The Morocco Ultra Toubkal Atlas Trail will take place in October. Its main characteristics are its length (105km -65,6 miles) its differences in height (-6,500m) and its altitude (from 2,600m to 3,450m).
One’s maximum endurance capacity is reduced in high mountains because of the diminution of oxygen in the blood. The runner must therefore change the intensity of his or her training, the management of his or her efforts, his or her food and drink-taking in order to avoid this reduction in terms of results.
Why is one’s endurance capacity hindered by altitude ?
One often hears that oxygen (O2) is reduced in altitude. This is only partly true. The oxygen percentage remains constant whatever the altitude (20,95%). What is reduced is the pressure in O2(PpO2) due to reduction in the barometric pressure (Pb). At sea level this pressure is of 760 mmHg. At an altitude of 1800m it reaches 596 mmHg whereas at the top of Mont Blanc (4,810m) it falls to 430 mmHg. – Reducing the barometric pressure – e.g. part reduction in oxygen – results in a diminution of oxygen to the muscles. The ultimate consequence of this phenomena called hypoxia is the diminution of the maximum oxygen consumption, since it depends on the cardiac output and the arterial-venous difference in oxygen. This difference is reduced by approximately 9% every 1,000m. Several studies have shown that this phenomena called “hyposical stress” occurs at a height of about 600m even with trained runners.
In order to limit this hypoxia the human body sets up a number of physiological adaptations as soon as the blood pressure falls under its normal level : Extra ventilation is produced to thwart reduction of SaO2 and satisfy the muscles’ demand in O2. This extended activity of the breathing muscles partly explains why one burns more energy at 2,000 m than at 1,000m.
In order to cope with these adaptations, the Ultra Toubkal Trail runner who doesn’t live above sea level must try and arrive a few days before the run in order to adapt to the hights/ His VO2max will however remain always lower than that at sea level.