Why train at altitude?

Julien Chorier, multiple winner of ultras trails and trail ambassador for Val Thorens, gave us some advice on how to make the most of your sporting holiday at altitude. First of all, you need to know that there is an optimum altitude for sleeping and training. Then, the benefits are not the same depending on the athlete's speciality and the planning of the course, you also need to take into account the acclimatisation time, the frequency of training... we explain it all in this article!

At what altitude should you train?

When choosing the location for your training course, you need to take altitude into account. In theory, the higher you go above sea level, the greater the effect, but be careful not to go higher than 3,000 metres, because beyond that altitude, the fatigue will become too great! In reality, altitude only becomes beneficial from around 1,700 metres and, for a traileur, the optimum zone is around 2,300-2,500 metres for sleeping and training in order to feel the physiological benefits. 2,300 metres... That's why Julien Chorier chose Val Thorens for his training courses!

Obviously, the longer you stay, the greater the benefits.

Julien Chorier

This altitude is particularly advantageous for runners, as they never run at the same pace, whereas sprinters, for example, are quickly limited because they cannot run at their specific pace, but at a lower speed. They may even lose their usual running pace, because by repeating the same strides but at a lower speed, they will keep that habit and that speed when they return to the flat!

On the other hand, it's a good idea for sprinters to sleep at altitude in order to increase their rate of production of red blood cells, but then come down to the plain (to Moûtiers in the case of Val Thorens) to work on their strides".

Change altitude to optimise your sports preparation

Julien's second piece of advice for optimising his preparation is to change altitude during his stay, i.e. sleep at 2,300m but go up to train at 3,000m. "Be careful, though, that you're already well acclimatised to the altitude, and that you change gradually, as acclimatisation can be slow for some people and any effort becomes complicated. The best strategy is to start your preparation slowly with a short jog, for example at the Bruyères lake (in Les Menuires) when you're in Val Thorens, then gradually climb back up to altitude to acclimatise gently.

You can also alternate hiking and running, with the added bonus that hiking is an activity you can share with your family! People who are not used to running for long periods or often need to be all the more careful about acclimatisation; it would be a shame to want to increase your usual training frequency too quickly and then be so tired after 4 days that you can't train any more...".

What is the optimum length of stay at altitude?

For top-level athletes, sportsmen and women who are used to or react well to altitude: the trip starts to become interesting after two weeks, or sometimes even a week. For a week, allow 2 or 3 days for acclimatisation, during which you need to be patient and not try to make the most of your time, otherwise you'll be more tired than you'll benefit, followed by 4 or 5 days of training. It's therefore more worthwhile to stay longer in order to train more and get more lasting benefits after the course. In fact, for a one-week course, you'll only feel really fit during the week following your stay at altitude.

For beginners or those unaccustomed to altitude, we recommend a minimum of 2 weeks on site and ideally 3 weeks: a week of gradual acclimatisation, a week of work and a week of recovery on site to optimise the stay.

For a stay before a major race, the benefits of a major training course can be felt:

  • 2 to 3 days after your return,
  • between 10 and 15 days after the end of the course.

Between these two periods, the body absorbs the fatigue of the course and needs to rest.

Julien, for example, tries to come to Val Thorens regularly for a refresher course, training for a week at each school term and for two or three weeks at the beginning of August so that he's in good shape for the UTMB!

Don't forget to let us know if you feel any improvement after your stay in the mountains!


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