Rannama Indrek, Zusa Anna, Latash Mark L
School of Natural Sciences and Health, Tallinn University, Narva mnt 25, Tallinn, 10120, Estonia.
Latvian Academy of Sport Education, Riga Stradiņš University, Riga, Latvia.
Exp Brain Res. 2024 Dec 31;243(1):37. doi: 10.1007/s00221-024-06990-w.
Accurate control of force on the environment is mechanically necessary for many tasks involving the lower extremities. We investigated drifts in the horizontal (shear) active force produced by right-footed seated subjects and the effects of force matching by the other foot. Subjects generated constant shear force at 15% and 30% of maximal voluntary contraction (MVC) using one foot. Visual feedback of shear force magnitude was provided for the first 5s, then turned off for 30s. During the 30% MVC task, we observed parallel drops in active shear and vertical force magnitudes leading to consistent drifts in the resultant force magnitude, not in its direction. Force matching by the other foot resulted in significantly lower forces when feedback was available throughout the trial. No feedback was provided for the matching foot. When the matching foot began exerting force, the task foot experienced a notable drop in all force components, with a change in force direction only for the task foot. After this initial drop, the downward drift in the task foot stopped or reversed. Subjects were unaware of these drifts and errors. Our findings suggest that shear force production involves setting a referent coordinate vector, which shows drifts and matching errors, while its direction remains stable. Involvement of the matching foot appears to perturb the neural commands to the task foot, with minor differences observed between feet. The discrepancy between the consistent force drifts and lack of awareness of the drifts indicates a difference between force perception-to-act and perception-to-report.
对于许多涉及下肢的任务来说，精确控制作用于环境的力在机械上是必要的。我们研究了右利脚坐姿受试者产生的水平（剪切）主动力的漂移情况以及另一只脚进行力匹配的影响。受试者用一只脚以最大自主收缩（MVC）的15%和30%产生恒定的剪切力。在前5秒提供剪切力大小的视觉反馈，然后关闭30秒。在30%MVC任务中，我们观察到主动剪切力和垂直力大小平行下降，导致合力大小持续漂移，但其方向不变。当在整个试验过程中都有反馈时，另一只脚进行力匹配会导致力显著降低。匹配脚没有提供反馈。当匹配脚开始施加力时，任务脚的所有力分量都出现明显下降，只有任务脚的力方向发生了变化。在这个初始下降之后，任务脚的向下漂移停止或逆转。受试者并未意识到这些漂移和误差。我们的研究结果表明，剪切力的产生涉及设定一个参考坐标向量，该向量显示出漂移和匹配误差，而其方向保持稳定。匹配脚的参与似乎会干扰对任务脚的神经指令，两只脚之间观察到细微差异。持续的力漂移与对漂移缺乏意识之间的差异表明了力感知到行动和感知到报告之间的区别。
