1. DL Riddle, PT, PhD, is Associate Professor, Department of Physical Therapy, Medical College of Virginia Campus, Virginia Commonwealth University, 1200 E Broad St, Richmond, VA 23298-0224 (USA).
2. JK Freburger, PT, PhD, is NRSA Postdoctoral Research Fellow, Cecil G Sheps Center for Health Services Research, and Assistant Professor, Division of Physical Therapy, University of North Carolina at Chapel Hill, Chapel Hill, NC