I'm getting really confused about the calories I burn during exercise. I just got a heart rate monitor and have been looking at the calories that it tracks. The thing is that it only starts counting calories burned once my heart rate is about 100. If I'm walking I'm still burning calories, right? Even though my heart rate may be below 100? And the calories burned are pretty low on my monitor. An hour long exercise video I did said I only burned 250 calories. That seems really low for that much exercise. I'm confused! The on-line calorie counts for different activities is pretty high, but based on my monitor I don't think I would burn as many. Help!!