High vs Low Intensity Exercise Impact on Coronary Heart Disease Patients

BACKGROUND: A vast amount of literature exists on the improvements in work capacity, reduction of risk factors, and an increased feeling of well-being among coronary heart disease patients after physical training programs. Previous observations of short-term training programs which resulted in an increase in physical working capacity have not usually shown a cardiac change. The National Exercise and Heart Disease Project did not show such changes, but the exercise level may have been inadequate. Several other studies suggested that more prolonged and intense training could result in improved cardiac function. DESIGN NARRATIVE: Patients were randomized to high intensity or low intensity long-term exercise groups. Compliance was strengthened by randomizing following a sequence of eligibility visits and after a test period of subject reaction to an exercise program. The primary endpoint was change in exercise ejection fraction at one year. Secondary endpoints included changes in lipid levels, body composition, blood pressure and heart rate measurements, glucose tolerance, quality of life measures, compliance, and progression of disease. Patients were classified into one of four strata based on the documented history of myocardial infarction and resting left ventricular ejection fraction. Within each stratum, patients were assigned in equal numbers to the two intensity levels of exercise intervention. All exercise prescriptions were based on exercise testing of patients maintained on their usual medical regimen including drugs. Patients underwent standardized multistage treadmill exercise testing monitored by Doppler echocardiogram at baseline, just prior to randomization and at the three month, six month, one year and two year visits. Patients participated in the structured group exercise sessions three days per week. Each exercise session was preceded by and ended with a five to fifteen minute warm-up and cool-down session. Each patient was given an exercise prescription that included a 30 minute period of walking or of walking and jogging sequences and 15 minutes of arm-leg bicycle ergometer exercise. Recruitment started in May 1987. The last patient was enrolled in March 1990.