Steven K. Charles

Learn More
Given the vast complexity of human actions and interactions with objects, we proposed that control of sensorimotor behavior may utilize dynamic primitives. However, greater computational simplicity may come at the cost of reduced versatility. Evidence for primitives may be garnered by revealing such limitations. This study tested subjects performing a(More)
The control of wrist rotations is critical for normal upper limb function, yet has received little attention. In this study, we characterized path shape of wrist rotations in order to better understand the biomechanical and neural factors governing their control. Subjects performed step-tracking wrist rotations in eight directions "at a comfortable speed"(More)
Because damage to the cerebellum results in characteristic movement incoordination known as "ataxia," it has been hypothesized that it is involved in estimation of limb dynamics that occur during movement. However, cerebellar function may extend beyond movement to force control in general, with or without movement. Here we tested whether the cerebellum is(More)
Because wrist rotation dynamics are dominated by stiffness (Charles SK, Hogan N. J Biomech 44: 614-621, 2011), understanding how humans plan and execute coordinated wrist rotations requires knowledge of the stiffness characteristics of the wrist joint. In the past, the passive stiffness of the wrist joint has been measured in 1 degree of freedom (DOF).(More)
When humans rotate their wrist in flexion-extension, radial-ulnar deviation, and combinations, the resulting paths (like the path of a laser pointer on a screen) exhibit a distinctive pattern of curvature. In this report we show that the passive stiffness of the wrist is sufficient to account for this pattern. Simulating the dynamics of wrist rotations(More)
Because the dynamics of wrist rotations are dominated by stiffness, understanding wrist rotations requires a thorough characterization of wrist stiffness in multiple degrees of freedom. The only prior measurement of multivariable wrist stiffness was confined to approximately one-seventh of the wrist range of motion (ROM). Here, we present a precise(More)
Coordinated movement requires that the neuromuscular system account and compensate for movement dynamics. One particularly complex aspect of movement dynamics is the interaction that occurs between degrees of freedom (DOF), which may be caused by inertia, damping, and/or stiffness. During wrist rotations, the two DOF of the wrist (flexion–extension and(More)
  • 1