Effects of Clenching on Exercise Performance: Verification Using Spinal Function Assessments
【Supercategory：7. DESCENTE SPORTS SCIENCE Subcategory：7.43 Vol.43】
ABSTRACT
Teeth clenching has a significant impact on exercise performance, but the optimal clenching strength for peak exercise performance is unknown. Therefore, this study aimed to determine the relationship between exercise performance and spinal function as a function of clenching strength.
Two experiments were conducted in this study using two groups of 20 healthy adults. The four clenching conditions in Experiment 1 were 0, 12.5, 25, and 50% of the maximum voluntary contraction （MVC） of the masseter muscle, and Experiment 2 consisted of three conditions: no-bite condition, moderate effort, and maximum effort （max condition）．In Experiment 1, measurements of spinal function and ankle dorsiflexion tasks were performed for each clenching condition, and the ankle dorsiflexion task was performed in Experiment 2. Regarding spinal function, we measured spinal reciprocal inhibition （RI） and the excitability of spinal anterior horn cells. For the ankle dorsiflexion task, ankle dorsiflexion MVC was pseformed for 3 s under each clenching condition. The items analyzed were the reaction time, peak ankle dorsiflexion torque, and soleus（Sol） /tibialis anterior（TA） electromyography（EMG）ratio.
The results of Experiment 1 illustrated that RI was significantly attenuated or eliminated with increasing clenching strength （>25% MVC）．The excitability of spinal anterior horn cells increased significantly with increasing clenching strength. The peak torque was significantly higher at 50% MVC than at 0% MVC condition. In Experiment 2, the peak torque was significantly higher under the moderate and max conditions than under the no-bite condition, and the Sol/TA EMG ratio was significantly higher under the max condition than under the moderate condition. The present results illustrated that during high-strength clenching （?50% MVC），antagonist muscles are activated simultaneously to increase muscle strength. Highstrength clenching improved kinetic performance （joint fixation）， whereas lowstrength clenching（<50% MVC） enhanced exercise performance（joint movement）．
DECENTE SPORTS SCIENCE Vol.43/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE
Teeth clenching has a significant impact on exercise performance, but the optimal clenching strength for peak exercise performance is unknown. Therefore, this study aimed to determine the relationship between exercise performance and spinal function as a function of clenching strength.
Two experiments were conducted in this study using two groups of 20 healthy adults. The four clenching conditions in Experiment 1 were 0, 12.5, 25, and 50% of the maximum voluntary contraction （MVC） of the masseter muscle, and Experiment 2 consisted of three conditions: no-bite condition, moderate effort, and maximum effort （max condition）．In Experiment 1, measurements of spinal function and ankle dorsiflexion tasks were performed for each clenching condition, and the ankle dorsiflexion task was performed in Experiment 2. Regarding spinal function, we measured spinal reciprocal inhibition （RI） and the excitability of spinal anterior horn cells. For the ankle dorsiflexion task, ankle dorsiflexion MVC was pseformed for 3 s under each clenching condition. The items analyzed were the reaction time, peak ankle dorsiflexion torque, and soleus（Sol） /tibialis anterior（TA） electromyography（EMG）ratio.
The results of Experiment 1 illustrated that RI was significantly attenuated or eliminated with increasing clenching strength （>25% MVC）．The excitability of spinal anterior horn cells increased significantly with increasing clenching strength. The peak torque was significantly higher at 50% MVC than at 0% MVC condition. In Experiment 2, the peak torque was significantly higher under the moderate and max conditions than under the no-bite condition, and the Sol/TA EMG ratio was significantly higher under the max condition than under the moderate condition. The present results illustrated that during high-strength clenching （?50% MVC），antagonist muscles are activated simultaneously to increase muscle strength. Highstrength clenching improved kinetic performance （joint fixation）， whereas lowstrength clenching（<50% MVC） enhanced exercise performance（joint movement）．
DECENTE SPORTS SCIENCE Vol.43/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE
| Researcher | Ryo Hirabayashi, Mutsuaki Edama, Hideaki Onishi |
|---|---|
| University or institution | Niigata University of Health and Welfare |
Keywords
H-reflex, Electromyograph, Masseter muscle, Electrical stimulation, Remote facilitation