Running on thin air
The 1968 Mexico City Olympic Games have had sport scientists’ minds racing for decades. It was an Olympics where some records were smashed beyond comprehension, and others were completely untouchable.
Why? The answer is up in the air. Literally. Mexico City sits 2,240 metres above sea level where the high altitude and thin air can wreak havoc on the human body.
For Professor Chris Gore, Head of Physiology at the Australian Institute of Sport (AIS), understanding the effects of altitude has become a fixation.
“It’s been my passion for 15 years. I think it’s fascinating and I’m always trying to find new ways to help athletes and coaches use altitude training more effectively.”
So what happens to the air at high altitudes to affect our bodies so much?
Any given volume of air is comprised of 79% nitrogen, 20.9% oxygen and 0.1% other gases such as argon and krypton. But as you get higher and higher above sea level, the pressure of the atmosphere decreases.
This is due to the effects of gravity (which keeps air close to the ground) and heat (as you get closer to the sun) which cause molecules to bounce off one other and expand. So as you reach higher altitudes, the air expands.
While the composition of the air stays the same, the expansion means that the air is ‘thinner’ – so in essence, at higher altitudes you inhale less oxygen and nitrogen molecules than you would at sea level.
This drives a cascade of physiological responses in the human body. To begin with, your body increases its heart rate and respiratory rate to increase the amount of oxygen taken in and circulated around the body. So for example, while an athlete might normally run with a heart rate of 150 beats per minute, at high altitude it might increase to 165.
Then the body begins to respond and adapt to the altitude (a process called acclimatization). More than 200 genes are turned on in response to altitude, and one that is most commonly thought of is that which induces the creation of more red blood cells thereby increasing the amount of hemoglobin in the blood.
Hemoglobin is the protein that binds oxygen molecules to red blood cells. The more hemoglobin in the blood cells, the more efficient the cells will be at carrying oxygen around the body. This means that even though less oxygen is taken into the lungs, it is more easily transported to the muscles.
Finally, as you breathe faster and faster, the amount of carbon dioxide in the blood is reduced, which leads to the blood becoming less acidic. To counter this, the kidneys release blood bicarbonate to try to balance the PH level. For athletes, this is a big advantage since blood bicarbonate is the primary source of protection for muscles against lactic acid – the waste that builds up during exercise and leaves muscles feeling stiff and sore.
While most of the scientific world has focused on the benefits of more haemoglobin following altitude training, Professor Gore and his colleagues have looked at the range of other effects.
His work has proven that muscle buffering capacity is improved and that blood lactate levels during exercise are lowered. Additionally, the AIS scientists have found that athletes become more efficient after altitude exposure. Just like high altitude natives, athletes are able to use less oxygen to do the same amount of work after they have been at simulated altitude.
The down side however, is that many of these physiological responses do not occur straight away. It can take days, even weeks for the human body to fully adapt to the effects of altitude and for athletes to reap the benefits of better muscle protection and more efficient oxygen transportation.
Scientists have determined that at high altitudes of 2,400 meters plus, we inhale approximately three quarters of the amount of oxygen molecules that we would at sea level. This decreases as you go higher. As a reference, on the summit of Mount Everest (8,848m above sea level) we inhale only a third of the amount of oxygen we would at sea level, which is not enough to sustain human life.
Altitude Training at the AIS
To simulate this low atmospheric pressure, enabling athletes to get the benefits of altitude training without having to travel to high altitude areas, scientists at the Australian Institute of Sport have developed an ‘altitude house’.
This house, comprised of 12 beds, bathroom, kitchen and a lounge, simulates what it would be like to live at high altitude. The AIS recreate the low pressure atmosphere of 2500 metres by changing the composition of the air within the house to approximately 85% nitrogen and 15% oxygen. The air is not thinner, but the presence of less oxygen is physiologically equivalent to being at altitude.
Athletes from endurance sports like cycling, rowing, race walking and swimming live in the house for 3-4 weeks at a time, a couple of times a year. At the same time, they maintain their standard training regime in the normal atmosphere in Canberra, which is 600 metres above sea level.
According to Professor Gore, this ‘live high, train low’ program enables athletes to reap the benefits of high altitude living, while still enabling them to train with the same intensity and frequency.
“Australia is at a disadvantage to other countries because we don’t really have big mountains for our athletes to live or train on, so the altitude house allows us to simulate what other countries have already,” Professor Gore said.
“And this way we get similar benefits from the altitude house that we would get from natural altitude by flying the athletes to train in say Europe, but without having to sacrifice their access to their physios, doctors, nutritionists, friends and family.”
Some athletes use the house as preparation for events where they will be competing at high altitudes. Mainly however, coaches are using the ‘altitude’ house as a way to improve performance at sea-level events.
“By living in the house for 12 hours or so a day, the athlete’s red blood cell counts increase, their haemoglobin increases. As well, their muscle buffering capacity, ability to handle lactic acid and their efficiency also improves. They can then use these factors to their advantage in training and competitions.
“Overall, we’re talking about a 1-2% increase in performance, which mightn’t sound like much, but can be the difference between a medal and failing to qualify,” Professor Gore said.
But the effects don’t last forever. For example, Professor Gore quotes a study where Kenyan runners who lived and trained in high altitude all their lives were taken to a low-altitude region of Germany to train. After 6 weeks they runners had lost 5% of their haemoglobin showing a relatively fast de-adaptation[i].
“The verdict is still out, but we’re looking at benefits lasting for between 2-4 weeks for sea level athletes who return to normal sea level training.”
For Professor Gore, one of the most interesting things about altitude is its ability to both hinder and help athletes, depending on their event.
“In cycling for example, the thin air means there is less drag, and in short stints in particular, athletes’ ability to absorb oxygen is not badly affected. This is true of almost all explosive events, including sprints, long jump and triple jump.
“But for endurance events, like the ones our altitude training athletes compete in, kayaking, rowing and race walking, they are hit hard by the lack of oxygen and the lack of air resistance means little,” Professor Gore concluded.
[i] N. Prommer, S. Thoma, L. Quecke, T. Gutekunst, C. Volzke, N. Wachsmuth, A. M. Niess, and W. Schmidt. Total hemoglobin mass and blood volume of elite Kenyan runners. Med.Sci.Sports Exerc. 42 (4):791-797, 2010.