From gym expierence you burn between 700 and 900 calories if you are being realistic. After 1 hour it tends to slow down as you are more tired and so dont put in as much effort. so for 2 hours it would be between 1300 -1500 roughly.
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About 120 every mile. Keep at a decent pace, it's not about how hard you work out, but how long you do. Working out harder will only raise calorie burning by a small margin. You will burn more...
I use an eliptical for 35 minutes and burn about 400 calories. Usually it's about 10-15 per minute, depending on how fast you're going and your resistance.
On average, humans move to the beat of 180 strides per minute. Assuming a 24" stride (each elliptical is a bit different) that puts it at 4 miles per hour. I know it looks slow but the fixed 24"...