1. Department of Mechanical Engineering, University of Washington , Stevens Way, Box 352600, Seattle, WA 98195 ; , ms 151, 1660 South Columbian Way, Seattle, WA 98108
2. RR&D Center for Limb Loss and Mobility (CLiMB) Veterans Affairs Puget Sound Health Care System , Stevens Way, Box 352600, Seattle, WA 98195 ; , ms 151, 1660 South Columbian Way, Seattle, WA 98108
3. School of Medicine, Department of Mechanical Engineering, University of Washington , 1959 NE Pacific Street, Seattle, WA 98195
4. Department of Orthopaedic Surgery, School of Medicine, The Jikei University, Minato City , 3 Chome-25-8 Nishishinbashi, Tokyo 105-8461, Japan
5. Departments of Mechanical Engineering, Orthopaedics & Sports Medicine, University of Washington , Stevens Way, Box 352600, Seattle, WA 98195 ; , ms 151, 1660 South Columbian Way, Seattle, WA 98108