Failure to improve cardiopulmonary fitness in cardiac rehabilitation.

Purpose: A primary goal of cardiac rehabilitation (CR) exercise is to increase cardiopulmonary fitness. The aim of this study was to identify characteristics of CR participants who fail to improve peak oxygen uptake (peakV(O(2))).

Methods: The study cohort included 385 consecutive patients with directly measured peakV(O(2)) prior to and upon completion of CR. Patients were classified as a "nonimprover" if exit peakV(O(2)) was less than or equal to entry peakV(O(2)).

Results: Eighty-one (21%) patients failed to improve peakV(O(2)). Baseline characteristics predicting nonimprovement included the following: lower handgrip strength, lower peak exercise respiratory exchange ratio, a nonsurgical diagnosis, female status, and more medical comorbidities. The number of sessions attended and exercise duration were similar between groups. Nonimprovers, however, exercised at lower exercise intensity despite a similar rating of perceived exertion. By multivariate analysis, independent positive correlates of percentage change in peakV(O(2)) included exercise training intensity and baseline handgrip strength. Negative correlates included baseline peakV(O(2)), comorbidity score, self-reported physical function, and a diagnosis of diabetes (cumulative total r = 0.51, adjusted R = 0.26, P < .0001).

Conclusions: Twenty-one percent of CR participants failed to improve peakV(O(2)) primarily due to exercise training performed at lower relative intensity despite a similar rating of perceived exertion. For patients with baseline characteristics associated with nonimprovement, alternative training protocols should be considered.