"Burn" can mean a lot of things- What kind of burn? Usually it means you're making some lactic acid, normal, and buiding muscle, good. Sounds to me like you're doing the right thing. Do you know how to use gears? If your heart hurts shift down. (overload for your conditioning level) If your legs hurt shift up. You're muscles want resistance to work against and if you're too strong or fast for the gear you're in they complain.
Remember Jane Fonda? "Feel the burn!"? Getting into shape is tough at first and can be confusing. Usually, burn is good. If it becomes actual pain, stop and ask sombody, either your shop, if they're nice guys, or us.

missliz