Things that Belong into Your Gymbag: A Well-Adjusted Boil & Bite. Study Shows Decreased Cortisol Response After Intense Exercise with Custom-Fit Performance Mouthpiece

Image 1: An Under Armour Performance Mouthpiece - hitherto not a bodybuilder's 1st choice from the Under Armour line-up; something that may change when Cutler & co get wind of its effects on post exercise cortisol levels ;-)

Any (semi-)professional boxers out there? No? Football players? Ice-hockey? Lacrosse? Did you ever think of wearing your mouthpieces in the gym? No? Well, I guess then you have not heard about the surprising performance enhancement the stabilization of your temporomandibular joint by a well-adjusted mouthpiece may have on exercise performance and recuperation, have you? Studies into the effects of mouthpieces on exercise performance date back to the late 1970's and early 1980's, when Stephen David Smith published two studies on the effects of mouthguards and jaw posture on strength and exercise performance in the New York State Dentist Journal (Smith. 1978; Smith. 1982). In spite of that, a proper, experimentally verified explanation for the underlying mechanism by which the proper alignment of temporomandibular joint could have influenced muscular strength in these early studies had still to be provided.

In a very recent paper that is soon to be published in the Journal of Strength and Conditioning Research, Dene P. Gardner, Wesley D. Dudgeon and Erica J. Mc Divitt, from the Department of Health, Exercise and Sport Science at The Citadel in Charleston, South Carolina, report the results of an experiment that may well provide some insights into the performance enhancing effects of a piece of equipment that was originally invented to protect the teeth and jaws of boxers, football players and other athletes engaging in full-contact sports (Garner. 2011).

Illustration 1: Exercise protocol used in the study (adapted from Garner. 2011)

Based on animal studies by Hori et al. (Hori. 2004) and human data from Tahara et al. (Tahara. 2007) the scientists knew that biting or chewing could reduce the stress-induced release of corticotrophin releasing hormonen (CRH) from the hypothalamus and thus reduce the ACTH-stimulated release of well-known stress hormone cortisol from the adrenal glands. Garner et al. thusly speculated that they would find statistically significant differences in the cortisol response to 1h of intense resistance exercise (for details on the exercise protocol see illustration 1, on the right) in a group of 28 division I football players, who were randomly assigned to the use of a custom-fit mouthpiece in one of two identical training sessions (=within subject-design). Salivary cortisol samples were taken during both exercise bouts immediately before and at 25min, 45min, and 60min during, as well as 10 minutes post exercise.

As the data in figure 1 goes to show, there was indeed a direct interaction between mouthpiece-use and cortisol levels.

Figure 1: Cortisol response (expressed relative to pre-values) to identical 1h exercise bouts with and without a custom-fit Under Armour Performance Mouthpiece in 28 collegiate football players (data calculated based on Garner. 2011)

Unlike the slight amelioration of the immediate cortisol response during the 1h exercise bout, the difference in cortisol levels at 10 min post exercise is statistically highly significant and would validate the hypothesis that the correct alignment of the temporomandibular joint (TMJ)

Image 3: The temporomandibular joint

[...] leads to the activation of the motor area of the cerebrum, which then resulted in a decreased hypothalamic–pituitary response and thereby a reduction in cortisol release

as it has already been proposed by Hori et al. (Hori. 2004). Another possible explanation is related to earlier findings from Garner's laboratory, which showed that

[...] this product [the custom-fit Performance Mouthpiece] specifically creates a forward movement and increased space between the upper and lower teeth leading to improved airway dynamics.

which is why the scientists cite "the repositioning of the mandible and the improved airway response" as another possible explanation for the favorable post-exercise cortisol response.

Image 3: Although this is common practice and nothing shady, it is important to note that this research was "partially supported" by BiteTech, the manufacturer of the mouthpiece used in the study

There are two things I still want you to know before you skip to another of the highly educative SuppVersity posts ;-) Firstly, the study was "partially supported" by Bite Tech Incorporated from Minneapolis. In view of the fact that scientists have known about the potential benefits of mouthpieces for decades, now and considering the fact that the scientists openly declare that the financial support by Bite Tech, I do not doubt that the data they presented is 100% accurate. That being said, "sponsorship", and this may sound like an unfortunate truth, is becoming more and more essential for scientists (in all fields) and there is absolutely nothing wrong with that, IF (as it is the case with Garner et al.) the scientists explicitly state the involvement of the third party.... ah, you are waiting for secondly? Ok, here we go - I want to give a shout-out to my buddy Sean Casey from CasePerformance and wish him all the best for the upcoming exams ;-)

So, while it is now increasingly clear that the performance benefits, which by the way are not restricted to strength training, but have also been observed in endurance athletes by Garabee back in 1981 (Garabee. 1981), are related to the modulatory effect the use of a well-adjusted (!) mouthpiece has on the stress-response to (intense) exercise. In the end, I suppose, few athletes will be interested in whether this is due to a direct connection of their jaw muscles to some areas of their hypothalamus or improvements in airway dynamics, as long as it could give them the 0.1% edge that makes the difference between victory and defeat.