1. Human Engineering Research Laboratories, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, Pennsylvania, United States
2. School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
3. Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
4. Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
5. Center of Assistive Technology, University of Pittsburgh Medical Centre, Pittsburgh, Pennsylvania, United States