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Why Exercise Is Essential for Strong Bones

A recent study of mice has revealed that a hormone called irisin, which is secreted by active muscle cells, can trigger our bones to get stronger. Here's how to take advantage of the "exercise hormone." 

By
Brock Armstrong,
Drawing of a skeleton running

Osteoporosis is low bone mass and deterioration of bone tissue, which can lead to increased risk of bone fractures (among other things). For years we have been told to take calcium supplements, drink plenty of milk, and (more recently) take Vitamin D supplements to keep our bones strong. But lately, we are seeing “weight-bearing exercise” being promoted as a way to prevent or treat osteoporosis. Why is that?

Exercise and Bones

If we want bone to grow, we need to start by squeezing cells called mechanoreceptors in those bones. Without squeezing these mechanoreceptor cells, the delicious bone-growing nutrients that we ingest to support bone growth won’t be able to do their job. Your body can have plenty of them around but it won’t know what to do with them.

Along comes a hormone called irisin (also known as the “exercise hormone”) which is secreted by our muscles when we exercise. When it is secreted in vast quantities, irisin has been shown to have beneficial effects on adipose tissue (fat), cognition (brain), and bones.

The squeezing I mentioned is best created by exercising because movement stimulates the release of molecules from skeletal muscle. One of those molecules is the aforementioned irisin, which is produced most when we do high-intensity training.

Once irisin is generated, it will go to work on improving bone density.

Once irisin is generated, it will go to work on improving bone density by stimulating osteocytes, which are the master regulator of bone remodeling. Now we get to the cool part of the latest study done on irisin.

Not only does irisin stimulate osteocytes but it also stimulates something called sclerostin. Sclerostin launches a process opposite that of the osteocytes—it stimulates break down of bone.

What?

I know, right!?

The idea that irisin would promote the production of osteocytes and sclerostin seems counterproductive. But the authors of the study say that "It is this bit of bone breakdown that signals the body to engage in some skeletal renovation." And as we all know, renovations don't get completed if the workers are sitting on their lunch pails.

Breaking Down Bone

So, it would appear that the body needs to break down bone in order to rebuild it. Which, if we follow the logic, means that taking all the calcium in the world is not going to help your bones if you don’t move, bounce, twist, and squeeze those cells.

For optimal bone generation and regeneration, you need as much movement as possible.

For optimal bone generation and regeneration, you need as much movement as possible. And it's even better if your bones are supporting a decent amount of weight while moving, too. The research done on bone in conjunction with exercise has shown that moving around while carrying some weight will indeed create the greatest bone development.

Weight-bearing exercises are the best (walking, resistance training, supporting your own weight). Non-weight bearing (swimming, cycling, working in zero gravity) are not.

It is the physical act of moving and working a muscle—making the muscle pull on the bone—that stimulates both the breakdown and the remodelling effects of irisin. Which, by the way, may also play a protective role in disorders such as Alzheimer’s Disease, Parkinson’s Disease, and ALS. Jus' sayin'.

For more bone info, skeletal tips, and to join the hormonal conversation, head over to Facebook.com/GetFitGuy, twitter.com/getfitguy or BrockArmstrong.com.

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Running skeleton image courtesy of Shutterstock.

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