One trick I learned when I was training as a competitive cyclist was “Don’t Stop” during your training rides. No, I don’t mean blowing through stop signs. Don’t stop during your training ride, even for a short break. I found it’s all about creating and maintaning momentum that keeps you focused. And that focus helps you ignore the pain or discomfort you are feeling. Not stopping also develops muscular endurance in your legs.
Think of your Indoor Cycling Class as a very compressed training ride. As the Instructor you should be doing everything you can to help your students maintain their focus and maintain a constant effort. You will be helping them develop as endurance athletes and they will thank you for it!