[Electromyography activities of the head, neck and upper trunk muscles with mandibular movement in normal adults].
OBJECTIVE
To investigate the activities of head, neck and upper trunk muscles with mandibular movement in normal adults.


METHODS
The integral data of surface electromyography (EMG) had been recorded to analyze the activities of anterior temporal (Ta), posterior temporal (Tp), sternocleidomastoid (SCM) and trapezius (TRAP) muscles with mandibular movement in ten normal adults.


RESULTS
The former mentioned muscles acted constantly when the mandible was in the rest position. The activities of Ta, Tp and SCM muscles increased with protrusion of mandible, mouth opening, tapping, maximum clenching, and chewing movements. The amplitudes of the increased activity of these muscles were correlated significantly with each other. When the activities of Ta and Tp muscles increased to 56 times and 25 times respectively, the activity of SCM muscle increased to 5 - 6 times. The activity of trapezius muscle increased with protrusion of mandible and opening movement, but tended to stop with the maximum clenching and chewing movement. The correlations of left and right sides of the same muscles had been found.


CONCLUSIONS
The muscles of head, neck and upper trunk can act as contributors to keep the mandibular positions and take part in the mandibular movements.
Jiang
Ting
T
Department of Prosthodontics, Peking University School of Stomatology, Beijing 100081, China.
Yang
Zhaohui
Z
Zhang
Zhenkang
Z
Feng
Hailan
H
D000328:Adult; D004576:Electromyography; D005260:Female; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008297:Male; D008334:Mandible / Q000502:physiology*; D008409:Mastication / Q000502:physiology; D009068:Movement; D018482:Muscle, Skeletal / Q000502:physiology*; D009334:Neck Muscles / Q000502:physiology; D016059:Range of Motion, Articular; D012782:Shoulder / Q000502:physiology; D013704:Temporomandibular Joint / Q000502:physiology