What piece of exercise equipment sells for under $20, fits into a briefcase, can be used by the whole family, and improves cardiovascular fitness while toning muscle at the same time? And using it for just 15-20 minutes will burn off the calories from a candy bar? The answer: a jump rope.

Jumping rope is a great calorie-burner. You'd have to run an eight-minute mile to work off more calories than you'd burn jumping rope. Use the WebMD Calorie Counter to figure out how many calories you'll burn for a given activity, based on your weight and the duration of exercise.

"It's certainly good for the heart," says Peter Schulman, MD, associate professor, Cardiology/Pulmonary Medicine, University of Connecticut Health Center in Farmington. "It strengthens the upper and lower body and burns a lot of calories in a short time, but other considerations will determine if it's appropriate for an individual."

He sees rope-jumping as something fit adults can use to add spice to their exercise routine. "You're putting direct stress on knees, ankles, and hips, but if done properly it's a lower-impact activity than jogging."