1. SL Wolf, PhD, PT, FAPTA, is Professor and Director of Research, Department of Rehabilitation Medicine, Professor of Geriatrics, Department of Medicine, and Associate Professor, Department of Anatomy and Cell Biology, Emory University School of Medicine, Center for Rehabilitation Medicine, 1441 Clifton Rd NE, Atlanta, GA 30322 (USA).
2. HX Barnhart, PhD, is Assistant Professor, Division of Biostatistics, School of Public Health, Emory University.
3. GL Ellison is employed by the School of Public Health, Department of Epidemiology and Statistics, University of South Carolina, Columbia, SC 29208.
4. CE Coogler, ScD, PT, is Assistant Professor, Division of Physical Therapy Education, Department of Rehabilitation Medicine, and Instructor of Geriatrics, Emory University School of Medicine.