Anyone here spin? If so, what are your experiences? Were you already physically fit / athletic before beginning the classes? My school offers 3 spin classes a week, and I want to go but I'm a bit wary. Up until about a month ago, I wasn't very active other than walking and the occasional run. I now go to the gym 5 days for ~30 minutes each time. I use the exercise bikes (upright not recumbent) and I've been pretty consistent with maintaining 90+ RPM through the workout. I guess my question is, would it be wise to keep up with the exercise biking for the next month or two and start spinning in January once I'm a bit more fit? Or would it be ok to jump into it now? I will also mention that I had knee surgery a year ago (one year and 11 days to be exact!) and I do find my knee gets sore at the beginning of a workout but is usually ok by the end. I guess I really just don't want to be that one person huffing and puffing and dying while everyone else can keep up. Thoughts?