Earlier this week, World No. 1 women's tennis player, Iga Swiatek of Poland, turned heads when she practiced with a strip of tape over her mouth.
The purpose, she told reporters at the Omnium Banque Nationale tournament in Montreal, was to improve her endurance since it's harder to breathe only through your nose. (Swiatek will compete in the tournament semifinal today.)
"For sure you can see the difference in how everything you do on the court is getting more and more hard with that tape on your mouth," Swiatek said during the tournament's media day, according to the Women's Tennis Association blog. "So I guess it's the way to kind of work on my endurance by not having me run so fast and do extreme things."
Practicing nasal breathing has become increasingly popular in recent years, aided in part by TikTok videos and popular books, including "Breath: The New Science of a Lost Art," by James Nestor and "The Oxygen Advantage," by Patrick McKeown, that extol its benefits. Some scientists believe nasal-only breathing can even improve athletic performance.
But is it a good idea to put a tape over your mouth while training? We asked exercise scientists and otolaryngologists, who are ear, nose and throat specialists, about the potential benefits of nasal-only breathing during exercise.
- - -
Benefits of nasal breathing
There are several advantages to breathing through your nose.
"It helps to filter warm and humidified air," said Brett Comer, a professor of otolaryngology at the University of Kentucky. "It's preparing the air that goes through the nose and preparing it to go down in the lungs."
Breathing through the nose also releases nitric oxide. "If it comes out of the sinuses and then is taken down in the lungs, that can help to dilate blood vessels," Comer said.
Some of those advantages are lost when we breathe through the mouth, experts say. George Dallam, a professor in exercise science at Colorado State University in Pueblo, compares breathing through your mouth to running a car without an air filter.
"You could argue that temporarily you might even get a little more horsepower because you're not restricting airflow into the engine," he said. "But, of course, any mechanic will tell you, don't run your car without your air filter."
- - -
Nasal breathing and exercise
During exercise, people typically start out with nasal breathing, and then eventually their mouths will drop open as a way to supplement oxygen.
"Our body by default is going to do whatever it takes to get that oxygen in," Comer said. "There's a reason our mouth drops open. It's body survival mode."
But Dallam said that the presumption that everyone has to open their mouths to get more oxygen at a higher intensity during exercise "may be short sighted." It's his view that people should breathe through their nose whenever they can.
In a small study published in 2018 in the International Journal of Kinesiology and Sports Science, Dallam and his co-authors tested 10 runners - five men and five women - who utilized a nasal-only breathing pattern during all training and racing for at least six months prior to the study. The researchers only wanted to include athletes who had used nasal breathing long enough to have fully adapted to it, Dallam said.
For the study, participants were asked to complete two treadmill tests - one at an increasingly challenging speed and one at a steady pace - under different conditions. In one version, they had their mouths taped shut with duct tape to ensure nasal-only breathing. In the other, they wore a nasal clip to force them to breathe through the mouth.
The study found that "nasal breathing was far more efficient," Dallam said. "Because they didn't have to breathe as much."
A recent pilot study by researchers at Baylor University found that while exercising, nasal-only breathing was found to increase blood flow to the brain. "If you can send more blood to your brain area, you will increase your memory function and your ability to move your body a little bit better," said Yunsuk Koh, the principal investigator of the study.
- - -
How to practice nasal-only breathing
When Swiatek tapes her mouth shut, her heart rate will go up, because the heart has to work harder to compensate for not getting as much oxygen in, Comer said. This happens because, "at first when you try nasal-only breathing, your ability to provide enough air flow nasally isn't there," Dallam said. "That changes over time."
But that doesn't mean recreational athletes should be taping their mouths shut during exercise, experts say.
Nicholas Rowan, an associate professor of otolaryngology, head and neck surgery and neurosurgery at Johns Hopkins, fears that people can aspirate the tape or have an allergic reaction to it. "You can actually have a hard time breathing when you're doing it in an unsupervised environment," he said.
Instead, Rowan recommends being mindful of your breath during exercise. He advises "making a conscious effort to keep your mouth closed."
"Breathe through your nose during exercise, whether that is exclusively in through your nose and out through your nose, or whether it's in through your nose and out through your mouth," Rowan said.
You can also do slow breathing exercises through your nose, Dallam said. It will take time to get used to nasal-only breathing, and you might not be able to exercise at the intensity that you're accustomed to while breathing through your mouth.
"It's a worthwhile thing to do, but it does require you to slow down," Dallam said.