立位での一側下肢への側方体重移動が腰背筋群・足部周囲筋の筋活動パターンに与える影響

Activity of Back and Foot Muscles during Lateral Weight-Shifting in the Standing Position

要旨

目的：立位での一側下肢への側方体重移動における腰背筋群・足部周囲筋の役割を解明する目的で，側方移動中の姿勢変化と腰背筋群・足部周囲筋の筋活動パターンを検討した．

方法：対象は健常男性24名（24.3±2.6歳）．直立位から2秒間で側方移動させ，そのときの足底圧中心（COP）と両側多裂筋・腸肋筋・最長筋，移動側足部内反筋群・腓骨筋群の筋電図波形，ビデオ画像を計測した．

結果：骨盤は水平移動した後，COPの移動側変位途中から非移動側挙上を生じた．下肢では側方移動に伴い移動側足部回内による下腿の外側傾斜を生じた．このとき，COPが移動側へ変位する途中から非移動側多裂筋・腸肋筋・最長筋，移動側足部内反筋群・腓骨筋群の筋活動が増加した．

結論：非移動側多裂筋・腸肋筋・最長筋は骨盤非移動側挙上に対する胸腰部非移動側側屈に関与した．このとき，足部内反筋群・腓骨筋群は足底接地した状態での足部回内に関与した．

【Objective】

To investigate the role of the back and foot muscles during lateral weight-shifting in the standing position by examining the corresponding muscle activity patterns associated with a postural change.

【Methods】

The subjects were 24 healthy men (age 24.3 ± 2.6 [mean ± SD] years). The following parameters were recorded : center of pressure (COP) ; surface electromyograms of the multifidus, iliocostalis, longissimus (bilateral), peroneus, and foot supinator (on the moving side) muscles ; and video imaging during lateral weight-shifting after 2 seconds in the standing position.

【Results】

Horizontal movement of the pelvis resulted in elevation of the non-moving side from the middle of the COP, with moving side displacement. In the lower limbs, lateral weight shifting resulted in an outward tilt due to foot pronation. Activity of the multifidus, iliocostalis, and longissimus muscles on the non-moving side, and the peroneus and foot supinator muscles on the moving side, tended to increase with displacement of the COP on the moving side.

【Conclusion】

The multifidus, iliocostalis, and longissimus muscles were involved in lateral flexion of the thoracolumbar area and elevation of the pelvis on the non-moving side. Simultaneously, the foot supinator and peroneus muscles were involved in pronation of the grounded foot.