"Indoor cycling, as an organized activity, is a form of exercise with classes focusing on endurance, strength, intervals, high intensity (race days) and recovery, that involve using a special stationary exercise bicycle with a weighted flywheel in a classroom setting."
The gym uses The Sunnto Fitness Solution for it's spin classes. Which is a heart rate belt linked to some software, that shows you on a big screen your heart rate and your fitness levels during the class.
This is the screen you see during the class with your colour coded heart rate levels.
The added bonus of the system is that you get an email with your stats at the end of the session!
Here is today's stats.
It's worth the effort even if I do feel exhausted start afterwards. I sweat loads during the class. I know I don't put the same effort into a regular gym session. It's perfect for 45minutes.