How to prepare for high-altitude conditions?

ALTITUDE PRINCIPLE

In general, ski mountaineering takes place at relatively high altitudes. For instance, the highest point in the Patrouille des Glaciers (PDG) is Tête Blanche, situated at an altitude of 3650 meters. What are the consequences of altitude on our bodies and what adaptations does it require? How can one best prepare to cope with these challenges?

Altitude affects the human body in several ways due to the decrease in atmospheric pressure and oxygen levels as altitude increases. These decreases trigger short-term and long-term adaptation mechanisms.

WHAT ARE THE SHORT-TERM ADAPTATION MECHANISMS?

As previously mentioned, altitude induces a decrease in the partial pressure of oxygen as altitude increases. This reduction leads to a decrease in the amount of oxygen available for breathing, resulting in hypoxemia (low blood oxygen levels), which can manifest as symptoms such as shortness of breath, fatigue, headaches, and dizziness. To compensate for the decrease in oxygen levels in the short term, the body increases its respiratory rate (hyperventilation) to try to offset this decrease. In addition to hyperventilation, the body responds to the decreased availability of oxygen by increasing heart rate and blood pressure in order to supply more oxygen to the tissues.All these factors will have a significant impact on performance. So, it's important to keep that in mind when you're training at altitude.

WHAT ARE THE LONG-TERM ADAPTATION MACHANISMS?

Long-term adaptations to altitude encompass various physiological adjustments that gradually develop in response to prolonged exposure to high altitudes. The speed and extent of these adaptations vary from individual to individual and are influenced by factors such as genetics, prior fitness level, and the speed of ascent to altitude. Typically, the body requires an adaptation phase of at least 8 days. These multiple adaptations aim to enhance the body's ability to function effectively in high-altitude environments. Here are some examples of long-term adaptation mechanisms. In response to chronic hypoxia, the body stimulates the production of red blood cells and blood volume to improve oxygen transport to tissues, thereby enhancing the utilization of available oxygen. This also leads to an increase in the synthesis of hemoglobin, a protein present in red blood cells that binds and transports oxygen throughout the body. Additionally, capillary density increases, promoting the diffusion of oxygen from blood vessels to muscle tissues, contributing to improved altitude adaptation.

HOW BEST TO INCORPORATE ALTITUDE INTO PREPARATION FOR THE PDG?

In order to prepare for facing the high altitudes of the Patrouille des Glaciers, it is important to consider the aforementioned elements. Chronic exposure to altitude allows for good acclimatization and thus helps to mitigate the effects of altitude sickness.

What is meant by chronic exposure?

Typically, chronic exposure to hypoxia refers to when arterial oxygen saturation (SaO2) increases compared to the measurement taken upon arrival at altitude. This adaptation process generally takes about a week to establish.

How to proceed?

Since the acclimatization process is not instantaneous, it is wise to spend time at altitude to prepare for the patrol. The best way is to organize a training camp at altitude. As discussed earlier, this should last at least 1 week to derive real benefit from it. However, spending time in hypoxia is more complex than it seems, and it is important to adjust your program accordingly. Since it is a severe environment, each effort will induce greater fatigue, and recovery will take longer.

Some basic principles:

• Since oxygen is bound to hemoglobin by iron molecules (Fe), a person deficient in iron should avoid excessive exposure to hypoxia. If this applies to you, then iron supplementation before and during the stage is important.
• As hypoxia is a severe environment, adjusting your pace is crucial. You cannot expect to ascend at the same rate when you are at 3000m as when you are at 2000m. Typically, you should reduce intensity by about 7% per 1000m of altitude gain. So, if you are able to maintain a base endurance pace of 800m/h at 2000m altitude, you should aim for around 700m/h at 3500m.
• To gauge our fatigue level, it is important to continuously measure our heart rate (HR). Indeed, it should decrease during sub-maximal exercise as well as at rest, which is evidence of good acclimatization. The same goes for SaO2. It can be measured using a pulse oximeter, but some smartwatches also allow for this type of measurement.
• Nutrition should be adapted. During chronic exposure to altitude, our metabolism will preferentially degrade carbohydrates. It is therefore important to consume them in quantity to replenish stocks. Additionally, since mountain air is drier than at lower elevations, proper hydration is crucial.

What to avoid?

If you plan to undertake altitude training, it is important to arrive in good shape at the beginning. Acclimatization mechanisms to hypoxia take longer to establish if you are tired. Just because the PDG goes to extreme altitudes does not mean you should seek to do your entire camp at a similar or nearby altitude. Indeed, sleep quality is greatly affected by hypoxia, and camping at too high an altitude could lead to detrimental overfatigue for performance. Typically, an altitude between 2200 and 2500m for sleeping is ideal, and training can be done a bit higher. During the acclimatization phase (1st week), it is necessary to respect reduced paces and a lower training volume compared to what one is accustomed to.

To learn more about altitude and hypoxic training:

• Bonetti, Darrell, et Will Hopkins. 2009. « Sea-Level Exercise Performance Following Adaptation to Hypoxia ». Sports medicine (Auckland, N.Z.) 39 (février): 107‑27. https://doi.org/10.2165/00007256-200939020-00002.
• Chapman, Robert F., James Stray-Gundersen, et Benjamin D. Levine. 1998. « Individual variation in response to altitude training ». Journal of Applied Physiology 85 (4): 1448‑56. https://doi.org/10.1152/jappl.1998.85.4.1448.
• Garvican-Lewis, Laura A., Iona Halliday, Chris R. Abbiss, Philo U. Saunders, et Christopher J. Gore. 2015. « Altitude Exposure at 1800 m Increases Haemoglobin Mass in Distance Runners ». Journal of Sports Science and Medicine14 (2): 413‑17.
• Issurin, Vladimir. 2007. « Altitude Training: An up-to-Date Approach and Implementation in Practice ». https://www.vdu.lt/cris/handle/20.500.12259/139370.
• Levine, Benjamin D. 2002. « Intermittent Hypoxic Training: Fact and Fancy ». High Altitude Medicine & Biology 3 (2): 177‑93. https://doi.org/10.1089/15270290260131911.
• Millet, G. P., & Schmitt, L. (2011). S'entraîner en Altitude. De Boeck.
• Richalet, Jean-Paul, Paul Robach, Sébastien Jarrot, Jean-Christophe Schneider, Nicholas P. Mason, Emmanuel Cauchy, Jean-Pierre Herry, Annick Bienvenu, Bernard Gardette, et Claude Gortan. 1999. « Operation Everest III (COMEX ‘97) ». In Hypoxia: Into the Next Millennium, édité par Robert C. Roach, Peter D. Wagner, et Peter H. Hackett, 297‑317. Advances in Experimental Medicine and Biology. Boston, MA: Springer US. https://doi.org/10.1007/978-1-4615-4711-2_23.