Hong S L, Lee M-H, Newell K M
Dept of Kinesiology, The Pennsylvania State University, University Park, PA 16802-6501, USA.
Motor Control. 2007 Apr;11(2):119-35. doi: 10.1123/mcj.11.2.119.
This experiment examined the magnitude and structure of force variability in isometric index finger force production tasks at 5, 15, 25, 35, 45, 55, 65, 75, 85, and 95% of maximal force in two different finger orientations. In the finger flexion task, the participants generated a downward isometric force through index finger flexion. In the finger abduction task, isometric force was generated by adducting the index finger (mediolateral motion of the middle finger and forearm were restricted). The task-related, normal force (Fz) and tangential forces (Fx and Fy) were collected with a three-dimensional force transducer. The standard deviation (SD) of the task-related force output (Fz) increased exponentially with force level. With increasing force level, approximate entropy (ApEn, a measure of irregularity) of Fz followed an inverted-U function for finger flexion, but decreased linearly in finger abduction. However, changes in the ApEn of the tangential forces were generally opposite to that of Fz, revealing compensations in the irregularity of force output between force dimensions. The findings provide evidence that force variability is related to muscle force-length characteristics (Feldman, 1966; Gottlieb %%% Agarwal, 1988).
本实验研究了在两种不同手指方向上，等长食指用力任务中，在最大力的5%、15%、25%、35%、45%、55%、65%、75%、85%和95%时力变异性的大小和结构。在手指屈曲任务中，参与者通过食指屈曲产生向下的等长力。在手指外展任务中，通过内收食指产生等长力（限制中指和前臂的内外侧运动）。使用三维力传感器收集与任务相关的法向力（Fz）和切向力（Fx和Fy）。与任务相关的力输出（Fz）的标准差（SD）随力水平呈指数增加。随着力水平的增加，手指屈曲时Fz的近似熵（ApEn，一种不规则性度量）遵循倒U形函数，但在手指外展时呈线性下降。然而，切向力的ApEn变化通常与Fz相反，揭示了力维度之间力输出不规则性的补偿。这些发现提供了证据，证明力变异性与肌肉力-长度特性有关（费尔德曼，1966；戈特利布%%%阿加瓦尔，1988）。
