Bodybuilders often develop concentric cardiomyopathy rather than dilated. Also bad, since chamber volume is decreased to the extent that their total output goes down even in the presence of a numerically "good" ejection fraction which is ultimately a percentage of a smaller volume. Also thicker cardiac muscle "squeezes" coronary arteries more in the systolic phase. diastolic phase shortens with higher heart rates and the heart is starved of blood supply resulting in their increase risk of serious cardiac events when exercising in higher zones ( more rapid heart rate).