How does heat acclimation alter sweat rate and plasma volume?

How does heat acclimation alter sweat rate and plasma volume?

• A. Heat acclimation increases sweat rate and earlier onset of sweating, and expands plasma volume to improve thermoregulation.
• B. Heat acclimation decreases sweat rate and later onset of sweating, with no change in plasma volume.
• C. Heat acclimation increases sweat rate but decreases plasma volume.
• D. Heat acclimation has no effect on sweating or plasma volume.

Answer: (A)

Heat acclimation improves the body's ability to dissipate heat by adjusting sweating and plasma volume. Repeated heat exposure expands plasma volume, which helps maintain blood pressure and cardiac output when skin blood flow increases for cooling. This supports more stable circulation and better endurance during heat stress. It also makes sweating more effective: sweating begins earlier at a lower core temperature and the total sweat rate increases, boosting evaporative cooling. Together, the combination of an earlier, greater sweat response and a larger plasma volume enhances thermoregulation in hot conditions. Patterns of reduced sweating, later sweating, or no change in plasma volume would impair cooling and are not typical adaptations to heat exposure.