I call Bullshit on your iApp Chumley. That level of calorie burn is equivalent of sitting on the couch! If you're having sex for a hour at a vigorous pace a) go you! and b) you're burning more than 51 calories.
Maybe you'd only burn 51 calories if you are the partner on the bottom? I'd buy that there were times when my wife burned 51 calories while I burned 250.
