I'm not a very active person and I work behind a desk, but I am trying to be more active and get into better shape. I am overweight, but not obese. (According to this chart.) I bike, walk, have been doing some indoor, low impact exercises, and I chase around my 3.5 year old. But doing these physical activities makes me yawn A LOT. Doing these things is hard enough when I'm in poor shape and don't have much endurance, but yawning makes it just that much more difficult. I'm trying to figure out what could cause this and what I can do about it. I don't have any idea where to start.
I get intermittent yawning-attacks during workouts too. I ignore it, and go about my business. I've read this and that about it, but nothing conclusive. The most plausible one is that you're simple tired from lack of sleep. Barring that, some say it's because you're rapidly heating up, and yawning is an attempt to cool down.
In a study in 2007 in the journal Evolutionary Psychology, researchers reported that subjects who cooled their brains by breathing through their noses or holding cold packs to their foreheads — proven brain-cooling strategies — were less likely to yawn when shown videos of other people yawning.
There's no ready explanation for your "aerobic yawn." Perhaps your alveoli need a boost to stay open. Or maybe your brain needs cooling to stay alert. Or it may simply be a reflex. Whatever the case, there's probably no reason to worry about it, and you should keep up with your aerobic exercise.
But note, this is referred to as a "novel theory". Could be a legitimate reason, or it could be circumstantial.
Like I said, it's been hard to find anything conclusive on the topic of yawning during exercise.