Prescribing cardiorespiratory exercise intensity in cardiac rehabilitation: do updated guidelines capture true individual effort responses?

Abstract Background Optimising exercise intensity is central to cardiovascular rehabilitation (CR), and emerging discussions emphasise that guideline-recommended intensities must truly reflect individual physiological responses to ensure a metabolic stimulus equivalent across individuals. The first and second ventilatory thresholds (VT1 and VT2) mark the transitions from low to moderate and moderate to vigorous exercise, respectively, providing a framework for personalised, metabolism-guided CR prescriptions. Purpose To assess the validity of the updated American Heart Association/ American Association of Cardiovascular and Pulmonary Rehabilitation (AHA/AACVPR) Scientific Statement (2024/2025) for recommended percentages of heart rate reserve (%HRR) for moderate-intensity cardiorespiratory exercise by comparing them with actual heart rate (HR) responses at ventilatory thresholds (VTs) in a large multicentre cohort of patients with cardiometabolic disease (CMD). Methods This retrospective study involved 12 centres across 9 countries. In 2,554 individuals with CMD who underwent cardiopulmonary exercise testing (CPET), HR at VT1 and VT2 were compared with values estimated by the AHA/AACVPR moderate-intensity range (40–59% HRR). Analyses comprised Wilcoxon tests, intraclass correlation coefficients (ICC), median absolute percentage error (MdAPE), and Bland–Altman plots. Results The cohort was predominantly male (79.2%), median age 63, with 71.7% having coronary artery disease, 22.5% HFrEF, and 75.3% on beta-blockers. HR at VT1 closely matched 40% HRR (P = .826), whereas HR at VT2 significantly exceeded 59% HRR (P < .001). ICCs were 0.844 (95% CI: 0.833–0.855) at the lower and 0.768 (95% CI: 0.053–0.915) at the upper limit, both classified as ‘good’. The wide CI at the upper limit indicated substantial inter-individual variability, and MdAPE and Bland–Altman analyses confirmed reduced accuracy and agreement at VT2. Conclusions The AHA/AACVPR recommended %HRR range for moderate-intensity exercise closely matched VT1, representing the lower limit of moderate intensity, but substantially underestimated VT2, the upper limit, in patients with CMD. Revising %HRR targets to better reflect CPET-derived ventilatory thresholds could improve exercise prescription, enhance clinical outcomes, and strengthen research validity.For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.