In contrast, at the last gym where I actually enjoyed spinning classes, there were 2 very popular instructors (compared to several very unpopular ones).

The first one was a road cyclist and racer. He taught "base training" and endurance workouts in the fall, as much as he could given time constraints. He educated people on building a good fitness base. By the end of the fall, we'd maybe get a few long intervals at 85%--like TT intervals. He would break each set into a range for the less experienced/fit and the more fit. He taught correct form for standing on a spin bike and never ever did jumps or anything you wouldn't do outside. I'd leave his class feeling energized and educated. He really helped me by giving me some advice about getting into road cycling.

The other instructor taught the Johnny G method, even down to those pushup things to kill your triceps. The good thing about his class was that you learned how to push at AT. Lots of interval training helped recovery time. Some of the moves helped develop explosive power. He was also very good about telling newbies to skip a certain interval or how to modify it. Ultimately, though, unless you were trying to be a sprinter, these workouts were very tough on the body. They stressed my joints and every single muscle. Any minor discomfort with bike fit and pedal float and hot spots from the SPDs were magnified over time. It was a little too much at or above AT and really nothing for endurance. That wasn't too bad for most people but on Saturdays he'd teach 2 back to back. I'd usually take both and he'd definitely chill out in the second class. Was it that good for my body? Probably not. I'd leave feeling sore and achy most of the time, more like I'd been lifting weights heavily or done a boot camp class than cycled.

So sure, people like torture, and those who recognize that need to at least make some modifications based on who is in the class for their safety. Newcomers and those with poor form need to be watched closely. That is probably the only reason I trusted instructor #2, because he would really keep an eye on people. At the same time, he'd pick on those who were more fit. Good to be pushed out of one's comfort zone, but sometimes, it seemed like a lot. I think a lot of people don't know the difference between "tough" and careless. I don't think enough instructors are aware about the potential for injury.

My experience with instructor #1 at least made it clear that you can make a popular class based upon good cycling techniques. One day, that guy showed up in full kit because he'd ridden to the gym straight from a ride, and people seemed MORE intimidated by him than by the instructor (#2) who was known to kick your *** in every type of class he taught (he did a lot of stuff). It was like they felt like they weren't hardcore enough to take a class from a cyclist, because they just wanted a good cardio workout, and they were kind of scared. So I guess enough people saw it as a challenge to make it popular even if the workout was basically tempo that day. Those of us who had an interest in road cycling loved it.