (p = 0.031) had significantly poorer vascular reperfusion than endurance trained men regardless of age. This study demonstrated not only that age-related slowing ofVO 2 kinetics can be eliminated in endurance trained individuals, but also that inactive lifestyle negatively impacts theVO 2 kinetics response of young healthy individuals.