Cardiovascular rehabilitation (CR) significantly improves outcomes in patients with cardiovascular diseases (CVD), especially coronary heart disease and heart failure (HF). Although CR is often considered as an exercise training (ET) programfor patients following CVD events, CR ismore than just ET as it involves education, dietary and psychological counseling, as well as a multi-factorial risk factor modification. However, a major component of ET involves efforts tomeasure and improve levels of cardiorespiratory fitness (CRF). In this state-of-the-art review, we analyze the data, including from our John Ochsner Heart and Vascular Institute, evaluating CRF and its impact on psychological improvements and major outcomes with CR, especially long-term survival. (C) 2021 Elsevier Inc. All rights reserved.