The purpose of current study was to clarify the influence of preceding muscle activity on the force production and movement-related cortical potential (MRCP) during superimposed ballistic contractions. The participants performed the ballistic force production at 40 % of maximum voluntary contraction (MVC) using the isometric abduction force of the metacarpophalangeal joint of the index finger. They were asked to match the peak of force curve with a horizontal target line displayed on the computer monitor. We compared the MRCP amplitude during force exertion detected from Fz, C4, C3, Cz and Pz electrodes during ballistic force production with (active condition) and without (resting condition) preceding muscle activity. The results showed that the MRCP amplitudes of Fz, C4, C3 and Cz electrodes were significantly smaller for the active condition than the resting condition. This was the case even though the peak force values during both conditions were identical. This result suggests that the facilitation of spinal motoneuron excitability by preceding muscle activity could reduce the required central motor command to produce the identical force level. In addition, we examined the MRCP amplitude during ballistic force production of the active condition without a visually displayed target. In this condition, the participants had to perform the force production based on aiming point of target force level (40 %MVC). As a result, the mean of peak force without a visual target was 54 %MVC, which overshot the aiming force level. However, the MRCP amplitudes of five electrodes during the 54 %MVC force production in the active condition were equivalent to the case of the 40 %MVC force production in the resting condition. These results suggest that the MRCP amplitude is consistent with participants' sense of effort involved in the force production, rather than the actual produced force level.

译文

当前研究的目的是阐明叠加弹道收缩过程中先前的肌肉活动对力产生和与运动相关的皮质电位 (MRCP) 的影响。参与者使用食指掌指关节的等距外展力在最大自愿收缩 (MVC) 40% 时产生弹道力。他们被要求将力曲线的峰值与计算机监视器上显示的水平目标线匹配。我们比较了在弹道力产生期间从Fz,C4,C3,Cz和Pz电极检测到的力施加期间的MRCP振幅 (活动状态) 和没有 (静息状态) 之前的肌肉活动。结果表明,活动状态下Fz,C4,C3和Cz电极的MRCP幅度明显小于静止状态。即使两种情况下的峰值力值相同,情况也是如此。该结果表明,通过先前的肌肉活动促进脊髓运动神经元的兴奋性可能会降低产生相同力水平所需的中央运动命令。此外,我们在没有视觉显示目标的情况下检查了活动状态的弹道力产生期间的MRCP振幅。在这种情况下,参与者必须根据目标力水平的瞄准点 (40% MVC) 进行力产生。结果,没有视觉目标的峰值力的平均值为54% MVC,超过了瞄准力水平。但是,在活动条件下产生54% MVC力的过程中,五个电极的MRCP幅度等于在静止条件下产生40% MVC力的情况。这些结果表明,MRCP振幅与参与者参与力产生的努力感相一致,而不是实际产生的力水平。

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