Heat acclimation expands plasma volume to improve thermoregulation. What is a direct consequence of plasma volume expansion during heat exposure?

Heat acclimation expands plasma volume to improve thermoregulation. What is a direct consequence of plasma volume expansion during heat exposure?

• A. Maintenance of stroke volume and improved thermoregulation during heat exposure.
• B. Decreased stroke volume and impaired thermoregulation.
• C. No change in heart function.
• D. Increased risk of dehydration with exercise.

Answer: (A)

Heat acclimation raises plasma volume, which increases venous return to the heart. That extra preload helps preserve end-diastolic volume, so stroke volume can be maintained even as the body warms and skin blood flow increases for heat loss. With stroke volume kept up, cardiac output remains adequate to support thermoregulation, improving how the body dissipates heat during exposure. So the direct consequence is maintenance of stroke volume and improved thermoregulation. If plasma volume didn’t expand, stroke volume would tend to fall as heart rate rises, impairing heat dissipation. The idea that dehydration risk is increased isn’t supported by plasma volume expansion—it's typically the opposite, and saying no change in heart function ignores the preload boost that helps sustain stroke volume.