1. A.D. Kuo, PhD, is Professor, Departments of Mechanical Engineering and Biomedical Engineering, University of Michigan, 2350 Hayward St, Ann Arbor, MI 48109-2125 (USA).
2. J.M. Donelan, PhD, is Assistant Professor, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada.