Trimble M H, Koceja D M
University of Florida, Department of Physical Therapy, Gainesville, FL 32610-0154.
Int J Neurosci. 2001 Jan;106(1-2):1-20. doi: 10.3109/00207450109149734.
The present study provides evidence that a reflex at the segmental level can adapt over a two hour experiment in a functionally appropriate manner in response to a balance training task. Subjects (N=9) received soleus (S) H-reflexes in blocks of seven trials while free standing on a normal base-of-support (NBOS) and while standing on a plafform with a reduced base-of-support (RBOS) in the sagittal plane. During the RBOS condition, the H-reflex served as a postural perturbation. Subjects were instructed to suppress the H-reflex when it was evoked, as an attempt to maintain a balanced state. Background EMG from the S and tibialis anterior muscles, the S M-wave, and stimulus current were maintained at a constant level during the experiment. Subjects initially received a block of NBOS trials, followed by 4 RBOS blocks (training), a second NBOS block, four additional RBOS blocks, and a third NBOS block with the protocol repeated on three different days (D1, D2 and D3) within the same week. The S H/M ratio was depressed 9% upon standing on the RBOS. With training the S H/M ratio decreased by 22% on Dl, 18% on D2 and 6% on D3. The ratio between the H-reflex and background S EMG (H-reflex gain) decreased 10% on D1, 40% on D2 and 23% on D3 when the first NBOS and first RBOS blocks were compared. Due to a slight increase in the S EMG across blocks, the H-reflex gain decreased considerably more across blocks than the H/M ratio. Although the S H/M ratio underwent an 7% decrease from D1 to D3, the differences were not significant. Individually, however, six of the nine subjects decreased their H/M ratios from 12-42% across days. The results may reflect the inception of longer-term adaptations of the segmental stretch reflex system.
本研究提供了证据，表明在一个两小时的实验中，节段水平的反射能够以功能上合适的方式，响应平衡训练任务而发生适应性变化。受试者（N = 9）在自由站立于正常支撑面（NBOS）时以及站立于矢状面支撑面减小的平台（RBOS）上时，以七个试次为一组接受比目鱼肌（S）H反射。在RBOS条件下，H反射作为一种姿势扰动。受试者被指示在H反射被诱发时抑制它，以试图维持平衡状态。在实验过程中，来自比目鱼肌和胫前肌的背景肌电图、比目鱼肌M波以及刺激电流保持在恒定水平。受试者最初接受一组NBOS试次，随后是4组RBOS试次（训练），第二组NBOS试次，另外4组RBOS试次，以及第三组NBOS试次，该方案在同一周内的三天（D1、D2和D3）重复进行。站立于RBOS时，比目鱼肌H/M比值降低了9%。经过训练，D1时比目鱼肌H/M比值下降了22%，D2时下降了18%，D3时下降了6%。当比较第一组NBOS和第一组RBOS试次时，H反射与比目鱼肌背景肌电图之间的比值（H反射增益）在D1时下降了10%，D2时下降了40%，D3时下降了23%。由于各试次组间比目鱼肌肌电图略有增加，H反射增益在各试次组间的下降幅度比H/M比值大得多。尽管从D1到D3比目鱼肌H/M比值下降了7%，但差异不显著。然而，就个体而言，9名受试者中有6名在不同天数内其H/M比值下降了12% - 42%。这些结果可能反映了节段性牵张反射系统长期适应性变化的开始。
