First question: are you fully rested? Are you getting 7-8 hours of sleep every night? You could just be fatigued....
Yawning is caused by slowed breathing / lack of oxygen.
As with any exercise, you need to seriously focus on your breathing. It's just as important as proper form and technique. Breathe through both your nose and mouth at the same time, taking concentrated, deep breaths. This will help with endurance and energy, and will prevent your heart rate from coming up too quickly.
If you're still having problems, it could be a heart/ blood pressure issue and you should see your primary care physician.
Fitness Minutes: (212,880)
72,744 6/21/13 3:43 A
To get extra air into your body
Fitness Minutes: (2,769)
6/20/13 9:34 P
Here's an interesting article that may shed some light (possibly) on why you are yawning during your run. Though the "jury is still out on this one", it is just one of many theories... www.webmd.com/brain/news/20110923/why-we-y awn
6/20/13 10:49 A
I thought that was why but I don't feel like I am over exerting myself, I have been running/jogging for a few months. I'm just weird ;)
Yawning is just another way for your lungs to get some extra air. It happens when you're sleepy and your breathing slows. It can also happen when you're exerting yourself, so your lungs can get that extra oxygen.
6/20/13 9:17 A
I have noticed that whenever I run on the treadmill I start to yawn uncontrollably. I'm not sleepy and it doesn't happen when I run outside or when I go walking. Just when I run. Why is that?