Q. I’ve heard that jumping is good for your bones, but I’m worried about getting injured. Isn’t high-impact exercise unsafe for the joints?

A. Highimpact exercise is safe—the human body is designed to walk, run and jump. Jumping or running, or other forms of impact exercise, are all beneficial. Performed properly, jumping is great for most bodies because it helps activate the power-producing muscle fibers that often get neglected with softer, slower workouts, and the impact helps build bone, or in older people, helps delay the rate of bone breakdown that occurs with aging.

But that doesn’t mean that everyone can go straight into 20 minutes of jumping rope or launch into a five-mile run. As with any type of exercise, you need to start easy and work up to longer and harder levels of intensity gradually. And if you have already-ailing joints, you many require minimal or modified impact.

Back in the ’80s, when millions of women took up high-impact aerobic dance, there were media reports of injuries from overly enthusiastic aerobicisers. This wasn’t because the activity itself was unsafe, though. It was because women who weren’t very fit to start with dove straight into a very-high-intensity, high-impact workout. Women who had never exercised before pounded away with jumping jacks, jogging and high kicks during hour-long aerobics classes. The intensity of that workout was the equivalent to running six or seven miles—not something that first-timers should do without proper prep. In addition, many fitness studios at the time had concrete, rather than sprung wood, floors, and fitness shoes were not built for maximum shock absorption. Injuries were bound to happen, and they did. But it wasn’t because the impact workouts are unsafe, it’s because they weren’t performed properly.

The dose of impact you give your body is key. If you have not been exercising or doing exercise that involves impact (such as jumping, hopping or running), then you need to start with a few seconds to a few minutes of light- to moderate-impact activity and build up to longer and/or harder impact slowly. Even if you’re an avid cyclist or Pilates practitioner (both low- or non-impact workouts), and are very fit and able to work at advanced levels doing what you already do, you will still need to take it easy when you start adding a new impact stimulus to your body (kickboxing classes, boot-camp style workouts that include lots of jumping jacks, running and/or high-impact aerobic dance).

The good news is that bones don’t need a whole lot of impact to show improvements in bone density. Researchers testing different exercise regimens on post-menopausal women often give a dose of only two minutes per day of jumping rope — and still see beneficial results.

So how do you build up from no- or low- impact to high-impact? Here’s my five-step plan:

• Start by marching in place (walking counts, too). This is traditional low-impact movement. Then march a little harder—stomp your feet!. This increases the impact without adding all your body weight. Do this for five to 15 minutes, alternating between marching and stomping. Work up to longer periods. (If you’re already fit, have healthy lower body joints and are a regular walker, you can skip this step.)
• Add 10 to 30 seconds of jogging or low jumping: Intersperse these high-impact moves with longer periods of lower impact moves like walking or marching (three to five minutes.) Continue alternating these intervals for about 20 to 30 minutes, and work up to longer periods.
• Gradually shift the ratio of low-impact to high-impact intervals so that you have a longer proportion of higher-impact intervals. For example, if you start off doing 30 seconds of jumping and four minutes of low-impact marching or walking, shift to 45 seconds, then 60 seconds, then 90 seconds of jumping over time and gradually shorten the walking/marching periods.
• When you’ve shifted your low-impact to high-impact ratio to 1 to 1, or you are doing longer periods of high-impact activity, you may be ready to do a longer-duration high-impact session, like running a mile or two. But once you shift into a higher-impact mode without lower-impact intervals, shorten your total session time. If you’ve been doing a 45-minute walk/run routine in which you walk for two or three minutes and run for six or seven minutes, for example, start with a 10- or 12- minute run  instead of launching straight into a 45-minute run, then then gradually add more running minutes.
• If you’re really ready to challenge your body, and have been regularly participating in jumping activities, you can add plyometric jumps to your workouts. These are more sports-specific forms of jumping.

At every stage, remember to warm up and cool down before and after every workout by moving slowly (walking is a good way to warm up.) Choose good surfaces for impact: dirt roads that are level and firm instead of concrete sidewalks, treadmills instead of asphalt. If you make sudden surface changes, dial down your workout minutes. And make sure you wear supportive, shock-absorbing sneakers (now is not the time to try barefoot workouts!)

How long you take to progress through these five phases all depends on how fit you are to start, how frequently you are exercising and how you feel during the workouts. Challenge yourself, but don’t overload your joints. If you feel achy in the day or two after a workout, you probably did too much. Stay in one phase for several weeks before progressing, and stick with a certain amount of high-impact time for several weeks before incrementally increasing the amount of impact. If you take the time to give your body calibrated doses of jumping, your body tissues will adapt to the new stress by getting stronger and allowing you to handle more.