I do not know what it is, but when I chew gum whilst running I always look like I’m smiling, it is just a thing. Honestly, I don’t think I could run long distance without chewing gum. Having gum or a sip of water in your mouth stimulates your brain during a long distance run. Sometimes, I just have water in my mouth and spit it out in double digit mileage so my brain stays vibrant in all that mileage. What kind of gum do you chew running? I like anything mint and have a new piece of gum with every gel every five miles. Espresso flavored gels and mint gum every 3-5 miles are my safe go to for running double digit miles.