Steldt Robert E, Schmit Brian D
Dept. of Biomedical Engineering, Marquette University, PO Box 1881, Milwaukee, WI 53201-1881, USA.
J Neurophysiol. 2004 Aug;92(2):673-85. doi: 10.1152/jn.00677.2003. Epub 2004 Mar 24.
Individuals with chronic spinal cord injury (SCI) often demonstrate multijoint reflex activity that is clinically classified as an extensor spasm. These responses are commonly observed in conjunction with an imposed extension movement of the hips, such as movement from a sit to a supine position. Coincidentally, afferent feedback from hip proprioceptors has also been implicated in the control of locomotion in the spinalized cat. Because of this concurrence, we postulated that extensor spasms that are triggered by hip extension might involve activation of organized interneuronal circuits that also have a role in locomotion. If true, imposed oscillations of the hip would be expected to produce activity of the leg musculature in a locomotor pattern. Furthermore, this muscle activity would be entrained to the hip movement. The right hip joints of 10 individuals with chronic SCI, consisting of both complete [American Spinal Injury Association (ASIA) A] and incomplete (ASIA B,C) injuries, were subjected to ramp and hold (10 s) movements at 60 degrees /s and sinusoidal oscillations at 1.2, 1.88, and 2.2 rad/s over ranges from 40 to -15 degrees (+/-5 degrees ) using a custom servomotor system. Surface EMG from seven lower extremity muscles and sagittal-plane joint torques were recorded to characterize the response. Ramp and hold perturbations produced coactivation at the hip, knee, and ankle joints, with a long duration (5-10 s). Sinusoidal perturbations yielded consistent muscle timing patterns that resulted in alternating flexor and extensor joint torques. EMG and joint torques were commonly entrained to the frequency of movement, with rectus femoris, vastus medialis, and soleus activity coinciding with hip extension and medial hamstrings activity occurring during hip flexion. Individual muscle timing patterns were consistent with hip position during normal gait, except for the vastus medialis. These results suggest that reflexes associated with extensor spasms may occur through organized interneuronal pathways, such as spinal centers for locomotion.
患有慢性脊髓损伤（SCI）的个体常常表现出多关节反射活动，临床上将其归类为伸肌痉挛。这些反应通常在髋关节进行强制性伸展运动时出现，比如从坐姿转变为仰卧位的动作。巧合的是，髋关节本体感受器的传入反馈也被认为参与了脊髓损伤猫的运动控制。鉴于这种一致性，我们推测由髋关节伸展引发的伸肌痉挛可能涉及激活那些在运动中也发挥作用的有组织的中间神经元回路。如果真是这样，对髋关节施加振荡预计会使腿部肌肉以运动模式产生活动。此外，这种肌肉活动会与髋关节运动同步。使用定制的伺服电机系统，对10名患有慢性脊髓损伤的个体的右髋关节进行了测试，这些个体既有完全性损伤（美国脊髓损伤协会（ASIA）A级），也有不完全性损伤（ASIA B、C级），测试内容包括以60度/秒的速度进行斜坡和保持（10秒）运动，以及在40至 -15度（±5度）范围内以1.2、1.88和2.2弧度/秒的频率进行正弦振荡。记录了来自七个下肢肌肉的表面肌电图和矢状面关节扭矩，以表征反应情况。斜坡和保持扰动在髋关节、膝关节和踝关节处产生了共同激活，持续时间较长（5 - 10秒）。正弦扰动产生了一致的肌肉定时模式，导致屈肌和伸肌关节扭矩交替出现。肌电图和关节扭矩通常与运动频率同步，股直肌、股内侧肌和比目鱼肌的活动与髋关节伸展同步，而半腱肌内侧头的活动在髋关节屈曲时出现。除股内侧肌外，个体肌肉定时模式与正常步态期间的髋关节位置一致。这些结果表明，与伸肌痉挛相关的反射可能通过有组织的中间神经元通路发生，比如脊髓运动中枢。
