What Heat Acclimatisation Is
Heat acclimatisation is the body's adaptation to repeated heat exposure - typically over a 10-14 day period of training or living in hot conditions. The adaptations are real, measurable, and useful for anyone training or competing in heat.
What Actually Adapts
Plasma volume expansion. Blood volume increases, which improves cardiovascular efficiency during heat stress.
Earlier sweating onset. An acclimatised body starts sweating sooner, getting evaporative cooling underway earlier in a session.
Higher peak sweat rate. Sweat output can increase substantially with acclimatisation.
Reduced sweat sodium concentration. Counterintuitively, an acclimatised body conserves sodium better, sweating less salty.
Lower core temperature at the same workload. The overall effect is that the same effort costs less heat-stress strain.
The Timeline
Most of the adaptations happen in the first 7-10 days of repeated heat exposure. By day 14, you've captured most of what acclimatisation offers. The adaptations decay if you stop exposing yourself to heat - within 2-3 weeks back in cool conditions, most of the benefit fades.
Practical Implications for Australian Athletes
For athletes preparing for a hot race or a hot training camp, deliberate heat acclimatisation in the 2 weeks beforehand is well-supported in the research. For everyday active Australians, gradually building outdoor exposure across spring before the worst of summer makes the summer-training months noticeably easier.
Hydration During Acclimatisation
Acclimatisation works best when you're well-hydrated. Don't dehydrate yourself trying to "toughen up" - that's the old-school approach that the research has long since moved past. Drink to thirst plus a sodium-containing product as needed.
Sources
Authoritative references this article draws on. External links open in a new tab.
Frequently Asked
How long does heat acclimatisation take?
Most adaptations happen in the first 7-10 days of repeated heat exposure. By day 14, you've captured most of what acclimatisation offers.
Do you lose heat acclimatisation?
Yes - within 2-3 weeks back in cool conditions, most of the adaptation fades. Maintenance needs ongoing heat exposure.
How can I acclimatise for a hot race?
Train in heat (or use heat exposure protocols like sauna sessions) in the 2 weeks before the event. Keep hydrating well - dehydration counteracts adaptation.
