Exercise-Induced Coronary Remodeling and the Atherosclerotic Paradox in Endurance Athletes: Toward a Unified Mechanobiological Framework.

Regular endurance exercise is consistently associated with lower cardiovascular mortality, a favorable cardiometabolic profile, and superior cardiorespiratory fitness. However, coronary imaging studies in master endurance athletes have raised a clinically relevant paradox: despite a low burden of conventional risk factors, some athletes-particularly older men with high lifetime exercise exposure-show a greater prevalence of coronary artery calcium and subclinical coronary plaque than sedentary or less active controls. This observation has challenged the long-standing assumption that high-volume endurance exercise is uniformly protective against coronary artery disease. A binary interpretation of this literature is inadequate. Coronary flow reserve and ischemic threshold may remain adequate in some athletes, although this concept is supported by limited functional and outcome data. Based on experimental vascular biology and indirect human evidence, repetitive high-flow states during endurance exercise generate sustained laminar shear stress, cyclic wall strain, and marked increases in coronary blood flow, thereby activating endothelial mechanotransduction pathways and influencing vascular smooth muscle cell behavior, extracellular matrix remodeling, and calcification biology. These adaptations may culminate in positive arterial remodeling, luminal enlargement, and, in some individuals, a predominantly calcified plaque phenotype. Importantly, structural remodeling does not necessarily equate to functional impairment. In selected athletes, when outward remodeling and endothelial responsiveness are preserved, coronary flow reserve and ischemic threshold may remain adequate, although this concept remains supported by limited functional and outcome data. This narrative review integrates the clinical imaging literature with current concepts in vascular mechanobiology to propose that coronary remodeling in endurance athletes exists along an adaptive-maladaptive continuum shaped by cumulative exercise load, aging, sex, conventional risk factors, and biological susceptibility. This framework may help clinicians interpret CAC/CCTA findings in athletes more appropriately and avoid equating plaque burden with equivalent functional or prognostic significance.