1. a The Department of Physical Therapy and Rehabilitation Science , University of California San Francisco , Box 0625, San Francisco, CA 94143 – 0625, USA
2. b Department of Kinesiology , The Pennsylvania State University , University Park, PA, USA
3. c Department of Rehabilitation Medicine , University of Amsterdam , Amsterdam, The Netherlands
4. d The Department of Biomedical Engineering , The Cleveland Clinic Foundation , Cleveland, OH, USA