1. Human Engineering Research Laboratories, VA Pittsburgh Healthcare System, 6425 Penn Avenue, Suite 400, Pittsburgh, PA 15206; Department of Rehabilitation Science and Technology, University of Pittsburgh, Pittsburgh, PA
2. School of Medicine, University of Pittsburgh, Pittsburgh, PA
3. Human Engineering Research Laboratories, VA Pittsburgh Healthcare System, 6425 Penn Avenue, Suite 400, Pittsburgh, PA 15206; Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA