For immediate release from Ye Olde Rambling Question Dep't.:

I'm on some elliptical at the gym, have been doing it 40 minutes three
times a week, each session the machine read-out claims I've lost
~850-900 calories (range due to variable intensity)...how accurate is
that? I find it hard that with 40 minutes of sweat I've burned that
many calories. It doesn't feel too hard, relatively speaking (though
I do Level 15 out of 20 available, with 20 as the hardest).

There's also the heart rate monitor that has me at the upper celing of
my target heart range (which is supposed to be ~142-157 for a 35 y.o.)
for almost all 40 minutes, which I find incredible, too...I definitely
look like I'm fit -- Greco-Roman statue and all -- but it all feels
much easier than I'd expected (though there is surely a psychological
component involved, and I've learned fairly well to tune out
unpleasantries like fatigue, etc.), so I'm wondering whether such
devices are trustworthy...how are such numbers calculated, anyway? On
this elliptical, the target heart rate seems to come from sensors in
the handles....