Heat acclimatisation is the set of adaptations the body makes when repeatedly exposed to exercise in hot conditions over 1-2 weeks: increased plasma volume, earlier and greater sweating, lower sweat sodium concentration, reduced heart rate and lower core temperature at a given intensity. These adaptations significantly improve performance and safety in the heat. Some evidence suggests heat training (and the plasma volume expansion it causes) can also modestly benefit performance in cool conditions, leading some athletes to use it like altitude training.
Key points
- Adaptations from 1-2 weeks of heat exposure
- Increased plasma volume, earlier sweating
- Lower heart rate and core temperature in heat
- May modestly benefit cool-weather performance too