[DeusXM]

As to how much you exert, well, that really depends on what you're doing. I exercise in a strict regime which ensures my heartrate is between 130 and 160 a minute, which is the most efficient range for fat burning for someone of my age. So I usualy end up doing something like 120 steps a minute on my elliptical. It doesn't massively tire me out if I do that for half an hour, just works up a bit of a sweat and the endorphines. I usually do this every other day.