It's all a matter of how high you crank the resistance and how hard and fast you push the pedals - some classes are more "interval" oriented and some more "endurance" but I like to get completely out of breath at least three times during the course of a class. I cycle and spin for general fitness, not training to race, so I don't mind the "pushups" and other "odd and pointless stuff". I spend 15 minutes on the gym machines and do upper body stuff before the class so while spinning isn't the greatest fun (wish I could choose the music!) I'm probably fitter during the winter than in the spring/summer/fall when I just ride.