Q. I have recently started running, since I heard that it’s the best way to lose weight. But I’m heavy. Is it safe to run if I am overweight? Or should I lose weight first, or try another kind of exercise instead?
A. A common misconception is that heavy people should lose weight before they start to exercise. In fact, you should start to be more active, no matter what your weight is. You can reap immediate benefits from working out. Several landmark studies by Steven Blair, Ph.D., and others have shown that exercise can reduce your health risks tremendously, even if you are still fat. Exercising now, rather than later, is always a good idea, not just for the health benefits, but because you’ll have a healthy and more sustainable weight loss if you are exercising, too.
But how much and what type of exercise you should do if you are unfit and/or overweight deserves careful consideration. When it comes to weight loss and fitness, running is definitely one of the most effective activities around. That’s because it burns lots of calories for a given amount of time, compared with activities such as walking or cycling, and the effort is challenging—you work at a moderate to vigorous intensity, depending upon your speed, fitness level and/or environmental conditions (like running up hills).
Impact forces of walking and running
That said, running is a high-intensity workout with lots of impact on the joints. The more vertical motion that is added to the walk-run motion, the greater the impact to the joints as each foot lands from each forward step. But the style and the speed of running also affect levels of impact. A study in the journal Clinical Biomechanics analyzed the ground reaction forces of walking, slow jogging and running in men and women. On average, ground reaction forces increased linearly from about 1.2 times body weight when walking at around 2.7 mph to up to 2.5 times body weight when running at 5.6 mph.
Slower jogging was found to have greater amounts of impact and loading forces than faster running, believe it or not. That’s because the faster one runs, the less vertical the movement tends to become, since momentum helps propel the body forward, resulting in less lifting and lowering of the body. In addition, the length of your strides when walking or running and the frequency of your strides can also affect the impact your joints experience. A very long step may result in higher landing impact forces.
So running faster may be slightly easier on the joints than a bouncy jog. Of course, you have to be pretty fit to run fast. So if you are new to fitness and not a trained runner, this might not be an option.
Is impact unsafe?
But before assuming that running is, therefore, too hard on the joints, it’s important to step back and reflect on the bigger picture. Often, people assume that impact is “bad,” and so they conclude that greater amounts of impact are unsafe. This logically leads one to conclude that running is not safe since it’s a higher-impact activity. Some people also take this one step further and conclude that low-impact or even nonimpact activities such as an elliptical trainer or yoga are, therefore, better than a high-impact activity such as running.
What’s important to keep in mind is that bodies were designed for impact. The human body is structurally built to walk, run and jump. In theory, anyone of any age has the capacity to do so. On the other hand, bodies do not appear to be designed to twist into complex pretzel shapes—that’s why it takes yogis or dancers years to become flexible enough to get their joints into extreme ranges of motion.
The body thrives on some impact—especially bone cells. More and more research is elucidating the importance of impact forces to building and preserving bone mass. And jumping is better than walking, when it comes to bones.
That said, the body may not be designed to pound on concrete surfaces or for hours at a time (such as when running a marathon). One can train oneself to do these things, and get fitter and stronger in the process, but there may also be concurrent weakening in some physiological areas (such as the immune system) or biomechanical areas (chronic joint degradation).
How much impact can an overweight body handle?
The more weight that’s pounding on a joint, the more stress that joint experiences. A 350-pound person will experience much less knee strain from walking or running if he or she drops down to 250 or 200 pounds, for example. So, there’s a case to be made that heavier people should take it easy on the impact until they’ve built up to greater loads.
Many people, especially those carrying extra weight, have joint weaknesses in the ankles, knees and/or hips that may be exacerbated by running. It’s a good idea to get a qualified professional to evaluate the strength and integrity of your joints before embarking on a serious running program. A physical therapist or highly qualified personal trainer with training in biomechanics should be able to spot vulnerable areas. As a start, you might even have a friend watch what your legs do from behind as you run. Do your knees cave inwards? Do your feet splay out or do your ankles collapse? Do your hips tilt side to side? Any of these imbalances could lead to joint strain once you start doing vigorous activity. Often, all you need to do are corrective strengthening exercises to rectify your imbalances.
The best way to start running
If you’re not used to running, no matter what size or shape or fitness level you’re at, a smart way to train would be to start with fast walking. You can sneak very short jogging intervals in—start with 15 to 20 seconds at a time. Walk for three to five minutes in between bouts of jogging. Gradually add more time to your running increments. Over time (and I’m talking many months) build up to longer periods of running and longer total distances.
A general recommendation is to increase the amount, duration and intensity of any activity by no more than 5 percent per week. Exercise is a controlled dose of stress, and you should increase only when your body has adapted to a small overload. (This applies to all exercisers, undertaking any new activity, not just overweight, sedentary folks starting out.)
Other factors also affect joint loads. So make sure you are walking or running in a good pair of running shoes and choose softer surfaces (such as a treadmill or softer tracks instead of concrete sidewalks).
It’s always a good idea to do several kinds of activities—or to cross train. You develop better all-around fitness and minimize overuse stress to the body by doing too much of the same thing. So in addition to integrating a walk-run routine into your week, try the different cardio machines as well.
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