In the summer period, many athletes choose to go to the mountains to practice sports. In addition, many of them take advantage of the good weather to do "Concentrations in height" in order to take advantage of the benefits of this training.
But it is important that they do not forget a fundamental aspect during these stays in height: nutrition, since not everything is training and resting.
What happens to our body in height?
To see how nutrition affects this type of trainingThe first thing is to see what happens to the body when training in these conditions.
When you are in altitude, the atmospheric pressure decreases (although the oxygen concentration does not), also decreasing the amount of oxygen that we can breathe in with each breath.
When the amount of oxygen you breathe in is reduced, so does your peak oxygen uptake (VO2max) and therefore overall performance (decreases every 1.000 meters of height)
There is a example that shows this in a very clear way:
A study with endurance athletes showed that VOXNUMX2max decreased an average of 6,3% for every 1.000 meters of altitude with respect to sea level (1).
Taking as an example, High Performance Center of Sierra Nevada (2.300 meters), athletes would experience a drop in VOXNUMX2max of around 12%.
In addition, they experienced an even greater loss of performance (14,5% per 1.000 meters of height) in a test they did until exhaustion at VOXNUMX.2max.
The importance of carbohydrates when exercising at altitude
Carbohydrates are the main source of energy during exercise, especially when performed at high intensity (> 60 - 80% VO2max).
When you exercise at altitude, this carbohydrate intake increases.
Traditionally it was believed that this is because the body needs less oxygen to generate energy from carbohydrates than other substrates such as fats.
A study shows that carbohydrate metabolism increases when exercising at height.
A study published in the journal PNAS (2) showed that, indeed, carbohydrate metabolism increases when exercising at height.
However, the researchers found that the same amount of carbohydrates is metabolized at the same percentage of VO always (both at sea level and at altitude)2max.
That is, if we exercise at 60% of our VO2max, we are going to metabolize the same amount of carbohydrates whether we are at altitude or at sea level, although that same physiological intensity will mean a lower external intensity (that is, a lower speed or power) when exercising at altitude.
This means that you have to eat more carbohydrates when exercising at height, since it is done with a higher relative intensity than if we do it at sea level.
Supplementing with carbohydrates in height, is it more necessary?
It is known that carbohydrate supplementation is beneficial in any type of endurance sport, although when it is done in height they are more evident.
Another study of 41 mountaineers (at 5.192 meters) who underwent a kind of time trial showed that the group that had taken carbohydrates had a perception of effort 18% lower in addition to completing the test 17% faster than those who took the placebo (3).
In another study conducted on trained athletes (4), they did a cycling time trial at sea level. Later they did another at 3 and 10 days after climbing to 4.300 meters. Half of these athletes had carbohydrates during the test and the other half a placebo drink.
The results showed that in height the oxygen saturation was similar in both groups and all the subjects worsened their performance with respect to sea level.
But we must take into account another data from the study, which showed that the performance drop was less (almost a 20% difference from the placebo group) in the carbohydrate group.
It is important to note that in this study the subjects were in a caloric deficit, something common in stays at height - since our body increases basal energy consumption, and the amount of energy for the same exercise is also increased -.
However, another subsequent study conducted in people who habitually resided in height and who did not have a caloric deficit did not observe benefits from carbohydrate supplementation (5).
Conclusion: So you have to eat more carbohydrates?
Carbohydrates are the main source of energy when doing intensity exercise. If training is done at altitude this relative intensity increases.
Therefore, for the same effort (for example, jogging at 5 min / km) the consumption of carbohydrates will be much higher when training in height, so supplementation would help to delay the depletion of glycogen and thus improve performance, or at least to mitigate the decline or loss of it.
The results of these studies are especially relevant in athletes who have little acclimatization to altitude (1 - 2 weeks) and especially if they are in energy deficit.
Wehrlin JP, Hallén J. Linear decrease in VO2max and performance with increasing altitude in endurance athletes. Eur J Appl Physiol. 2006; 96 (4): 404–12.
Mcclelland GB, Hochachka PW, Weber JM. Carbohydrate utilization during exercise after high-altitude acclimation: A new perspective. Proc Natl Acad Sci US A. 1998; 95 (17): 10288-93.
Oliver SJ, Golja P, MacDonald JH. Carbohydrate supplementation and exercise performance at high altitude: A randomized controlled trial. High Alt Med Biol. 2012; 13 (1): 22–31.
Fulco C, Kambis KW, Friedlander AL, Rock PB, Muza SR, Cymerman A. Carbohydrate supplementation improves time-trial cycle performance during energy deficit at 4,300-m altitude. J Appl Physiol. 2005; 99 (3): 867–76.
Fulco CS, Zupan M, Muza SR, Rock PB, Kambis K, Payn T, et al. Carbohydrate supplementation and endurance performance of moderate altitude residents at 4300 m. Int J Sports Med. 2007; 28 (5): 437–43.