Treadmill - 15% incline @ 9 mph

This activity burns approximately 1,572 calories per hour

Even if you typically run outside, one of the best ways to improve your aerobic fitness capacity is to bring your workout indoors onto a treadmill. After you've leveled off at a 9-mph pace, slowly increase the inclination by 1 to 2% every 5 minutes until you reach a 15% grade.