Fig 1.
The apparatus and parameter definition.
(A) A custom-designed apparatus consists of two force/torque transducers. The common coordinate system is described in the red color; (B) The definition of coordination angle and projection angle.
Fig 2.
The experimental protocol (A), precision grip performance (B) and visual feedback for fatigue task (C).
Fig 3.
Force vector components of the thumb and index finger and the time course of coordination angle and projection angle before and after left fatigue from a representative subject.
(A)—(F): the absolute values of Fz, the Fx and the Fy before and after fatigue; (G)—(H): coordination angle of two digit force vectors; (I)–(J): projection angle of the thumb and index finger forces.
Table 1.
Means and standard deviations of grip forces during precision grip.
Fig 4.
Mean of the coordination angle and projection angle under non-fatigue, left-fatigue and right-fatigue. (A) and (B) mean of the coordination angle for the left and right hands, respectively; (C) and (D) mean of the projection angle for the left and right hands, respectively. * p < 0.05; ** p < 0.001.
Fig 5.
Standard deviation of the coordination angle and projection angle under non-fatigue, left-fatigue and right-fatigue. (A) and (B) standard deviation of the coordination angle for the left and right hands, respectively; (C) and (D) standard deviation of the projection angle for the left and right hands, respectively. * p < 0.05.