If you want to run like a Kenyan marathoner, the current thinking goes, you have to spend lots of time breathing thin air like you'd find in the Kenyan highlands. Need proof? Just try to find a medalist from any endurance event at the 2012 Olympics who didn't prepare either by training in the mountains or sleeping in a special oxygen-reduced chamber for weeks at a time.
But as your mother warned you, the fact that everyone is doing it doesn't make it right.
At a conference hosted by the University of Calgary last month, researchers raised questions about the supposed benefits and possible risks associated with prolonged altitude training. Meanwhile, athletes are experimenting with an alternative protocol that involves minutes, rather than weeks, at a time in low oxygen – an approach that is far more accessible to the average person.
The verdict? It's not yet clear, but here's a look at the current evidence.
The status quo: Live high, train low
If, like most Canadian athletes, you were born near sea level, then heading to altitude will trigger an increase in the number of red blood cells that deliver oxygen to your muscles. The downside is that, as a native lowlander, you won't be able to run (or swim, row, etc.) as fast in the thin air – so you'll gain endurance but lose speed.
The solution: Live high, train low (LHTL). You live in the mountains, but drive down to lower elevation a few times a week to do hard and fast workouts with full oxygen. Alternatively, you stay at sea level, but spend as much time as possible (including nights) in a pressurized house or altitude tent with reduced oxygen.
At the Calgary conference, University of Zurich physiologist Dr. Carsten Lundby presented data from the first double-blind, placebo-controlled study of the LHTL method. In earlier studies, athletes who knew they were assigned to the altitude group may have been motivated to train harder than those in the sea-level group.
Sixteen cyclists were confined to altitude-controlled rooms for 16 hours a day at a training centre near the French Alps, with half the rooms randomly set at high elevation and half at low elevation. After four weeks, there were no differences in cycling performance or red-blood cells between the two groups.
It may be that altitude training is most effective for those with low red-blood cell levels, Lundby says; the elite athletes in this study already had high levels, and had little room to improve. The fact remains that athletes followed a relatively standard LHTL protocol under carefully controlled conditions and failed to improve.
The health risks
Dr. Marc Poulin uses a specially designed altitude chamber at the University of Calgary to study sleep apnea. Healthy volunteers are subjected to oxygen levels that plummet and then rise again as often as 30 times an hour, mimicking the repeated airway blockages suffered each night by sleep apnea patients.
After several days of daily sessions, the volunteers begin to display some of the health problems associated with sleep apnea, such as chronically elevated blood pressure and impaired blood-vessel function. Poulin believes the underlying cause may be the reduction in oxygen reaching the brain – and he notes that lowland athletes who sleep in altitude tents for prolonged periods may expose themselves to similar risks.
"Carsten's work shows that it's not clear this type of training helps performance," Poulin says, "so there's a need for caution, given these sorts of acute physiological changes that may be harmful."
The alternative: Live low, train high
At the Institut national du sport du Québec in Montreal, meanwhile, Dr. François Billaut is experimenting with a very different approach. "Intermittent hypoxic training" is essentially the opposite of live-high, train-low: You spend the vast majority of your time at sea level, but do a few strenuous workouts a week with a "hypoxicator" device that simulates the low-oxygen air at high altitude.
While the technique dates back to Soviet research in the 1980s, researchers are still divided about its effectiveness. Billaut believes it's most helpful for speed and power athletes, since it improves the body's anaerobic (oxygen-free) energy pathways, and is also useful for team-sport athletes.
For recreational athletes, the approach's key attraction may be its smaller time commitment and relative accessibility. Hypoxicator-maker GO2Altitude, for example, lists on its website seven locations across Canada where you can book time on a machine.
Alex Hutchinson blogs about exercise research at sweatscience.runnersworld.com.