Elevation training masks have adjustable flux valves to restrict airflow into the nose and mouth.eclipse_images/Getty Images
During a recent workout in my condo weight room, an acquaintance walked in wearing a bulky, black mask over his nose and mouth; it had a plastic plate with cylindrical slits that made it look more hazmat than N95. His breathing was so audible that, by the time he finished his set of burpees, he sounded like he was about to crush the Rebel Alliance.
In this era of influencers-at-the-gym, I’ve seen it all (the day before, there was a guy by the dumbbell slapping himself in the face on Instagram live). But curiosity got the best of me because I had been noticing more gymgoers donning this particular, Star Wars-y disguise. So I asked him about it.
What he was wearing was an ETM, or elevation training mask: a device that restricts oxygen consumption while exercising. These masks are meant to simulate the effects of training at high altitudes.
At higher elevations, the air contains less oxygen, prompting the body to adapt by producing more red blood cells. After several weeks, this increase in red blood cells makes more oxygen available to the muscles, ultimately enhancing performance. The ETM attempts to replicate this effect by using adjustable flux valves to restrict airflow into the nose and mouth, over time ostensibly bolstering endurance by improving lung capacity and VO2 max (the body’s capacity to use oxygen).
As a runner myself, the proposition sounded too good to be true. I thought: If these 60-something-dollar masks can improve my endurance by even a percentage point, shouldn’t I and every other runner already be wearing them, and wheezing up a storm on our sea-level trails?
Scientists from the University of Wisconsin put that very question to the test. In a randomized, placebo-controlled study, they prescribed six weeks of high-intensity aerobic training to two groups of people: one of which wore the elevation training mask, and a control group that did not. They found no difference in how VO2 max, pulmonary function, or hemoglobin levels improved between groups, concluding that the mask should not be considered a substitute to altitude training. They did, however, find that the group of mask wearers improved the strength of their respiratory muscles such as the diaphragm and intercostals, as compared with their non-masked counterparts.
“These masks might not do what they say they do, but there could be some value to them anyway,” said Dr. Greg Wells, a performance physiologist who studies breathing and athletic performance.
Dr. Wells explains that strengthening the intercostal breathing muscles could in time make them more efficient, leaving more oxygenated blood available for other working muscles that we need for exercise, such as the arms and the legs, and delaying fatigue. But he agrees with the Wisconsin scientists that the claims of simulating altitude training sound baseless.
To stimulate the creation of red blood cells, the oxygen pressure in the bloodstream must drop to nearly half of its normal level at sea level and typically remain at that level for extended periods of time. This is why most endurance athletes hold training camps at high altitudes for at least three weeks. He believes that wearing a mask for even an hour a day would not provide the intensity or duration needed to create the same training adaptations.
The masks, however, could have an unexpected effect: capturing exhaled breath rich in carbon dioxide and causing the wearer to breathe it back in, leading to a higher concentration of CO2 in the bloodstream. While this is more uncomfortable than dangerous – since high levels of CO2, or hypercapnia, cause the uneasy sensation experienced when holding your breath for too long – it could also have a desensitizing effect. Mask wearers, eventually, might become better at holding their breath for longer.
Dr. Wells said the effect is not dangerous, but also is not convinced there is much value in reducing our physiological urge to exhale. That being said, he sees no immediate danger in using the ETM.
“I don’t think it’s necessarily bad; it’s just the impact it’s having is probably not what people think,” he said. “And that’s fine – we just need to be aware of what it actually does.”