EMG Activity of the Popliteus Muscle during Walking and Standing

本研究の目的は, 健常者を対象にして歩行中および立位保持中に膝窩筋筋電図を導出し, その機能を明らかにすることであった。対象は健常男性10名であり, 課題動作は自然歩行および膝関節0度, 30度, 60度および90度屈曲位での立位保持であった。筋電図の導出にはワイヤー電極を使用し, 電気刺激を行うことにより電極が膝窩筋内に入っていることを確認した。各動作時に得られた筋電図は全波整流したのち移動平均処理を行い平滑化し, 最大等尺性下腿内旋運動時に得られた筋電図をもとに正規化した。歩行中の膝窩筋筋活動は, 立脚初期, 立脚後期および遊脚後期に強い活動を示した。特に立脚期9.3%時点では膝窩筋の筋活動は最も強く, 下腿最大内旋運動時の72.2±14.8%を示した。また, 立位保持中における膝窩筋の筋活動は膝関節屈曲角度の増加に伴い増加した。これらの結果から, 膝窩筋は, 歩行時には遊脚後期から立脚初期にかけては膝関節過伸展を防御し, 立脚後期から遊脚初期にかけては膝関節の屈曲運動に関与することが推察された。また, 立位保持時には脛骨の前方移動を防ぐように活動していると考えられた。The purposes of this study were to detect the electromyographic activity of the popliteus muscle during walking and standing, and to clarify the popliteus muscle function. The healthy male volunteers participated in this study. The electromyographic activity during walking and standing at 0, 30, 60 and 90 degrees of knee flexion was recorded. Bipolar fine wire electrode was inserted into the right popliteus muscle, and electrical stimulation was used to confirm the location of the electrode. The EMG raw data were rectified and averaged, then the smoothed EMG was normalized by the value that was obtained during the maximum isometric internal rotation of the tibia. The popliteus muscle showed some activity in each phase of the gait cycle. Within this continuum, however, there were three phases of peak electromyographic activity. These peaks occurred at loading response, preswing and terminal swing phases. The activity of the popliteus muscle during standing increased with the increase of the knee flexion in standing. These data suggested that the popliteus muscle help to protect the knee from the hyperextension during terminal swing and loading response phases of the gait cycle, and may assist the initiation of knee flexion at preswing phase. In addition, the popliteus muscle could increase its activity in an attempt to limit the anterior tibial shearing during standing with knee flexion