19th Century physician Julius Wolff was not your stereotypical wolf: he didn’t chase little pigs, and he definitely wasn’t interested in attacking dear old Grandma. In fact, Wolff was a German surgeon and anatomist who studied how bone reacts to pressure, and his theories—known as Wolff’s Law—are widely accepted to this day.

Wolf's Law

Wolff’s Law states that bone is created and reinforced by the body in places where it is needed. This is why baseball pitchers will have larger, denser bones in their throwing arm. More muscle strain, more use, more stress on the bone results in the body laying down more bone. Did you know astronauts come back from outer space weaker and with less bone density? Yep, also Wolff’s Law. Without the strain of muscles pulling on bones to move the body, the body doesn’t reinforce the skeleton, and bone mass decreases.

So how does Grandma come into play? Osteoporosis is the well-known disease where bones become weak and brittle. Under examination, we can actually see the webbing (or trabecular pattern) that makes up bones is thinner and more porous, like a sponge with too many holes. 

These bone mass changes start as early as our thirties, and can be affected by genetics, diet, and lifestyle. But understanding Wolff’s Law gives us an edge: we know that the body keeps bone where bone is being used. Therefore, some of the best prevention and treatment of osteoporosis is…movement! Even simple activities like walking, yoga or water aerobics (strengthening, not merely floating), carrying light weights such as groceries and wrist weights will cause muscles to pull on bones. And when the bone feels the strain of that muscle—even from small, gentle activities—Wolff’s Law will kick in and the body will reinforce that bone, provided that the body has the resources to do so.

Appropriate supplementation and proportional physical activity are two of the best things we can do to prevent or slow osteoporotic changes, and it’s never too soon to start. Some studies suggest that Wolff’s Law even applies to youth, saying that healthy stress patterns in bones developed from childhood activities will be carried into adulthood.

Which means that this is a story that ends with us thanking the wolf—Dr. Wolff, to be exact—who helped us understand how bone is formed and maintained throughout our lives. So, what are you waiting for? Get moving!