The Effects of Selective Muscle Weakness on Muscle Coordination in the Human Arm

Figure 1

Experimental setup and design. (a) Lateral view of the experimental setup. A cable robot (shown schematically) was used to record the hand position and 3D forces generated at the hand (see [48, 49] for details concerning the robot). A subject grasps the central end-effector (a gimbaled handle mounted on a six degrees of freedom load cell) via cables (depicted by black lines) connected to a spatial array of motors (indicated by black filled squares). The right-handed coordinate system (i.e., X-axis is out of the page) is indicated at the top center. (b) Ultrasonographic view of the brachialis muscle. The green circle indicates the position of the needle tip, inserted to inject lidocaine. (c) The distribution of 54 targets for the 3D isometric force target matching protocol. Force targets (black filled circles) were homogeneously distributed to avoid bias in force direction. (d) The distribution of 16 targets for the 2D force target matching protocol. Force targets (filled black circles) were defined on the circumference of a circle in the frontal plane. The direction information is indicated for the right arm.

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