Is It Safer and More Beneficial to Work Heart Failure Patients Harder? An Editorial Commentary

Exercise training is undoubtedly beneficial to heart failure patients in terms of improved physical fitness and quality of life,1,2 although a clear survival benefit has yet to be demonstrated.3 The results of some previously published exercise training trials may have been affected by several factors. First, exercise adherence is often below desired targets, which may lead to much smaller improvements than expected. Second, studies may have been affected by crossover to the exercise intervention in up to one-third of sedentary controls, which was the case in the largest trial to date, HF-ACTION (Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training).3 Finally, moderate-intensity continuous exercise has historically been the cornerstone of exercise programming, although a small volume of recent work has shown high-intensity interval exercise training to be superior for eliciting improvements in peak VO2 and systolic heart function.4,5 Exercise training guidelines have emerged in the last 20 years, for both subclinical and clinical populations. The American Heart Association (AHA) recently published physical activity guidelines for people with type II diabetes,6 which is especially interesting as it was perhaps the first to adjust weekly exercise time according to various activity intensities. Guidelines have been developed on the relatively large volume of data from clinical exercise training trials of moderate-intensity continuous exercise (MICE). There seem to be 3 pillars, or established reasons, why there exists an historical preference for MICE therapy in people considered to be medium to high risk for cardiovascular events. First, the stimulus from MICE is considered sufficient to stimulate health benefits. Second, the risk of serious medical events from MICE is considered acceptable, whereas intuitively high-intensity exercise is considered by many to carry a higher risk of serious illness. Third, MICE is well tolerated by most people and is not suspected to detract from exercise adherence. Recently, there have been a number of high-intensity intermittent exercise (HIIE) studies and study protocols published in the scientific literature. A notable study of HIIE for clinical populations was Wisloff et al’s work in heart failure patients,5 which produced unsurpassed clinical improvements. These improvements included 46% improvements in peak VO2, which is regarded as the best predictor of prognosis in these patients. Wisloff et al’s study