Uncertainty in Exercise Intensity Prescription for Cardiac Rehabilitation: A Methodological Review of Measurement Error, Physiological Variability, and Clinical Decision-Making

OBJECTIVES This study examines the pathways through which uncertainties—such as measurement errors and physiological variability—enter cardiac rehabilitation exercise prescriptions, proposing a framework for clinical interpretation and minimum reporting.METHODS We searched PubMed/MEDLINE (2000-2026) and synthesized 39 core sources regarding prescription errors and variability, conducting a structured methodological narrative review guided by SANRA transparency standards.RESULTS Prescription uncertainty was classified into four domains: measurement, estimation, physiological variability, and application/transfer uncertainty, which ultimately converge on clinical decision-making. Specifically, predictive equations for maximum heart rate in patients on beta-blockers, ventilatory threshold interpretations in heart failure, and wrist-worn device measurements exhibited substantial clinical deviations.CONCLUSIONS Fixed target zones must be interpreted as evidence-qualified decision ranges specifying input provenance and potential errors, rather than absolute physiological boundaries. The proposed Uncertainty Chain model contributes to enhancing prescription safety, though future prospective clinical validations are required.