Why? "EPOC, or excess post-exercise oxygen consumption" says Thomas Storer, Ph.D., associate director of the Exercise Physiology Research Lab at UCLA and Q advisory board member. "After intense exercise, the body needs to recover from the demand placed on it during the session through functions such as replenishing used glycogen stores and resynthesizing its triglycerides, and there is an energy cost to that," says Storer, "the larger the deficit, the harder the body has to work to replenish, and the more calories your body burns to get you there."But, Storer warns, these results depend strongly on one's ability to sustain a vigorous exercise intensity over a considerable period of time, which is not a feat of Lance Armstrong-esque proportions, but would certainly require a solid aerobic base. "Less-than-fit individuals cannot workout at this intensity for 47 minutes — maybe not even 17 minutes," he says, "nonetheless, this is a very exciting study that adds outstanding data to other research that has shown similar increases in EPOC."

Reason number 2656 to hit that cycling class: A new study published by the American College of Sports Medicine found that about 45 minutes of vigorous cardio can keep your metabolism humming for 14 hours.Subjects were first asked to spend a day in a metabolic chamber (essentially a supped up prison cell with a bed, couch, computer, toilet and sink conducive to measuring energy expenditure) while scientists documented the calories they burned. Days later, the same group performed a similar routine in the chamber, but this time, around 11 a.m., they were given bikes and told to pedal at 73 percent of their maximum oxygen uptake (considered vigorously) for 47 minutes.After monitoring their calorie burn after the cardio stint, researchers determined the participants torched 37 percent more calories over the course of the day than they did when they were sedentary — even while they slept.