Which of the following is a symptom of heat stress?

Heat stress can manifest in various symptoms due to the body's inability to properly cool itself when exposed to excessive heat. Among the common symptoms, extreme fatigue is a significant indicator. This fatigue results from the body’s efforts to manage heat and can lead to a decrease in physical performance and overall energy levels.

When the body overheats, it diverts energy towards cooling mechanisms, leaving less energy available for physical activity, thus causing extreme fatigue.

High fever typically indicates an infection or illness rather than heat stress specifically. Swollen hands and feet might occur for different reasons, such as edema, but they are not direct symptoms of heat stress, which primarily affects the body's temperature regulation. Headaches can occur with heat stress, but they are more often associated with dehydration or heat exhaustion, rather than being a defining symptom of heat stress itself.

Thus, extreme fatigue is the most accurate symptom listed that reflects the physiological impact of heat stress on the body.