Exercise training in heart failure: which training modality works best?

During the last three decades, exercise interventions in chronic heart failure patients have seen a remarkable career: Until the late 1980s, standard cardiology textbooks recommended a reduction of physical activity levels as standard of care in heart failure patients. It was a true paradigm shift when Coats et al. (3) compared exercise training and activity restriction in a prospective randomized crossover trial for the first time and proved that exercise training was safe and significantly improved exercise tolerance, peak oxygen consumption, and symptoms. Coats et al. (3) were able to show that there is no correlation between left ventricular ejection fraction (LVEF) and exercise capacity in heart failure (HF) patients but a clear relation between skeletal muscle mass and exercise capacity. In consequence, peripheral factors became therapeutic targets for training interventions: skeletal muscle atrophy and metabolic dysfunction, reduced strength of respiratory muscles, endothelial dysfunction, and systemic inflammatory activation. Due to its practicability, safety, and the ease to monitor blood pressure, heart rate, and ECG steady state, aerobic ergometer training became a standard modality for exercise training in heart failure. However, there are multiple ways to change the training method: 1) Training intensity (% of V̇O2max or max. heart rate); 2) Type of training (endurance, resistance, combined); 3) Method of training (continuous or steady state, intermittent, interval); 4) Training modality (concentric vs. eccentric); 5) Training target (systemic vs. regional training, e.g., respiratory training); 6) Training control (supervised vs. nonsupervised); and 7) Training location (hospital based, outpatient, home based). Of these, 1 to 3 and 5 to 7 have been extensively studied. Since only moderate-intensity endurance training has proven prognostic benefits for the patient [reduced rehospitalization rate (10), reduced mortality (6, 11)], only this type of training received a IA guideline recommendation (12). Recently, hopes that high-intensity interval training would prove better results than continuous steady-state training were shattered by the publication of the SMARTEX study, in which previous results of single center studies regarding better exercise capacity after high-intensity interval training (14) could not be reproduced (4). Pure resistance training is ineffective in improving exercise capacity in heart failure patients while combined endurance-resistance training is effective in improving exercise capacity and vascular function (9).