There’s a perception that running pounds the body, and that this impact is what leads to up to half of all runners getting hurt every year. But scientific evidence collected from one of the world’s leading biomechanists and sports-shoe researchers, Benno Nigg, Ph.D. , of the University of Calgary, indicates that it’s not the impact itself that forces so many to temporarily hang up their sneakers. It’s how your muscles respond to that impact.
Consider that for every step you take during a run—about 150 to 170 per minute on average—your body’s “internal active forces” (the sum of all your muscles contracting and expanding) are far greater than the force of the impact your body feels from striking the ground. How much greater? Nigg says those internal forces are 500 percent more powerful.
But Nigg also says that, for the most part, those forces fall within an “acceptable range.” They aren’t a problem unless they overload a particular structure. For example, your calves may work extra hard during an activity if your ankles are weak.
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One way to think of it is to imagine your body is a car. There’s a strong, durable frame (your bones) supported by shock absorbers (your muscles, tendons and ligaments). If everything is working together, you can cover mile after mile without any problems. But if a shock fails, your car w…