Abstract des Autors

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 (tVO2, tVCO2, tVE) and heart rate (tHR). There was a significant slowing of ventilation and gas exchange kinetics across age with linear regression yielding an increase of 0.67 s/yr for tVO2 (39 s in young to 61 s in old), 0.57 s/yr for tVCO2, and 0.65 s/yr for tVE, whereas tHR (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 tVCO2 compared with tVO2 across age may reflect reduced CO2 storage capacity with loss of muscle tissue. The tVE change across age was similar to that for tVCO2 (tVE/tVCO2 unchanged). The present study demonstrated marked age-related slowing of gas exchange dynamics at exercise onset. Verf.-Referat