骨盤回旋位での股関節屈曲運動における筋活動の性差

Differences between Sexes in Muscle Activity during Hip Flexion with Pelvic Rotation : Electromyographic Analysis

要旨：本研究の目的は，異なる骨盤回旋位置における股関節屈曲運動の筋活動を調査し，性別による差を検討することである．対象は健常成人15例30肢（男性5例10肢，女性10例20肢）（平均年齢28.8±7.1歳），運動課題は仰臥位で膝関節90°屈曲位にて床面と垂直に股関節を屈曲することである．条件は骨盤正中位，検肢側5度回旋位，反対側5度回旋位の3つであり，大腿筋膜張筋（TFL），大腿直筋（RF），大腿二頭筋（BF），半腱様筋（ST），両側内腹斜筋（OI）の筋活動値を表面筋電図計で計測した．骨盤正中位での活動値を基準とし，骨盤回旋位の値を百分率で算出した．男性の各筋活動値は，正中位と回旋位で有意差は認められなかった．一方，女性では反対側回旋位におけるTFLが111.2％と有意に高かった（p＜0.05）．また，対側OIは検肢側，反対側回旋位ともに有意に高く活動（検肢側回旋：117.5％，反対側回旋：109.8％）した（p＜0.05）．女性は男性に比べ骨盤横径が大きく，骨盤にかかるモーメントが強くなるため，骨盤を安定化させる対側OIが等尺性に緊張したと推察される．女性の股関節屈曲筋訓練では骨盤回旋による影響に配慮する必要がある．

Abstract : Purpose : We verified electromyogram activity during hip flexion under different pelvic rotation positions, investigated the effects of pelvic rotational position and defined the difference between males and females. Subjects : 15 healthy adults (5 male, 10 female) with a mean age of 28.8 years participated in this study. Method : We recorded surface electromyograms of the tensor fasciae latae muscle (TFL), rectus femoris muscle (RF), biceps femoris muscle (BF), semitendinosus muscle (ST), and the bilateral internal oblique muscle (OI) during flexion of the hip joint in a supine position with three different pelvis rotation conditions. Results : Males showed no significant differences at all muscle activity levels. Meanwhile, TFL muscle activities were significantly higher for females in other side rotation of the pelvis than in the pelvis neutral position (p＜0.05). Moreover, opposite side of OI muscle was activated significantly highly in both side rotation position (p＜0.05). Conclusion : Generally, the transverse diameter of the pelvis in females is longer than that in males. When the lower extremity is elevated in the pelvis rotation positions, the moment of force on the pelvis is thought to be higher in females. Therefore, the stabilizing muscles of the pelvis, like the OI, need to be activated isometrically in females.