My legs always burn

ornumc

I'm wondering why my quads and hamstring muscles ALWAYS burn.

I did the elliptical for a while and stopped because my legs burned so much afterwards. Now I do Les Mills RPM (stationery cycling) which I LOVE. During the lessons when I do a climb my muscles burn like CRAZY. Also, just going up stairs, they burn, bending my knee to stretch the quads burns both hamstring and quads.

I always have a good stretch after my cardio session, so I don't if I need to stretch even more, or just pray at some point my legs will get used to exercising.

I'm not talking about muscle ache, I know what that feels like, I'm talking about a stinging sensation.

Thanks.