I'm surprised no one has mentioned Kevin Costner, David Marshall Grant (Kostner's character's brother), Luca Bercovici (Muzzin) or Robert Townsend (Jerome) who all rode in American Flyers.

Then again, there's Dennis Quaid and Dennis Christopher (Stoller) from Breaking Away.

Alexandra Paul (Baywatch) competed in a number of Triathalons.

Wonder if any or all continued riding....