i'm not really sure about this one but i know that you burn most calories in a range of heartrate... i think its 70-90 beats per minute, thats what i heard from biology class in highschool but our science department was **** so dont trust everyhting i say, but you can look that up.
dude sorry, its not 80-90 per minute. its aroun 115-130. thats meant to be where its most effective. somewhere on this forum theres a guy thats saying he's not losing any more weight even though he's doing 200 beats per minute. wel there goes. :P