Part Three
MOUNTAIN TRAINING IS MAINLY USED FOR THE FOLLOWING REASONS:
- improve the ability to use oxygen (via oxidation): training at sea level and recovery at sea level;
- to improve oxygen transport capacity: stay at height (21-25 days) and qualitative training at sea level;
- to improve aerobic fitness: high-altitude training for 10 days.
MODIFICATIONS DUE TO STAY IN HIGH ALTITUDE:
- increase in resting heart rate
- increase in blood pressure during the first days
- endocrinological adaptations (increase in cortisol and catecholamines)
Athletic performance at high altitude
Given that the main purpose of training in altitude is the development of performance, at the center of this training there must be the development of the basic resistance and the resistance to force / speed: however, it must be ensured that all the training methods applied are aimed in the direction of "aerobic shock".
With exposure to high altitude there is an immediate reduction of VO2max (about 10% every 1000 m of altitude starting from 2000m). At the top of Everest the maximum aerobic capacity is 25% above sea level.
For protracted performances, especially aerobic ones (cycling), the advantage deriving from the reduction of the resistance opposed to air is more than offset by the disadvantage due to the reduction in VO2max.
The air density decreases as the altitude increases because atmospheric pressure decreases, but it is also influenced by temperature and humidity. The decrease in air density as a function of altitude has positive effects on respiratory mechanics.
The lactic acid work must be carried out over short distances, with speeds equal to or greater than the race rhythm and with longer recovery pauses than those carried out at low altitude. Load peaks and high lactic stresses should be avoided. At the end of the stay at altitude one or two days of bland aerobic work should be planned. We must avoid mixing training for aerobic power with lactic acid training, as two opposite effects are generated and at the expense of adaptation. After intensive loads, gentle aerobic fitness exercises must be continuously introduced. In acclimatization phases, high workloads must not be applied.
Daily training checks should be conducted in order to: body weight, resting heart rate and in the morning; control of training intensity by heart rate monitor; subjective evaluation of the athlete.
After seven to ten days after returning from the altitude the positive effects can be assessed. The preparation of an important competition should never be preceded by an altitude training for the first time.
The altitude of carbohydrates in the daily diet is important in altitude: it must be equal to sixty / sixty five percent of the total calories. In hypoxia the body requires more carbohydrates on its own because it needs to keep the oxygen requirement low.
A rational diet with an adequate supply of fluids are essential conditions for fruitful high-altitude training.
HIGH LEVEL AGONISM
In the face of a physiological literature rich in data concerning work at high altitudes with the results resulting from acclimatization, the indications aimed at establishing generic suitability (or aptitude) for practicing sports activities of intense competitive commitment in the environment appear reduced or non-existent similar or only slightly lower as height.
A typical example is the Mezzalama Trophy, established about fifty years ago to perpetuate the memory of Ottorino Mezzalama, the absolute pioneer of ski-mountaineering: this race, which arrived at the XVI Edition (2007), unfolds on a highly suggestive and extremely demanding course, that goes from the Plateau Rosa of Cervinia (3300 m) to Lake Gabiet of Gressoney-La Trinité (2000 m), through the snowfields of Verra, the peaks of the Naso del Lyskamm (4200 m) and equipped sections and from "crampon" of the group del Rosa.
Quota factor and intrinsic difficulties create a big problem for the sports physician: which athletes are suitable for such a race and how to evaluate them a priori to reduce the risks of a race that mobilizes hundreds of men to trace the route and guarantee the rescue in this can it really be called a challenge to nature?
The Institute of Sports Medicine of Turin, in assessing more than half of the competitors (about 150 from non-European sources), has developed an operational protocol based on clinical and anamnestic, laboratory and instrumental data. Among these we note as more significant the exercise test: a closed circulator ergometer and a spirometer was used, with an initial load at sea level in O 2 at 20.9370, then repeated at a simulated altitude of 3500 m, obtained by reducing the percentage of O 2 in the air of the spirometric circuit, up to 13.57% corresponding to a partial pressure of 103.2 mmHg (equal to 13.76 kPa).
This test allowed us to introduce a variable: that of the adaptation to the height. In fact, all the routine data did not give significant modifications or alterations for the athletes examined, allowing only one judgment of generic suitability: with the aforementioned test it was possible to analyze the behavior of the pulse of 02 (ratio between consumption of 02 and heart rate, index of cardio-circulatory efficiency), both at sea level and at altitude. The variation of this parameter for the same workload, that is the extent of its decrease in passing from normoxic conditions to an acute hypoxic state, has allowed us to draw up a table to define the aptitude for work at height.
