Bones and joints

How does exercise build bone and prevent osteoporosis?

Bone responds to the load you put on it. Long periods of inactivity tend to reduce bone mass, while loading the bone through exercise tends to increase it¹. The harder the load, the stronger the response⁵. High loads, such as resistance exercise, can stimulate bone-forming cells to lay down new bone⁶. Impact activities and progressive resistance training are the types that bone responds to best. Better muscle strength, balance and mobility also lower the risk of falls, and so of fractures⁴.

Which exercise works best?

Weight-bearing impact exercise (such as aerobic dance) and exercise that loads the muscles (such as resistance training) have been shown to improve bone density². Walking, cycling and swimming have minimal or no bone-building effect for most people. The exception may be people whose bones have had very little stimulation because of long inactivity or bed rest². Keep doing them if you enjoy them, because every bit of activity counts for your general health.

A good week includes something from three groups⁷:

• Weight-bearing impact exercise, such as dancing.
• Resistance training, using free weights, elastic bands, your body weight or machines.
• Posture and balance exercise, such as tai chi.

How often, and how to start

For bone strength, aim for impact and strength training on at least 2 days a week². Three sessions a week is the ideal³.

Start gently. For resistance training, the usual target is the heaviest weight you can lift 8–12 times, building up to three sets of each exercise. Begin with lighter effort while you learn good technique⁸. Take the first 3–6 months slowly, and leave out explosive or fast movements at the start².

Much of the research is in postmenopausal women, so the results may not carry over in the same way to men or younger adults.

When to check with a health professional

If you're starting exercise after a long break, it's always a good idea to see your doctor first.

If you have osteoporosis or low bone density, check with your doctor or a physio before starting impact or strength work. They can help you pick exercises that suit you². For an injury or a health condition, see a health professional, such as your doctor or a physio.

If you have osteoporosis, avoid heavy, repeated bending or arching of the spine under load. Keep trunk exercises light and slow, and ask a physio to show you safe ways to do them². Jumping and other explosive movements are not for the first weeks. Build up to them gradually, and only with advice if you have osteoporosis².

A sore muscle or joint, or soreness a day or two later, is a sign to ease off. Build up gradually and don't push through pain¹. See a doctor or other health professional if it persists or gets worse.

If you are at risk of falls, ask a physio about balance and strength work suited to you. Simple, low-risk ways of landing safely can be learned, but more demanding falling techniques need close supervision by experienced staff^2,3.

Call your local emergency number for chest pain or pressure (or pain spreading to the arm, neck, jaw or back, especially with sweating or feeling sick), severe breathlessness, fainting or collapse, signs of a stroke, a serious injury, or someone who isn't safe.