What is a primary characteristic of heat exhaustion?

Heat exhaustion is primarily characterized by dehydration and fatigue. This condition arises when the body is subjected to high temperatures and excessive fluid loss, often due to strenuous physical activity in hot weather. When the body becomes dehydrated, it loses essential fluids and electrolytes that are necessary for normal physiological function, leading to symptoms such as extreme fatigue, weakness, and sometimes dizziness. Dehydration impairs the body's ability to regulate temperature, creating a situation where the affected individual can feel overwhelmed and exhausted.

In contrast, rapid muscle contractions are associated with conditions like muscle cramps or heat cramps, which may occur during heat-related illnesses but are not a primary characteristic of heat exhaustion itself. Increased body temperature can occur with heat exhaustion, but it is not as defining as the combination of dehydration and fatigue. Joint swelling does not typically relate to heat exhaustion and is more aligned with inflammatory conditions or injuries rather than heat stress. Therefore, the highlighting of dehydration and fatigue encapsulates the essence of heat exhaustion effectively.