Koyano K, Kim Y J, Clark G T
UCLA Dental Research Institute, Center For The Health Sciences 90024-1668, USA.
Arch Oral Biol. 1995 Mar;40(3):221-7. doi: 10.1016/0003-9969(95)98811-c.
Twelve individuals (2 males, 10 females) with chronic masticatory muscle pain and 11 individuals (2 males, 9 females) without, had their bite force and surface electromyography from the right and left superficial masseter and anterior temporalis muscles recorded before, during and after a 30-s sustained submaximal clenching task. This task was performed at 50% of the force level of each subject's maximum voluntary contraction (MVC) for 30 s. Brief (3 s) 50% MVC efforts were recorded at 15-s intervals, three times before and six times after the sustained clench. Each subject performed this pattern of activities three times with a 15-min rest between each trial. The centre frequency (CF) of the electromyographic power spectrum was calculated by fast Fourier transformations. The mean CF at the end of the 30-s clench and the rate of change at the CF during the clenching task were analysed between groups, sides and muscles. The data indicated that the masseter CF decreased at a significantly faster rate for the first clenching trial in the muscle-pain group. Conversely, the rate of change of the temporalis CF did not significantly differ for the two groups during the three clenching trials. By the third trial the CF of the exercised masseter in the non-pain group exhibited a similar rate of change to that in the pain group. This suggests that both repeated exercise and the presence of chronic inflammation increase the rate of change of the electromyographic signal of the contracting masseter. The mechanism underlying this increased change is unknown.
12名患有慢性咀嚼肌疼痛的个体（2名男性，10名女性）和11名无慢性咀嚼肌疼痛的个体（2名男性，9名女性），在进行30秒持续次最大紧咬任务之前、期间和之后，记录了他们的咬合力以及右侧和左侧浅表咬肌和颞肌前束的表面肌电图。该任务在每个受试者最大自主收缩（MVC）力水平的50%下进行30秒。在持续紧咬前，每隔15秒记录一次短暂（3秒）的50%MVC用力，共记录三次；紧咬后记录六次。每个受试者按照这种活动模式进行三次，每次试验之间休息15分钟。通过快速傅里叶变换计算肌电图功率谱的中心频率（CF）。分析了两组之间、两侧之间以及肌肉之间在30秒紧咬结束时的平均CF以及紧咬任务期间CF的变化率。数据表明，在肌肉疼痛组中，第一次紧咬试验时咬肌CF下降的速度明显更快。相反，在三次紧咬试验期间，两组颞肌CF的变化率没有显著差异。到第三次试验时，非疼痛组中运动咬肌的CF变化率与疼痛组相似。这表明重复运动和慢性炎症的存在都会增加收缩咬肌肌电信号的变化率。这种变化增加的潜在机制尚不清楚。
