Directional Variability of the Isometric Force Vector Produced by the Human Hand in Multijoint Planar Tasks
Directional Variability of the Isometric Force Vector Produced by the Human Hand in Multijoint Planar Tasks
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DOI：
10.1080/00222895.2011.626812
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发表时间：
2011-01-01
影响因子：
1.4
通讯作者：
Zatsiorsky, Vladimir M.
中科院分区：
文献类型：
--
作者：
Friedman, Jason;Latash, Mark L.;Zatsiorsky, Vladimir M.
许多研究已经检查了力大小的控制，但相对较少的研究考虑了力方向控制。受试者对手柄施加等长力，作者比较了在不同方向产生力时的试验内变异性。平行于规定的力产生方向的力的标准偏差随着目标力水平线性增加，垂直于指示方向的力的标准偏差也是如此。与此相反，标准差的角度的力产生的力水平的增加而下降。在仅1个关节（肩关节或肘关节）的关节扭矩产生终点力的4个（共8个）指示力方向上，力空间中的主分量轴与规定的力产生方向完全一致。在其他方向上，沿2个力轴的方差约沿着相等。由第一主成分解释的方差在扭矩空间中比在力空间中显著更大，并且大多对应于关节扭矩之间的正相关。这种协调的变化表明，扭矩的变化主要是由于共同驱动的变化，肌肉服务2个关节，虽然这一说法需要支持的肌肉激活在未来的直接研究。
Numerous studies have examined control of force magnitude, but relatively little research has considered force direction control. The subjects applied isometric forces to a handle and the authors compared within-trial variability when force is produced in different directions. The standard deviation of the force parallel to the prescribed direction of force production increased linearly with the targeted force level, as did the standard deviation of the force perpendicular to the instructed direction. In contrast, the standard deviation of the angle of force production decreased with increased force level. In the 4 (of 8) instructed force directions where the endpoint force was generated due to a joint torque in only 1 joint (either the shoulder or elbow) the principal component axes in force space were well aligned with the prescribed direction of force production. In the other directions, the variance was approximately equal along the 2 force axes. The variance explained by the first principal component was significantly larger in torque space compared to the force space, and mostly corresponded to positive correlation between the joint torques. Such coordinated changes suggest that the torque variability was mainly due to the variability of the common drive to the muscles serving 2 joints, although this statement needs to be supported by direct studies of muscle activation in the future.