Why is exercise good for bone health?

We’ve heard for years now about the health benefits of moderate exercise, especially in our later years. But in the case of bone condition, this is actually true.

There is actually more to bones than just a mechanical framework for our bodies allowing us to move, breathe and do stuff. Without going into the biological intricacies, here are some interesting facts to think about.

Bone structure is complex
When a fracture occurs, bone cells begin to deposit or “knit” new hydroxyapatite (HA), a special form of calcium phosphate that “fills the gaps”. This is the mineral component that provides toughness, a bit like a ceramic. Drop a plate, and it breaks into pieces. But drop a bone, and it will bounce across the floor. This is because about one-third of bone is comprised of collagen, which allows it to bend slightly. Long bones are tubular, a structure which can resist bending, and can take quite an impact. The cortical layer is also porous but highly organized, making them light but reinforced internally where it is needed. In short, healthy bones are light and strong.

Bones are constantly turning over
Bone cells cycle, laying down new hydroxyapatite on a regular basis. There are two basic types of cells that live in bone – the “building” cells (osteoblasts) and the “eroding” cells (osteoclasts). Osteoblasts make new bone cells, which make new minerals. But the osteoclasts “eat” bone around the edges, which creates the pores. Both remain in a kind of balance, although the balance can favour the osteoclasts in some health conditions, resulting in loss of bone density.

Bone density responds to gravity
As we walk or run, the shock that travels through a leg, pelvic and spinal bones can actually stimulate bone cell growth. This is a very special mechanism. Cells respond to the microscopic pressures that travel through the bone with each step, and the more steps or loading, the more pressure is created. This stimulates osteoblasts to make more cells and more mineral. Limited loading and mobility during after a fracture has also been shown to accelerate healing[1].

Using muscles can strengthen bones and joints
When babies learning to balance their heads on their own, they’re neck muscles begin to strengthen. This, in turn, increases the density of the bone where the muscles are attached. Similarly, strengthening muscles around joints is believed to be beneficial in supporting the joint itself. The forces that travel through bones during a light weight session can also improve the strength of the bones to which the muscles, tendons and ligaments are attached.

Bones need nutrients to stay healthy
Optimal health of the bone cells requires optimal nutrition. The cells require energy from carbohydrates, and amino acids from protein, to make more cells and support the active population at any one time. They also need micronutrients, the most important of which are calcium and phosphorus, which cells use to make new HA. Bone cells also need micronutrients like, zinc, magnesium, vitamins D and K, as you have already read about in NextG cal. And, don’t forget to stay hydrated.

And finally… rest your bones!
Recovery from physical exertion, heavy or light requires sleep. This is especially for the spine, which holds up your body from morning to night. A lack of suitable repair time, especially after regular exercise, means that bones might be more susceptible to damage, such as micro-fractures[2]. The same applies to muscles, joints and connective tissue, and recovery periods are often incorporated in sports training programs for these reasons.

 

[1] Buckwalter J & Grodzinsky A. .J Am Acad Orthop Surg. 1999 Sep-Oct;7(5):291-9.

[2] Donahue S & Galley SA. Crit Rev Biomed Eng. 2006;34(3):215-71.