Suresh Nina L, Concepcion Nicole S, Madoff Janina, Rymer W Z
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, 345 E Superior Street, Room 1378, Chicago, IL, 60611, USA,
Exp Brain Res. 2015 Jan;233(1):15-25. doi: 10.1007/s00221-014-4061-3. Epub 2014 Sep 17.
Hemispheric brain injury resulting from a stroke is often accompanied by muscle weakness in contralateral limbs. In neurologically intact subjects, appropriate motoneuronal recruitment and rate modulation are utilized to optimize muscle force production. In the present study, we sought to determine whether weakness in an affected hand muscle in stroke survivors is partially attributable to alterations in the control of muscle activation. Specifically, our goal was to characterize whether the surface EMG amplitude was systematically larger as a function of (low) force in paretic hand muscles as compared to contralateral muscles in the same subject. We tested a multifunctional muscle, the first dorsal interosseous (FDI), in multiple directions about the second metacarpophalangeal joint in ten hemiparetic and six neurologically intact subjects. In six of the ten stroke subjects, the EMG-force slope was significantly greater on the affected side as compared to the contralateral side, as well as compared to neurologically intact subjects. An unexpected set of results was a nonlinear relation between recorded EMG and generated force commonly observed in the paretic FDI, even at very low-force levels. We discuss possible experimental as well as physiological factors that may contribute to an increased EMG-force slope, concluding that changes in motor unit (MU) control are the most likely reasons for the observed changes.
中风导致的大脑半球损伤常伴有对侧肢体肌肉无力。在神经功能正常的受试者中，会利用适当的运动神经元募集和频率调制来优化肌肉力量的产生。在本研究中，我们试图确定中风幸存者患侧手部肌肉无力是否部分归因于肌肉激活控制的改变。具体而言，我们的目标是确定与同一受试者的对侧肌肉相比，患侧手部肌肉的表面肌电图（EMG）幅度是否会随着（低）力量的变化而系统性地增大。我们在10名偏瘫患者和6名神经功能正常的受试者中，围绕第二掌指关节在多个方向上测试了一块多功能肌肉，即第一背侧骨间肌（FDI）。在10名中风受试者中的6名中，与对侧相比，以及与神经功能正常的受试者相比，患侧的肌电图 - 力量斜率显著更大。一组意外的结果是，即使在非常低的力量水平下，在患侧FDI中通常观察到记录的肌电图与产生的力量之间存在非线性关系。我们讨论了可能导致肌电图 - 力量斜率增加的实验因素和生理因素，得出结论认为运动单位（MU）控制的变化是观察到的变化的最可能原因。
