I want to make my legs more symmetrical to my upper body. They need to catch up slightly. I can easily achieve that with weights but I wish to achieve it with body weight exercises instead since I suffer from lower back pain and prefer not to squat with weights.
So far I have been doing sprints and pistols. Both were helpful but it seems like I got the maximum out of these. Also I am not a big fan of the pistols for they really make my knees feel not right. I combine them with some easier exercises like wall squats or jump squats but I am not mentioning these for they don't do all that much. I need something that will stimulate the muscles more. If not an exercise than a different strategy of how to combine these - sets, reps, etc.?
I have been looking online for materials but can't really find anything good for gaining muscle mass in the legs. Any suggestions are welcome, thank you in advance.