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 ."

Basic Requirements

For novices, a beaded rope is recommended because it holds its shape and is easier to control than a lightweight cloth or vinyl rope.

• Adjust the rope by holding the handles and stepping on the rope.
• Shorten the rope so the handles reach your armpits.
• Wear properly fitted athletic shoes, preferably cross-training shoes.

You'll need a four-by-six-foot area, and about 10 inches of space above your head. The exercise surface is very important. Do not attempt to jump on carpet, grass, concrete, or asphalt. While carpet reduces impact, the downside is it grabs your shoes and can twist your ankle or knee. Use a wood floor, piece of plywood, or an impact mat made for exercise.

How To Jump

If you haven't jumped rope since third grade, it can be humbling. It demands (and builds) coordination. Initially, you should practice foot and arm movements separately.

• Hold both rope handles in one hand and swing the rope to develop a feel for the rhythm.
• Next, without using the rope, practice jumping.
• Finally, put the two together. You'll probably do well to jump continuously for one minute.

Alternate jumping with lower intensity exercise, such as marching, and you'll be able to jump for longer periods. You'll probably never want to jump for a solid 10 minutes. Rather, incorporate it into a varied exercise routine, such as one developed by Edward Jackowski, PhD, author of Hold It! You're Exercising Wrong. He uses rope-jumping intervals, initially 50-200 repetitions, in a combined aerobic and strengthening program.

The highest intensity workout involves one jump each time the rope passes. Slowing the rope to adding an extra little jump reduces the intensity. Pay attention to your target heart-rate zone. That's where you're exercising with enough intensity to benefit from the exercise and not so vigorously as to endanger your health.

Here's how to determine your maximal heart rate: 220 minus your age. The high end of your target zone is 85% of that number; the low end is 70% . If you're 40 years old, your maximal heart rate is 180, and your target zone is 126-153 beats per minute.

Preventing Injury

Check with your doctor if you have any doubts about your ability to withstand the impact and high aerobic intensity of rope-jumping. As mentioned, shoes and jumping surface are important. As with all exercise, warming up, stretching and cooling down are important. How you jump will determine the impact on your body.

"The real key is to make sure you jump properly," says Roger Crozier. He teaches physical education at Fox Run Elementary School in San Antonio, Texas, and coaches a competitive jump-rope team. "Stay high on the toes. When you walk or run, you impact your heel. With rope jumping you stay high on your toes and use your body's natural shock absorbers." Crozier says rope-jumping is lower impact than jogging or running if done properly. If not, it's considerably more impact.

"Beginners usually jump higher than necessary. With practice, you shouldn't come more than one inch off the floor.

Jump Rope for Heart

For nearly 25 years, Jump Rope for Heart has promoted fitness among elementary school students and raised money for heart research and education. It's sponsored by the American Heart Association, and Crozier is a volunteer who's developed training videos for participating schools. His students raised $11,000 in 2002.

"Jump Rope for Heart fits so well with physical education because we're fighting heart disease , the number one killer, and stroke , the number three killer," he says. "It's a chance to improve their own health while doing something good for someone else."

He teaches rope-jumping to kids in kindergarten through sixth grade. To say Crozier is enthusiastic about rope-jumping would be an understatement. "If you took all my P.E. equipment away except one thing, I can teach more with a jump rope than with any other piece of equipment."

He says besides being a great exercise in its own right, rope-jumping skills transfer to most athletic endeavors. "One of the key things as an educator I didn't realize until I started working with it is how it builds body awareness. With rope-jumping, you have to be aware of what your body is doing, and it's a great skill for connecting the brain's neurons."

While boxers come to mind as macho guys who jump rope, the U.S. Amateur Jump Rope Federation's national competition is televised. Yet there's still something of a gender issue. "The idea of it as a little girls' recess game is fading as the sport of jump rope grows," Crozier says. "Our competitive team is more heavily weighted with girls, but part of that is because boys have more options. In P.E. classes, it appeals to boys and girls equally."

Crozier says some parents become inspired to jump rope after watching their kids. "They're usually amazed at how hard it is," he says.