Last updated: 4 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
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.
- 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
In practice
Training in heat triggers genuine physiological heat-acclimatization adaptations — increased sweat rate, earlier sweating onset, and improved plasma volume — typically developing over 1-2 weeks of consistent heat exposure, which is why athletes preparing for a race in hot conditions often deliberately train in warm environments beforehand rather than relying solely on cooler-climate training and hoping to adapt on race day itself.
FAQ
How long does it take to acclimatize to hot weather training?
Most heat-acclimatization adaptations (increased sweat rate, improved plasma volume, earlier sweating onset) develop over roughly 1-2 weeks of consistent heat exposure, though some benefits continue improving with longer exposure.
Why do athletes deliberately train in heat before a hot-weather race?
Heat acclimatization provides genuine physiological adaptations that improve performance and reduce heat-related risk in hot conditions, so deliberately training in similar heat beforehand is considered far more reliable than hoping to adapt during the event itself.