athlete's heart

or athletic heart


noun

nonpathological enlargement of the heart resulting from intensive aerobic exercise.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Medicine definitions for athletic heart

athletic heart
[ ăth-lĕtĭk ]

n.

Enlargement of the heart observed in some athletes.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.