Effects of Interval Training on Risk Markers for Arrhythmic Death: a Randomized Controlled Trial

Objective: To compare the effects of high-intensity interval training versus moderate-intensity continuous training on risk markers of arrhythmic death in patients who recently suffered from an acute coronary syndrome.

Design: Double-blind (patient and evaluator) randomized controlled trial.

Setting: Cardiovascular Prevention and Rehabilitation Centre (EPIC Centre) of the Montreal Heart Institute, Montreal, Canada.

Subjects: A total of 43 patients were randomized following an acute coronary syndrome.

Interventions: Patients were assigned to either high-intensity interval training (n = 18) or isocaloric moderate-intensity continuous training (n = 19), three times a week for a total of 36 sessions.

Main Measures: Heart rate recovery for 5 minutes, heart rate variability for 24 hours, occurrence of ventricular arrhythmias, and QT dispersion were measured before and after the 36 sessions of training.

Results: Among the 43 patients randomized, 6 participants in the high-intensity interval training group stopped training for reasons unrelated to exercise training and were excluded from the analyses. Heart rate recovery improved solely in the high-intensity interval training group, particularly at the end of recovery period ( < 0.05). There were no differences in heart rate variability, occurrence of ventricular arrhythmias, or QT dispersion parameters between the groups at study end.

Conclusion: Despite the lack of power to detect any large difference between the two interventions with respect to risk markers of arrhythmic death, high-intensity interval training appears safe and may be more effective at improving heart rate recovery relative to moderate-intensity continuous training in our patients following acute coronary syndrome.