Ok this Sunday was my first real time out on my new fixed bike. I locked the back wheel up around 8 times playing around and getting the hang of things. I was out for a couple hours. Next day OMG, inside both legs from the knee up for about 8 inches hurt like hell. I figured oh well, different than road bike. Today is Thursday and noticed no pain. Went out but I cant lock up the rear wheel, not sure why. My back hurts when I try but it just seems like Im doing something wrong. After the first ride I moved the seat up and lowered it just a bit, could that have anything to do with it? How do you guys normaly stop anyhow? oh, and my bike's 48x16, dont know if that makes any difference.thanks......