“Pure oxygen,” the new trend in athletic performance claims to be a breath of fresh air – but it might just be a bunch of smoke blowing around.

Before you read this article, take a moment to fully inhale and exhale. During that deep breath, the average healthy individual will take in about a liter of air. The consumption costs you absolutely nothing – so why, then, are retailers selling cans of oxygen as a performance enhancer?

Recreational oxygen desperately wants to be the hot new legal performance enhancer in endurance sports. In a population that is always looking to get an edge over its competition, it makes sense that canned air would be a marketable product. And it certainly is marketable – these portable canisters of pure oxygen, which are equipped with dispensers to allow users to inhale through the nose or mouth, claim to do everything from increase endurance, boost energy levels, and speed up recovery time. The major basis for these claims come from a 2018 meta-analysis from Brock University, which found small-to-moderate ergogenic effect in general performance and recovery during exercise supplemented with hyperoxia.

“Hyperoxia means an increase in the amount of oxygen,” explains Dr. Michael Koehle, Director of Sport and Exercise Medicine at the University of British Columbia. “In this context, it means more oxygen than what is readily available in the surrounding air.”

Hyperoxia was originally developed for medical application. In certain clinical conditions, such as Chronic Obstructive Pulmonary Disease, the oxygen levels in the blood can be lower than normal (called hyperoxemia), making day-to-day tasks more challenging. These patients can be treated with home oxygen, a form of hyperoxia, to improve their quality of life.

In time, hyperoxia was found to help people with other forms of severe respiratory disease as well. In people with pulmonary fibrosis, for example, supplemental oxygen can improve exercise performance. These individuals require a continuous source of oxygen, often in the range of one to three liters per minute. From here, the practice was extrapolated – if hyperoxia boosted performance in people with breathing problems, think of what it could do for those with healthy lungs!

But Koehle warns that logic isn’t necessarily sound.

“For starters, most endurance athletes don’t have severe respiratory disease. In healthy individuals, hypoxemia only occurs under very specific conditions.” These conditions may – but don’t always – include exercising at altitude, or in some elite athletes exercising at their maximal output. The average healthy person will typically never see low oxygen levels in the blood during a training session, and therefore doesn’t require supplemental oxygen.”

In fact, hyperoxia can cause more problems for a healthy athlete. There is such a thing as too much oxygen – a condition known as oxygen toxicity. “During high levels of oxygen for prolonged periods, certain chemical reactions can occur, damaging the lungs,” explains Koehle.

Canned oxygen available in retail settings typically isn’t large enough to cause oxygen toxicity, as their contents – ranging in size from .5 liters to 7 liters – would typically run out in three minutes or less. The delivery system is also not ideal, says Koehle – “When you spray oxygen into your mouth with a nozzle, or even a mask-like attachment – much is wasted and does not even get to the lungs.”

What does work: good, old-fashioned breathing the normal way. “A large adult male exercising at very high intensity can breathe up to 200 liters per minute. These very small bottles of oxygen would be consumed in a matter of seconds. That’s a lot of packaging for something with negligible benefit that gets used up in seconds.”

In other words, save your money. “It may sound boring, but the proven strategies to increase breathing function are following a consistent and well-designed training program,” says Koehle. “Training not only improves the physiological function of our heart and locomotor muscles, but it also makes our breathing muscles stronger and more effective.”