Škarabot Jakob, Alfonso Ruben Perellón, Cronin Neil, Bon Jure, Strojnik Vojko, Avela Janne
Neuromuscular Research Centre, Department of Biology of Physical Activity, University of Jyväskylä, PL 35, 40014, Jyväskylä, Finland.
Department of Neurology, University Medical Centre Ljubljana, Zaloška cesta 2, 1000, Ljubljana, Slovenia.
Eur J Appl Physiol. 2016 Dec;116(11-12):2197-2214. doi: 10.1007/s00421-016-3475-y. Epub 2016 Sep 14.
Interhemispheric inhibition may play a role in the expression of bilateral deficit in force (BLD). This study investigated whether the degree of BLD is reflected in the nature of interhemispheric interaction during unilateral and bilateral contractions.
Subjects divided into three groups, 'bilateral' (n = 7), 'unilateral' (n = 5) and 'control' (n = 8), performed unilateral and bilateral maximal voluntary isometric knee extensions while receiving electrical stimulation, and transcranial magnetic stimulation of the target and ipsilateral muscles. Main variables of interest included peak force for subsequent calculation of bilateral index, voluntary activation level (VAL), motor evoked potential amplitudes (MEPs) and silent period durations (SPs).
BLD was noted only for the whole sample (p = 0.009), but not for any of the groups. VAL was significantly higher during bilateral compared to unilateral contractions (~97 vs. 92 %, p = 0.023), with no differences between groups. MEPs of target and ipsilateral muscles were significantly bigger during bilateral contractions (p = 0.042 and p = 0.022, respectively), with no differences between groups. No differences in SPs were observed.
Higher values of MEPs and VAL during bilateral contractions, in conjunction with unaltered SPs, do not support the concept of inhibition related to BLD, but rather suggest the possibility of cortical facilitation. Based on the existing literature, this behavior may be specific to the lower limb musculature, but the possibility of sub-cortical or higher-order neural alterations cannot be excluded.
半球间抑制可能在双侧力量缺陷（BLD）的表现中起作用。本研究调查了在单侧和双侧收缩过程中，BLD的程度是否反映在半球间相互作用的性质上。
将受试者分为三组，即“双侧组”（n = 7）、“单侧组”（n = 5）和“对照组”（n = 8），在接受电刺激以及对目标肌肉和同侧肌肉进行经颅磁刺激的同时，进行单侧和双侧最大自主等长膝关节伸展。主要关注变量包括用于后续计算双侧指数的峰值力量、自主激活水平（VAL）、运动诱发电位幅度（MEP）和静息期持续时间（SP）。
仅在整个样本中观察到BLD（p = 0.009），但在任何一组中均未观察到。与单侧收缩相比，双侧收缩期间VAL显著更高（约97%对92%，p = 0.023），组间无差异。双侧收缩期间目标肌肉和同侧肌肉的MEP显著更大（分别为p = 0.042和p = 0.022），组间无差异。未观察到SP的差异。
双侧收缩期间MEP和VAL较高，同时SP未改变，这并不支持与BLD相关的抑制概念，而是提示了皮质易化的可能性。根据现有文献，这种行为可能特定于下肢肌肉组织，但不能排除皮质下或高级神经改变的可能性。
