Moderate lifting three times a week ranked best for most bones

Bone mineral density declines with age, and low density raises fracture risk, so resistance training is widely recommended to protect the ageing skeleton. But recommendations rarely specify how hard or how often to train, and it is plausible that different skeletal sites respond differently to different combinations of intensity and frequency. Without that detail, two people following the same broad advice could load their bones very differently. This analysis set out to rank intensity and frequency combinations against each other, site by site, to identify the strategy with the best chance of improving bone density in middle-aged and older adults.

Researchers searched PubMed, Embase, Cochrane, Web of Science, Google Scholar and Scopus for randomised controlled trials of resistance training with bone mineral density outcomes. Thirty-four trials with 1746 participants were included, and study quality was assessed with a standard risk of bias tool. A network meta-analysis then compared different intensity and frequency combinations, ranking each by its probability of being the best option at the lumbar spine, femoral neck, total hip, trochanter, Ward's triangle and total body.

Moderate-intensity resistance training three times per week ranked highest for five sites: the lumbar spine, femoral neck, total hip, trochanter and Ward's triangle. For total body density, high-intensity training twice weekly ranked top. Against control, the moderate three-times-weekly strategy significantly improved density at the femoral neck and trochanter, and both strategies significantly improved total body density. Importantly, no statistically significant differences were found between interventions at the lumbar spine, total hip or Ward's triangle, so the rankings at those sites rest on probability rather than proven superiority.

That resistance training benefits bone in this age group confirms a substantial existing literature; the site by site ranking of intensity and frequency combinations is the useful extension. Subgroup analyses suggested that frequency, intensity, programme duration, session length, sex, bone health status and age all influenced responses at different sites, underlining how conditional these effects are. Because several comparisons between strategies were not statistically significant, direct trials pitting the top-ranked approaches against each other would be needed to settle the question properly.

For anyone training with bone health in mind, this is a reason to think moderate loads performed regularly, three times a week in these trials, are a credible strategy for the hip and spine, and that maximal intensity is not obviously necessary for most sites. High-intensity work twice a week looked strongest for whole-body density, so the best approach may depend on the goal. Given how many differences between strategies failed to reach significance, the honest reading is that doing resistance training consistently matters more than the fine print of the protocol.