This attitude is all the greater, the lower the O 2 pulse decreases from sea level to altitude.
It was considered reasonable, to grant eligibility, for the athlete not to present reductions above 125%. For more marked reductions, in fact, the security on the state of global physical efficiency appears at least doubtful, even if the uncertainty of an exact definition of the most exposed district remains: heart, lungs, hormonal system, kidneys.
HYPOXIA AND MUSCLES
Whatever the responsible mechanism, the reduced arterial oxygen concentration determines in the organism a whole series of cardio-respiratory, metabolic-enzymatic and neuro-endocrine mechanisms, which in more or less short times lead man to adapt, or rather, acclimatize to the altitude.
These adaptations have as their main objective the maintenance of an adequate tissue oxygenation. The first responses are to the cardiorespiratory apparatus (hyperventilation, pulmonary hypertension, tachycardia): having less oxygen available per unit of volume of air for the same job, it is necessary to ventilate more, and, transporting less oxygen for each stroke volume, the heart must increase the frequency of contraction to bring the same amount of O 2 to the muscles.
The reduction of oxygen at the cellular and tissue levels also induces complex metabolic changes, gene regulation, and mediator release. An extremely interesting role is played in this scenario by oxygen metabolites, better known as oxidants, which act as physiological messengers in the functional regulation of cells.
Hypoxia represents the first and most delicate problem of altitude, since since the medium altitude (1800-3000 m), it causes in the organism that it is exposed to adaptive modifications, the more important the more the altitude increases.
In relation to the time spent at high altitude, acute hypoxia is distinguished from chronic hypoxia, since the adaptive mechanisms tend to change over time, in an attempt to reach the most favorable equilibrium condition for the organism that is exposed to hypoxia. Finally, to try to keep the oxygen supply to tissues constant even in hypoxic conditions, the body adopts a series of compensation mechanisms; some appear quickly (eg hyperventilation) and adjustments are defined, others require longer times (adaptation) and lead to that condition of greater physiological balance which is acclimatization.
In 1962 Reynafarje observed on biopsies of the sartorius muscle of subjects born and resident at high altitude that the concentration of oxidative enzymes and myoglobin was greater in those born and resident at low altitude. This observation served to establish the principle that tissue hypoxia is a fundamental element of the adaptation of skeletal muscles to hypoxia.
An indirect proof that the reduction of aerobic power in altitude is not caused only by the reduced amount of fuel but also by the reduced operation of the engine, comes from the measurement of VO2max at 5200 m (after 1 month of stay) during O2 administration such as to recreate the condition that occurs at sea level.
But the most interesting effect of adaptation due to staying in altitude, is the increase in hemoglobin, red blood cells and hematocrit, which allow to increase oxygen transport to tissues. The increase in red blood cells and hemoglobin would cause a 125% increase compared to sea level, but the subjects reached only 90%.
The other apparatuses show adaptations sometimes not always surely explainable. For example, from the respiratory point of view, the native at altitude presents under stress a pulmonary ventilation smaller than the resident, even if acclimatized.
Currently it is agreed with the statement that permanent exposure to severe hypoxia has harmful effects on the muscles. The relative scarcity of atmospheric oxygen leads to a reduction of the structures involved in the use of oxygen which involves, among other things, the protein synthesis that is compromised.
The mountain environment has disadvantageous living conditions for the organism, but it is above all the reduced partial pressure of oxygen, characteristic of high altitudes, which determines most of the physiological adaptation responses necessary to at least partially reduce the problems caused by altitude.
The physiological responses to hypoxia affect all the functions of the organism and constitute the attempt to reach, through a slow process of adaptation, a condition of tolerance to altitude called acclimatization. Acclimatization to hypoxia means a condition of physiological equilibrium, similar to the natural acclimatization of the natives of regions located at high altitude, which makes it possible to stay and work up to altitudes of around 5000 m. At higher altitudes it is not possible to acclimatize and a progressive deterioration of the organism takes place.
The effects of hypoxia begin to appear generally starting from the medium altitude, with considerable individual variations, related to age, health conditions, training and habit of staying at high altitude.
The main adaptations to hypoxia are therefore represented by:
a) Respiratory adaptations (hyperventilation): increased pulmonary ventilation and increased O2 diffusion capacity
b) Blood adaptations (poliglobulia): increase in the number of red blood cells, changes in the acid base balance of the blood.
c) Cardio-circulatory adaptations: increase in heart rate and reduction in stroke volume.
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Edited by: Lorenzo Boscariol
