I have been reading a lot about interval training when using the treadmill or elliptical. It sounds like a great idea and I have tried it a few times. I still have to wonder if it burns as much and gives as good a workout as just going at high intensity for most of the workout with a warm up and a cool down phase. When I have tried the interval training, it has been a good workout and I have felt better overall, but I just didn't feel quite as exhausted. Maybe that is a good thing, I am not sure. I am currently experimenting with a few different kinds of workouts and trying to make out a plan that works for me. Simply put, I want what works best so I am not wasting a bunch of my time and energy.