But not too many of the instructors at my gym actually ever ride bikes. Sometimes I just refuse to do what they are doing - or modify it to fit what I think I need to do to improve.

They don't talk a lot about form, so a lot of the women in the class seem to be running in place or have a WHOLE lot of upper body movement. There are a lot of chatty folks too. I usually don't mind - except when they complain to me that they're working out so hard and not losing weight. I get a lot of that 'cause I dropped 30 pounds - and have kept it off for almost a year so the "oldtimers" know I use to be hefty.