Heat Acclimatisation: The Legal Performance Edge Almost Nobody Uses

Before a major race in the mountains, most athletes focus on altitude preparation, live high, train high, or some variation of the protocol. Far fewer consider heat acclimatisation, and yet the physiological adaptations it produces are well documented, genuinely significant, and available to any athlete willing to run a bit warmer for a few weeks.

Heat acclimatisation triggers a cascade of adaptations: increased plasma volume, lower heart rate at a given effort, earlier and more efficient sweating, and improved cardiovascular stability during exercise. Crucially, the increased plasma volume translates directly to better performance even in cool conditions, making heat training a tool with broader application than its name implies.

The Protocol

You don't need a heat chamber or a desert climate. A practical approach involves performing a portion of your training in conditions warmer than you would normally choose, finishing a run in the warmest part of the day, wearing an extra layer during easy sessions, or spending time in a sauna post-workout. The key variable is core temperature: you need to elevate it meaningfully and sustain that elevation for 30 to 60 minutes per session.

A typical protocol runs 10 to 14 days. Research suggests that significant adaptations begin to appear within five to eight sessions, and the gains are largely retained for two to four weeks after the protocol ends, making timing relative to your target event something worth planning carefully.

Doing It Safely

Heat training carries real risks if approached carelessly. Hydration becomes critical, you are sweating more than usual and plasma volume expansion requires adequate fluid intake. Never push intensity in the heat the way you would in cool conditions; the cardiovascular strain is meaningfully higher. Start with easy efforts and shorter durations, building across the protocol just as you would build any other training load.

Monitor your resting heart rate and general wellbeing as you go. Some fatigue is expected. Significant performance degradation or sleep disruption suggests you are overdoing it. Like all training stimuli, the adaptation comes during recovery, not during the session itself. Respect that, and the heat will work for you in ways that will show up on race day.