1. Department of Physical Medicine and Rehabilitation, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
2. Department of Physical Medicine & Rehabilitation, Inje University Sanggye-Paik Hospital, Seoul, Korea
3. Department of Biostatistics, Gillings School of Global Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
4. Stromatec, Burlington, Vermont, USA
5. Department of Neurology, University of Vermont, Burlington, Vermont, USA