Well I haven't been on my bike for 2.5 years so I got it shipped out here to Wisconsin and tuned up. Its a large frame, Trek 6700 hard tail with some good tires, etc. Needless to say I felt like a challenge and cranked out 30 hilly miles. This area of Wisconsin is where the last glacier split (called "driftless region") so its all hills, valleys, and "dales". When I got off it my legs felt like they wanted to spasm and cramp so I had to kind of do some knee bends and such to keep this off.
I think Mountain Biking or road biking is a great complement to bulking though, keeps the heart and lungs working moderately and your legs can grind at whatever pace the muscle tissue can handle.
Any thoughts on biking?