1. JH Kahn, PT, DPT, NCS, is Research Physical Therapist, Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois.
2. TG Hornby, PT, PhD, is Assistant Professor, Department of Physical Therapy, University of Illinois at Chicago, 1919 W Taylor St, Chicago, IL 60612 (USA), and Research Scientist, Sensory Motor Performance Program, Rehabilitation Institute of Chicago.