Exercise intensity prescription after myocardial infarction in patients treated with beta-blockers

The aim of our study was to answer the following questions: (1) Is it possible to estimate the exercise training intensity according to heart rate in patients treated with beta-blockers after myocardial infarction? and (2) Are there any other appropriate alternate possibilities to estimate the training intensity?

This study involved 112 men (60.2 +/- 8.6 years) with a previous myocardial infarction treated with beta-blockers. Patients underwent exercise echocardiography and also completed a symptom-limited cardiopulmonary ramp test to determine peak exercise capacity, maximal heart rate, heart rate (HR) at the anaerobic threshold (AT), peak oxygen uptake (VO2peak) VO2 consumption at AT, and exercise capacity at AT.

The mean value of HR at AT was 104.7 +/- 13.3 bpm, corresponding to 81.0% +/- 8% of VO2peak and 87.9% +/- 5.6% of HRpeak. The mean HR at 80% HRpeak was 96 +/- 13.7 bpm, at 70% heart rate reserve (HRR) 103.3 +/- 13.1 bpm and at 80% HRR 108 +/- 14.4 bpm. A close correlation was observed between HR at AT and values at 80% HRpeak (r = 0.86, P < .01). A similar correlation was found also for 70% and 80% HRR (r = 0.87 and 0.88, respectively, P < .01). Exercise intensity at AT occurred close to the value of 1 W/kg(bodyweight).

As an upper limit in determining training intensities, the assessment of AT is the gold standard. However, findings suggest that %HRpeak, %HRR, and %VO2peak can be used alternatively. The use of workload expressed as in W/kg also appears useful.