Ankle dorsiflexion force control is essential for performing daily living activities. However, the involvement of the corticospinal pathway during different ankle dorsiflexion tasks is not well understood. The objective of this study was to compare the corticospinal excitability during: (1) unilateral and bilateral; and (2) ballistic and tonic ankle dorsiflexion force control. Fifteen healthy young adults (age: 25.2 ± 2.8 years) participated in this study. Participants performed unilateral and bilateral isometric ankle dorsiflexion force-control tasks, which required matching a visual target (10% of maximal effort) as quickly and precisely as possible during ballistic and tonic contractions. Transcranial magnetic stimulation (TMS) was applied over the primary motor cortex to elicit motor-evoked potentials (MEPs) from the right tibialis anterior during: (i) pre-contraction phase; (ii) ascending contraction phase; (iii) plateau phase (tonic tasks only); and (iv) resting phase (control). Peak-to-peak MEP amplitude was computed to compare the corticospinal excitability during each experimental condition. MEP amplitudes significantly increased during unilateral contraction compared to bilateral contraction in the pre-contraction phase. There were no significant differences in the MEP amplitudes between the ballistic tasks and tonic tasks in any parts of the contraction phase. Although different strategies are required during ballistic and tonic contractions, the extent of corticospinal involvement appears to be similar. This could be because both tasks enhance the preparation for precise force control. Furthermore, our results suggest that unilateral muscle contractions may largely facilitate the central nervous system during movement preparation for unilateral force control compared to bilateral muscle contractions.

脚踝背屈力控制对于进行日常生活活动至关重要。然而，在不同的踝背屈任务中皮质脊髓途径的参与还不是很清楚。这项研究的目的是比较以下期间的皮质脊髓兴奋性：（1）单侧和双侧；（2）弹道和强直性踝背屈力控制。15名健康的年轻人（年龄：25.2±2.8岁）参加了这项研究。参与者执行单侧和双侧等距踝背屈力控制任务，这需要在弹道和强直性收缩期间尽可能快速，准确地匹配视觉目标（最大努力的10％）。经颅磁刺激（TMS）应用于初级运动皮层，以在以下时间内从右胫骨前部诱发运动诱发电位（MEP）：（i）收缩前阶段；（ii）上升收缩阶段；（iii）平稳期（仅限于紧张的任务）；（iv）休息阶段（控制）。计算峰-峰值MEP振幅以比较每​​种实验条件下皮质脊髓兴奋性。与收缩前阶段的双侧收缩相比，单侧收缩期间的MEP振幅显着增加。在收缩阶段的任何阶段，弹道任务和进补任务之间的MEP振幅均无显着差异。尽管在弹道和强直性收缩过程中需要采取不同的策略，但皮质脊髓受累的程度似乎相似。这可能是因为这两个任务都为精确的力控制做好了准备。此外，我们的研究结果表明，与双侧肌肉收缩相比，单侧肌肉收缩在运动准备单侧力控制的过程中可能大大促进中枢神经系统。