Purpose: This study examined the effects of age and training status on the pulmonary oxygen uptake (VO2p) kinetics of untrained and chronically trained young, middle-aged and older groups of men.
Methods: Breath-by-breath VO2p and NIRS-derived muscle deoxygenation ([HHb]) were monitored continuously in young (20-39 yr) trained (YT; n=8) and untrained (YuT; n=8), middle-aged (40-59 yr) trained (MT; n=9) and untrained (MuT; n=9), and older (60-85 yr) trained (OT; n=9) and untrained (OuT; n=8) men. On-transient VO2p and [HHb] responses to cycling exercise at 80% of the estimated lactate threshold (3 repeats) were modeled as a mono-exponential. Data were scaled to a relative % of the response (0-100%), the signals time-aligned and the individual [HHb]-to-VO2p ratio was calculated as the average [HHb]/VO2 during the 20-120s period following exercise onset.
Results: The time constant for the adjustment of phase II pulmonary VO2 ([tau]VO2p) was larger in OuT (42.0+/-11.3 s) compared to YT (17.0+/-7.5 s), MT (18.1+/-5.3 s), OT (19.8+/-5.4 s), YuT (25.7+/-6.6 s), and MuT (24.4+/-7.4 s) (P<0.05). Similarly, the [HHb]/VO2 ratio was larger than 1.0 in OuT (1.30+/-0.13; P<0.05) and this value was larger than observed in YT (1.01+/-0.07), MT (1.04+/-0.05), OT (1.04+/-0.04), YuT (1.05+/-0.03), and MuT (1.02+/-0.09) (P<0.05).
Conclusion: This study showed that the slower VO2 kinetics typically observed in older individuals can be prevented by long-term endurance training interventions. Although the role of O2 delivery relative to peripheral utilization cannot be elucidated from the current measures, the absence of age-related slowing of VO2 kinetics appears to be partly related to a preservation of the matching of O2 delivery to O2 utilization in chronically trained older individuals, as suggested by the reduction in the [HHb]/VO2 ratio.
(C) 2014 American College of Sports Medicine