Lazy Bones – A quick look at bone health and exercise
Osteoporosis can be defined as a progressive disease in which bones lose their density and become brittle and prone to fractures. It is generally preceded by osteopaenia (also spelled osteopenia), a condition in which the bones begin to lose their density and become thinner.
Most people think that osteoporosis is a disease of elderly, post-menopausal women but it isn’t. Osteoporosis can affect anyone at any age.
“When I found out that I had osteoporosis, I was pretty shocked. I thought it was, you know, for old ladies basically…but I got diagnosed when I was 37. Osteoporosis has affected my life in many ways. Mainly I’m a lot more aware of my health now. I’m aware of just taking it a little more easy with physical activities, I exercise regularly, I gave up smoking… in fact, I probably feel better now than I have ever felt!”
Kirk Pengilly (member of INXS)
What are the risk factors or causes of osteoporosis and osteopaenia?
- Low levels of oestrogen – for example, women who are underweight either due to an eating disorder or over-exercising; women with amenorrhoea; post-menopausal women; and nursing mothers.
- Prolonged use of certain drugs – especially alcohol, some diuretics, cortisone and tetracycline.
- Cigarette smoking.
- Calcium deficiency or malabsorption syndromes.
- Vitamin D deficiency.
- A lack of weight-bearing exercise.
- A family history of osteoporosis.
Can you prevent or treat osteoporosis or osteopenia?
One of the most important things you can do to maintain bone health is weight-bearing exercise. Weight-bearing exercise includes any form of exercise where the person is on their feet and their bones are supporting the weight of their body.
Examples of weight-bearing exercise include:
- Carrying something heavy (or doing weights in a gym)
- Climbing stairs
These are all simple weight-bearing exercises that you can do to strengthen your bones. Be aware that some exercises, although still good for you, are not weight-bearing and so will not help your bone health. Swimming and cycling are examples of non weight-bearing exercises and unfortunately you can have a very fit swimmer who still struggles with bone density loss.
In addition to doing weight-bearing exercises, we also need to do exercises that improve our balance and stability so that we do not fall easily. Yoga and tai chi are both good for your balance.
Why is weight-bearing exercise important?
To understand why weight-bearing exercise is so important in strengthening our bones, it helps to have a basic knowledge of bone physiology.
Our bones are fascinating, ever-changing structures that do so much more for us than simply hold up our bodies and provide attachment for muscles. They support and protect our bodies, allowing for movement and mineral homeostasis and they are also a site of blood cell production as well as energy storage. They are living tissues constantly reshaping, rebuilding and repairing themselves through a process called remodelling and approximately every 10 years every bone in our body is completely reformed.
Bone tissue, known as osseous tissue, is a connective tissue whose matrix is composed of water, protein, fibres and mineral salts. The fibres are made of a protein called collagen and it is this collagen that enables bones to resist being stretched or torn apart. Without collagen bones become hard and brittle. The mineral salts are mainly calcium carbonate and a crystallised compound called hydroxyapatite. These salts give bone its hardness.
To be able to carry out this process of remodelling, bone tissue is composed of four different cell types:
- Osteoprogenitor cells – stem cells that develop into osteoblasts
- Osteoblasts – cells that secrete collagen and other organic components to form bones
- Osteocytes – mature bone cells that maintain the daily activities of bone tissue
- Osteoclasts – cells found on the surface of bones that destroy or resorb bone tissue.
Integral to remodelling is mechanical stress (for example the pull of gravity or the pull of skeletal muscles). Weight-bearing exercise puts mechanical stress onto the bones and so promotes bone remodelling. Without mechanical stress, bones weaken or lose density. This phenomenon is seen in astronauts who experience weightlessness in space. It is also seen in people who are bedridden – their bones weaken quickly.
As we age, a natural decrease in collagen production causes our bones to become more brittle and prone to fracturing. The process of remodelling also changes and the amount of bone deposited during the remodelling process does decrease. However, I want to emphasise here that the process of remodelling only decreases – it does not stop – and so, no matter how old we get, we should not give up on our bones.
In addition to weight-bearing and balance exercises, it is important to maintain healthy levels of Vitamin D, calcium and collagen – sitting in the sunshine, sipping a cup of bone broth is a great way to do this 🙂
“Never in my wildest dreams did I think I would be a candidate for osteoporosis. I know now, I should have paid more attention to my personal risk factors; I should have taken better care of my bones. You know what? So should you. So come on, Beat the Break, take responsibility for your bones."
Joan Rivers, Comedienne
By the way, if you enjoy learning about the body and how it works, then would you like a free copy of one of the chapters from my anatomy and physiology textbook? It's the chapter on hormones....really interesting! Sign up here for your free copy.