Love 'em or hate 'em, hills sure do burn calories—more than 400 in 35 minutes with Ryan's Hit the Hills workout, which alternates between sprinting at no or low inclines, jogging at mid-range elevation, and walking steep hills. “Walking on a higher elevation activates more muscles, keeping the calorie burn high even though you're going slower," Ryan says. This is an intense interval session, so adjust the interval lengths, inclines and/or speed to best fit your fitness level.
