Solution:
During strenuous activity, a well-trained athlete can achieve a cardiac output double that of a sedentary person, in part because training causes hypertrophy (enlargement) of the heart. Even though the heart of a well-trained athlete is larger, resting cardiac output is about the same as in a healthy untrained person, because stroke volume (volume of blood pumped by each beat of a ventricle) is increased while heart rate is decreased. The resting heart rate of a trained athlete oft en is only 40–60 beats per minute (resting bradycardia).
