IB Sports, exercise and health science A.1.2.2 Acute and Long-term Responses to the Heat Notes

Heat Transfer Mechanisms in a Hot Environment

1. When exposed to hot environments, the body works to maintain an optimal internal temperature (around 37 ± 1°C) by using several mechanisms of heat transfer.
2. These mechanisms allow the body to either lose or gain heat, depending on the environmental conditions.

Radiation

1. Heat is transferred through infrared radiation between objects.
2. The body radiates heat into the surroundings, and conversely, heat can be absorbed from the sun or surrounding objects that are warmer than the body.
3. Radiation is most effective when the environmental temperature is lower than the body's core temperature.

Conduction

1. Heat transfer through direct contact with objects or surfaces.
2. When the body comes into contact with a cooler object (e.g., sitting on a cold surface), it loses heat.
3. However, if the object is warmer than the body (e.g., sitting on a hot metal surface), the body absorbs heat.
4. Conduction is less effective than radiation or evaporation, but it still contributes to heat transfer.

Convection

1. The transfer of heat through the movement of air or liquid.
2. Cool air passing over the skin absorbs heat from the body, and warm air can be carried away by wind or ventilation.
3. When air temperature increases, the effectiveness of convection diminishes.

Evaporation

1. Evaporation of sweat from the skin's surface is the primary cooling mechanism in hot environments.
2. As sweat evaporates, it absorbs heat from the body and lowers body temperature.
3. Evaporation is highly effective but depends on humidity levels.
4. In highly humid environments, evaporation is less efficient because the air is already saturated with moisture, reducing the ability of sweat to evaporate.

Acute Responses to Heat