Exercise Intensity and Delivery in Cardiac Rehabilitation for Heart Failure: From Comparative Efficacy to Achieved Dose and Patient-Centred Implementation

Exercise-based cardiac rehabilitation improves functional capacity and quality of life in clinically stable patients with heart failure, but the comparative value of high-intensity interval training (HIIT) and moderate-intensity continuous training (MCT) remains uncertain. This narrative review updates evidence through August 2026 from PubMed/MEDLINE, publisher records, and professional-society sources, prioritizing randomized trials, systematic reviews, meta-analyses, and guidance documents. Rehabilitation probably reduces all-cause hospital admission and improves quality of life, although a short-term mortality reduction has not been established. Meta-analyses report a modest average HIIT advantage in peak oxygen uptake, about 1.5–1.8 mL/kg/min, but heterogeneity is substantial. SMARTEX-HF did not show HIIT superiority in heart failure with reduced ejection fraction, and OptimEx-Clin did not show a clinically important advantage in heart failure with preserved ejection fraction. Outcomes are influenced by achieved intensity, weekly duration, total work, adherence, frailty, comorbidity, supervision, and access. MCT remains a broadly applicable foundation, whereas supervised HIIT is reasonable for selected patients who can reach and recover from the intended workload. Home-based and hybrid models may extend access when assessment, feedback, safety escalation, and programme fidelity are maintained. Exercise prescription should be individualized around the dose patients can safely receive.