After several weeks of exercise, a human athlete's resting heart rate is typically lower than before because
A) the body needs less oxygen than before.
B) the body temperature has increased.
C) the stroke volume has increased.
D) the cardiac output has decreased.
E) the body produces less carbon dioxide than before.

Question

Quizplus · Accepted Answer

With exercise, the heart becomes more efficient in pumping blood. As a result, the stroke volume (the amount of blood pumped per beat) increases. As a result, the heart does not need to beat as frequently to maintain the same level of cardiac output, leading to a decreased resting heart rate.

After Several Weeks of Exercise, a Human Athlete's Resting Heart