http://www.scwfitness.com/index.php?story=1773&fmt=1 This company sends me their silly newsletter ever since I was registered with Les Mills on the east coast.
Anyway, somewhat aware of these factors, I knew I was kind of a tool for finding the burnt-calorie measurement on the treadmill so motivating. It's really the only interesting thing about running in one place on a machine, though, aside from my ipod and hip pain.
No harm, though, really. Ultimately we face the actual results of our workouts regardless of what the treadmill or the elliptical or even the scale says. When I was in Olympia around the holidays a couple ladies at Lacey Athletic would use calorie watches during BodyStep and I remember one woman clocking 720 at the end of the workout, which was great to see, as she was older and didn't even go for all the "high" options. Based on the best study done, the average range of caloric expenditure for BodyStep is 550-650, depending on work intensity, muscle volume and body weight.
We CAN know much more accurately how much caloric energy we put IN versus how much exactly we put out, but it's all a huge pain in the ass to track so precisely. Bottom line, you are a human animal and you should be doing something vigorous every day, but you should take lighter days after your very hard days.
Basal metabolic rate is an interesting bit of potentially accurate information, though.
http://www.bmi-calculator.net/bmr-calculator/ Not taken into account directly, though, is that the more muscle you have and the fitter you are, the more efficient your metabolic rate.