Does rating of perceived exertion result in target exercise intensity during interval training in cardiac rehabilitation? A study of the Borg scale versus a heart rate monitor

Abstract Objectives To assess whether rating of perceived exertion using the Borg 6–20 scale is a valid method for achieving target exercise intensity during high-intensity interval training in cardiac rehabilitation. Design A single-group cross-over design. Methods Ten participants (56 (6.5) years) who were enrolled in a high-intensity interval training cardiac rehabilitation program were recruited. A target exercise intensity of Borg 17 (very hard) was used for exercise intensity guidance in the initial four exercise sessions that took place before a cardiopulmonary exercise test, as in usual care rehabilitation. The heart rate was recorded and blinded to the participants. After performing the test, the participants were then instructed using heart rate monitors openly for exercise guidance in four subsequent exercise sessions, at an intensity corresponding to 85–95% of peak heart rate. Results The mean exercise intensity during high-intensity bouts was 82% (6%) of peak heart rate for the rating of perceived exertion and 85% (6%) using heart rate monitors ( p = 0.005). Bland–Altman limits of agreement analysis with a mean bias showed a bias of 2.97 (−2.08, 8.02) percentage points for the two methods. Exercise intensity was highly repeatable with intra-class correlations of 0.95 (95% CI 0.86–0.99, p < 0.001) and 0.96 (95% CI 0.88–0.99, p < 0.001) in the exercise sessions using rating of perceived exertion and percentage of peak heart rate for intensity control, respectively. Conclusions Rating of perceived exertion results in an exercise intensity below target during high-intensity interval training bouts in cardiac rehabilitation. Heart rate monitoring should be used for accurate intensity guidance.