Mazzaro Nazarena, Grey Michael J, do Nascimento Omar Feix, Sinkjaer Thomas
Center for Sensory-Motor Interaction (SMI), Aalborg University, 9220 Aalborg, Denmark.
Exp Brain Res. 2006 Sep;173(4):713-23. doi: 10.1007/s00221-006-0451-5. Epub 2006 Apr 26.
The aim of this study was to investigate the contribution of proprioceptive feedback to the amplitude modulation of the soleus muscle activity during human walking. We have previously shown that slow-velocity, small-amplitude ankle dorsiflexion enhancements and reductions applied during the stance phase of the step cycle generate, respectively, increments and decrements on the ongoing soleus activity. We have also shown that the increments in soleus activity are at least partially mediated by feedback from group Ia fibres. In the present study, we further investigated the afferent-mediated contribution from muscle group II afferents, cutaneous and proprioceptive afferents from the foot, and load-sensitive afferents to the soleus EMG. Slow-velocity, small-amplitude ankle trajectory modifications were combined with the pharmaceutical depression of group II polysynaptic pathways with tizanidine hydrochloride, anaesthetic blocking of sensory information from the foot with injections of lidocaine hydrochloride, and modulation of load feedback by increasing and decreasing the body load. The depression of the group II afferents significantly reduced the soleus response to the ankle trajectory modifications. Blocking sensory feedback from the foot did not have an effect on the soleus muscle activity. Changes in body load affected the ongoing soleus activity level; however, it did not affect the amplitude of the soleus EMG responses to the ankle trajectory modifications. These results suggest that the feedback from group II afferents, and possibly from load-sensitive afferents, contribute to the amplitude modulation of the soleus muscle activity during the stance phase of the step cycle. However, feedback from cutaneous afferents and instrinsic proprioceptive afferents from the foot does not seem to contribute to this muscle activation.
本研究的目的是调查本体感觉反馈在人类行走过程中对比目鱼肌活动幅度调制的作用。我们之前已经表明，在步周期的站立阶段施加的低速、小幅度踝关节背屈增强和减弱，分别会使持续的比目鱼肌活动增加和减少。我们还表明，比目鱼肌活动的增加至少部分是由Ia类纤维的反馈介导的。在本研究中，我们进一步研究了II类肌传入纤维、足部皮肤和本体感觉传入纤维以及负荷敏感传入纤维对比目鱼肌肌电图的传入介导作用。将低速、小幅度的踝关节轨迹改变与用盐酸替扎尼定对II类多突触通路进行药物抑制、用注射盐酸利多卡因对来自足部的感觉信息进行麻醉阻断以及通过增加和减少身体负荷来调节负荷反馈相结合。II类传入纤维的抑制显著降低了比目鱼肌对踝关节轨迹改变的反应。阻断来自足部的感觉反馈对比目鱼肌活动没有影响。身体负荷的变化影响了持续的比目鱼肌活动水平；然而，它并没有影响比目鱼肌肌电图对踝关节轨迹改变的反应幅度。这些结果表明，II类传入纤维以及可能来自负荷敏感传入纤维的反馈，在步周期的站立阶段对比目鱼肌活动的幅度调制有贡献。然而，来自足部皮肤传入纤维和固有本体感觉传入纤维的反馈似乎对此肌肉激活没有贡献。
