Task readiness impedance in human arm movements for virtual ball-catching task

The dynamic characteristics of human upper extremities can be modeled with mechanical impedance. Although many studies have been reported on the human hand impedance properties in static tasks with arm posture maintained, there are no reports for human arm movements in dynamic tasks including interactions with environments. The human impedance should be regulated before motion in some tasks. In the ball-catching task, for instance, a human must regulate his/her hand impedance to catch a ball before the hand contacts the ball. The paper examines human impedance in preparation for task operations, i.e., "task-readiness impedance," and proposes a method of measuring hand impedance during tasks using a virtual-reality technique. Experiments are then conducted to examine task-readiness impedance as well as the virtual trajectory in a virtual ball-catching task.