1. Biomechanics Laboratory, San Francisco General Hospital, Rm. 3A36, 1001 Potrero Ave., San Francisco, CA 94110
2. Orthopedic Biomechanics Laboratory, Department of Orthopedic Surgery, Charles A. Dana Research Institute, Harvard-Thorndike Laboratory, Beth Israel Hospital and Harvard Medical School, Boston, MA 02215
3. Division of Applied Sciences, Harvard University, Cambridge, MA 02138