It’s no secret that exercise helps strengthen thin, weak bones, even in people with osteoporosis. Explaining why it works can be a bit of a challenge — unless you understand the five principles that we at Better Bones use as the basis for our program.
The very idea that exercise can help strengthen bones makes no sense at all unless you understand the close relationship between the bones and the muscles. They work together in supporting and moving the body, but can’t do much separately. Remove the bones from an arm or leg, and the muscles have nothing to attach to; eliminate the muscles, and the bones hang uselessly, unable to move or function.
Once you view them as a unit, it makes intuitive sense that lean muscle mass predicts bone mass (rather than total body weight). It also makes sense that chronically strong muscles are associated with strong bones, and by the same token, chronically weak muscles are associated with weaker bones. Both bone mass and muscle mass are lost with aging, but we can do a great deal to limit this loss through modifications of lifestyle (including exercise) and nutrition.
In all her wisdom, Mother Nature is economical. Energy and resources are spent to build the amount of bone and muscle that an individual’s activity patterns shows they need. That is, bone acclimates itself to the load put upon it: More activity tells the body that more muscle and bone are required; less causes muscle and bone to decrease. Intermittent spurts of higher-impact loading, in particular, stimulate the strengthening of bone.
You don’t, unfortunately, get a full-body effect for a partial-body workout. The muscles pulling on the tendons that in turn pull on the bone send an important signal to build bone strength, but that signal is localized — meaning, if we exercise in such a way as to work the hip and leg, such as in jumping or hopping, we will build bone strength in the hip and leg, but not necessarily in the arms, wrists, or upper skeleton. Similarly, a right-handed tennis player will have stronger bone in their right arm, which moves more, than in their left arm. So if overall bone strength is your goal, you need to exercise in ways that work all (or most) of the major muscle groups.
Building bone is not all about working the muscles, though. Rest is very important for both the bone and muscle renewal process. We show the bone and muscle we need them to be stronger by the stress we put upon them during our activities, but it is in the recovery period, when we’re at rest, that bone and muscle renewal take place.
Even small amounts of exercise benefit bones, but the bone-strengthening benefits of exercise are increased with a higher dose of exercise. The more frequent your exercise sessions are, and greater the intensity per session, the greater the strength you’ll impart to your bones.
There are plenty of people in their later years who are worried about osteoporosis. They sometimes say, “I wish I’d started exercising when I was still young enough!” But if I were to add a sixth principle to this list, it would be this: It is never too late to build bone strength with exercise. Studies have shown that even wheelchair-bound 90-year-old seniors can build bone with weight bearing exercises, and even a little bit helps a lot.