Effect of exercise training on postexercise oxygen uptake kinetics in patients with reduced ventricular function

Background: The time required for oxygen uptake ((V)over dot O-2,) to retur n to baseline level (recovery kinetics) is prolonged in patients with reduc ed ventricular function, and the degree to which it is prolonged is related to the severity of heart failure, markers of abnormal ventilation, and pro gnosis. In the present study, we sought to determine the effect of exercise training on (V)over dot O-2 recovery kinetics in patients with reduced ven tricular function. Methods: Twenty-four male patients with reduced ventricular function after a myocardial infarction were randomized to either a 2-month high-intensity residential exercise training program or to a control group. (V)over dot O- 2 kinetics in recovery from maximal exercise were calculated before and aft er the study period and expressed as the slope of a single exponential rela tion between (V)over dot O-2 and time during the first 3 min of recovery. Results: Peak (V)over dot O-2 increased significantly, in the exercise grou p (19.4 +/- 3.0 mL/kg/min vs 25.1 +/- 4.7 mL/kg/min, p < 0.05), whereas no change was observed in control subjects. The (V)over dot O-2 half-time in r ecovery, was reduced slightly after the study period in both groups (108.7 <plus/minus> 33.1 to 102.1 +/- 50.5 s in the exercise group and 122.3 +/- 6 8.7 to 107.5 +/- 36.0 s in the control group); neither the change within or between groups was significant. The degree to which (V)over dot O-2 was pr olonged in recovery was inversely related to measures of exercise capacity (peak (V)over dot O-2 watts achieved, and exercise time; r = -0.48 to -0.57 ; p < 0.01) and directly, related to the peak ventilatory equivalents for o xygen (r = 0.59, p < 0.01) and carbon dioxide (r = 0.57, p < 0.01). Conclusion: Two months of high-intensity training did not result in a faste r recovery of (V)over dot O-2 in patients with reduced ventricular function . This suggests that adaptations to exercise training manifest themselves o nly during, but not in, recovery from exercise.