E. Physiologic Hypertrophy
The left ventricular mass of trained athletes is approxi¬mately 40% greater than that of age-matched controls. The athlete’s heart becomes enlarged mainly in end diastolic cavity dimensions with lesser changes in end systolic dimension and in posterior wall and septal wall thickness. The hypertrophied heart has a 30–60% increase in stroke volume at rest and during exercise. This type of cardiac hypertrophy occurs within three to six months of vigorous training, and usually reverts back to baseline values within three to four weeks of detraining. Hyper¬trophy of heart muscle caused by exercise is an absolute increase in cardiac mass and does not result from hyper-plasia (an increase in the number of cardiac muscle cells). Hypertrophy of the heart caused by exercise produces electrocardiographic and echocardiographic abnormalities (see the chapter Athletes and Sudden Cardiac Death).

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