Segment Interactions of the Arm during the Practice of a Novel, Multijoint Throwing Skill

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Abstract
The purpose of this investigation was to determine, for a planar, multijoint throwing skill, if the interactions of segment energetics change over the course of practice. Eighteen men threw a weighted ball with their dominant arm at a target while the motion was restrained to a horizontal plane. From video data and body segment inertia! estimations, the energy transferred by the net joint force and the mechanical work attributed to the net joint moment were calculated for selected practice trials. Performance scores showed an expected improvement over trial blocks. An energetics analysis indicated that, for the throw, the mechanical work generated by muscle and transferred through muscle (i.e., via the net joint moment) across the elbow joint and the energy transferred by the net joint force across the wrist joint increased early in practice; however, no changes were observed in the relative contributions made by these components. The results indicated that, although performance increased significantly, the movement strategy used by subjects was intact throughout practice.