I have recently developed an interest in both mountain and road biking for my cardio. My question is, is that if neither are done to a great extent (not more than 3-4 days a week) would they be good for adding muscle in my quads?
Maybe somewhat, but you have to remember “If repetitions induced hypertrophy, marathon runners would have the largest legs in the world.”
RIT Jared
Being from a family that loves cycling I know that if you don’t have big quads to begin with, you’re not likely to get them from cycling alone.
It depends on what you do. Find yourself some ugly hills and your quads will be all nice and sculpted within a few weeks (assuming you spend enough time per session). Play on the flats and you’ll build up some good endurance but this is where that marathon statement comes in.