Guzmán-Venegas Rodrigo A, Biotti Picand Jorge L, de la Rosa Francisco J Berral
Laboratorio Integrativo de Biomecánica y Fisiología del Esfuerzo, Escuela de Kinesiología, Facultad de Medicina, Universidad de los Andes, Santiago, Chile.
Facultad de Odontología, Universidad de los Andes, Santiago, Chile.
PLoS One. 2015 Feb 18;10(2):e0116923. doi: 10.1371/journal.pone.0116923. eCollection 2015.
Some muscles have demonstrated a differential recruitment of their motor units in relation to their location and the nature of the motor task performed; this involves functional compartmentalization. There is little evidence that demonstrates the presence of a compartmentalization of the superficial masseter muscle during biting. The aim of this study was to describe the topographic distribution of the activity of the superficial masseter (SM) muscle's motor units using high-density surface electromyography (EMGs) at different bite force levels. Twenty healthy natural dentate participants (men: 4; women: 16; age 20±2 years; mass: 60±12 kg, height: 163±7 cm) were selected from 316 volunteers and included in this study. Using a gnathodynamometer, bites from 20 to 100% maximum voluntary bite force (MVBF) were randomly requested. Using a two-dimensional grid (four columns, six electrodes) located on the dominant SM, EMGs in the anterior, middle-anterior, middle-posterior and posterior portions were simultaneously recorded. In bite ranges from 20 to 60% MVBF, the EMG activity was higher in the anterior than in the posterior portion (p-value = 0.001).The center of mass of the EMG activity was displaced towards the posterior part when bite force increased (p-value = 0.001). The topographic distribution of EMGs was more homogeneous at high levels of MVBF (p-value = 0.001). The results of this study show that the superficial masseter is organized into three functional compartments: an anterior, a middle and a posterior compartment. However, this compartmentalization is only seen at low levels of bite force (20-60% MVBF).
一些肌肉已显示出其运动单位根据其位置和所执行运动任务的性质进行差异性募集；这涉及功能分区。几乎没有证据表明在咬合过程中浅层咬肌存在分区现象。本研究的目的是使用高密度表面肌电图（EMG）描述不同咬合力水平下浅层咬肌（SM）运动单位活动的地形分布。从316名志愿者中选取了20名健康的天然牙列参与者（男性：4名；女性：16名；年龄20±2岁；体重60±12千克，身高163±7厘米）纳入本研究。使用咬力计，随机要求参与者进行从20%到100%最大自主咬合力（MVBF）的咬合。使用位于优势侧SM上的二维网格（四列，六个电极），同时记录前部、前中部、中后部和后部的EMG。在20%至60% MVBF的咬合范围内，前部的EMG活动高于后部（p值 = 0.001）。当咬合力增加时，EMG活动的质心向后部移动（p值 = 0.001）。在高水平MVBF时，EMG的地形分布更均匀（p值 = 0.001）。本研究结果表明，浅层咬肌分为三个功能区：前部、中部和后部。然而，这种分区仅在低咬合力水平（20 - 60% MVBF）时可见。
