Department of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
J Exp Biol. 2010 Mar 1;213(5):775-81. doi: 10.1242/jeb.037762.
Mechanical food properties influence the neuromuscular activity of jaw-closing muscles during mastication. It is, however, unknown how the activity profiles of the jaw muscles are influenced by long-term alterations in masticatory load. In order to elucidate the effect of reduced masticatory load on the daily habitual activity profiles of three functionally different jaw muscles, the electromyograms of the masseter, temporalis and digastric muscles were recorded telemetrically in 16 male rabbits between seven and 20 weeks of age. Starting at eight weeks of age the experimental animals were fed significantly softer pellets than the control animals. Daily muscle activity was quantified by the relative duration of muscle use (duty time), burst number and burst length in relation to multiple activity levels. The daily duty time and burst number of the masseter muscle were significantly lower in the experimental group than in the control group at 5% and 10% of the maximum activity during the two weeks following the change in food hardness. By contrast, altered food hardness did not significantly influence the activity characteristics of the temporalis and digastric muscles. The findings suggest that a reduction in masticatory load decreases the neuromuscular activity of the jaw-closing muscles that are primarily responsible for force generation during mastication. This decrease is most pronounced in the weeks immediately following the change in food hardness and is limited to the activity levels that reflect muscle contractions during chewing. These findings support the conclusion that the masticatory system manifests few diet-specific long-term changes in the activity profiles of jaw muscles.
力学食物特性会影响咀嚼过程中闭口肌肉的神经肌肉活动。然而，咀嚼负荷的长期变化如何影响咀嚼肌的活动模式尚不清楚。为了阐明咀嚼负荷降低对三种功能不同的咀嚼肌日常习惯性活动模式的影响，16 只雄性兔在 7 至 20 周龄之间使用遥测技术记录了咬肌、颞肌和二腹肌的肌电图。从 8 周龄开始，实验组的兔子比对照组的兔子吃明显更软的颗粒。通过与多个活动水平相关的肌肉使用率（工作时间）、爆发次数和爆发长度来量化日常肌肉活动。在改变食物硬度后的两周内，实验组的咬肌每日工作时间和爆发次数明显低于对照组，在 5%和 10%的最大活动水平下。相比之下，改变食物硬度并没有显著影响颞肌和二腹肌的活动特征。研究结果表明，咀嚼负荷的降低会降低咀嚼肌的神经肌肉活动，而咀嚼肌主要负责咀嚼时的力量产生。这种减少在改变食物硬度后的几周内最为明显，并且仅限于反映咀嚼时肌肉收缩的活动水平。这些发现支持咀嚼系统在咀嚼肌的活动模式上很少表现出特定于饮食的长期变化的结论。
