title: Invited commentary.
authors.affiliation: Division of Biokinesiology and Physical Therapy, Department of Pediatrics, Keck School of Medicine, University of Southern California, 1540 Alcazar St, CHP 155, Los Angeles, CA 90033 (USA).
authors.forename: Linda
authors.initials: L
authors.lastname: Fetters
authors.forename: John P
authors.initials: JP
authors.lastname: Scholz