title: Invited commentary.
authors.affiliation: Dan Aaron Stay Fit Exercise Program for Individuals With Parkinson Disease or Multiple Sclerosis, Arcadia University, 450 S Easton Rd, Glenside, PA 19038, USA.
authors.forename: Carol
authors.initials: C
authors.lastname: Leiper
mesh_terms: D001642:Bicycling / Q000502:physiology*; D006233:Persons with Disabilities / Q000534:rehabilitation; D006801:Humans; D009043:Motor Activity; D009103:Multiple Sclerosis / Q000534:rehabilitation*; D016896:Treatment Outcome; D016138:Walking / Q000502:physiology*