I'd missed about 2 weeks of spin classes due to schedule conflicts and some, um, gastro-intestinal issues (January is bad for me in all kinds of ways), but finally got back there last night. It wasn't pleasant, but I'm glad I went and glad I stuck it out. Legs felt like lead, and had no snap in them at all, and I was getting a little winded just warming up. But it's OK - a couple of weeks and I'll be back where I was.