Endurance training at rest: which statement best describes stroke volume and resting heart rate?

• A. Q increases with training
• B. Resting heart rate decreases with training
• C. SV decreases
• D. SV increases due to hypertrophy

Answer: (D)

Endurance training prompts the heart to adapt by increasing the size and efficiency of the left ventricle, which raises the amount of blood pumped with each beat at rest. This comes from eccentric hypertrophy, where the chamber enlarges and fills more easily during diastole, leading to a higher stroke volume. At the same time, resting heart rate tends to fall because of greater parasympathetic (vagal) tone and improved cardiovascular efficiency, so overall resting cardiac output remains similar or may be slightly reduced.

Saying that stroke volume increases due to hypertrophy captures the main resting-state change: the heart beats more blood per beat because the ventricular chamber has grown and contracts more effectively. The other statements don’t describe this combination as accurately: resting heart rate lowering is true but incomplete in describing stroke volume, and the idea that cardiac output increases at rest or that stroke volume decreases don’t fit the typical resting adaptations of endurance training.