Like any other deer hunter, John Porcari must drag his killed quarry out of the forest. But unlike most others, he knows just how many calories that effort takes him: 13 per minute. (That means he needs to drag a deer 12 minutes to burn off each 3-ounce venison steak he eats.) Porcari also knows the number of calories burned by a vigorous game of paintball (7 per minute), yoga (4 per minute), and sex (5 per minute).
Porcari is not so much an exercise nut as an exercise physiologist, at the University of Wisconsin, La Crosse. For the last 20 years he has been measuring the caloric expenditure of various tasks. As recently as 15 years ago, that meant that subjects had to breathe into a meteorologic balloon while they roller-bladed, at which point Porcari used the balloon's oxygen concentration to derive calories burned.
Today, he straps a several-pound, ...
