The Cold, Hard Evidence on Better Breathing for Athletes

This article originally appeared on Outside

I'm a big fan of breathing, both as an endurance athlete and in my daily life. Sucking in oxygen and exhaling carbon dioxide are both absolutely vital to health and performance. But what I don't know, even after decades as an athlete and years writing about sports science, is whether it's possible to breathe better.

The standard take on the human respiratory system is that it's overbuilt, meaning that it's never the limiting factor in your ability to sustain exercise. Sure, you'll breathe heavily if you run a 5K race--but even if you were magically able to breathe 5 percent harder, you wouldn't run any faster, because the real limiters are the beating of your heart, the circulation of blood, the metabolic byproducts accumulating in your muscles, and so on.

More recently, though, researchers have concluded that there are situations where the respiratory system--the upper airways of the nose and mouth, the lower airways leading to the lungs, along with the lungs themselves and the muscles powering them--struggles to meet the demands placed on it. Most notably, for our purposes, highly trained endurance athletes and people visiting high altitudes sometimes push their breathing system close to its limits.

So it's not entirely implausible that you might be able to breathe better in some way--and there is, indeed, an entire industry that promises to teach you how and/or sell you devices to that end. What's tricky is distinguishing between plausible, research-backed claims and implausible, unsupported claims. That's what a major new review in the European Journal of Applied Physiology aims to do. Led by Camilla Illidi of McGill University and dogged pseudoscience-debunker Nicholas Tiller of UCLA, along with researchers from two British universities, the review offers a practical guide to the current evidence on various respiratory interventions. Here are the key takeaways for outdoor athletes.

Nasal Dilators

Made famous among runners by Galen Rupp, Breathe Right strips look like a small band-aid across your nose and experienced their first wave of popularity among athletes at the 1996 Olympics in Atlanta. The goal is to keep your nasal passages open and make breathing easier. There are other devices, including some that insert within the nostrils, that serve the same purpose. They're touted to help snoring, congestion, and sleep apnea, and some athletes believe they help you breathe better during exercise.

There has been plenty of research, and the general conclusion is that they do open up your nasal passages, and some people report positive results like better subjective sleep quality, but they don't change any measurable health-related outcomes. For athletes, the research finds no benefits in heart rate, perceived effort, oxygen consumption, lactate, or recovery. If there are performance benefits, they probably start with P and rhyme with gazebo.

Nasal Breathing

This one is more nuanced. The review summarizes some interesting evidence that breathing through your nose generates higher levels of nitric oxide, which in turns dilates blood vessels and potentially helps keep airways relaxed and open. Whether this leads to clinically significant health improvements remains an open question, but it's plausible.

Does this mean you should breathe only through your nose during exercise? The first objection is that most people can only manage to breathe through their nose up to about 80 percent of VO2max, beyond which they experience the "unacceptable sensation of air hunger." That said, there's evidence that you can habituate over time to become able to stick with nasal breathing at higher intensities, perhaps even maximal effort.

Let's assume for the moment that you can breathe through your nose during exercise. Should you? There have only been a few small studies, and they produced conflicting results about whether nasal breathing offers any advantages. Overall, Illidi and Tiller conclude that breathing through your nose is probably feasible, but there's "little to no data" supporting the idea that it's useful for athletes.

Respiratory Muscle Training

It takes a lot of muscle work to power your lungs. Just like your leg muscles, those respiratory muscles can get tired. And when they get tired, they may start working less efficiently and consequently draw oxygen-rich blood away from other muscles like your legs. That's the rationale for training your breathing muscles by doing exercises with a kazoo-like device that makes it harder to inhale.

I've written about the idea of respiratory muscle training several times, most recently about the idea of doing it before heading to altitude, where your breathing muscles have to work extra-hard and end up consuming 15 to 30 percent of the total oxygen you inhale. More generally, numerous studies have investigated whether this sort of training can make you faster in sports like running, cycling, and swimming (the latter of which is a particularly good candidate, because having limited time with your head above water makes breathing even more challenging).

Overall, Illidi and Tiller are remarkably positive about this one. It's well-established that respiratory muscle training can improve the strength and endurance of respiratory muscles, they conclude, and there's "convincing evidence" that it can improve performance in athletes.

Canned Oxygen

Remember that in the previous section Illidi and Tiller gave a thumbs-up to respiratory muscle training. That proves that they're not just curmudgeons who say nothing works. So, with that in mind, trust them when they say there's no valid evidence that canned oxygen is useful, and very little reason to expect that it would.

Nutritional Interventions

This perhaps merits a whole article of its own, but I'll just hit the highlights without digging into all the nuances of conflicting evidence. The main rationales for thinking that supplements can boost respiratory function are that anti-inflammatory or antioxidant effects might reduce airway inflammation, and that ramping up immune function might ward off respiratory infections. For these purposes, Illidi and Tiller don't think vitamin D is useful unless you're deficient. Chronic vitamin C is unlikely to be useful, though it's possible short bouts might help fight colds or upper respiratory tract infections. There's also evidence that prebiotics and probiotics help protect against respiratory infections and might reduce airway inflammation in people with asthma-like symptoms triggered by exercise.

"Systematized Breathing Strategies"

This catch-all category lumps together various approaches that combine elements like inhaling through the nose, focusing on using the diaphragm to inhale, deep or slow breaths, breath-holds between inhaling and exhaling, and exhaling slowly or through pursed lips.

Most of the research focused on using these approaches to help manage conditions such as asthma and chronic obstructive pulmonary disease, and the evidence is fairly positive. In these situations, it seems clear that it is possible to breathe better.

Is the same true for healthy people, and specifically for athletes? That's less clear. In these situations, Illidi and Tiller write, any benefits likely result from changes in parasympathetic nervous activity and consequent physiological changes like lowered resting heart rate and blood pressure and increased heart-rate variability. This is basically a scientific way of saying that deep breathing helps you relax and de-stress--which, to be fair, is no small thing.

Personally, I find it much easier to wrap my head around things like respiratory muscle training and Breathe Right strips. They're straightforward physiological interventions--plumbing, in essence--and scientists can test whether they work in a relatively straightforward manner. The broader category of breathing interventions is more nebulous, though. Their benefits depend on the interaction of mind and body. That's harder to test. It doesn't mean they don't work, but it does mean that it's harder to sort out reliable and reproducible effects from hype and hucksterism.

To that end, full credit to Illidi and Tiller and their team, both for taking a hard-nosed look at the current evidence and for acknowledging the limitations of that evidence. Their full paper is freely available to read, so you should check it out if there's any particular topic where you want a deeper dive into the evidence. My overall take is that, as with all corners of the multi-trillion-dollar wellness industry, there's plenty of pseudoscience floating around in the "better breathing" world. But there are also some kernels of intriguing science that merit further exploration.

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