Rudy Garcia Tolson is a double amputee with no legs who is training for ironman competitions (yup, a 112 mile bike ride).
He uses double leg prostheses, but keep in mind that he has NO quads or calves, so all of his bike pushing is done with his glutes only, which makes it very hard for him to generate enough power to go fast.
He missed the bike time cutoff last year, but he did finish the bike (and the swim - he's a top notch swimmer) entire 112 mile course.
Pretty amazing.