Discordance and Clinical Selection of Aerobic Exercise Intensity Indices in Cardiovascular Rehabilitation and Selected Cardiometabolic Diseases: A Clinical Review

OBJECTIVES This focused clinical review examined discordance among heart rate reserve (HRR), oxygen uptake reserve (VO2R), ventilatory thresholds (VTs), and rating of perceived exertion (RPE), and developed a stepwise framework for selecting an index when classifications conflict in cardiovascular rehabilitation and selected cardiometabolic diseases.METHODS PubMed/MEDLINE was searched through August 31, 2026, with citation tracking and review of guidelines, position statements, and consensus documents from major cardiovascular rehabilitation and exercise medicine societies. The search yielded 1,493 PubMed records. The records were reassessed by title and abstract using the stated population, exercise-intensity index, and clinical-relevance criteria. Fifty-seven publications were reviewed in detail, and 38 were included (8 guidelines or consensus statements, 24 original studies, and 6 reviews or methodological papers). Included publications compared indices, evaluated disease-, medication-, or rhythm-related discordance, or materially informed clinical selection. Evidence was synthesized narratively according to measurement assumptions, physiological validity, feasibility, discordance conditions, and triangulation strategies.RESULTS Discordance reflected invalid measurement assumptions, altered physiological responses, and context-dependent perception. HRR was vulnerable to estimated peak heart rate, medication changes, chronotropic incompetence, arrhythmia, pacing, and transplantation. VO2R represented metabolic demand but required valid gas-exchange data. VTs identified individualized physiological domains but depended on test quality and interpretation. RPE remained useful when heart rate was unreliable, although education, symptoms, and exercise format altered the direction and magnitude of error.CONCLUSIONS Discordance should be resolved by assessing each index’s validity and physiological relevance rather than averaging conflicting values. Valid VT data define physiological domains, whereas VO2R quantifies relative metabolic demand. Without gas-exchange data, measured HRpeak-based HRR, RPE, and work rate should be triangulated; symptoms, blood pressure, rhythm, and glucose remain safetymonitoring variables. Prospective validation is required before the proposed sequence can be considered a clinical decision rule.