The use of a custom-made mouthguard stabilizes the electromyographic activity of the masticatory muscles among Karate-Dō athletes.

Aims: To analyze and compare the electromyographic activity of the temporal (anterior portion) and masseter muscles among Karate-Dō athletes before and after training, with and without the use of a mouthguard.

Methods: Twenty athletes (14 males and 6 females) with a mean age of 23.7 ± 7.5 years participated. They had surface electromyography recordings taken of their bilateral temporal and masseter muscles before and after training under the following conditions: no mouthguard, with a ready-made mouthguard, and with a custom-made mouthguard. Activity was examined at mandibular rest, while clenching, and at maximum voluntary contraction. The data were normalized using the mean maximum voluntary contraction.

Results: The right (p = 0.005) and left (p = 0.015) temporal muscles showed significantly lower electromyographic activity with a custom-made mouthguard compared with no mouthguard after training while clenching. The electromyographic activity of the temporal and masseter muscles did not show significant differences when tested at mandibular rest and while clenching before or after training with a custom-made mouthguard (p > 0.05).

Conclusion: The use of a custom-made mouthguard preserved participants' electromyographic profiles before and after training; thus, they allow for stable muscle activity during the training of Karate-Dō athletes.