How can i stop gaining muscle on my legs?

Exercise your legs..: Exercise your legs to keep them toned, but avoid high resistance. An example would be "spinning, " versus powering up a hill at low rpm. Work on high velocity but low force muscular activity. This will maintain vascularization and increase endurance rather than strength. Expend calories, since your legs constitute 37% of your muscle mass. Just do more cardio with them.