Konishi Y, McNair P J, Rice D A
Department of Physical Education, National Defense Academy, Kanagawa, Japan.
Health and Rehabilitation Research Institute, Auckland University of Technology, Auckland, New Zealand.
Int J Sports Med. 2017 Mar;38(3):253-257. doi: 10.1055/s-0042-118183. Epub 2017 Feb 13.
Quadriceps weakness is a notable problem following knee damage. Research has shown effectiveness of TENS in improving Quadriceps weakness associated with arthrogenic muscle inhibition. However, these studies were not focused upon short term delivery of TENS, nor did they examine the potential mechanism(s). The present study examined the effect of 25-30 s of TENS upon weakness induced temporarily by a prolonged vibration. Subjects performed eccentric MVCs under 2 conditions (TENS and no-TENS). First, MVC was measured at baseline. For the TENS condition, TENS was applied to each subject's knee joint during a second MVC measurement after vibration. For no-TENS condition, TENS was not applied during the 2 MVC measurement. MVC between pre-and post-vibration stimulation were compared across the 2 conditions. The results showed that MVC and EMG of TENS-condition was larger than that of no-TENS condition. Our results suggest that TENS could partially restore α-motoneuron activation, despite the induced dysfunctional γ-loop. These results suggest that mechanisms independent of the γ-loop such as a direct facilitation of the QF α-motoneuron pool by a long latency spinal-reflex and/or supraspinal mechanisms appear more likely to be responsible. The findings provide further support for utilizing TENS, even when γ-loop dysfunction is present following joint damage.
股四头肌无力是膝关节损伤后一个显著问题。研究表明，经皮电刺激神经疗法（TENS）在改善与关节源性肌肉抑制相关的股四头肌无力方面具有有效性。然而，这些研究并非聚焦于TENS的短期应用，也未探究其潜在机制。本研究考察了25 - 30秒的TENS对长时间振动暂时诱发的无力的影响。受试者在两种条件下（TENS和无TENS）进行离心性最大自主收缩（MVC）。首先，在基线时测量MVC。对于TENS条件，在振动后的第二次MVC测量期间，将TENS应用于每个受试者的膝关节。对于无TENS条件，在两次MVC测量期间均不应用TENS。比较两种条件下振动前后刺激的MVC。结果显示，TENS条件下的MVC和肌电图（EMG）大于无TENS条件。我们的结果表明，尽管诱发了功能失调的γ-环路，TENS仍可部分恢复α运动神经元的激活。这些结果表明，诸如通过长潜伏期脊髓反射和/或脊髓上机制直接促进股四头肌（QF）α运动神经元池等独立于γ-环路的机制似乎更有可能起作用。这些发现为即使在关节损伤后存在γ-环路功能障碍时仍使用TENS提供了进一步支持。
