Bytagread the publication "Heat acclimatization: what is the Garmin indicator really worth?"
Every year, the scenario repeats itself: the first big heatwaves arrive, and despite solid training, the sensations are bad. We plateau more quickly, we sweat profusely, and the watts are harder to get out. This phenomenon, well-known to cyclists, is called heat acclimatization. But for the past few years, Garmin GPS devices have been displaying a heat acclimatization indicator. An intriguing piece of data: is it reliable? What does it correspond to? And above all, how long does it actually take for our bodies to adapt to the heat?
By Jeff Tatard – Photos: depositphotos.com, D.R.
To get a clearer picture, we spoke with José Lopez, coach reconnaked and experienced, who follows many amateur and professional athletes. His analysis qualifies technological certainties.
Data integrated into the Garmin ecosystem
The heat acclimatization indicator is offered by Garmin GPS devices compatible with the Firstbeat platform. To work, several criteria must be met:
- Outdoor outings, with ambient temperature measurement via GPS.
- A temperature above 22°C during activity.
- Wearing a heart rate monitor, and ideally a power meter.
Based on this, Garmin displays an acclimatization rate that is supposed to reflect your current ability to withstand heat.
But José Lopez tempers: " What Garmin is measuring isn't a deep physiological adaptation; it's your recent heat exposure. It's a good indication of context, but it's not a definitive verdict on fitness. »
How long does it really take to acclimatize?
According to scientific literature, complete heat acclimatization requires approximately 7 to 14 days of regular exposure. But it requires well-targeted efforts, carried out in the heat, at an intensity sufficient to generate heat stress. José explains: " The first outing in temperatures below 30°C, even when well-trained, is always difficult. It takes about a week for the body to begin to react: a more stable heart rate, more efficient sweating, less overheating. »
Physiologically, adaptation involves:
- An increase in plasma volume, which improves heat transport.
- Faster and less salty sweating, therefore more effective.
- A lower heart rate at equivalent intensity.
- A perception of effort that gradually softens.
This is why we often observe a great difficulty in the first heat, a little less in the second, and a clear improvement after several close exposures.
What Garmin says (and doesn't say)
Garmin does not directly measure this physiological adaptation, but relies on your warm-weather training history. The higher the temperature you ride in, the higher your score will be. If you stay cool for a few days, it will drop. José Lopez sums it up: " This isn't a measure of your potential, but a useful guide to adapting your current training. If your rate is low, there's no point in striving for high intensities; you risk burning yourself out. »
A relevant tool, but one to be used with discernment
In practice, this indicator can be a decision-making tool:
- If your score is low, stay modest on the intensities.
- If you are preparing for a summer race, gradually expose yourself to the heat 10 to 15 days beforehand.
- Monitor your sensations, your heart rate and your recovery.
Garmin can also encourage you to vary your outing times: “ Training at 28°C is sometimes worth more than a threshold block below 20°C when preparing for a heatwave race. " insists José.
In conclusion
Garmin's heat acclimatization indicator doesn't replace experience, but it can enhance it.It allows you to put a session into context, to modulate the intensity, or to validate a thermal adaptation phase.
But as always, it is the athlete who remains at the center of the game: " You can be 100% on Garmin and still explode on the route if you forget the essentials: drink, listen to your body, manage your effort. »
A tool, not an absolute truth — but a real way to train smarter when the thermometer rises.
