What is the function of the cardiovascular system during exercise, and how does stroke volume respond to regular endurance training?

• A. It delivers oxygen and nutrients to working muscles and removes waste products; stroke volume decreases with endurance training due to heart fatigue.
• B. It transports hormones to tissues and assists in temperature regulation during exercise; stroke volume remains unchanged with endurance training.
• C. It delivers oxygen and nutrients to working muscles and removes waste; stroke volume increases with endurance training due to heart adaptations, improving cardiac output.
• D. It removes carbon dioxide from bloodstream and helps regulate pH; stroke volume becomes unpredictable with training.

Answer: (C)

The main idea here is how the cardiovascular system supports exercise by delivering oxygen and nutrients to working muscles and removing waste products, and how regular endurance training changes how much blood is pumped with each beat.

During exercise, muscles need more oxygen and nutrients and produce more waste, so the heart and blood vessels work to boost blood flow to those muscles. Stroke volume is the amount of blood the heart ejects with each beat. With regular endurance training, the heart adapts, especially the left ventricle, allowing it to fill more effectively and contract more efficiently. This increases end-diastolic volume and the strength of the contraction, so stroke volume rises. As a result, the heart can deliver more blood per minute at a given effort, boosting cardiac output (stroke volume times heart rate) and improving endurance performance. Training also often lowers resting and submaximal heart rate, making the system more efficient.

The other descriptions don’t fit as well: delivering hormones or regulating temperature isn’t the primary function highlighted during exercise in this context, and stroke volume does not stay unchanged or become unpredictable—it tends to increase with endurance adaptations.