Why do we clench our teeth when doing something hard such as unscrewing a tight lidded jar?

Question

Why do we clench our teeth when doing something hard such as unscrewing a tight lidded jar?

In: Biology

Answer 1

You clench your jaw to prevent from biting your tongue. When your body tenses with your mouth agape such as when carrying out a labour intensive task or exercise, you might lose purchase and bang your head, possibly biting off your tongue or injuring your jaws or teeth. Your body knows of this danger and evolved over a long time to prevent you from doing this.