About two to three hours of brisk walking a week was linked to meaningful gains in bone density

Design

Bayesian network and dose-response meta-analysis of randomised trials

Population

124 trials, 18,429 adults aged 40 and over

Primary outcome

Bone mineral density at spine, femoral neck and total hip

Effect

Brisk walking or jogging total hip +0.021 g/cm² (95% CrI 0.005 to 0.038); meaningful gain at about 600 MET-min/week

A BMJ network meta-analysis pooled 124 randomised trials (18,429 adults aged 40 and over) comparing structured exercise with no exercise or with other types of exercise.

Brisk walking or jogging and combined aerobic-resistance training improved lumbar spine bone density (both about 0.013 g/cm² over control). Brisk walking or jogging was the only type to improve total hip density (0.021 g/cm²). Gains followed an inverted U with dose: a clinically meaningful change appeared at about 400 MET-minutes a week for the spine and 600 for the hip, roughly two to three hours of brisk walking. In 26 trials reporting fractures, mixed aerobic exercise (OR 0.29) and mind-body exercise such as tai chi (OR 0.58) were associated with fewer fractures, on low-certainty evidence.

This gives clinicians a specific prescription to offer: weekly brisk walking at a defined dose, with resistance work alongside, rather than general advice to keep active.

• Prescribe about two to three hours a week of brisk walking or jogging to adults over 40 concerned about bone health.
• Add resistance exercise to aerobic work where the patient can manage it.
• Suggest tai chi or similar mind-body exercise for older adults, especially those at risk of falls.
• Keep exercise alongside, not instead of, drug treatment for established osteoporosis.

Why it matters

It turns 'stay active' into a dose a patient can follow and a clinician can check.

Don't overread it

Fracture reduction rests on low-certainty evidence; the bone density changes are the firmer finding.

The statistics, in plain English

The bone density gains are small in absolute terms (around 1% to 2%), which is typical for exercise trials. The fracture results come from fewer trials and have wide credible intervals, so they suggest rather than show a reduction.

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