title: Effects of age and long-term endurance training on VO2 kinetics.
abstract: OBJECTIVE
  This study examined the effects of age and training status on the pulmonary oxygen uptake (VO2p) kinetics of untrained and chronically trained young, middle-age, and older groups of men.
  
  
  METHODS
  Breath-by-breath VO2p and near-infrared spectroscopy-derived muscle deoxygenation ([HHb]) were monitored continuously in young (20-39 yr) trained (YT, n = 8) and untrained (YuT, n = 8), middle-age (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 (three repeats) were modeled as monoexponential. Data were scaled to a relative percentage 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- to 120-s period after exercise onset.
  
  
  RESULTS
  The time constant for the adjustment of phase II pulmonary VO2 (τVO2p) was larger in OuT (42.0 ± 11.3 s) compared with that in 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 that 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).
  
  
  CONCLUSIONS
  This study showed that the slower VO2kinetics typically observed in older individuals can be prevented by long-term endurance training interventions. Although the role of O2 delivery relative to peripheral use cannot be elucidated from the current measures, the absence of age-related slowing of VO2 kinetics seems 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.
authors.affiliation: 1Canadian Centre for Activity and Aging, University of Western Ontario, London, Ontario, CANADA; 2School of Kinesiology, University of Western Ontario, London, Ontario, CANADA; 3Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, CANADA; and 4Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA.
authors.forename: Tyler M
authors.initials: TM
authors.lastname: Grey
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Spencer
authors.forename: Glen R
authors.initials: GR
authors.lastname: Belfry
authors.forename: John M
authors.initials: JM
authors.lastname: Kowalchuk
authors.forename: Donald H
authors.initials: DH
authors.lastname: Paterson
authors.forename: Juan M
authors.initials: JM
authors.lastname: Murias
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply; D010101:Oxygen Consumption; D010806:Physical Education and Training; D010807:Physical Endurance / Q000502:physiology*; D011659:Pulmonary Gas Exchange; D019265:Spectroscopy, Near-Infrared; D013997:Time Factors; D055815:Young Adult