Originally Posted by
hsuBM
“Cycling”: no. Not at all. It won’t even “build your glutes” like many people think it will, no matter how hard & long you ride. It can be really great cardio work, though.
bmxing (sprinting/climbing while standing up & bunny hopping as big as you can over/up onto everything you can 40-80 times per ride, at least three rides per week): yes. It’ll cut & build your entire core. Stick with it for a few years and you’ll even develop “back-abs”.
There is truth in this. General road cycling, no, you won't gain large muscles. But there are some cycling disciplines, like BMX, where you are going to build and strengthen your core.