Can an Exercise Program Worsen Heart Disease?

In brief This article presents five case reports of patients whose heart disease worsened while they were participating in an exercise program. The purpose is not to imply a relationship between exercise and the deterioration of the subjects' conditions but to illustrate the danger of making broad conclusions from case reports or unusual patients. After considering all the benefits of exercise and the other factors that could explain these patients' deterioration, the authors believe that moderate exercise is a sane prescription. They are currently undertaking a randomized scientific investigation that may provide valid evidence to support this belief.