Distinguish thermoregulatory acclimation from metabolic acclimation in heat adaptation.

• A. Thermoregulatory acclimation reduces resting metabolic rate
• B. Thermoregulatory acclimation improves heat dissipation efficiency and fluid balance; metabolic acclimation involves changes in resting metabolic rate and substrate utilization
• C. Metabolic acclimation improves skin vasodilation
• D. Thermoregulatory acclimation only occurs at night

Answer: (B)

Thermoregulatory acclimation and metabolic acclimation are two ways the body adapts to heat. Thermoregulatory acclimation involves improving the body's ability to lose heat and manage fluids—think more efficient sweating, better skin blood flow for heat dissipation, and expanded plasma volume to support circulation and cooling. Metabolic acclimation focuses on how energy metabolism changes with heat exposure, including shifts in resting metabolic rate and substrate use to reduce heat production and improve energy efficiency.

This is why the best statement says that thermoregulatory acclimation improves heat dissipation efficiency and fluid balance, while metabolic acclimation involves changes in resting metabolic rate and substrate utilization. The other options mix these concepts: skin vasodilation is a thermoregulatory process, not metabolic; resting metabolic rate changes are metabolic acclimation, not solely thermoregulatory; and thermoregulatory acclimation is not restricted to nighttime.