Relationship between Bite Occlusive function and dynamic movement of lower extremity in human

Research Project

Project/Area Number	10680056
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	体育学
Research Institution	Toho University School of Medicine
Principal Investigator	MURO Masuo Toho University, School of Medicine, Professor, 医学部, 教授 (80112887)
Co-Investigator(Kenkyū-buntansha)	TADANO Chigaya Toho University,School of Medicine, Assistant Professor, 医学部, 助手 (40261094)
Project Period (FY)	1998 – 1999
Project Status	Completed (Fiscal Year 1999)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1999: ¥700,000 (Direct Cost: ¥700,000) Fiscal Year 1998: ¥1,400,000 (Direct Cost: ¥1,400,000)
Keywords	Masseter / Soleus / Sternocleiodomastoid / Shortening / Plantar flexion / Motor units / Tonic vibratory reflex / H reflex / 咬合力 / 下腿三頭筋運動ニューロン
Research Abstract	The purpose of this study was to quantify the coupling of the activity levels of the masseter and sternocleiodomastoid, and triceps suare muscles during various bite occlusions, and to explain the relationship between the facilitation with isometric and shortening contractions and the activation level of the masseter or sternocleiodomastoid muscles. All bite occlusions and neck flexions were performed by the subjects in positions of maximal intercuspation and maximal flexion. H reflex responses were elicited in muscles that act via the soleus(SOL) and medial gastrocnemius(MG) motoneurones by electrical stimulation of the posterior tibial nerves of seven subjects. EMG recordings were made simultaneously from the SOL, MG, and masseter Mus by using intramuscular wire electrodes during voluntary occlusion and tonic vibratory reflex(TVR) occlusion by vibration on the mandible location. All subjects showed co-activation of the sterno-cleiodomastoid muscles during the strong clenching occlusi … More on effort. However, the co-activation of the sternocleiodomastoid muscles was very small during the weak clenching occlusion and the TVR of the masseter muscles. In the TVR of the masseter muscle, a weak contraction developed slowly as the vibration continued and when the frequency of the vibration increased, the contraction disappeared within a few seconds. The low-threshold and high-threshold motor units were recruited into action by the TVR. The low-threshold motor unit was recruited by the low frequency vibrations. In contrast, the high-threshold motor unit was recruited by high frequency vibrations. When a weak contraction maintained by vibration continued, all subjects demonstrated excitation of the SOL-MNs and the MG-MNs during maximal voluntary occlusion, but in the weak bite occlusion from 1 to 4 kg, the excitation of the MG-MNs was only slightly increased. During TVR, however, the excitations of the SOL-MNs and the MG-MNs were clearly increased as compared to the voluntary occlusion. On the other hand, when voluntary isometric contractions and shortening contractions in plantar flexion were performed during voluntary occlusion or TVR, the excitation of the MG-MNs was markedly increased with both bite occlusions, as compared to the excitation of the SOL-MNs. Consequently, the degree of excitation in the MG-MNs is increased, particularly with shortening contractions in plantar flexion, during TVR of the masseter Mus. These results suggest that dynamic muscle movement is strongly linked to the neural connection mediating the activation of the masseter motor neurons. Less