Abstract：
Transcranial magnetic stimulation studies have indicated that the physical practice of a force production task increases corticospinal excitability during motor imagery (MI) of that task. However, it is unclear whether this practice-induced facilitation of corticospinal excitability during MI depends on a repeatedly practiced rate of force development (RFD). We aimed to investigate whether corticospinal excitability during MI of an isometric force production task is facilitated only when imagining the motor task with the same RFD as the physically practiced RFD. Furthermore, we aimed to examine whether corticospinal excitability during MI only occurs immediately after physical practice or is maintained. Twenty-eight right-handed young adults practiced isometric ramp force production using right index finger abduction. Half of the participants (high group) practiced the force production with high RFD, and the other half (low group) practiced the force production with low RFD. Questionnaire scores indicating MI ability were similar in the two groups. We examined the force error relative to the target force during the force production task without visual feedback, and motor evoked potential (MEP) amplitudes of the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles during the MI of the force production task under practiced and unpracticed RFD conditions before, immediately after, and 20 min after physical practice. Our results demonstrated that the force error in both RFD conditions significantly decreased immediately after physical practice, irrespective of the RFD condition practiced. In the high group, the MEP amplitude of the FDI muscle during MI in the high RFD condition significantly increased immediately after practice compared to that before, whereas the MEP amplitude 20 min after practice was not significantly different from that before practice. Conversely, the MEP amplitude during MI in the high RFD condition did not change significantly in the low group, and neither group had significant changes in MEP amplitude during MI in the low RFD condition. The facilitatory effect of corticospinal excitability during MI with high RFD observed only immediately after physical practice in the high RFD condition may reflect short-term functional changes in the primary motor cortex induced by physical practice.
摘要：
经颅磁刺激研究表明，力量产生任务的物理实践会在该任务的运动图像（MI）期间增加皮质脊髓的兴奋性。然而,目前尚不清楚MI期间这种实践诱导的皮质脊髓兴奋性促进是否取决于反复实践的力发育率(RFD).我们旨在研究仅在使用与物理实践的RFD相同的RFD想象运动任务时，在等距力产生任务的MI期间皮质脊髓兴奋性是否得到促进。此外，我们的目的是检查MI期间皮质脊髓兴奋性是否仅在体育锻炼后立即发生或维持。28名惯用右手的年轻人使用右手食指外展进行等距斜坡力的产生。一半的参与者(高组)以高RFD练习部队生产，另一半（低组）以较低的RFD进行了部队生产。两组中显示MI能力的问卷评分相似。我们在没有视觉反馈的情况下检查了力产生任务期间相对于目标力的力误差，在以前的实践和未实践的RFD条件下，在部队生产任务的MI期间，第一背侧骨间（FDI）和短肌外展肌（APB）的运动诱发电位（MEP）振幅，紧接着,和20分钟后的物理练习。我们的结果表明，在两种RFD条件下的力误差在物理练习后立即显着降低，无论实践的RFD条件如何。在高级组中，在高RFD条件下，MI期间FDI肌肉的MEP振幅在练习后立即显着增加，而练习后20分钟的MEP振幅与练习前没有显着差异。相反，在高RFD条件下MI期间的MEP振幅在低组中没有显着变化，在低RFD条件下，两组在MI期间的MEP振幅均无明显变化。仅在高RFD条件下进行物理练习后立即观察到的MI期间皮质脊髓兴奋性的促进作用可能反映了物理练习引起的初级运动皮层的短期功能变化。
