1. Sanford School, Hockessin, DE 19707, USA
2. Pediatric Mobility Lab, Department of Physical Therapy, University of Delaware, Newark, DE 19716, USA
3. Independent Researcher, Boulder, CO, USA
4. Neurorehabilitation and Biomechanics Research Section, Rehabilitation Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA