Del Santo Francesco, Gelli Francesca, Ginanneschi Federica, Popa Traian, Rossi Alessandro
Dipartimento di Scienze Neurologiche e del Comportamento, Sezione di Neurofisiologia Clinica, Italy.
Brain Res. 2007 Aug 13;1163:79-85. doi: 10.1016/j.brainres.2007.06.012. Epub 2007 Jun 16.
Evidence exists that shoulder joint geometry influences recruitment efficiency and force-generating capacity of hand muscles [Ginanneschi, F., Del Santo, F., Dominici, F., Gelli, F., Mazzocchio, R., Rossi, A., 2005. Changes in corticomotor excitability of hand muscles in relation to static shoulder positions. Exp. Brain Res. 161 (3), 374-382; Dominici, F., Popa, T., Ginanneschi, F., Mazzocchio, R., Rossi, A., 2005. Cortico-motoneural output to intrinsic hand muscles is differentially influenced by static changes in shoulder positions. Exp. Brain Res. 164 (4), 500-504]. The present study was designed to examine the impact of changing shoulder joint position on the relation between surface EMG amplitude and isometric force production of the abductor digiti minimi muscle (ADM). EMG-force relation of ADM was examined in two shoulder positions: 30 degrees adduction (ANT) and 30 degrees abduction (POST) on the horizontal plane, i.e. under higher and lower force-generating capacity, respectively. The relation was studied over the full range isometric force (10-100% of maximum force in 10% increments, 3 s duration) by analysing root mean square (RMS), median frequency (Mf) of the power spectrum and non-linear recurrence quantification analysis (percentage of determinism: %DET) of the surface EMG signals. We found that in POST, the slope of the RMS-force relation was significantly higher than in ANT, while its general shape (strictly linear) was preserved. Averaged Mf of the EMG power spectrum was significantly higher in POST that in ANT, while no difference in %DET was observed between the two shoulder positions. The higher slope of the EMG-force relation in POST than in ANT is interpreted in terms of increased gain of the excitatory drive-firing rate relation. It is concluded that discharge from sensory receptors signalling shoulder position may act to regulate the gain of the excitatory drive-firing rate relation of motoneurones in order to compensate for reduced recruitment efficiency.
有证据表明，肩关节的几何结构会影响手部肌肉的募集效率和力量产生能力[吉南内斯基，F.，德尔·桑托，F.，多米尼西，F.，杰利，F.，马佐基奥，R.，罗西，A.，2005年。与静态肩部位置相关的手部肌肉皮质运动兴奋性变化。《实验脑研究》161(3)，374 - 382页；多米尼西，F.，波帕，T.，吉南内斯基，F.，马佐基奥，R.，罗西，A.，2005年。肩部位置的静态变化对手部固有肌肉的皮质-运动神经元输出有不同影响。《实验脑研究》164(4)，500 - 504页]。本研究旨在探讨改变肩关节位置对小指展肌（ADM）表面肌电图（EMG）幅度与等长力产生之间关系的影响。在两个肩部位置检查了ADM的肌电图-力关系：在水平面上内收30度（ANT）和外展30度（POST），即分别处于较高和较低的力量产生能力下。通过分析表面肌电图信号的均方根（RMS）、功率谱的中位数频率（Mf）和非线性递归量化分析（确定性百分比：%DET），在等长力的全范围内（最大力的10 - 100%，以10%递增，持续3秒）研究了这种关系。我们发现，在POST位置，RMS-力关系的斜率显著高于ANT位置，而其总体形状（严格线性）保持不变。POST位置的肌电图功率谱平均Mf显著高于ANT位置，而在两个肩部位置之间未观察到%DET的差异。POST位置的肌电图-力关系斜率高于ANT位置，这被解释为兴奋性驱动-放电率关系的增益增加。得出的结论是，来自信号指示肩部位置的感觉受体的放电可能起到调节运动神经元兴奋性驱动-放电率关系增益的作用，以补偿降低的募集效率。
