1. Department of Biomechanics and Center for Research in Human Movement Variability, University of Nebraska at Omaha, 6160 University Drive South, Omaha, NE 68182, USA.
2. Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, OP-32, Portland, OR 97239, USA.
3. Rehabilitation Engineering Center, Institute for Rehabilitation Science and Engineering, Madonna Rehabilitation Hospital, 5401 South Street, Lincoln, NE 68506, USA.
4. Department of Surgery and Research Service, Veterans Affairs Nebraska-Western Iowa Medical Center, Omaha, NE 68105, USA.
5. Department of Surgery, University of Nebraska Medical Center, 982500 Nebraska Medical Center, Omaha, NE 68198, USA.