1. Division of Physical Medicine and Rehabilitation, Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
2. Sports Medicine Center and Boswell Human Performance Laboratory, Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
3. Duke School of Medicine, Duke University, Durham, North Carolina, USA
4. Division of Epidemiology, Department of Health Research and Policy, Stanford University, Stanford, California, USA