Which individual would be at the highest risk of exertional heat stroke?

The individual at the highest risk of exertional heat stroke is a high school football player in the first few days of practice under hot and humid conditions. During this period, athletes are often exposed to intense physical activity, which increases their metabolic rate and generates significant internal heat. High temperatures in the 90s, combined with high humidity, hinder the body’s ability to cool itself through sweating; the effectiveness of evaporation decreases when the air is saturated with moisture.

Additionally, young athletes may not be fully acclimatized to the conditions, especially during the start of practice sessions, making them more susceptible to heat-related illnesses. They might not recognize the signs of heat stress, which can lead to a progression to heat stroke if not addressed promptly. The combination of strenuous activity and environmental factors places this individual in a heightened risk category compared to others listed in the question, where either insufficient physical exertion, better environmental conditions, or older age contribute to a lower risk profile for heat stroke.