Killer spin class last night. Our instructor tried to emulate Stage 9 of the Tour de France over the course of one hour. She told me before we started that it was the hardest class profile she had ever taught at our gym. After doing it, I believe her. I don't remember my time or calorie totals, but I know it was about 1 hour and 10 minutes or riding and that I averaged 76% of my max HR and peaked at 93% of max.