The athletes heart—from acute stimulus to chronic adaptation

INTRODUCTION: The complex phenomenon of the athlete's heart (AH) describes the chronic physiological structural and functional adaptation secondary to repeated exposure of an acute exercise stimulus. SOURCES OF DATA: This narrative review is based on published evidence. AREAS OF AGREEMENT: Highly trained athletic individuals frequently display cardiac parameters which are suggestive of an AH and can exceed the traditional 'normal' limits. AREA OF CONTROVERSY: The physiological processes underpinning the extent of cardiac adaption and how this is closely linked to exercise type, but also sex, ethnicity, and body size. GROWING POINTS: Since its seminal description by Morganroth and colleagues in 1975, our understanding of the AH has evolved in tandem with improvements in cardiac imaging techniques alongside the exploration of more diverse athletic populations. This narrative review aims to provide a balanced discussion of the multi-factorial nature of structure and function of the AH with specific reference to the unique physiological exercise stimuli. AREAS TIMELY FOR DEVELOPING RESEARCH: Despite great interest in cardiac adaptations across a broad spectrum of athletic populations, future research designs should consider the use of new and novel imaging techniques to enhance our understanding of the acute cardiovascular responses which ultimately mediates such adaptations, especially in athletic populations underrepresented in the literature.