1. KS Topp, PT, PhD, is Associate Professor, Department of Physical Therapy and Rehabilitation Science and Department of Anatomy, University of California, San Francisco, 1318 7th Ave, Box 0736, San Francisco, CA 94143-0736 (USA).
2. BS Boyd, PT, MSPT, is Staff Physical Therapist, Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco