Oxygen, to the well-trained modern athlete, is a luxury to be indulged in only in moderation.
By travelling to high-altitude mountain training camps, sleeping in depressurized altitude tents, and strapping on altitude-simulating masks for workouts, athletes force their bodies to adapt to the scarcity of oxygen so that, when it comes time to compete in normal air, they'll have an extra zip in their step.
But there may be a simpler and more economical way of reaping some of the same benefits, according to several recent studies: Just hold your breath while dashing through a series of short sprints.
The most recent study, published this month in the European Journal of Sports Science, involved 21 rugby players who completed seven sprint workouts over a four-week period, with half of them doing the sprints in a condition of "voluntary hypoventilation"– that is, holding their breath during the sprints. By the end, the breath-holders had increased the number of sprints they could complete during a testing session from 9 to 15, while those who breathed normally showed no significant improvement.
The idea of restricting your breathing during training actually has a long history, explains Xavier Woorons, a researcher at the University of Lille, in France, who led the new study. Starting in the 1970s, the legendary American swimming coach James Counsilman advocated training while breathing only every five or more strokes, instead of the customary two to three strokes, in order to force the body to adapt to lower levels of oxygen.
But there was a problem with Counsilman's approach, Woorons found when he began studying the idea in the mid-2000s. Inhaling a lungful of air and then holding your breath is uncomfortable because levels of carbon dioxide in your blood increase – but oxygen levels in your blood don't actually drop significantly.
Instead, Woorons tested the idea of holding your breath after a normal exhale, so that the supply of oxygen in the lungs is already depleted. This approach, he and his colleagues found, can bring oxygen levels in the blood down to 87 per cent of the maximum value by the end of a workout – an effect equivalent to training at 2,000 metres of altitude.
Still, the total amount of time spent with low oxygen during a workout like this only adds up to a few minutes. In comparison, endurance athletes spend several weeks at a time living and sleeping in thin mountain air in order to trigger an increase in red blood cell production.
So Woorons decided to combine his breath-holding idea with another altitude training protocol, developed by University of Lausanne researcher Grégoire Millet, which involves short all-out sprints performed in low-oxygen conditions (a simulated altitude chamber, for example). Instead of triggering red blood cell production, these sprint workouts force the muscles themselves to become more efficient at extracting oxygen from the blood.
The new study, with rugby players, involved a series of 40-metre sprints, which took the players about six seconds each to complete without breathing. The sprints were repeated every 30 seconds; the initial workouts involved two sets of eight sprints, with the load gradually increased until they were doing three sets of eight sprints in the final workout.
These workouts aren't easy, cautions François Billaut, a professor of kinesiology at the University of Sherbrooke who works with the national speed skating team and other elite athletes. "Training at low lung volume is also very hard mentally," he says, "so perhaps not doable for all athletes." In particular, Woorons adds, people with high blood pressure, heart, or lung conditions shouldn't try it.
The benefits appear to be primarily in the ability to repeat short sprints, so it's particularly useful for team and racket sports rather than endurance athletes, Woorons says.
In the end, if you have the choice between an altitude training camp in Banff or a bunch a painful sprints with empty lungs, you're probably better off on many levels choosing the former. But if that's not an option, you now have an alternative that's effective and easily accessible – and the price is right.
Alex Hutchinson is the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. Follow him on Twitter @sweatscience.