Which statement about the supine recovery after exercise is true?

Which statement about the supine recovery after exercise is true?

• A. It has no effect on venous return
• B. It decreases stroke volume
• C. It increases venous return, raising stroke volume and reducing cardiovascular stress at a given heart rate
• D. It increases heart rate more than standing

Answer: (C)

Lying supine after exercise changes how blood returns to the heart. When you lie down, gravity no longer pulls blood into the legs, so venous return increases. That extra return fills the heart more during diastole (higher preload), and the heart contracts more forcefully in response. This increases stroke volume via the Frank-Starling mechanism. If heart rate is held at the same value during recovery, the larger stroke volume boosts cardiac output and improves perfusion without requiring a higher heart rate, meaning the cardiovascular system is under less stress for that heart rate. So the statement is true. The other ideas don’t fit because venous return does increase with lying down, stroke volume does not decrease, and supine recovery does not cause a greater heart rate rise than standing.

Lying supine after exercise changes how blood returns to the heart. When you lie down, gravity no longer pulls blood into the legs, so venous return increases. That extra return fills the heart more during diastole (higher preload), and the heart contracts more forcefully in response. This increases stroke volume via the Frank-Starling mechanism. If heart rate is held at the same value during recovery, the larger stroke volume boosts cardiac output and improves perfusion without requiring a higher heart rate, meaning the cardiovascular system is under less stress for that heart rate. So the statement is true. The other ideas don’t fit because venous return does increase with lying down, stroke volume does not decrease, and supine recovery does not cause a greater heart rate rise than standing.