18 Great Cardio Workouts That Don't Require Running

Pump the treadmill up as high as it can go — some get all the way to 30 degrees — and start walking on it to get your heart rate soaring instantly. "It pushes your legs and lungs without the pounding of running," says Corkill. "That means this is a great form of cardio if you need to save your knees or hips." Don't hold on to the side bars and when you start to get tired, make sure you don't slouch over. Start out at a 3.2 to 4.0 speed, which will be plenty, and see if you can make it 15 minutes.