Essential guide to bones

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Bones: the lowdown

Your adult body contains 206 bones. They form a balanced and symmetrical skeletal structure that puts even the best Lego toys to shame. They’re also your primary defence against gravity, with your femur (thigh bone) alone capable of supporting up to 30 times your weight.

Of course, we runners tend to push gravity defiance to the limit. A single step during a distance run creates an impact force about two to three times your body weight. Luckily for us, bone is a living tissue that undergoes constant renewal. Under normal conditions, about four per cent of your bone is broken down and replaced through a process called remodelling. When you run, this process goes into overdrive. Just as your body strengthens muscle fibres by replacing damaged myofilaments, it also uses remodelling and modelling – a separate process that fortifies bone with extra bone tissue – to create bigger, stronger bones.

Where do things go wrong?

Rebuilding and fortifying your bones takes time. At the beginning of remodelling, cells called osteoclasts dig out old, damaged bone tissue, leaving tiny cavities in your bones. It then takes three to four months for other cells – called osteoblasts – to fill those cavities with new bone. In the interim, you’re left with porous bone that’s susceptible to injury. During this phase, runners who push too hard for too long often end up with a stress fracture. If that happens, then the waiting will begin again. It will take three to four months for your body to repair the fracture. Training too soon risks re-injury.

How do I build bone?

Strengthening your bones begins with nutrition - check out our nine best foods for bone health. Poor nutrition leads to weak bones. In fact, calcium deficiency in your diet can force your body to mine bones and teeth (which, combined, contain 99 per cent of your body’s stored calcium) for the mineral. If you’re diagnosed with a stress fracture, pool running is your best cross-training bet. Resistance training triggers improvements in bone strength, but more advanced runners might need to increase their usual volume of reps and sets by 25-50 per cent to continue strengthening their connective tissue.