Adherence to heart rate training zones in an exercise training program in adults with coronary artery disease

Objectives: To investigate the effect of exercise intensity on functional capacity in individuals with coronary artery disease, assess adherence to the heart rate training zone (HRTZ), and relationship between trained intensity and functional capacity. Methods: Retrospective study led with medical records of 54 outpatients with coronary artery disease in a public hospital. The prescribed intensity started at 50 ­60% of heart rate reserve, increasing monthly to 70 ­80% by the third month. Spearman's test was used to assess the correlation between improvement in distance in the incremental shuttle walk test (ISWT), exercise intensity, and rating of perceived exertion (Borg­RPE). Adherence was classified as 'below' when HRTZ was not achieved in any phase of the program, 'intermediate' when HR was within the HRTZ for one or two months, and 'above' when HR was at or higher than HRTZ two months. Improvement was tested with t-test and one-way ANOVA. Results: 51.9% of participants had an increase in ISWT of ≥70 m (p < 0.0001). In at least one month, 50.9% trained below HRTZ. Trained intensity did not go below 8.6% of the prescribed minimal threshold of HRTZ. Changes in ISWT were not significantly correlated with exercise intensity (p = 0.87) or Borg­RPE (p = 0.16). Conclusion: While a significant increase in functional capacity was found, considerable heterogeneity in changes were observed. This may, in part, be related to adherence to HRTZ with progressive exercise intensity and to the variability in exercise volume incardiovascular rehabilitation programs.