I didn't ride my bike to work at all last week. I took Friday off and didn't get to ride then, either. But yesterday (Sunday), I took a fun ride with a couple of friends. We went about 20 moderately hilly miles, and I rode my fixed-gear bike. Boy, that thing gives me a workout! Slowing the bike down uses muscles that I don't use for pedaling, so I'm sore in unusual places. And I take all of this as a good sign.