Spinning class, while a very good place to meet members of the fairer gender, KILL me! You do a lot of sweating, and you build up massive amounts of lactic in your legs, but you go nowhere! Good work out yes, but I just don't see the point.
My last supervisor when I was still working for the Air Force was a huge spin class nut...never missed a spin session at the base gym. He finally bought a road bike and the first time he came out with us he got absolutely chest stomped. It's almost as bad as guys who run marathons and then try cycling for the first time. It's two totally different types of fitness. If I tried to run a 5K tomorrow I would be beaten badly by Wounded Warriors with one leg and pregnant women pushing baby strollers.