Budini Francesco, Christova Monica, Gallasch Eugen, Rafolt Dietmar, Tilp Markus
Institute of Sport Sciences, University of Graz, Graz, Austria.
Institute of Physiotherapy, FH Joanneum - University of Applied Sciences, Graz, Austria.
Front Physiol. 2018 Jul 16;9:935. doi: 10.3389/fphys.2018.00935. eCollection 2018.
During the period when the ankle joint is kept in a dorsiflexed position, the soleus (SOL) H-reflex is inhibited. The nature of this inhibition is not fully understood. One hypothesis is that the decrease in spinal excitability could be attributed to post-activation depression of muscle spindle afferents due to their higher firing rate during the stretch-and-hold procedure. As the static stretching position is maintained though, a partial restoration of the neurotransmitter is expected and should mirror a decrease in H-reflex inhibition. In the present study, we explored the time course of spinal excitability during a period of stretching. SOL H-reflex was elicited during a passive dorsiflexion movement, at 3, 6, 9, 12, 18, 21, and 25 s during maximal ankle dorsiflexion, during plantar flexion (PF) and after stretching, in 12 healthy young individuals. Measurements during passive dorsiflexion, PF and after stretching were all performed with the ankle at 100° angle; measurements during static stretching were performed at individual maximal dorsiflexion. H-reflex was strongly inhibited during the dorsiflexion movement and at maximal dorsiflexion ( < 0.0001) but recovered during PF and after stretching. During stretching H-reflex showed a recovery pattern ( = 0.836, = 0.019) with two distinct recovery steps at 6 and 21 s into stretching. It is hypothesized that the H-reflex inhibition observed until 18 s into stretching is the result of post-activation depression of Ia afferent caused by the passive dorsiflexion movement needed to move the ankle into testing position. From 21 s into stretching, the lower inhibition could be caused by a weaker post-activation depression, inhibition from secondary afferents or post-synaptic inhibitions.
在踝关节保持背屈位期间，比目鱼肌（SOL）的Hoffmann反射（H反射）受到抑制。这种抑制的本质尚未完全明了。一种假说认为，脊髓兴奋性的降低可能归因于肌梭传入纤维在拉伸并保持过程中较高的放电频率导致的激活后抑制。然而，随着静态拉伸姿势的维持，神经递质有望部分恢复，且应反映出H反射抑制的减轻。在本研究中，我们探究了拉伸期间脊髓兴奋性的时间进程。在12名健康年轻个体中，于被动背屈运动期间、最大踝关节背屈时的3、6、9、12、18、21和25秒、跖屈（PF）期间以及拉伸后，引出比目鱼肌H反射。被动背屈、PF和拉伸后的测量均在踝关节处于100°角时进行；静态拉伸期间的测量在个体最大背屈时进行。H反射在背屈运动期间和最大背屈时受到强烈抑制（P<0.0001），但在PF期间和拉伸后恢复。在拉伸期间，H反射呈现出一种恢复模式（R² = 0.836，P = 0.019），在拉伸至6秒和21秒时有两个明显的恢复阶段。据推测，在拉伸至18秒之前观察到的H反射抑制是将踝关节移动到测试位置所需的被动背屈运动引起的Ia传入纤维激活后抑制的结果。从拉伸21秒起，较低的抑制可能是由较弱的激活后抑制、二级传入纤维的抑制或突触后抑制引起的。
