The hiker’s guide to the atmospherePosted: March 31, 2012
I always imagined myself trudging up foreign mountains behind a smiley, toothless Sherpa named Lakhpa or Nawang. Disappointingly, here in Colorado my Sherpa has all his teeth and his name is Derek. And by Sherpa, I mean the hiking enthusiast I met at the hostel. Sometimes things don’t go exactly as planned.
Regardless, Derek is about 30 and speaks with the Canadian gait I’ve come to love, pronouncing every letter and relying on ‘eh’ for questions, comments, and straight up salutations. The affection might also stem from the fact that, as well as leading me up a gruelling 26km hike in theRocky Mountains, he’s also agreed to be my scientific guinea pig.
I suspect that only a Canadian would be so enthusiastically helpful as to pop on a heart rate monitor without asking why. Before us looms the demanding Long’s Peak summit and I’ll be monitoring him, and myself, for the effects of altitude on our bodies. The hike is a 26km roundtrip and the summit towering 4346 metres above sea level, just over half the size ofMount Everest.
As a fitness fanatic, the effect of altitude has intrigued me since I first read about the curious 1968 Mexico City Olympics. In short distance athletic events like sprinting and long jump, world records were decimated. But in endurance competitions, some international champions couldn’t even make the distance. Ron Clarke, an Australian who had set 17 world records collapsed and almost died from altitude sickness in the 10,000 metre final.
Why? The answer was up in the air – literally.Mexico Citysits 2,240 metres above sea level, the highest summer Olympic Games in history.
As Derek and I begin the trek we’re feeling good – my heart rate hovers around 150 beats per minute (bpm), his at 140. The walk is tough, even more so since we started in the darkness of 4am, and the breaks frequent. But as we get higher and my altimeter clocks 3000, my breath starts getting noticeably shorter and my heart starts beating faster. The altitude has begun to take its toll.
On Earth, whether you are perched atop Mount Kilimanjaro, or draped across the white sands of the Whitsundays, any given volume of air is comprised of 79% nitrogen, 20.9% oxygen and 0.1% other gases. But as you rise higher and higher above sea level, the pressure of the atmosphere decreases and although the proportions stay the same, the number of molecules in the air decreases.
This is due to the effects of gravity, which works to keeps molecules close to the ground. As you reach higher altitudes the gravity is weaker, enabling the molecules to drift further apart from one another. While the composition of the air stays the same, the expansion means that the air is ‘thinner’ – so at higher altitudes you inhale less oxygen and nitrogen molecules with each breath than you would at sea level.
Scientists have determined that at heights above 2,400 meters, we inhale approximately three quarters of the amount of oxygen molecules that we would at sea level. By the time we reach the summit of Long’s Peak, Derek and I will probably only be taking in half the amount of oxygen that we would at sea level. On the tip ofMount Everest(8,848m above sea level) hikers inhale only a third of the amount of oxygen they would at sea level, enough to kill them.
Although mentally I’m just feeling incredibly unfit as we reach the half-way mark, inside me the lack of oxygen is driving a cascade of physiological responses. To begin with, my body has increased its heart and breathing rate to up the amount of oxygen molecules taken in and circulated in my bloodstream. This explains my skyrocketing pulse, which my monitor tells me is up to 182 bpm.
My head is also starting to spin and nausea has set in. Im certain I didn’t drink last night, but the effect of altitude is the equivalent of a wine-fuelled, my-best-friends-wedding-was-the-night-before hangover. As I soldier on, I can’t tell if I’m hallucinating or if the number ‘191’ on my heart monitor is laughing at me.
The scientific verdict is still out, but some researchers believe altitude sickness is a result of the brain swelling from a lack of oxygen. A recent study atStanfordUniversityshowed that ibuprofen, a common anti-inflammatory drug, can significantly reduce the incidence of altitude sickness by reducing swelling in the brain. But in the name of science (or perhaps stupidity) we persist without.
By the time we reach the three-quarter mark, I’m starting to wish we had decided to make this an overnight trip – given enough time, my body would begin to acclimatise to the altitude. More than 200 genes are activated when we acclimatise, including one that increases the production of red blood cells, thereby increasing the amount of haemoglobin in the blood.
Haemoglobin is the protein that binds oxygen molecules to red blood cells. The more haemoglobin in the blood stream, the more efficient the cells will be at carrying oxygen around the body. This means that even though less oxygen molecules are making it into the lungs, it is more easily transported to the muscles.
Once acclimatised, the rapid breathing would also reduce the amount of carbon dioxide in the blood, lowering its acidity. To counter this, the kidneys release blood bicarbonate to try to balance the PH level. It sounds like something from a vampire’s cookbook but 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.
The down side for Derek and I is that many of these physiological responses can take days, even weeks, before they kick in. As I’m considering it, a quick, woozy look around at the barren mountainside with its jutting cliffs and gnarled tree branches reminds me it’s not really ideal.
It’s hard to believe since I’m almost doubled over trying to keep my head from swimming, but sport scientists around the world have found that athletes actually become more efficient after altitude exposure. Researchers have shown that being acclimatised to altitude means our bodies are able to use less oxygen to do the same amount of work. More than that, they’ve translated their findings into a training regime.
Many athletes from low altitude countries do short stints of ‘altitude training’ overseas in places likeArizona,KenyaorSwitzerland. Here at home at the Australian Institute of Sport, athletes do stints in a man-made ‘altitude house’ which simulates high elevation 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.
According to the Head of Physiology at the AIS, Professor Chris Gore, the house allows Australian athletes to simulate what other countries have already.
“This way we get similar benefits to what we would get from natural altitude by flying the athletes to train in sayEurope, but without having to sacrifice their access to their physios, doctors, nutritionists, friends and family,” Professor Gore said.
“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,” he said.
“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.”
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 ofGermanyto train. After six weeks, the runners had lost 5% of their haemoglobin showing a relatively fast de-adaptation.
“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 Derek and I, the benefits are far beyond even our oxygen-deprived imaginations. After eight hours, we’ve made it to the summit and our celebration is marked by food and a nap sprawled on flat, sunshine-soaked boulders. I’m certainly not feeling up to Olympic standards, but my head feels clear. Perhaps it’s the giddy euphoria of making it to the top, or a very concerning lack of oxygen, but I’m starting to think that perhaps my real calling in life is as that toothless Sherpa I’d always imagined.