It has been demonstrated that excellent athletes usually have, not only a higher exercise capacity but also higher ability to maintain equilibrium which is important for assuming the various body postures required in different sports. It is thought that a method of training which enhances the sense of equilibrium will also increase the ability to perform certain of sports.
Many sensory organs and the central nervous system, which integrates these organs, are integrated to the maintenance of equilibrium. To maintain equilibrium, vestibular, visual and bathyesthetic inputs are integrated centrally (in the brainstem, cerebellum, etc.) and necessary commands are other tissues.
A series of studies which we performed demonstrated that the ability to maintain equilibrium was lower in individuals with imbalanced occlusion than in individuals with normal occlusion.
Imbalanced occlusion can be corrected by the appropriate use of rejin sprints. We recently examined the effects of such sprints on the equilibrium of athletes with imbalanced occlusion, using a gravity fluctuation analyzer. In this study, we raised the bite only within the amount of existing free way spce.
From these results, gravity fluctuation in athletes with imbalanced occlusion was greater than that in individuals with normal occlusion.However, when imbalanced occlusion was corrected by the use of rejin sprints, gravity fluctuation tended to decrease.
It these findings from the present study are combined with the knowledge that the exercise capacity of athletes has a positive correlation with their equilibrium maintenance ability. It appears that correction of imbalanced occlusion and the appropriate use of mouth protectors would contri-bute to improving the performance of athletes.

It is thought that for some sports so called the “agility” accomplishes the key role from the viewpoint of the improvement of the performance and the injury prevention. Therefore we examined the influence of bite up with the oral appliances on the agility.Tested sporting event were cervical retroflexed force. EVA mouthguard and resin splint were used for the oral appliances. Reaction time was measured as a response to stimulated light by the activating time of the masseter muscle and activating time of the main muscle.It is found the reaction time of neck muscles movement tends to be shortened by wearing of the oral appliances.These results were seemed to be based on decrease of a free way space by the bite up with the oral appliances resulted in shortening the reaction time of the masseter and the stabilized occlusion.(141 words)