【摘要】 <正> 在经典解剖学上,根据肌肉作用力的方向和电刺激的实验结果,对单个肌肉的作用已经有了详尽的研究。但是一个动作往往牵涉多个肌肉,由单一肌肉引起的动作,并不多见。应用肌电图的方法能同时显示出参加动作所有肌肉的活动情况,故对固定肌、拮抗肌的意义有了更进一步的阐明。一般认为:固定肌及拮抗肌在动作过程中更多还原

【Abstract】 Based on the principle of the pulse-height analysis in the nuclear physics, the authors had developed a quantitative technique to investigate the electromyographic characters of agonist, antagonist and fixation muscles during cubital flexion. Ten healthy male volunteers were involved in this experiment. The EMG impulses were picked up by surface electrodes from the right biceps brachii, triceps brachii and deltoids. The elbows of the volunteers were kept at right angle with their hands carrying the standard weights (0, 1, 5 kg.). The intergral frequencies of: <200μv, >200μv, >500μv, >1000μv were recorded with the EMG pulseheight analizer and the differential frequencies of:<200μv (Ⅰ class), 200—500μv (Ⅱ class), 500—1000μv (Ⅲ class) and >1000 μv (Ⅳ class) were calculated. The amplitude distribution curves could also be determined. The results were as follows: (1) When the hands did not carry weight, the triceps and deltoids were wholly relaxing, but the biceps had shown more considerable activities, its total frequency (T. F.) was 4534.8±514 c.p.m. (cycles per minute), the Ⅰ class impulses were the most numerous. The percentages of Ⅰ to Ⅳ class were: 88.54%, 10.78%, 0.68%, 0%, respectively. (2) When under 1kg. load, both triceps and deltoids exhibited slight contraction, T. F. 150.6±93, 538.8±417 cpm respectively, and 100% belonged to the Ⅰ class. While the amplitudes and frequencies of the biceps increased simultaneously, T. F.: 7530±349, Ⅰ to Ⅳ class: 40.32%, 34.87%, 15.34%, 8.97%, (3) When carrying the 5kg. weight, the total frequencies of triceps increased to 2838±579, but the Ⅰ class impulses were the most, (98.01%), Ⅱ class only 1.99%. The T. F. of deltoids increased to 6231.6±544, Ⅰ to Ⅳ class: 70.76%, 20.14%, 6.61%, 2.49%. The T. F. of biceps in creased to 8361.6±300, Ⅰ to Ⅳ class: 11.06%, 14.89%, 16.53%, 57.52%. Based on the results mentioned above, the authors concluded: (A) The biceps (agonist) was the most active one during cubital flexion, the deltoids (fixation) the second, while the triceps (antagonist) was the most inert. (B) When the load increased, not only the total frequencies of the agonist increased, but also its amplitude became greater and greater, thus the impulses of Ⅰ class gradually decreased while the Ⅳ class impulses increased steeply. This may be considered as the special character of the agonist which differed significantly from the antagonist and fixation muscle. (C) Antagonist showed no activity without load; and when carrying load, it showed a little contraction, the total frequencies increased while the amplitude exhibited no significant alteration. Such slight contraction played a considerable role to keep the action smooth, steady, even, correct and adequate. The antagonist could also be considered as a special fixation muscle to fix the insertion of the agonist. (D) When the upper limb hanged free, although the load increased to 10kg., the deltoids showed no activity. But when the elbow flexed, the deltoids fixed the shoulder joint. Under a light load (1kg.), the deltoids showed a little activity which did not differ significantly from that of the triceps. But during the load increased to 5kg., the activity of this fixation muscle was apparently greater than that of the antagonist. At the meanwhile, not only the total frequency but also the amplitude increased simultaneously. (E) When the elbow flexed without carrying a load, the deltoids showed no activity. At this time, the shoulder joint might be fixed by means of some other tissues, for example, ligment, articular capsule, etc. But when under load, the fixation of the upper articulation was maintained chiefly by the contraction of the fixation muscles. (F) The authors suggested that it was not enough to explain the function of a muscle merely based on the figure of its electromyogram, especially when it reacted against resistance. For when the action was intensified, more and more fixation muscles took part in contraction. It seemed necessary to use the quantitative E.M.G. method as the supplement for the usual E.M.G. investigation.更多还原