1 Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Cambridge, Massachusetts, USA.
2 Department of Family Medicine and Department of Orthopaedic Surgery, Division of Sports Medicine and Non-operative Orthopaedics, University of California, Los Angeles, California, USA.
3 Division of Sports Medicine, Boston Children's Hospital, Boston, Massachusetts, USA.
4 Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
5 Department of Family and Consumer Sciences, California State University, Long Beach, California, USA.
6 Department of Orthopaedic Surgery, Division of Physical Medicine and Rehabilitation, Stanford University Medical School, Palo Alto, California, USA.