Optimality versus variability: effect of fatigue in multi-finger redundant tasks.
Optimality versus variability: effect of fatigue in multi-finger redundant tasks.
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DOI：
10.1007/s00221-011-2963-x
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发表时间：
2012-02
影响因子：
2
通讯作者：
Latash, Mark L.
中科院分区：
文献类型：
--
作者：
Park, Jaebum;Singh, Tarkeshwar;Zatsiorsky, Vladimir M.;Latash, Mark L.
我们采用两种方法来解决两个方面的多指协同作用和他们的变化后，食指疲劳。分析逆优化（ANIO）被用来确定成本函数和相应的空间的最优解在广泛的任务参数。不受控制的流形（UCM）假设内的分析被用来量化的重复试验，有助于减少所有的手指一起产生的（稳定的）性能变量的变异性的手指力的共同变化。受试者产生稳态水平的总力和力矩的同时，尽可能准确地按下与右手的四个手指。在疲劳之前和疲劳期间，受试者对涵盖广泛范围的许多力-力矩组合进行了单次试验;数据用于ANIO分析。在两种力-力矩组合下进行了多项试验;这些数据用于UCM假设内的分析。通过食指进行1分钟最大自主收缩（MVC）运动来诱导疲劳。主成分（PC）分析表明，前两个PC解释了90%以上的总方差之前和疲劳期间。因此，得出的结论是，实验观察形成了一个平面的四维手指力空间之前和疲劳条件期间。在此基础上，提出了具有线性项的二次成本函数。最优解平面和实验观测平面之间的二面角非常小（几度）;疲劳过程中它会增加。有一个增加与疲劳的系数在二次项的食指力平衡的下降的系数为无名指和中指。在每个手指对（指数，中间和环小），“中央”手指的贡献，在疲劳过程中的时刻生产增加。拮抗剂力矩生产指数随疲劳而下降。疲劳导致更高的共变指数在旋前任务（食指是激动剂），但在旋后任务相反的效果。结果表明，协变指数的适应性变化，有助于稳定性能可能取决于疲劳元素，激动剂或拮抗剂的作用。
We used two methods to address two aspects of multi-finger synergies and their changes after fatigue of the index finger. Analytical inverse optimization (ANIO) was used to identify cost functions and corresponding spaces of optimal solutions over a broad range of task parameters. Analysis within the uncontrolled manifold (UCM) hypothesis was used to quantify co-variation of finger forces across repetitive trials that helped reduce variability of (stabilized) performance variables produced by all the fingers together. Subjects produced steady-state levels of total force and moment of force simultaneously as accurately as possible by pressing with the four fingers of the right hand. Both before- and during-fatigue, the subjects performed single trials for many force-moment combinations covering a broad range; the data were used for the ANIO analysis. Multiple trials were performed at two force-moment combinations; these data were used for analysis within the UCM hypothesis. Fatigue was induced by 1-min maximal voluntary contraction (MVC) exercise by the index finger. Principal component (PC) analysis showed that the first two PCs explained over 90% of the total variance both before and during fatigue. Hence, it was concluded that experimental observations formed a plane in the four-dimensional finger force space both before and during fatigue conditions. Based on this conclusion, quadratic cost functions with linear terms were assumed. The dihedral angle between the plane of optimal solutions and the plane of experimental observations was very small (a few degrees); it increased during fatigue. There was an increase with fatigue of the coefficient at the quadratic term for the index finger force balanced by a drop in the coefficients for the ring and middle fingers. Within each finger pair (index-middle and ring-little), the contribution of the “central” fingers to moment production increased during fatigue. An index of antagonist moment production dropped with fatigue. Fatigue led to higher co-variation indices during pronation tasks (index finger is an agonist) but opposite effects during supination tasks. The results suggest that adaptive changes in co-variation indices that help stabilize performance may depend on the role of the fatigued element, agonist or antagonist.
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影响因子：
2.4
作者：
KADEFORS, R;PETERSEN, I;HERBERTS, P
通讯作者：
HERBERTS, P
影响因子：
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通讯作者：
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影响因子：
2
作者：
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Zatsiorsky, VM
影响因子：
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作者：
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通讯作者：
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作者：
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通讯作者：
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