Abstract
Although aging has been associated to slower O2 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 the O2, 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.; peak O2 (O2peak), 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 determine O2 and deoxy-[Hb+Mb] kinetics, and the deoxy-[Hb+Mb]/O2 ratio. The time constant of O2 (τO2) 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). τO2 was greater in YR and OR compared with YT and OT (p < 0.05). The deoxy-[Hb+Mb]/O2 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]/ O2 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 of O2 kinetics can be eliminated in endurance trained individuals, but also that inactive lifestyle negatively impacts the O2 kinetics response of young healthy individuals.
Highlights
Studies assessing the physiological responses to exercise across the aging spectrum have demonstrated age-related declines within the O2 transport system, as determined by reductions in peak oxygen uptake (V O2peak) (Astrand, 1976; Fitzgerald et al, 1997)
V O2 amplitude and moderate intensity exercise (MOD) WR were greater in older endurance trained individuals compared to both inactive and recreationally active (p < 0.05), there was a progressive increase in the V O2 amplitude and MOD WR corresponding to any increase in fitness level in the younger groups (p < 0.05) (Table 2)
Average group data for the deoxy-[Hb+Mb]/V O2 ratio derived from the normalized responses of deoxy-[Hb+Mb] and V O2 adjustments to a moderate-intensity WR are portrayed in
Summary
Studies assessing the physiological responses to exercise across the aging spectrum have demonstrated age-related declines within the O2 transport system, as determined by reductions in peak oxygen uptake (V O2peak) (Astrand, 1976; Fitzgerald et al, 1997). To further understand age-related limitations within the path of O2 transport during submaximal exercise performed within the moderate intensity domain, researchers have investigated the mechanisms that control the dynamic adjustment of oxygen consumption (V O2) during square-wave exercise transitions from a given baseline metabolic rate, to a higher metabolic demand below the gas exchange threshold (GET) (Babcock et al., 1994; DeLorey et al, 2007; duManoir et al, 2010; Murias et al., 2010; Grey et al, 2015) Using this model, an instantaneous increase in metabolic demand [typically power output (PO)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
