• Heat stress reduces a person's ability to achieve maximal metabolic rates during exercise.

• Heat stress increases the total metabolic rate and anaerobic participation during submaximal exercise, and these increases are somewhat abated by heat acclimatization.

• Exercise-heat stress reduces hepatic blood flow and increases hepatic glucose release.

• Individuals routinely have sweating rates of 1 liter per hour when working in hot environments.

• Dehydration from sweat loss increases plasma tonicity and decreases blood volume, both of which reduce heat loss and result in elevated core temperature levels during exercise-heat stress.

• During exercise-heat stress, competing metabolic and thermoregulatory demands for blood flow make it difficult to maintain an adequate cardiac output.

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