Olson Michael, Solomonow Moshe, Li Li
Department of Kinesiology, Louisiana State University, Baton Rouge, LA, USA.
J Biomech. 2006;39(14):2545-54. doi: 10.1016/j.jbiomech.2005.09.009. Epub 2005 Oct 26.
The objective of this report was to study the influence of the orientation of gravitational loading on the behavior of anterior and posterior trunk muscles during anterior trunk flexion-extension. Participants (N=13) performed five (5) cycles of trunk flexion-extension while standing with gravity parallel to the body axis and five (5) cycles while in the supine condition (e.g. sit-ups) with gravity perpendicular to the body axis. Surface electromyographic (EMG) patterns from lumbar paraspinal, rectus abdominis, external oblique, rectus femoris, semimembranosis, and biceps femoris muscles were analyzed during each condition. EMG signals were synchronized with lumbar flexion and trunk inclination angles. Flexion-extension from the standing position resulted in a myoelectric silent period of the lumbar posterior muscles (e.g. flexion-relaxation phenomena (FRP)) as well as the hamstring muscles through deep angles during which activity was observed in abdominal muscles. Flexion-extension during sit-ups, however, resulted in a myoelectric silent period of the abdominal muscles and the quadriceps through deep angles during which the lumbar posterior muscles were active. In this condition, the FRP was not observed in posterior muscles. The new findings demonstrate the profound impact of the orientation of the gravity vector on the FRP, the abdominal muscles reaction to gravitational loads during sit-ups and its relationships with lumbar antagonists and thigh musculature. The new findings suggest that gravitational moments requirements dominate the FRP through the prevailing kinematics, load sharing and reflex activation-inhibition of muscles in various conditions. Lumbar kinematics or fixed sensory motor programs by themselves, however, are not the major contributor to the FRP. The new findings improve our insights into spinal biomechanics as well as understanding and evaluating low back disorders.
本报告的目的是研究重力加载方向对前躯干屈伸过程中前后躯干肌肉行为的影响。参与者（N = 13）在重力与身体轴线平行站立时进行了五（5）个周期的躯干屈伸，以及在仰卧位（如仰卧起坐）重力与身体轴线垂直时进行了五（5）个周期的躯干屈伸。在每种情况下，分析了腰旁肌、腹直肌、腹外斜肌、股直肌、半膜肌和股二头肌的表面肌电图（EMG）模式。EMG信号与腰椎屈曲和躯干倾斜角度同步。从站立位进行屈伸时，腰椎后部肌肉（如屈曲放松现象（FRP））以及绳肌在深度角度会出现肌电静息期，在此期间观察到腹肌活动。然而，仰卧起坐时的屈伸在深度角度会导致腹肌和股四头肌出现肌电静息期，在此期间腰椎后部肌肉活跃。在这种情况下，未在后部肌肉中观察到FRP。新发现表明重力矢量方向对FRP、仰卧起坐时腹肌对重力负荷的反应及其与腰椎拮抗肌和大腿肌肉组织的关系具有深远影响。新发现表明，在各种情况下，重力矩需求通过主导的运动学、负荷分担以及肌肉的反射激活 - 抑制作用来主导FRP。然而，腰椎运动学或固定的感觉运动程序本身并不是FRP的主要促成因素。这些新发现增进了我们对脊柱生物力学的理解，以及对下背部疾病的认识和评估。
