1. Human Engineering Research Laboratories, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA
2. Department of Rehabilitation Science and Technology, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA, USA
3. Center for Assistive Technology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
4. Division of Pulmonary, Allergy, and Critical Care Medicine, Emphysema COPD Research Center, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
5. Department of Physical Medicine and Rehabilitation, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
6. Adult Spina Bifida Clinic, University of Pittsburgh Medical Center, Pittsburgh, PA, USA