Question

Cardiac output (Q) in an endurance-trained athlete at rest is ________ cardiac output (Q) at rest for a sedentary individual.

a) Lower than
b) Equal to
c) Higher than

Answer 1

The cardiac output (Q) of an endurance-trained athlete at rest is similar to or slightly (A) lower than that of a sedentary individual.

Step-by-step explanation:

In the case of an endurance-trained athlete compared to a sedentary individual, the trained athlete’s cardiac output (Q) at rest tends to be about the same or slightly lower due to a greater stroke volume and a lower heart rate. When we look into the effect of exercise, especially endurance training, on cardiac efficiency, we see that the athlete's heart becomes more efficient due to exercise, thus even at rest it does not need to pump as often, if it can pump more blood per beat (higher stroke volume).

Turning our focus to changes in cardiac output when dealing with heart rates increasing beyond 160 bpm, for a healthy young adult, cardiac output actually begins to decrease past this point. The underlying reason for this decrease is a shortened ventricular filling time during diastole, which causes a reduction in stroke volume that eventually cannot be compensated for by the further increases in heart rate.

Thus, a high level of endurance training leads to an increased cardiac reserve, which is the difference between resting and maximum cardiac output, indicating the heart's ability to increase output during physical stress or exercise.