Final answer:
Regular endurance exercise results in a lower resting heart rate due to increased heart efficiency and the adaptation of heart muscles. The heart pumps more blood with each beat, decreasing the need for a higher rate at rest. This adaptation is a sign of improved cardiovascular health.
Step-by-step explanation:
The question is what happens to the resting heart rate as a result of regular endurance exercise. The correct answer is B) It decreases. Endurance exercise is a form of cardiovascular conditioning that strengthens the heart muscle, improving its efficiency. As a result, the heart doesn't need to work as hard to pump blood throughout the body when at rest, leading to a lower resting heart rate. Regular endurance exercise typically leads to a slower resting heart rate because of an increase in the cardiac reserve, which is the heart's ability to increase output during activity.
During endurance exercise, the heart adapts by improving the efficiency of its contractions and by increasing the amount of blood pumped per beat (stroke volume), allowing it to beat fewer times per minute and still meet the body's demands for oxygen and nutrients. This is why athletes or individuals who engage in consistent endurance training have lower resting heart rates compared to those who are less active.
It is important to note that while resting heart rates can decrease with regular exercise, extreme heart rates, such as increasing above 160 bpm in a healthy young adult, may lead to a plateau or even a decrease in cardiac output since the filling time for the heart becomes too short, reducing the efficiency of each heartbeat. However, this situation is generally associated with acute exercise rather than resting conditions.