Background: Exercise prescription based on percentage of peak exercise variables has many limitations in patients taking beta-blockers. The aim of this study was to evaluate efficacy and safety of a training protocol based on the rating of perceived exercise (RPE) in patients taking beta-blockers after cardiac surgical revascularization.
Design and methods: 71 patients treated with beta-blockers after recent coronary artery bypass grafting were randomly allocated to two different programmes with training intensity adjusted to keep heart rate close to first ventilatory threshold (36 subjects, AeT group) or RPE between grades 4 and 5 of 10-point category-ratio BORG scale (35 subjects, RPE group).
Results: In the RPE group, mean training workloads and heart rate values were significantly higher than in the AeT group; during the last week of the programme, six RPE patients were training very close to anaerobic threshold. Aerobic peak capacity increased similarly in the two groups. Considering the potential effects on training intensity of prescriptions based on percentages of peak exercise variables, we found that only percentage heart rate reserve and peak workload methods were reliable in defining a safe upper limit of training intensity, with values of 50% and 65% respectively.
Conclusions: Self-regulation of exercise training intensity between grades 4 and 5 of the 10-point category-ratio BORG scale is effective but may promote overtraining in some patients without significant functional advantages. For these reasons, RPE method should be integrated with objective indices based on percentage of heart rate reserve or of peak workload.