What is one sign of heat stress?

Profuse sweating and dizziness is indeed a sign of heat stress, reflecting the body's efforts to cool down from overheating. When physical activity occurs, especially in high temperatures or humid conditions, the body heats up. To counteract this, it produces sweat, which evaporates to cool the skin. However, when heat stress becomes severe, the body's mechanisms can become overwhelmed, leading to dizziness as blood flow to the brain is affected, possibly due to dehydration or electrolyte imbalance.

While the other signs listed, such as nausea and vomiting, cold clammy skin, and rapid heart rate with headache, are also indicators of heat-related illnesses, they represent different stages or types of heat-related conditions, such as heat exhaustion or heat stroke. The emphasis on profuse sweating coupled with dizziness specifically illustrates the early warning signs of heat stress.