I was feeling a bit stale doing the same road rides with the same people, and don't really love riding solo on the road, so I took the only MTB I had (at the time), and stripped it down to a singlespeed. The change of pace, scenery, and approach was revitalizing. I learned things about riding that I hadn't really paid much attention to. I also found that my body adapted with a different type of fitness - brute force.