1. Human Neuromechanics Laboratory, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109;
2. Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109 e-mail:
3. University of Michigan Orthotics and Prosthetics Center, 2850 South Industrial Highway, Suite 400, Ann Arbor, MI 48104;
4. Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI 48109
5. Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109;
6. School of Kinesiology, University of Michigan, Ann Arbor, MI 48109