Mao J J, Major P W, Osborn J W
Department of Oral Biology, Faculty of Dentistry, University of Alberta, Edmonton, Canada.
Arch Oral Biol. 1996 Dec;41(12):1141-7. doi: 10.1016/s0003-9969(96)00083-0.
Previous studies have identified both linear and curvilinear relations between increasing bite-force magnitude and the integrated electromyogram (EMG) of jaw-closing muscles. In an attempt to explain the discrepancy, bite forces of incrementally increasing magnitude were produced on the right-hand side in five specified directions by eight humans. Linear regression lines were fitted to normalized EMG activities of the left and right masseter and temporalis muscles against increasing bite-force magnitude in each direction. The grand mean of linear correlation coefficients was 0.79 (+/- 0.11 SD), suggesting an overall linear relation. Each set of individual data was fitted with polynomial lines up to the third order. The best fit was selected by statistical significance of coefficients and the least-square analysis of the sum of residues for each fitted line; 62% of individual data-sets were best fitted with linear regression lines, 31% with quadratic lines and the remaining 7% with cubic lines. Repeated analysis of residue variance of the pooled data showed that either a linear or quadratic line fitted every data set except one, for which a cubic line had the best fit. Working-side muscles had significantly larger linear correlation coefficients than corresponding balancing-side muscles for most bite-force directions. Analysis of variance of linear correlation coefficients revealed that the degree of linearity often depended upon the roles played by a muscle in producing forces in different directions. It appears that linearity or non-linearity of the EMG force relation is a determinant, among other variables, of the direction of the resultant force.
以往的研究已经确定了咬合力大小增加与咬肌闭合肌的肌电图（EMG）积分之间的线性和曲线关系。为了解释这种差异，8名受试者在右侧以5个特定方向产生了逐渐增大的咬合力。针对每个方向上咬合力大小的增加，对左右咬肌和颞肌的标准化肌电活动拟合线性回归线。线性相关系数的总体平均值为0.79（±0.11标准差），表明总体呈线性关系。每组个体数据都拟合了最高三阶的多项式曲线。通过系数的统计显著性和每条拟合曲线残差和的最小二乘法分析来选择最佳拟合；62%的个体数据集最佳拟合为线性回归线，31%为二次曲线，其余7%为三次曲线。对合并数据的残差方差进行重复分析表明，除了一个数据集最佳拟合为三次曲线外，每个数据集要么拟合为线性曲线，要么拟合为二次曲线。在大多数咬合力方向上，工作侧肌肉的线性相关系数显著大于相应的平衡侧肌肉。线性相关系数的方差分析表明，线性程度通常取决于肌肉在不同方向产生力时所起的作用。看来，肌电-力关系的线性或非线性是合力方向等其他变量的一个决定因素。
