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 Marco Polo's Million . The reference is specific to the great heights of the Pamir plateau (over 5000 m), where Marco Polo stayed a long time to recover his strength after the inconveniences of the crossing of Persia and Caucasian Georgia. The interest in the man-share relationship is therefore very ancient, especially when this combination is assessed 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 aside what concerns the Himalayan or Andean heights, since to our quotas the possible physiological data involve or can involve large masses of subjects (skiers, hikers etc. with more immediate practical implications and suitable to our vision of medical and sports.

At high altitudes, atmospheric pressure decreases, so that the partial pressures of the air gases diminish accordingly. In Denver, Colorado (the "Mile High City"), atmospheric air pressure is 630 mmHg, while at the top of Mount Everest is 250 mmHg. The partial pressures of oxygen and carbon dioxide in these two places are:

Denver: Po ₂ = (0.21) x (630 mmHg) = 132.3 mmHg

P co ₂ = (0.0003) x (630 mmHg) = 0.2 mmHg

Mount Everest P o ₂ = (0.21) x (250 mmHg) = 52.5 mmHg

P co ₂ = (0.0003) x (250 mmHg) = 0.1 mmHg

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

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 alone. The direct consequence is that with the altitude the partial pressures of the individual gases that make up the atmosphere diminish; however it is the reduction of the partial pressure of O2 that makes the survival of the organisms at great altitudes more problematic.

The knowledge of the characteristics of the mountain, of the processes of adaptation to the altitude, of the appropriate technical preparation, of the basic notions of meteorology and orientation, constitute the fundamental basis for those who want to attend the mountain safely.

The air we breathe consists of a mixture of gases present in constant percentages (78% nitrogen, 21% oxygen, 0.04% carbon dioxide and inert gases such as argon, helium, ozone etc. - see: air composition) that do not they change due to the quota . Instead, solar irradiation increases with increasing altitude due to the decrease in atmospheric dust in the air, water vapor and snow glare. It follows the need to take precautions ( appropriate clothing, headgear, sunglasses, protective creams) that protect the body from excessive exposure to the action of sunlight. The most intense solar radiation at high altitude can cause high sweating and vasodilation, with consequent dehydration due to loss of water and mineral salts.

The air in 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 a serious state of dehydration if the liquids are not replenished. The cold produces vasoconstriction (to reduce heat loss), chills and tremors (to produce heat, with a relative increase in metabolism and energy consumption). Finally, isolation, a situation of objective risk and of fear that can arise, the lack of a rapid rescue, the unexpected variation of the climate, are conditions that can worsen situations already made difficult by the environmental conditions.

In general, it can therefore be stated that the mountain climate is characterized by a reduction in barometric pressure and temperature, by insolation and finally by the quality of air and time. It has been shown that the altitude climate stabilizes the neurovegetative system in our body and causes an increase in specific hormones. The quality of the air in the high mountains is certainly 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:

Barometric pressure reduction

reduction of the partial pressure of oxygen PIO2

air density reduction

Humidity reduction

reduction in the amount of Aeroallergens

reduction of Aero-pollutants

increased windiness

increase in solar radiation

As the altitude increases, there is also a smaller amount of oxygen that reaches our lungs with each breath (due to the reduction of atmospheric pressure); the circulatory system brings less oxygen to the muscle tissues, with a progressive decrease in the body's efficiency.

It has been calculated that our capacities 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 matured experience, good "acclimatization" can be achieved by minimizing the inconveniences caused by the altitude.

Many of the people who go up quickly in the European mountains above 2, 500 m have annoying disorders, usually transient, that disappear after two or three days of acclimatization. Failure to acclimatize can already give rise to heights of 2000 m to a series of symptoms that are defined as " acute mountain sickness ". They consist of nausea, vomiting, headache, muscle fatigue, dizziness and insomnia. These disorders are subjective, they vary with the rapidity with which a certain altitude is reached and tend to be reduced until they disappear as the stay in high altitude continues.

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

High altitude sickness:

Symptoms: the disorders are characterized by headache, loss of appetite, nausea and vomiting, ringing in the ears, dizziness, slight difficulty in breathing, tachycardia, asthenia, difficulty sleeping; all these are included under the term of altitude sickness.

Therapy: in most cases everything is solved with aspirin and a little rest.

NB: altitude sickness is caused mainly by the decrease in oxygen in the air, but also the decrease in the external temperature and dehydration have some influence.