Stronger bones and strength training -- does it help?

Strength training, also known as resistance training, has a proven positive effect on bone density in adults. Multiple studies and a meta-analysis of 17 studies show that bone mineral density in the spine and hip increases by approximately 1 to 3 percent with regular strength training. That may sound modest, but every percentage point of bone density counts as protection against fractures.

The most compelling evidence comes from a controlled study (PMID 28975661) of a heavy strength training programme known as the HiRIT protocol. Postmenopausal women who already had low bone mass trained twice a week for eight months under supervision. The training group saw bone density in the lumbar spine rise by 2.9 percent, while the control group lost 1.2 percent. In the hip the difference was comparable: plus 0.3 percent for the trainers, minus 1.9 percent for the non-trainers. This is a clinically meaningful difference for a group that is already vulnerable.

Beyond bones, strength training also helps preserve muscle mass and reduce the risk of falls in older adults. Falling is one of the leading causes of fractures in later life, so this indirect effect is at least equally important. A well-structured programme of 2 to 3 sessions per week, with sets of 5 to 8 repetitions at 50 to 80 percent of maximum strength, is recommended and is also feasible for older adults at home.

On safety: in the HiRIT study only one minor incident occurred across the entire training group (a mild back spasm), and there were no fractures, even in women with already weakened bones. One important caveat, however: the participants were otherwise healthy and strictly selected, and direct professional supervision was always present. Simply starting heavy lifting at home without guidance is therefore not what these studies tested.

Strength training is recommended by guidelines as a supplement to medication, adequate calcium (1000-1200 mg per day) and vitamin D (600-800 IU per day) in the treatment and prevention of osteoporosis. In cases of severe osteoporosis, strength training alone is not sufficient; drug treatment remains necessary. Aerobic exercise such as walking is less effective than strength training for strengthening specific bones such as the hip and spine.

One nuance is that the quality of evidence for certain outcomes, such as the effect on hot flushes and functional capacity in postmenopausal women, is rated as low to very low by the researchers themselves. The positive effects on bone density have been demonstrated more consistently, but even there the caveat applies: studies are not always large enough or long enough, and the ideal training structure (how heavy, how often, which exercises) has not yet been precisely established by science.