physiology of training

High ground and altitude sickness

Second part

Already at altitudes of around 2900 m, 57% of people, according to some studies, have at least one symptom of altitude sickness ; of these, 6% cannot continue the excursion. At the altitude of Capanna Margherita (4559 m), 30% of people must reduce activity or stay in bed, and 49% accuse milder symptoms. The most periculous consequence is represented by cerebral edema (HACE).

The most frequent and dangerous mountain sickness (AMS) is the acute type, that is the one that appears suddenly during a climb at high altitude.

The main cause of altitude sickness is the decrease in oxygen in the blood or hypoxemia, which causes an increase in capillary permeability with consequent leakage of fluids (edema) in the lungs and brain.

Pulmonary edema ( HAPE ) is due to the passage of water in the alveoli that normally contain air; causes severe respiratory failure. It manifests itself with difficulty in breathing and tachycardia, cough initially dry and then with pink and frothy spit, noisy breath (rattle), chest tightness and severe prostration. High altitude pulmonary edema occurs more frequently in young people, especially males.

The rate at which pulmonary edema occurs seems to vary from place to place. For example, in the Peruvian Andes almost all cases occur after ascents at 12, 000 feet (3, 600 meters) and beyond, in the Himalayas at 11, 000 feet (3, 300 meters); in the United States, cases of pulmonary edema have been described after ascensions to only 8, 000-9, 000 feet (2, 400-2, 700 meters).

Pulmonary Edema (HAPE): Frequency

Less than 0.2% for trekking or ascents in the alpine area

4% of people affected by trekking in Nepal at altitudes above 4200

Pulmonary Edema (HAPE): Symptoms

At least 2 between: - Shortness of breath (dyspnea) at rest - Dry cough - Tiredness - Decrease in capacity - Constriction or chest congestion

Pulmonary Edema (HAPE): Signs

Wheezing or rales rising on the lungs

Cyanosis

Quick and labored breathing

Tachycardia

Pulmonary Edema (HAPE): Prevention

- Slow and gradual ascent, and, if possible, without the use of transport at high altitude

Acclimatization at high altitude

Nifedipine (ADALAT) 20 mg x 3 per day (starting from 24 hours before the excursion)

Dexamethasone

HAPE therapy

Oxygen

Nifedipine and possibly Desametazone

Descent - Patient evacuation

In cerebral edema (swelling of the brain) there is headache resistant to analgesics, vomiting, difficulty walking, progressive numbness up to the coma.

Severe mountain sickness occurs after lighter symptoms, or suddenly.

Symptoms

- Severe respiratory disorders up to the deadly acute pulmonary edema, that is to the passage of blood in the pulmonary alveoli; edema is determined by pulmonary hypertension and the increased permeability of the alveolar-capillary membrane. A persistent dry cough first appears in succession, then, after a few hours, blood foam in the mouth, great difficulty in breathing and a sense of suffocation; death occurs within about 6 hours if no action is taken.

- Brain edema with strong analgesic-resistant headache, dizziness, jet vomiting, mental confusion, space-time disorientation, hallucinations, apathy, fainting, wrist slowing and arterial hypertension. The skull is rigid and the swelling of the brain compresses the nerve centers causing the disorders described up to the coma, that is, to the complete loss of consciousness followed by death if no action is taken.

Prevention of altitude sickness

It would be advisable for every visitor to the mountain to undergo periodic screening tests, among which we recommend:

• Medical examination

• Basic laboratory tests • Exercise ECG

• Spirometry

- Slow and gradual ascent, and, if possible, without the use of transport at high altitude

- Acclimatization at altitude

- Acetazolamide (DIAMOX) 250 mg x 2 per day (starting from 24 hours before the excursion)

The Barometric pressure and the PIO2 at different heights can be summarized as follows:

ALTITUDE (m) PB mmHg PIO 2
0760159
1000674141
2000596124
3000526100
400046296
500040584

Training at height

The share of interest, for physiological changes, is the one that is between 2500 and 4500 m as the maximum point (Capanna Regina Margherita, Monte Rosa, Alagna Valsesia slope). That these heights already caused problems for their patrons (who, due to the mere fact of getting there on foot, carried out intense physical and sporting activities) was already known at the end of the 19th century, so much so that it binds the mind and heart of one of the great physiology, the Italian Angelo Mosso. It was this passion that led him to create a true laboratory of observation and research, in the first decade of the 1900s, at the Col d'Olen (3000 m, right at the base of the final stretch that allows reaching 4500 m of Capanna Margherita sul Rosa ).

Today the quoted quota is considered as medium-high, according to a sum of observations of climatic meteorological barometric order and, obviously, altimetric.

The altitude can be defined according to various criteria; the most interesting classification takes into account biological and physiological factors, distinguishing 4 distinct levels of quotas based on the modifications induced in the human organism. These limits should not be considered in a rigid manner, as other factors can modulate the response of the organism to hypoxia (subjective response, latitude, cold, air humidity, etc.).

