Altitude and training

First part

Characteristics of the mountain climate

The first news about a possible influence of altitude on man's physical efficiency are even contained in Million by Marco Polo. The reference is specific to the great heights of the Pamir plateau (over 5000 m), where Marco Polo stayed for a long time to recover after the hardships of crossing Persia and Caucasian Georgia. The interest in the relationship between man and height is therefore very ancient, especially when this combination is evaluated in terms of physical activity, work or sporting practice.
The purpose of this article is to evaluate a more "local" share, that of the "European Alpine habitat, leaving out what concerns the Himalayan or Andean heights, since at our altitudes any physiological data involve or may involve large masses of subjects (skiers , hikers etc. with practical implications more immediate and suited to our medical and sports vision.
At high altitudes, the atmospheric pressure decreases, so that the partial pressures of the air gases decrease accordingly. In Denver, Colorado (the "Mile High City"), the atmospheric pressure of the air is 630 mmHg, while at the top of the Mount Everest is 250 mmHg. The partial pressures of oxygen and carbon dioxide of these two places are:

Denver: Po2= x (630 mmHg) = 132.3 mmHg
P.co2 = x (630 mmHg) = 0.2 mmHg

Mount Everest Po2 = x (250 mmHg) = 52.5 mmHg
P.co2 = x (250 mmHg) = 0.1 mmHg

The atmospheric pressure at sea level is equal to about 760 mm Hg and decreases with the altitude, until it decreases by about half at the altitude of 5500 m a.s.l. (379 mm Hg), to reach 259 mm Hg on Mount Everest (8848 meters above sea level).

The atmospheric pressure is given by the sum of the individual partial pressures of the gases that compose it.

The partial pressure of a gas corresponds to the pressure that that gas would exert if it occupied the entire volume by itself. The direct consequence is that the partial pressures of the individual gases that make up the atmosphere decrease with altitude; however, it is the reduction of the partial pressure of O2 that makes the very survival of organisms at high altitudes more problematic.
The knowledge of the characteristics of the mountain, of the adaptation processes to the altitude, of the suitable technical preparation, of the basic notions of meteorology and orientation, constitute the fundamental basis for those who want to attend the mountains in safety.
The air we breathe is made up of a mixture of gases present in constant percentages (nitrogen 78%, oxygen 21%, carbon dioxide 0.04% and inert gases such as argon, helium, ozone etc. - see: air composition) that do not they change due to the effect of the altitude. The solar irradiation increases with the increase of the altitude, due to the decrease of the atmospheric dust in the air, of the water vapor and of the snow reverberation. It follows the need to adopt precautions (suitable clothing, headgear, sunglasses, protective creams) that protect the body from "excessive exposure to" the action of the sun's rays. The most intense solar radiation at high altitudes can cause high sweating and vasodilation, with consequent dehydration due to the loss of water and mineral salts.
The air at altitude is colder and drier, the effort, if short, is more pleasant, but increases the loss of water (about 8 liters per day at 5000 meters) with severe dehydration if the fluids are not replenished. The cold produces vasoconstriction (to reduce heat loss), chills and tremors (to produce heat, with relative increase in metabolism and energy consumption). Finally, isolation, a situation of objective risk and fear that can arise, the lack of rapid aid, the unexpected change in climate, are conditions that can worsen situations already made difficult by environmental conditions.
In general, it can therefore be said that the mountain climate is characterized by a reduction in barometric pressure and temperature, by the sun and finally by the quality of the air and the weather. It has been shown that the altitude climate stabilizes the autonomic system in our body and causes an increase in specific hormones. The quality of the air in the high mountains is undoubtedly better than that in the plains where there is a high concentration of gas and polluting particles.
At high altitude, during sunny periods, UV radiation increases the ozone rate.

The peculiar characteristics of the mountain climate can be summarized as follows:

reduction of barometric pressure
reduction of the partial pressure of the oxygen PIO2
reduction of air density
reduction of humidity
reduction in the amount of Aeroallergens
reduction of air pollutants
increase in windiness
increase in solar radiation

As the altitude increases, there is also less oxygen reaching our lungs with each breath (due to the reduction in atmospheric pressure); the circulatory system brings less oxygen to the muscle tissues, with a progressive decrease in the efficiency of the organism.

It has been calculated that our abilities decrease by 30% on Mont Blanc, and by 80% on Everest.

If the reaction to the rarefaction of the air is substantially congenital, thanks to a trained physique, good materials and the experience gained, a good "acclimatization" can be achieved by minimizing the inconveniences caused by the altitude.
Many of the people who quickly ascend European mountains above 2,500m have annoying, usually transient, ailments that disappear after two or three days of acclimatization. Lack of acclimatization can give rise to a series of symptoms already at heights of 2000 m which are defined as "acute mountain sickness". They consist of nausea, vomiting, headache, muscle weakness, dizziness and insomnia. These disturbances are subjective, vary with the speed with which a certain altitude is reached and tend to reduce until they disappear as the stay on the high ground is prolonged.

At altitudes above 3000 m there may be acute hypoxia disorders which consist, in addition to those already listed, in difficulty in concentration and a sense of loss or euphoria, conditions that can lead the subject to perform risky and dangerous gestures. In these cases, immediate treatment consists in returning the subject to lower rates. In very rare cases, after 2-3 days of stay above 3500 m, the typical symptoms of acute mountain sickness can become complicated and lead to pulmonary edema or cerebral edema. In both cases it is advisable to promptly bring the subject back to altitudes below 2500 m, subjecting him to oxygen therapy associated with diuretic therapy.

Altitude sickness in brief:

Symptoms: the disorders are characterized by headache, loss of appetite, nausea and vomiting, ringing in the ears, dizziness, mild difficulty in breathing, tachycardia, asthenia, difficulty sleeping, all of which are included under the term altitude sickness.
Therapy: in most cases everything is resolved with aspirin and a little rest.
NB: altitude sickness is mainly caused by the decrease in oxygen in the air, but also the decrease in external temperature and dehydration have some influence.