Gupta A
Department of Orthopaedic Surgery, Maulana Azad Medical College & Associated L. N. Hospital, New Delhi, India.
J Biomech. 2001 Apr;34(4):491-6. doi: 10.1016/s0021-9290(00)00213-x.
Electromyographic activity of the erector spinae was studied in 25 healthy, young individuals during forward bending and then coming back to erect posture. Sudden onset of electrical silence called the flexion-relaxation phenomenon was seen to occur in all at 57% of the maximum hip flexion and at 84% of the maximum vertebral flexion. Abrupt re-commencement of the activity was seen at almost similar flexion angle while coming back to erect position. The experiment was repeated with the buttocks held against the wall so as to prevent the posterior migration of the pelvis and also the hip flexion to some extent. The effect was to produce inhibition of the electrical activity earlier at 75% of maximum vertebral flexion (p<0.001) while reactivation of erector spinae occurred soon after the extension started from the maximum trunk flexion. Eleven male subjects repeated the experimental task holding 22 lb weight in front and then on their back tied around the iliac crest. In both the instances the myo-electrical silence was found to occur at greater vertebral flexion. It is concluded that the passive equilibrium between gravity induced tensile torque and the extension torque of stretched posterior vertebral ligaments is responsible for the flexion-relaxation phenomenon than the stretch receptors.
在25名健康的年轻个体向前弯腰然后恢复直立姿势的过程中，对竖脊肌的肌电图活动进行了研究。在所有个体中，当髋关节屈曲达到最大角度的57%、脊柱屈曲达到最大角度的84%时，均出现了一种突然的电静息状态，称为屈曲-松弛现象。在恢复直立姿势时，在几乎相同的屈曲角度下观察到活动突然重新开始。实验重复进行，让受试者臀部靠墙，以防止骨盆向后移动，并在一定程度上防止髋关节屈曲。结果是在脊柱屈曲达到最大角度的75%时更早地抑制了电活动（p<0.001），而竖脊肌在从最大躯干屈曲开始伸展后不久就重新激活。11名男性受试者重复了实验任务，一次在身前手持22磅重物，另一次在身后将重物系在髂嵴周围。在这两种情况下，均发现肌电静息在更大的脊柱屈曲角度时出现。得出的结论是，重力诱导的拉伸扭矩与拉伸的后脊柱韧带的伸展扭矩之间的被动平衡比拉伸感受器更能导致屈曲-松弛现象。
