What's Actually Happening
Bone is living tissue that's constantly being broken down and rebuilt. When breakdown consistently outpaces rebuilding — which becomes more common with age, and accelerates sharply for women around menopause — bone density falls. Osteopenia (T-score between −1.0 and −2.5 on a DEXA scan) and osteoporosis (T-score −2.5 or lower) describe how far bone density has dropped below that of a healthy young adult. The real consequence isn't the number itself — it's fracture risk, particularly at the hip and spine, which is a leading cause of loss of independence in older adults.
How Resistance Training Actually Helps
Bone adapts to the mechanical strain placed on it — load it adequately and consistently, and it remodels to better resist that strain; leave it unloaded, and it has no signal to preserve density. The catch is that the loading has to be substantial enough to actually register as a stimulus — light, low-intensity movement generally isn't enough. This is why the research specifically on higher-intensity resistance training, and training that adds impact loading, shows the clearest results.
The Evidence
A Cochrane review of 43 randomized controlled trials in postmenopausal women (Howe et al., 2011) found that progressive resistance strength training for the lower limbs was the most effective single intervention for preserving bone density at the hip, and combined exercise programs were most effective at the spine.
The single most important trial here is LIFTMOR (Watson et al., Journal of Bone and Mineral Research, 2018), which tested genuinely high-intensity resistance and impact training — not modified or watered-down loading — in postmenopausal women who already had osteopenia or osteoporosis. The trial found significantly greater improvements in lumbar spine and femoral neck bone density and physical function compared to a lower-intensity program, directly challenging the old assumption that people with diagnosed low bone density need to avoid heavy loading. A companion trial, LIFTMOR-M (Harding et al., 2020), found similar bone-strength benefits from supervised high-intensity training in middle-aged and older men with low bone mass — this isn't a women-only finding.
The Myth Worth Retiring
“Don't lift heavy if you have osteoporosis” was reasonable caution before this generation of trials existed, but it isn't what the current evidence supports. LIFTMOR and LIFTMOR-M were specifically designed to test both efficacy and safety of high-intensity loading in people who already had diagnosed osteopenia or osteoporosis, under proper supervision and progression — and the programs improved bone density and function rather than causing harm. The key words are supervised and progressed appropriately — this is a case where working with someone who can assess your specific bone density, fracture history, and movement quality before loading you up genuinely matters, not a case for avoiding resistance training altogether.
Where to Start
If you have a diagnosed T-score in the osteopenia or osteoporosis range, get your physician's clearance and ideally a recent DEXA result before starting anything higher-intensity, especially if you have a prior fracture. From there, the trials above generally used supervised sessions 2 times per week combining free-weight compound lifts (squat, deadlift variations, overhead press) with some form of impact loading, progressed gradually over months — not years of caution before adding real load. If you don't yet have a diagnosis but are past menopause or over 50, this is exactly the kind of programming worth building proactively, before density is already lost.