Exercise is hard work and it can be tiring. But exercise can also help improve sleep and maintain more regular sleep patterns, Paul M. Gallo, EdD, a fellow at the American College of Sports Medicine (ACSM) and director of exercise science and wellness at Norwalk Community College, tells LIVESTRONG.com
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"People who exercise sleep more consistently throughout the evenings," he says.
A yawn, which is usually associated with being tired or bored, is an innate reflex by the central nervous system — namely, the brain. That means you can't control when and where you yawn, Gallo explains. So just because you yawn a couple of times during a workout, it doesn't mean you should try to make it stop.
But here's why you might find yourself yawning during a workout.
1. You're Stressed or Anxious
The idea that yawning increases the amount of oxygen you take in — you're gulping a big breath of air, right? — has been debunked, Gallo says, according to a November 1987 study published in Behavioral and Neural Biology. A yawn can, however, increase blood flow to the brain, which can improve focus and concentration, he says.
Perhaps you're about to start a workout or a big athletic event, or you're a few minutes into it, Gallo says, you might start yawning as a way to improve your focus and concentration. That's because yawning can cool your brain temperature, he explains.
"Before a workout, game or event, you might have anxiety and stress — but the good kind of stress — and that might elicit a yawn," Gallo says. "Your body's fight-or-flight response kicks in, and a yawn opens the jaw, which increases blood flow for the working muscles."
A runner, for example, might yawn in the moments leading up to a race due to anxiety. That yawning should stop once she's moving, Gallo says, because running is a steady-state exercise.
"When you're in a steady-state of aerobic exercise your brain knows you need to breathe consistently," he says.
A yawn, he points out, disrupts that consistent breathing. In other words, your body prioritizes breathing over increasing blood flow or cooling down your body temperature — another reason you might be yawning during a workout.
2. You're Too Hot
Perhaps the biggest reason you might yawn during a workout is to bring your core body temperature down, Gallo says. This is called thermoregulation.
"When you inhale a large amount of ambient air that's cooler than your body temperature, it helps lower your core temperature and brain temperature," he explains.
This happens because when you yawn, your jaw musculature contracts, increasing blood flow to those muscles. When you gulp in cool air, it cools the blood in the jaw muscles, which is then delivered to the brain and other parts of the body, Gallo explains.
This is a type of insensible perspiration — perspiration that does not involve a loss of pure water or associated loss of solute.
"A major way we cool is by breathing," Gallo says.
Case in point: Researchers in a May 2014 study in Physiology & Behavior recruited 120 pedestrians to walk during the winter (December to March) and summer (June to October) and found that the participants who walked in the summer reported more yawning than those in the winter. This study supports evidence that yawning is used as a means of thermoregulation.
But when the ambient temperature is hotter than your core temperature, yawning will subside, according to Gallo and a January 2013 review published in the International Journal of Applied and Basic Medical Research.
3. You're Doing High-Intensity Work
Whether you yawn during a workout depends on what you're actually doing, Gallo says. The exercises that most commonly cause yawning include high-intensity interval training (during the rest interval) and those that target large muscle groups, like heavy lifting for the lower body.
"You're using more musculature, which increases the core temperature," Gallo says.
Gallo explains that if you yawn during a HIIT workout, it will be during the rest or lighter workload interval.
"If you really feel that you must reduce your yawn frequency, you can try methods to better thermoregulate," Gallo says. "Methods that have worked are drinking cold water/liquids, doing an ice water mouth rinse (shown to be very effective for disease populations, such as multiple sclerosis), wearing moisture-wicking clothing and using appropriate ventilation to lower environmental temperatures."
When to See a Doctor
Because yawning is a reflex, there usually isn't any reason to try to stop it from happening, Gallo says. But if you're experiencing excessive yawning during a workout, it might indicate something more serious.
"If you're yawning excessively during moderate to vigorous activity, that yawning can lead to lightheadedness or dizziness," Gallo says. It could mean very low blood pressure or a hyperactive vagus nerve.
Low blood pressure is associated with a host of underlying medical conditions, according to the American Heart Association. Some of those include pregnancy, bed rest, medications, allergic reactions and problems with hormone-producing glands.
A hyperactive vagus nerve can be caused by extreme stress. The nerve works overtime to decrease heart rate and blood pressure, but in some cases, it brings down blood pressure too much, causing severe low blood pressure, according to an article from Society for Science and the Public.
"If you're yawning during exercise but not experiencing any negative side effects, don't worry too much," he says. "But if you're dizzy or lightheaded, that warrants a conversation with your doctor."
- Behavioral and Neural Biology: "Yawning: No Effect of 3–5% CO2, 100% O2, and Exercise"
- International Journal of Applied and Basic Medical Research: "Yawning and Its Physiological Significance"
- Society for Science and the Public: "Explainer: What is the Vagus?"
- American Heart Association: "Low Blood Pressure—When is Low Blood Pressure Too Low"
- Physiology & Behavior: "A Thermal Window for Yawning in Humans: Yawning as a Brain Cooling Mechanism"