Have you checked out Chimaira? They're another band on roadrunner records (like Spineshank, Ill Nino, etc).
Also, some others that you've prolly heard of: Fear Factory, Mchine Head, Static X, Nonpoint (have some good tunes, not as heavy though), Hatebreed, Soulfly, Sepultura...
Also, and other band I like listening to while working out is alexisonfire. It's more punk/screaming, but it's fast, and it'll get ya going.
-Kev