Mouth Guards for Weight Training; Maryland Personal Trainer

A good bit of research has been coming out lately stating that clenching the jaw when performing a physical task (such as jumping or lifting a weight) increases strength and power (1). This phenomenon has been dubbed concurrent activation potentiation and is essentially a fancy way of saying "when one muscle contracts hard (or a group of muscles), other muscles like to contract hard too".

An easy way to demonstrate this is to shake friend's hand as hard as you can. After doing the test run, retry, but this time tense up your body first. If you did it right, your strength will go up and your friend will be thoroughly impressed by your handshaking prowess.

Jaw clenching is not particularly new in strength circles. Powerlifters, Olympic weightlifters, and other strength athletes have been using tension to increase weight totals for years. However, when this new research started pouring out, so did new products.

Why weren't mouth guards this cool when I was growing up?

Enter the mouth guard for weight lifting. While mouth guards have long been a staple for contact sports, the weight lifting mouth guard was created in the same spirit as the mouth guards designed for people who grind their teeth at night and suffer from the resulting tooth damage and jaw pain. Therefore with this miraculous product you can clench your jaw during your entire workout and experience big strength gains without damaging your teeth, right? Not so fast...

So what's the catch?

My issue is that products are being marketed to the average trainee - lately I have seen people wearing these for the duration of a normal workout. The problem with jaw clenching is that even though you may recruit more motor neurons, you are also training your jaw at the same time for increased tension. Often the only demand we consider in training is that of the targeted muscle group while in reality we are always adapting on a whole-body level. No study needed - this is just the application of the SAID principle (Specific Adaptation to Imposed Demand), which is the cornerstone of exercise physiology. In short, if you regularly train by clenching your jaw, you are going to get good at creating tension in your temporalmandibular joint (TMJ), which is not a desirable adaptation.

Getting to Know Your TMJ

The TMJ is a very sensitive area because it is a hotbed of motoneuron activity. Wait, what? Basically, there are a lot of nerve endings around the TMJ because it needs to both be able to create a lot of force in order to chew food, yet have very fine control in order to help produce speech. As a result, this area is often the site of various dysfunctional muscle activity. Unconscious jaw clenching is a well documented condition known as bruxism. This can lead to tooth damage, headaches, and in severe cases, extreme jaw pain. So why on earth would it be a good idea to create voluntary jaw clenching for any extended period of time? Wearing a mouth guard during a workout in order to jaw-clench on every set to squeeze out an extra tricep pushdown is simply not a worthwhile pursuit.

The Final Verdict

By no means am I saying that jaw clenching is a bad thing to do. If you are actively competitive in a strength sport, then risking developing jaw pain for an edge on the competition may very well be worth it. Even for non-athletes, there could be some merit in jaw clenching during very high intensity sets. However, the average weight trainer has no business purchasing a mouth guard in order to clench his jaw for all 10 sets of bicep curls. It is simply a surefire way to end up with a headache and a sore jaw with little to show for it.


References

1. Ebben, W.P., Flanagan, E.P., & Jensen, R.L. (2008). Jaw clenching results in concurrent activation potentiation during the countermovement jump. Journal of Strength and Conditioning Research, 22(6): 1850-4.