抄録
The shoulder joints and their connecting muscles participate in cooperation in the wide, smooth and expedient movements of the arm, which was once described by Codman so aptly as “ scapulohumeral rhythm” . And, there are numerous analysis of the mechanism studies. The present study was undertaken to establish a more reliable quantitative method for comprehending the dynamics of the electromyographic activity in relation to the measurement of elevation angles during the flexion, scapular abduction and abdution movement of the shoulder.
Materials and Methods;
Twenty shoulder of ten n ormal male students were the subjects of study.70 microns fine wire electrodes were assigned to the trapezius (upper fider), supraspinatus, deltoideus (asterior, middle and posterior fiber), pectralis major (clavicular head), latissimus dorsi, teres major and rhomboideus muscles. Examinees were asked to elevate their arm in each direction with or without the 2.6 kg load at their hands. The electromyograms and elevation angle obtained by the goniometer were recorded by using a magnetic tape data recorder simultaneously. The computer was used for integrating the action potentials from examined muscles at 10 degrees intervals of elevation angle. And, the percentage of integrated action potential in each examinee and each direction was analyzed to observe muscle activies.
Results;
The perc e ntages of integrated action potentials from the trapezius (upper fiber), supraspinatus, deltoideus (anterior and middle fiber), pectralis major (clavicular head) and rhomboideus muscles showed high and increased with the increasing magnitude of elevation angle. Though the anterior, middle and posterior fiber of deltoideus muscle were the same muscle, the difference of integrated action potential pattern in those fibers was observed. On the electromyogram, the action potential from the anterior fiber of deltoid was observed prior to that from middle fiber in flexion, but in abduction that pattern was reversed. The deltoideus (posterior fiber), latissimus dorsi and teres major muscles showed low percentage of integrated action potential.
