What happens to resting heart rate with endurance training and why?

• A. Increases due to higher metabolic demand
• B. Remains unchanged due to balanced changes
• C. Increases due to larger heart size
• D. Decreases due to higher stroke volume

Answer: (D)

Endurance training makes the heart more efficient at rest. The key change is an increase in stroke volume—the amount of blood ejected with each beat. This happens because the heart, especially the left ventricle, becomes larger and stronger, venous return and blood volume are higher, and the heart fills more effectively during diastole. With a greater stroke volume, the heart can maintain the same resting cardiac output with fewer beats per minute, so resting heart rate falls. There’s also a shift toward greater parasympathetic (vagal) activity at rest, which further lowers the rate.

That’s why the resting heart rate decreases after endurance training. The other options don’t fit because resting metabolic demand isn’t higher, net resting heart rate isn’t unchanged, and while heart size increases, the overall effect is a reduction in heart rate, not an increase.