1. Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
2. Functional & Applied Biomechanics Section, NIH Clinical Center, Bethesda, MD, USA
3. Department of Pediatrics, University of Gothenburg, Gothenburg, Sweden
4. Department of Physiotherapy, Stellenbosch University, Tygerberg, South Africa
5. Department of Bioengineering, Stanford University, Stanford, CA, USA