LITERALLY YAWNING THROUGH YOUR WORKOUT?
Ever had that weird experience where you are loving and smashing a workout but keep yawning? You are not tired, and you are not bored, so what is actually going on?
It turns out that there is very little research being done on the everyday physiological phenomenon called yawning. But, what is out there is really fascinating, we may have nerded out a little but here is what we have discovered.
What is a yawn?
A yawn is a semi-voluntary action that occurs in almost all mammals. The mouth gapes open wide triggering a large inhalation followed by a long exhalation. The muscles of the face and skull, particularly the temporal region contract to facilitate this action. Yawning is often associated with simultaneous stretching of both, or either, the upper and lower limbs. Yawning also creates an increase in surfactant around the alveoli (tiny air sacs in the lungs) allowing them to fully expand and remain open. Human foetuses begin yawning in-utero as early as 12 weeks.
Are we just Bored?
We commonly associate yawning with drowsiness secondary to being tired or bored. The evidence suggests that drowsiness may be a stimulus for yawning but not always, in fact, one study of chimpanzees observed that while some yawns were connected to sleep behaviours, the majority of yawns were in close proximity to activity such as playing, eating, or, mating.
Further research suggests that yawning results in a temporary spike in arousal immediately post-yawn. Participants showed similar rises in heart rate and skin conductivity as the subjects in a study measuring the arousal levels post caffeine consumption, thus it was concluded that yawning may in fact have an effect on the area of the brain responsible for arousal. This would explain why more yawning is experienced during low-stimulus activities such as during lectures or whilst reading, the body initiates a yawn in an effort to increase arousal in the absence of adequate stimuli. This doesn’t make sense however when we consider yawning during exercise, we would assume, and sincerely hope, that you are not bereft of sufficient stimuli while active. (But if you are - it's definitely time to mix up your workouts).
What does make sense is the long-held theory that yawning is initiated to increase available oxygen. The theory suggests that yawning is a result of decreased oxygen and increased carbon dioxide in the brain, the oxygen then causing drowsiness. In response, the body initiates a yawn to rapidly increase available oxygen thereby offsetting the drowsiness. This theory makes sense in the context of exercise, as we work hard, we crave more oxygen. As it turns out though, studies have shown that there is no significant increase in yawning when subjected to higher concentrations of carbon dioxide.
Keeping a Cool Head About It
More recent theories, that still have limited evidence, suggest that yawning may be initiated in an effort by the body to cool the brain. Studies in rats showed a significant drop in cortical temperature immediately post-yawn. The theory gained further weight with evidence that yawning frequency increased as the ambient temperature rose.
The physical act of yawning results in a constriction of blood vessels of the face and head, resulting in “warmed” blood being drawn away from the skull. The intake of cool air into the lungs during the yawn may result in a decreased temperature of oxygenated blood from the lungs returning to the brain, thereby potentiating an overall cooling effect.
Interestingly, patients with conditions that result in thermoregulatory disorders such as epilepsy, head trauma, and stroke, have been documented to have a reduced cortical temperature and a brief temporary cessation of symptoms immediately post yawn.
Just Suck it Up
Given that yawning improves the efficiency of the respiratory system by increasing aveoli surfactant, there may be some truth to the idea that yawning is a response to increased oxygen demand during exercise. Keeping alveoli open wider and for longer would enable more gas exchange across the alveolar membrane. However, there are many other proven breathing techniques that increase respiratory efficiency more effectively than yawning. The theory requires more study before any real conclusions can be drawn.
FYI - Can You Really “Catch a Yawn”
We don’t need scientific studies to tell us that for some bizarre reason, that always seems to take us by surprise, yawning is contagious.
Actually, the science is fascinating. It is believed that contagious yawning has something to do with the part of the brain responsible for empathy. Researchers have observed very little contagious yawning in children under the age of five, who are yet to reach the developmental stage where empathy becomes apparent. Similarly, people with brain trauma or psycho-social disorders which render them unable to show empathy, rarely experience contagious yawning.
So Why Do We Yawn When We Exercise?
It would seem that there is no definitive answer, and quite possibly it is a little bit of everything mentioned above. The strongest evidence, however, is for the “brain cooling” theory. Researchers in a controlled trial observed significantly more yawning in subjects exercising in higher ambient temperatures and therefore with higher core temperatures.
At the end of the day, as long as you are not yawning because you are bored, it doesn't really matter, just push through it and keep punching. If it bothers you, perhaps try working out in air-conditioning or at cooler times of the day. If you are yawning because you are tired, and you know you are tired, consider tracking your sleep habits for a few days to ensure you are getting optimal rest.
Important Note:
Excessive yawning may be a symptom of an underlying disease or a medication interaction. If you are concerned please consult your GP.