Effects of aerobic endurance training on gas exchange kinetics of older men.

The kinetics of gas exchange at the on-transient of exercise are appreciably slowed in older individuals. Eight older men (72 yr) completed 6 months of aerobic cycle training. Ventilation and gas exchange kinetics were determined at the onset of a below threshold (ventilatory threshold, V(E)T) square wave exercise function and compared with control values (N = 4, age 70 yr). Gas exchange data were measured breath-by-breath and signal averaged data were fit with a monoexponential function to determine the time constants (tau). The training group showed significant increases in VO2max (20%) and VO2 at V(E)T (21%). The tau for oxygen uptake kinetics decreased significantly (62.2 +/- 15.5 to 31.9 +/- 7.0 s). The tau VCO2 (70.9 +/- 10.9 to 43.8 +/- 11.4 s) and tau VE (89.2 +/- 18.0 to 50.4 +/- 11.3) also were significantly faster posttraining; however, tau HR (38.1 +/- 20.5 to 28.6 +/- 7.2) was not significantly altered. Thus, with a vigorous training program, the kinetics of gas exchange of older individuals were faster, and approached values reported in fit young subjects.