Increased rate of breathing:
To compensate for the decrease in the alveoli, breathing rate increases. This response develops of several days and not instantly. The demand for oxygen is the same except that the partial pressure is low therefore a fast and more frequent supply is needed. The increase in breathing reduces the partial pressure of carbon dioxide, which makes the blood too alkaline. This is a problem, so the kidneys secrete more alkaline in the urine to accommodate the problem.
Net effect:
The net effect of the human acclimatisation to altitude is to improve the working capacity of muscles to compensate for the reduced partial pressure of the atmospheric oxygen, and improve the capacity of the oxygen transport system to replace the oxygen debt.
“Pugh (1967) showed that at least 4 weeks of acclimatisation are required if sea-level athletes are stabilise their performance at altitude” (Physical Education and the study of sport, by Davis, Bull, Roscoe, Roscoe).
In the Mexico City Olympic Games the athletes that suffered the most were the long distance runners. High altitude is very popular method of training, which is used mainly by long distance runners in their preparation for a competition. However, the short and long-term benefits have been research and this has found that the benefits are minimal. The athletes that return to sea level after training at altitude encounter the complications of breathing through the changes, from low dense air at altitude to high dense air at sea level. This can cause extreme difficulties when performing at maximal oxygen levels. It suggested that altitude training can only be of any use if preparing for a competition at altitude, as this minimises the distressing affects of altitude sickness.
At altitude, the barometric pressure decreases and the air becomes less dense. In addition, the pressure of oxygen also decreases despite the oxygen content remaining constant at 20.94% (dry air).
This means that to obtain sufficient oxygen to train at altitude, a number of changes need to be made.
Above 6000 metres there is no benefits that have been noted and acclimatisation is not possible. The athlete will deteriorate rapidly, losing body weight with a decrease in performance levels.
Athletes who wish to train and compete at altitude need to decide whether they are going to complete a period of long gradual acclimatisation or a short, rapid, high quality session. The length of time it takes an individual performer to acclimatise depends on the altitude and level of hypoxic stress that an athlete is under.
Above 1500 metres, maximal oxygen consumption decreases by 3%, compared to sea level, for every 300 metres that body ascends. This means that the higher the body ascends the lower the maximal training levels. It takes about three weeks on average for the body to acclimatise to a moderate altitude of 2300m – 2700 metres, similar height to were the Mexico City Olympic Games were held (2242m). However, even after the acclimatisation the maximal oxygen consumption levels will still be 6% – 7% lower than those obtained at sea level.
The athletes from the Africans Nations are better adapted to competing at altitude as the African Nations are above sea level meaning that they already live at altitude. This is why the African Nations produced very good results in the Mexico Olympic Games, as they were already well equipped to cope with the altitude.
The results below indicate that the statement made above is correct, as in the Mexico Olympic Games 1968 the top 8 competitors in the 10,000 m race had either trained at altitude or lived at altitude, i.e. African Nations. The results in table show a comparison between the top 8 competitors in the 10,000 m race in Tokyo 1964 and Mexico Olympics in the following year 1968.
** Had lived at a high altitude for most their life.
* Trained at a high altitude foe an extended period prior to
the Games.
On the following page there is some tables showing the percentage of changes in time for each event from 100 metres to a marathon, between the two Olympics in Tokyo 1964 and in Mexico City 1968, for both men and women.
The de-saturation of arterial blood at altitude affects more than just the VO2 max. The cardiovascular responds to sub-maximal work are also affected. The blood is carrying less oxygen due to a lower inspired oxygen pressure meaning that more blood is needed to compensate. The heart rate increases in response to help try and compensate or balance the body’s needs.
At altitude the air is less dense, which means that there are fewer oxygen (O2) molecules per litre of air. The body would need to consume the same amount of air altitude as they would at sea-level, but for this to happen, the pulmonary ventilation would have to increase. At 5,600 metres above sea-level the atmosphere pressure (Barometric pressure) is one-half to that at sea-level and the number of molecules of oxygen (O2) per litre of air is reduced by one-half. This would mean that the body would need to take twice as many breaths to take in the same amount of O2 to compensate.
Quote on Acclimatisation:
“…adaptations produced by a change in the natural environment, whether by change of season or place or residence. In contrast, ‘acclimation’ refers to adaptation produced in a controlled laboratory environment as occurs in special chambers that can stimulate high-altitude and hypoxic environments, as well as extremes of thermal stress.” (Mcardle, Katch and Katch)
Each adjustment to a higher altitude is progressive, and full acclimatisation requires time. To adapt to the physiology and metabolism that improves tolerance to altitude, it can take between weeks or even months just to adapt. When ascending a mountain it is important that the process is carried out in a gradual manner, because if attempted too rapidly to reach high altitudes they will become sick, the symptoms include headaches, dizziness, nausea, etc.