you definitly should. with mtb, it is necessary to coast in a lot of places, and absolutly pound away in others, so you dont get an even workout. I really think the two compliment each other, mtb for handling on slick surfaces , upper body and muscular strength, and road for cardiovascular strength and endurance. By restricting myself, I think that I was leaving holes in my fitness and riding ability. when I heal, I'll probably spend most of my offseason working w/ a mtb, then add in the road cycling a bit in late november.