Coming from a background in combat sports, I am used to seeing my teammates train while wearing their mouthpieces. It is accepted practice that training with the mouthpiece will help your cardio, as it makes breathing more difficult. Scientists have been investigating the idea that mouthpieces aid in performance for the last four decades with varying conclusions. A recent study published in the Journal of Strength and Conditioning investigated the use of a mouthpiece during resistance exercise, as research indicating that the mouthpiece aids in building muscle strength and endurance has been difficult to replicate.
Researchers in this study tested the players’ cortisol levels before, during, and after a resistance workout. Cortisol specifically was measured due to the desire to test the theory that clenching or biting during stress can lead to decreased cortisol release. Previously it was shown biting down or chewing during stressful mental exercise decreased stress response in humans. It was also demonstrated in rats that biting down on a stick caused a decrease in corticotrophin releasing hormone. This hormone is part of the hyothalamo-pituitary-adrenocortical (HPA) axis and is elemental to the production of cortisol. If mouthpieces were determined to decrease cortisol levels, some of their performance enhancing benefits could be scientifically explained.
Test subjects were all between 18-22 years of age and were Division I football players. They were given two identical resistance exercise workouts, two weeks apart, and wore the mouthpiece during one of them. Players were custom fitted with Under Armour mouthpieces by a dentist. The workouts consisted of a 10-minute plyometric warm-up followed by sets of hang cleans, dead lifts, and single leg overhead shoulder press. Various assistance and mobility exercises were performed in between the main lifts.
- 10 minutes post exercise there was a 51% difference in cortisol levels between players wearing and not wearing mouthpieces, with non-mouthpiece wearing having the higher cortisol levels.
- Mouthpiece wearers experienced a 29% drop in cortisol levels between the completion of their workout and 10 minute post-workout measurement.
- Non-mouthpiece wearers, on the contrary, experienced a 48% increase in cortisol from the beginning of their workout to the 10 minute post-workout measurement.
The data from this study showed that both groups, mouthpiece wearers and non-mouthpiece wearers, experienced a similar shift in cortisol levels during their actual workout, but the recovery post workout was dramatically different. Mouthpiece wearers recovered significantly faster, exhibiting much lower levels of cortisol within 10 minutes of the workout. This would indicate that cortisol was available to the athlete when necessary, but the mouthpiece allowed a better potential for recovery from physical effort without the protein degradation typically caused by excess cortisol.
Further research is being done on the HPA axis, which as stated earlier is essential to cortisol production, and the belief that it is connected to the jaw muscles. If wearing a mouthpiece leads to less stress on the jaw, the HPA could have a decreased stress response. Therefore wearing a mouthpiece could be a direct connection to controlling cortisol levels in an athlete, decreasing protein degradation, and increasing recovery.