title: Invited commentary.
authors.affiliation: Department of Cardiology, Children's Hospital of Michigan, 3901 Beaubien Blvd, Detroit, MI 48201, USA. rross@dmc.org
authors.forename: Robert D
authors.initials: RD
authors.lastname: Ross
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D017079:Exercise Tolerance; D018729:Fontan Procedure; D006801:Humans; D007223:Infant