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Exercise on-transient gas exchange kinetics are slowed as a function of age

BABCOCK MARK A.; PATERSON, DONALD H.; CUNNINGHAM, DAVID A.; DICKINSON, JOHN R.
Medicine & Science in Sports & Exercise: April 1994
Original Investigations: PDF Only

ABSTRACT

The purpose was to characterize gas exchange kinetics following the on-transient of exercise in men aged 30–80 yr. Forty-six men completed square wave exercise tests from loadless cycling to subventilatory threshold (VET) work rates with gas exchange measured breath-by-breath. Signal averaged data were fit with a monoexponential equation to derive time constants (T) for gas exchange and ventilation (V2, τVCO2, τVE) and heart rate (τHR). There was a significant slowing of ventilation and gas exchange kinetics across age with linear regression yielding an increase of 0.67 s·yr−1 for τVO, (39 s in young to 61 s in old), 0.57 s-yr−1 for τVCO2, and 0.65 s-yr−1 for τV2, whereas τHR (44 to 41 s) was not-changed significantly. The-slowed VO2 kinetics with age may reflect limitations in muscle blood flow or in control of the rate of oxidative metabolism. The less marked slowing of τVCO2 compared with τVO2 across age may reflect reduced CO2 storage capacity with loss of muscle tissue. The τVE, change across age was similar to that for τVCO2 (τVE/τVCO2 unchanged). The present study demonstrated marked age-related slowing of gas exchange dynamics at exercise onset.

©1994The American College of Sports Medicine