1. Mem. ASME Department of Physical and Environmental Sciences, Colorado Mesa University, 1100 North Avenue, Grand Junction, CO 81501 e-mail:
2. Department of Kinesiology, University of Massachusetts-Amherst, 110 Totman Building, 30 Eastman Lane, Amherst, MA 01003-9258 e-mail:
3. Department of Mechanical Engineering, Stanford University, 227 Durand Building, Stanford, CA 94305-4038;
4. Department of Orthopedic Surgery, Stanford University Medical Center, 227 Durand Building, Stanford, CA 94305-4038;
5. Bone and Joint Center of Excellence, Palo Alto, CA e-mail: