Kilian Jornet offers advice on proper acclimatization

Kilian Jornet divides his time between trail running and ski-mountaineering. This high-level athlete has also set his sights on climbing high-altitude peaks. In this article, learn more about the methods he uses to acclimatize at high altitude.

Why the need to acclimatize?

Physical activity at altitude is difficult because our bodies are starved for oxygen. Contrary to popular belief, the percentage of oxygen in the air does not change significantly as you rise in altitude; in reality, it all has to do with pressure.

The higher above sea level you are, the lower the atmospheric pressure (the air is “thinner”). Atmospheric pressure determines the density of the air, so the higher you go the less actual air there is to breathe. Although the percentage of oxygen in the air does not change, the number of oxygen molecules available to breathe decreases the higher you climb.

Oxygen provides fuel to our muscles during aerobic activity (endurance), and the reduced amount of oxygen to breathe means less fuel for our muscles, so our muscles feel tired and more sluggish than normal.

To offset this need for oxygen, the body adapts in different ways

• As we ascend to higher altitudes than normal, our breathing rate increases. This increases the body’s production of carbon dioxide (CO2), which in turn raises the level of acidity in the body. The kidneys regulate this acidity. To avoid kidney problems and their ability to regulate CO2 levels, it is important to stay well hydrated (drink a lot) and breathe warm, moist air. If you stop urinating, it means that you have a kidney problem.
• 24 hours after reaching altitude the body increases EPO production, raising the number of red blood cells in order to transport more oxygen. The creation of more red blood cells is referred to as blood acclimatization.
• After 7 days we see an increase in hematocrit and the effects of blood acclimatization.
• After 3 weeks / 400 hours, our body has finished acclimatizing (at a given altitude).

It is important to understand that SaO2 (Oxygen Saturation) decreases when we sleep (we breathe less and our body is in a state of rest), and the body reacts poorly at altitude to this phenomenon. It takes three to four hours after waking up to reach normal SaO2 levels. During this time it is difficult to be active or to continue ascending. When acclimatizing, the best way to recover at altitude is to remain awake when resting. 

The right altitude for training: pre-acclimatizing before heading to high altitudes

The body “remembers” how to acclimatize, and if you have already spent time at high altitude in the past, the body will have developed mechanisms to adapt more quickly and efficiently. Experience at altitude, a little or a great deal, does not mean that you will never have problems when acclimatizing. Every time you head back to higher altitudes you will need to acclimatize. Everybody experiences problems (Acute Mountain Sickness/AMS, and edemas in much rarer cases) at altitude at some point.

The altitude where you train and/or live also has an effect on pre-acclimatization

If you have been training at 4000m elevation for a few months, you will probably be able to head straight to 5000m and climb a 6000m summit in a relatively short period of time. If you live at sea level, the time to acclimatize will be longer and much more progressive. As a general rule, you should be able to comfortably ascend 1000m above the elevation where you live and/or train without any need to acclimatize.

Someone in good shape, with a solid aerobic base from training should be able to easily handle the first stages of acclimatization. However, being fit does not necessarily make acclimatization quicker and easier.

Why anaerobic workouts are so useful

Anaerobic workouts before venturing to high altitude are worthwhile. At altitude, most of us are able to maintain a normal pace (slow), but as soon as the cadence increases or we have to make an anaerobic effort for even a few seconds (sprint), the recovery time takes a while. It is hard for our bodies to eliminate the lactic acid at higher elevations and our muscles will feel sluggish for some time.

It is for this reason that anaerobic workouts are so useful; they contribute to improving the body’s ability to eliminate lactic acid and raise the intensity threshold at which our muscles produce lactic acid.

Training session examples: threshold workouts, 30”x30” intervals, or even Vertical Kilometer races.

Triggering body’s mechanism for acclimatizing

From an elevation at which we are comfortable, we have to ascend 1000m-2000m higher to trigger the body’s acclimatization mechanism. 

For example, if you live at sea level and your goal is to climb the 4810m-high Mont Blanc:

• Spend two days climbing to 3000m while sleeping each night at 2000m.
• Then, spend one or two more days climbing to an elevation between 3600-4000m, spending the night at 3000m.

If you feel good at these altitudes, you should be able to make a summit push (1000 meters above your prior high point).

Pay attention to the signs of Acute Mountain Sickness

At high altitude it is important to pay attention to the signs of AMS (Acute Mountain Sickness, aka Altitude Sickness). Here is a great rule of thumb: if you are not feeling well, it is most likely due to the altitude!

AMS (Acute Mountain Sickness)

• Headache – 1 point
• Nausea – 1 point
• Loss of appetite – 1 point
• Vomitting – 2 points
• Persistent headache – 2 points
• Extreme fatigue (beyond normal) – 3 points
• Unable to urinate – 3 points

If you experience one or more of these symptoms and they add up to 6 points, you have AMS and should immediately head down to a lower elevation. Choosing to continue will place you at risk for pulmonary or cerebral edema, or even death.

So make sure to prepare ahead of time, train, and gain altitude progressively in order to safely enjoy the beauty of the mountains!