The runners’ jaw mistake


Athletes often clench their jaws and grind their teeth during sprints and HIIT. That tension negatively impacts your training and puts unwanted stress on the bones, muscles, and joints in your mouth.


Tensing your jaw is a natural reaction to prepping for a heavy lift, but the habit hurts your cardio performance, says David Otey, personal training manager at Equinox Sports Club Upper West Side in New York City. Muscle-clenching uses glycogen, which you want to use as fuel so you can move as quickly as possible.

Over time, it can also lead to cracks or fractures in the teeth and painful inflammation of the temporomandibular joints (TMJ), says Jeffrey Laubmeier, dentist and member of the Academy for Sports Dentistry in Lakewood, Ohio.


Relaxing your jaw during cardio ups your power output and protects your teeth and jaw. Otey suggests inhaling through your nose and exhaling through your mouth at an even pace to minimize clenching. If you notice early signs of damage like soreness along the top of your jaw or tenderness when eating hard or chewy foods, consider wearing a mouthguard like this one while you train, Laubmeier says.