Since I've got at least two injuries that keep me from my usual running, plus it's about 0F around here, I decided to try a 6AM Spinning class at my health club. The thing is, my "club" is the recreational center for a local university, so the class was led by a 20-year-old phys-ed major and there were a few other students in the group. So my idea of keeping up and showing 'em what an old guy could do kind of went out the window (along with my stamina).
Seriously, though, it was a really good workout. I "kept up" for the entire hour, but definitely at a reduced cadence from the kids. The first time I did it I wore my typical workout shorts, t-shirt, etc. After seeing how soaked I got plus a sore butt, the next time I wore my cycling shorts, a Coolmax sleeveless tee, and I even dug out an old pre-helmet cycling cap to help keep the sweat out of my eyes. I could still use some other adjustments on the seat angle, but the 2nd session went better than the 1st.
You should try this if you have a chance -- you might surprise yourself (and show up some of the kids to boot!).