I’ve done a couple spin classes with a friend at her request. In the 45:00-60:00 minute classes it was pretty intense. A couple of times I had to relax before a particular intense “sprint” or “climb” was finished. But like others in this thread In the end I thought “Those people are good for an hour. They were completely exhausted at the end.” I don’t think they could hang with me on ride of 2, 3, 4 hours or more. I was tired…but I could have kept going in a real road situation. Maybe it comes down to pacing I guess. The thing I didn’t like was the ‘booming’ music, and the instructor yelling stuff. I like the serenity of my surroundings, and being outside…regardless of the weather conditions.
Dan