Exercise and bone loading: how movement supports bone strength

If you have been told your bones are thin, "stay active" is advice you have probably heard many times, and it can leave you wondering which activities help and which might hurt. This page explains how exercise acts on bone, the types of activity that named health bodies describe, what they say about people with low bone density or an earlier fracture, and what to expect. It supports our main guide to osteoporosis and bone health. Your own doctor or physical therapist has the final word on what is right for you.

How loading stimulates bone

Bone responds to the demands placed on it. When muscles pull on bone, or when your feet and legs carry your weight against gravity, the bone is put under force, and over time bone tends to adapt to that force. The U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) says weight-bearing exercises produce a force on bones that makes them work harder. The same page says exercise makes bone denser and replaces old bone with new bone, and that it helps prevent bone loss in adults.

The effect is local. The American Academy of Orthopaedic Surgeons' patient site, OrthoInfo, states that exercises to improve bone strength are site-specific. Walking and jumping mainly strengthen the legs and hips and not the wrist, while lifting and carrying weight can strengthen the hips and spine. In practice, that is why variety matters.

The three types of activity

NIAMS says a combination of three kinds of exercise is best for building and maintaining healthy bones and for preventing falls and fractures.

Weight-bearing

These are activities done on your feet. NIAMS gives brisk walking (3 to 4 miles per hour), jogging, racket sports, climbing stairs and dancing as examples. The Bone Health and Osteoporosis Foundation (BHOF) divides them into high-impact examples, such as jumping rope, jogging and high-impact aerobics, and low-impact ones, such as brisk walking, hiking on level ground and elliptical machines. It says the low-impact group can be a safe alternative if you cannot do high-impact exercise.

Resistance (muscle-strengthening)

Resistance work includes weight machines, free weights, resistance bands and bodyweight exercises. Muscles pulling on bone stress it, so these exercises help bone as well as muscle. OrthoInfo adds that heavier loads with fewer repetitions may build more bone density than lighter loads with more repetitions, and that each major muscle group can be worked at least twice a week with a day of rest between sessions. The BHOF includes everyday movements, such as rising from a chair or onto your toes, in this category.

Balance training

NIAMS says balance training is especially important for older adults. Its examples are tai chi, walking backwards, step-ups, lunges and shifting your weight forward and back while standing, and it describes the aim as improving balance and preventing falls. The International Osteoporosis Foundation (IOF) describes falls as a major cause of osteoporotic fractures, so balance work earns its place even though it does not load bone as much as the other two types.

How much activity guidance suggests

NIAMS cites at least 150 minutes (2.5 hours) a week of moderate-intensity exercise, or at least 75 minutes of vigorous exercise, plus muscle-strengthening activity at least twice a week. For older adults it says the weekly total should include a mix of balance, aerobic and muscle-strengthening work. The IOF gives a similar range for older adults, 150 to 300 minutes of moderate activity a week, and says healthy seniors can start with short sessions of 10 to 15 minutes.

These are general public recommendations. They are not a prescription, and a person with a health condition or limited mobility will often need a different plan.

If you have low bone density or a past fracture

This is the group for whom the advice is most cautious, and the sources are consistent on the first step: talk to a clinician. NIAMS tells people with low bone density or osteoporosis to talk to a health care provider before starting an exercise program.

The BHOF says that if you have broken a bone from osteoporosis, or are at risk of doing so, you may need to avoid high-impact exercises, and that correct body position is always important. It also warns of the risk of unintentional injury to the vertebrae during everyday activities, and suggests that a healthcare provider or an exercise specialist can help you exercise in safe positions.

OrthoInfo is more specific for severe osteoporosis. It advises care when lifting weights with the arms while standing, avoiding spine-bending or twisting movements, and avoiding contact sports. It describes floor-based core work and chair or wall exercises as safer options, notes that jumping may not be advised, and says that frail people or those with diagnosed thinning bone should ask their doctors which activities suit them. A physical therapist can help build a plan. If you are recovering from a recent break, see fracture recovery and rehabilitation.

Realistic expectations

Exercise is useful, but it is not a cure. NIAMS describes its benefits in terms of building strong bones in children, strengthening muscles and bones in adults, preventing bone loss, and helping prevent falls and fractures. It does not claim that exercise reverses established osteoporosis, and it gives no percentages or timelines for density gains. Expect gradual, modest effects that depend on consistency.

OrthoInfo states that even 20 to 30 jumps a day can have a positive effect on bone density, especially at the hip, but that applies to people who are cleared for impact exercise. For others, the IOF notes that weight-bearing exercise helps maintain bone density and that mixed loading exercises seem to be effective in reducing bone loss.

It also helps to think of exercise as one part of a bigger plan that can include nutrition, as covered in calcium and vitamin D basics, and, for some people, medicines, described in the medicines overview.

Exercise and fall prevention

For many people with fragile bones, falling is the real threat, and exercise is one of the ways to lower it. The IOF reports that simple weight-bearing programs improve gait speed, muscle strength and balance, and that this is associated with a 25 to 50 percent reduction in falls. It also says exercise programs for fall and fracture prevention should include balance training. A caution applies: the same source notes that tai chi reduces falls in healthy older adults, while frail older people and those who already fall frequently may not benefit as much. The IOF also reports that people with a sedentary lifestyle are more likely to have a hip fracture. Changes to the home environment are covered separately in fall prevention at home.

The short version

Bone adapts to the forces placed on it, so a mix of weight-bearing, resistance and balance activity is the pattern health bodies describe. People with low bone density or an earlier fracture are advised to check with a clinician first, since some high-impact and spine-bending movements may need to be avoided. Exercise supports bone and lowers fall risk, and it works best as part of a wider plan.