1 Human Engineering Research Laboratories, VA Pittsburgh Healthcare System, Pittsburgh, PA 15206, USA ; Department of Rehabilitation Science and Technology, University of Pittsburgh, Pittsburgh, PA 15260, USA.
2 Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA.
3 Amsterdam Rehabilitation Research Center, Reade, 1040 HG Amsterdam, The Netherlands ; University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, 9700 AB Groningen, The Netherlands.
4 Rehabilitation Engineering Research Program, Minneapolis VA Healthcare System, Minneapolis, MN 55417, USA ; Department of Physical Medicine and Rehabilitation, Program in Rehabilitation Science, University of Minnesota, Minneapolis, MN 55455, USA.