Born in Bouguenais, Loire-Atlantique, Guimard rode as a junior, an amateur and a professional, on the road, track and in cyclo-cross. He was national champion in all three forms: road in 1967 as an amateur, track sprint in 1970 and cyclo-cross in 1976. The riders ahead of him in the 1970 and 1971 professional road championships were disqualified and the titles not given. He said: "After those in front of me were disqualified for failing the drugs test, the federation never had the idea of giving me the titles.". Guimard was then president of the riders' union (see below) and the resentment that that created was why he was not named champion, he said, while others in the same position had been.