Heat acclimatisation
Heat acclimatisation is the degree to which your body is adapted to exercise in the heat. Someone who is used to it performs better and more safely on hot days than someone who goes in cold.
What happens during heat acclimatisation?
Training in the heat forces your body to shed heat, and after repeated exposure it adapts: you start sweating earlier and more freely, your sweat becomes lower in salt (you hold sodium back better), your blood volume increases and your heart rate at the same effort drops. Together those adaptations mean your core temperature rises more slowly and the effort feels less hard.
The adaptation comes fast but is fleeting: most people notice the first effects within about a week, with most of it in place after some two weeks of regular hot training. Stop, and the acclimatisation fades again over the course of weeks — it isn’t a lasting possession.
How do you build up heat acclimatisation?
The stimulus is regular, controlled exposure: easy to moderate sessions in the heat, built up gradually in duration, in the weeks before a hot race. Don’t force it with all-out work in full heat — that mainly raises the risk of overheating without speeding up the adaptation.
Mind the conditions: on hot days your sweat loss rises and with it your fluid and sodium needs, and overheating stays a real risk as long as you’re not yet used to it. Recognise the signs of heat trouble — dizziness, goosebumps, nausea or suddenly stopping sweating — and stop immediately. If someone becomes confused or loses consciousness: call 112.
How Trimetra personalises this
Trimetra tracks your heat acclimatisation based on your own training and the matching weather data, rather than a general rule. While you’re not yet used to the heat, the app gives suitable session guidance on hot days and tops up your drinking advice; as your acclimatisation grows, that scales back with it.
Frequently asked questions
How long does it take to adapt to training in the heat?
Most people notice the first effects within about a week; the bulk of the adaptation is there after roughly two weeks of regular warm training. The adaptation is fleeting though: stop, and it disappears again over the course of weeks.
Why is your heart rate higher on a warm day?
Your body has to cool as well as work: blood is routed to your skin and you lose fluid through sweat. As a result your heart beats faster at the same pace. As your heat adaptation grows, that effect shrinks.
How do you prepare for a hot race?
Build controlled exposure in the weeks before: easy to moderate sessions in the warmth, gradually longer. Don’t force it with brutal work in full heat — that mainly raises the risk of overheating without speeding up the adaptation.
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