At low altitudes ( up to 1800 m ) the atmosphere pressure ranges from 760 mm Hg to 611 mm Hg. The partial pressure of oxygen (PpO2) ranges from 159 mm Hg to 128 mm Hg. The temperature should decrease by about 11 ° C, in reality it is influenced by various factors (rain, snow, vegetation etc.) that make it very variable. Physiological adaptations are practically absent up to 1200 m asl, since the decrease in PpO2 and arterial oxygen saturation is minimal; the VO2max (maximum aerobic power) according to some authors does not show significant changes, according to others there is already a slight reduction; in any case, all sporting activities can be carried out without particular negative effects.

Up to about 3000 meters the atmospheric pressure varies from 611 mm Hg to 526 mm Hg. PpO2 ranges from 128 mm Hg to 110 mm Hg. Here too, the temperature is influenced by many environmental factors, but generally around 3000 m it reaches 5 degrees below zero. Acute exposure to these heights causes modest hyperventilation, increased heart rate (transient tachycardia), decreased systolic range and increased hematocrit (increase in the number of red blood cells in relation to the liquid part of the blood). After a certain period of time the heart rate tends to go to lower values, but it remains higher than at sea level, while the systolic range is further reduced. Furthermore, with the stay at altitudes above 2000 m the blood viscosity increases. It is therefore legitimate to assume that exposure to these quotas does not cause significant differences in the organism compared to those found at sea level. At these altitudes the increase in blood viscosity seems to be due more to a reduction in the fluid content in the body (which causes a relative increase in the hematocrit), than to a true increase in the production of red blood cells. Normally, during physical exercise there is a loss of fluids, which increases further in altitude and could be among the causes of the Hypoxic Syndrome and of the Mountain sickness, which can also arise at medium altitude. Above 2000 m altitude there is a reduction of VO2max directly proportional to the increase in altitude, which negatively affects endurance sports. While the sports of speed and power (jumps and throws) are favored by the lower force of gravity and the lower density of the air.

From 3000 to 5500 m atmospheric pressure varies from 526 mm Hg to 379 mm Hg. PpO2 ranges from 110 mm Hg to 79 mm Hg. The temperature reaches 21 degrees below zero. At these altitudes the physical activities suffer important limitations as the hypoxic stimulus becomes imposing and the adaptation mechanisms create evident variations in the physiological and metabolic structure. For this reason, physical activity cannot be tolerated for long without adequate acclimatization and training processes.

Extended stays of over 3000 m often result in loss of weight and liquids due to increased energy demands and particular environmental conditions. An adequate increase in caloric intake (especially protein) and salt water is therefore essential. The specific pathophysiology of these quotas includes: damage from cold, acute and chronic mountain disease, pulmonary edema and high altitude cerebral edema. Over 5500 m of altitude, perennial snows are present at any latitude, temperatures reach 42 ° C below zero. In these environments the physiological adaptations do not allow a prolonged permanence. Between 7500 and 9000 m the VO2max can be reduced by 30-40% and serious pathologies can easily affect anyone who stays at these altitudes, even if well acclimatized; the only precaution possible is to minimize the time spent there.

low altitude

average altitude

high altitude

Very hi. quote

Altitude m

0 ÷ 1800

1800 ÷ 3000

3000 ÷ 5500

5500 ÷ 9000

Atmospheric pressure mmHg

760 ÷ 611

611 ÷ 525

525 ÷ 379

379 ÷ 231

Theoretical average temperature ° C

+15 ÷ +5

+4 ÷ -4

-5 ÷ -20

-21 ÷ -43

Alps vegetation

varies

aghifoglie-lich.

lichens

-

Andes vegetation

forest equ.

deciduous

conifer-lichen

-

Himalaya vegetation

trop forest

deciduous

Hardwood-lichens

-

Hemoglobin saturation%

> 95%

94% ÷ 91%

90% ÷ 81%

80% ÷ 62%

VO2max%

100 ÷ 96

95 ÷ 88

88 ÷ 61

60 ÷ 8

symptomatology

absent

rare

frequent

very frequent

The "critical" factors of training in the mountains can be summarized as follows:

Required physical and mental commitment ("hostile environment")

Climatic factors

Experience, degree of training

Equipment adequacy

Age of the subject

Possible individual pathologies (often unknown or undervalued ...)

Knowledge of the itinerary

HYPOXIA

In recent years, many high-level athletes and athletic trainers have included, at various stages of programming, training periods to be held at altitudes between 1800 and 2500 meters, often obtaining significant competitive results in the resistance disciplines. However, the physiological-scientific data appear to be not univocal, achieving a frequent discrepancy between favorable field experiences and scientific research.

Edited by: Lorenzo Boscariol