title: Invited commentary.
authors.affiliation: San Francisco, Calif.
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Rapp
mesh_terms: D003097:Collateral Circulation; D005081:Exercise Therapy; D005260:Female; D005263:Femoral Artery / Q000503:physiopathology*; D006801:Humans; D007383:Intermittent Claudication / Q000628:therapy*; D018810:Magnetic Resonance Angiography; D019028:Magnetic Resonance Imaging, Cine; D008297:Male