BACKGROUND: The time required for oxygen uptake (O2) to return to baseline level (recovery kinetics) is prolonged in patients with reduced ventricular function, and the degree to which it is prolonged is related to the severity of heart failure, markers of abnormal ventilation, and prognosis. In the present study, we sought to determine the effect of exercise training on O2 recovery kinetics in patients with reduced ventricular 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. O2 kinetics in recovery from maximal exercise were calculated before and after the study period and expressed as the slope of a single exponential relation between O2 and time during the first 3 min of recovery. RESULTS: Peak O2 increased significantly in the exercise group (19.4 +/- 3.0 mL/kg/min versus 25.1 +/- 4.7 mL/kg/min, p < 0.05), whereas no change was observed in control subjects. The O2 half-time in recovery was reduced slightly after the study period in both groups (108.7 +/- 33.1 to 102.1 +/- 50.5 s in the exercise group and 122.3 +/- 68.7 to 107.5 +/- 36.0 s in the control group); neither the change within or between groups was significant. The degree to which O2 was prolonged in recovery was inversely related to measures of exercise capacity (peak O2, watts achieved, and exercise time; r = -0.48 to -0.57; p < 0.01) and directly related to the peak ventilatory equivalents for oxygen (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 faster recovery of O2 in patients with reduced ventricular function. This suggests that adaptations to exercise training manifest themselves only during, but not in, recovery from exercise.

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