Altitude Training

Here’s an extract from the book "Physiology of Sport and Exercise" describing a climber’s experience during an expedition up Mount Everest. The climber did this climb without supplementary oxygen at 8 600m above altitude. “Our pace was wretched. My ambition was to do 20 consecutive paces uphill without a pause to rest and pant, elbow on bent knee, yet I never remember achieving it - 13 was nearer the mark.”

A person’s ability to consume maximal amounts of oxygen during exercise at altitude decreases as the altitude exceeds 1500m. For every thousand metres above 1500m the individual’s VO2 max will decrease by 11%. This means at extreme altitudes people barely have sufficient oxygen to function properly let alone thinking about moving.

Firstly we need to realize that there is a lower atmospheric pressure of gases and also a lower partial pressure of oxygen at higher altitudes. The partial pressure of oxygen at sea level is 104mmhg when compared with 46mmhg at 4,300m above altitude. So from this you can see how altitude drastically decreases the partial pressure of oxygen, which in turn will affect the pressure gradient that is required in order to move gases in and out. So at higher altitudes there is a smaller gradient between the arteries and working tissues resulting in less oxygen being diffused into the required areas. This is why when you exercise at altitude you immediately start to breathe at a greater rate to compensate for the lower pressure gradients and to deliver the adequate amount of oxygen into your system.

The body has its own system which evolves to overcome this lack of oxygen being diffused to the working tissues. In my previous article I talked about the hemoglobin saturation curve, now if you remember at lower partial pressure oxygen that is bound to hemoglobin is released. At altitude the partial pressure of oxygen is very low, meaning that oxygen is getting released from the hemoglobin protein very rapidly, so to counter this the blood pH increases resulting in a term known as respiratory alkalosis. If you think back to what changes the saturation curve, two things affect it, one being temperature and the other being blood ph level. Both of these factors result in the curve shifting to the right. In terms of respiratory alkalosis it’s the opposite, the curve shifts to the left resulting in more oxygen being bound to hemoglobin at lower partial pressure.

Changes that occur during training at altitude include a decrease in blood volume and an increase in cardiac output. A person’s blood volume decreases due to an increase in urine production, and also due to a loss of respiratory water. At higher altitudes there is less humidity present resulting in the body losing more water because the water that is lost during sweating gets evaporated straight away. This can be detrimental to training because it means athletes can dehydrate very rapidly. There is also a greater production of erythropoietin meaning more red blood cells and more hemoglobin gets produced. This is to ensure that there is more oxygen within the blood when it circulates around the body. Cardiac output is the volume of blood to be pumped by the ventricle per minute. It takes into account the blood volume and heart rate, which can be expressed as heart rate multiplied by stroke volume. During acute altitude exposure cardiac output increases due to an increase in heart rate so that greater amounts of blood can flow around the body to deposit oxygen to the needed areas. This is to compensate for the decrease in partial pressure of oxygen.

Trev