Considerable evidence exists related to the behavioral outcomes of motor imagery-based training (MI). Comparatively, there is a relative gap in the literature on how corticospinal excitability, a precursor for experience-dependent plasticity, changes over the course of an MI session, and more specifically if there is an effect of varying the duration of the blocks in which MI is performed. As such, we probed corticospinal excitability during MI, whereby the duration of MI blocks within the session were manipulated yet total exposure to MI was kept constant. Participants performed a total of 24 min of MI of common motor tasks in blocks of 2, 4 or 6 min. Transcranial magnetic stimulation was used to assess corticospinal excitability throughout MI performance. All groups demonstrated increased corticospinal excitability over the session. Owing to a decrease in corticospinal excitability when engaging in 6 min blocks and the variability noted when engaging in 2 min blocks, findings suggest that MI performed in 4 min blocks may be preferable for the generation and maintenance of corticospinal excitability, at least relative to 2 and 6 min blocks. Overall, our findings provide physiological evidence that informs the structure of MI training sessions to optimize their effectiveness.

存在与基于运动图像训练（MI）的行为结果相关的大量证据。相对而言，文献中存在相对差距，即皮质激素兴奋性（依赖经验的可塑性的前体）如何在MI疗程中发生变化，更具体地讲，是否存在改变MI阻滞持续时间的作用被执行。因此，我们探究了MI期间皮质脊髓兴奋性，从而控制了会话中MI阻滞的持续时间，但总MI暴露保持恒定。参与者以2分钟，4分钟或6分钟的时间段执行了24分钟的常规常规运动任务的MI。经颅磁刺激用于评估整个MI表现中皮质脊髓兴奋性。在整个疗程中，所有组均显示皮质脊髓兴奋性增加。由于在进行6分钟的运动时皮质脊髓兴奋性降低，而在进行2分钟的运动时皮质醇兴奋性降低，因此发现，在4分钟的运动中进行MI可能更有利于皮质脊髓兴奋性的产生和维持，至少相对于2分钟和6分钟的块。总体而言，我们的发现提供了生理学证据，可为MI培训课程的结构提供信息，以优化其有效性。