1. A Shumway-Cook, PT, PhD, is Associate Professor, Division of Physical Therapy, University of Washington, Box 356490, Seattle, WA 98195 (USA).
2. S Brauer, PT, PhD, is Postdoctoral Fellow, Department of Exercise and Movement Science, University of Oregon, Eugene, Ore
3. M Woollacott, PhD, is Professor and Chair, Department of Exercise and Movement Science, and Member, Institute of Neuroscience, University of Oregon