Which statement best describes how plasma volume relates to endurance performance?

• A. Plasma volume has no effect
• B. Increased plasma volume may enhance venous return and EDV
• C. Plasma volume decreases during endurance training
• D. Increased plasma volume worsens endurance performance

Answer: (B)

Increasing plasma volume boosts the amount of blood returning to the heart, which raises preload or end-diastolic volume. This makes the heart pump more forcefully via the Frank-Starling mechanism, so stroke volume and overall cardiac output can meet the demands of endurance exercise more effectively. With a higher stroke volume, the body can maintain oxygen delivery to working muscles at a given effort more efficiently and often with a lower heart rate, helping to sustain performance. Plus, more plasma supports better thermoregulation during long bouts by aiding sweat production and skin blood flow. In endurance training, plasma volume expansion is a common adaptation that helps improve performance by improving venous return and end-diastolic volume.