Bone Abstracts

Background: Despite evidence that physical activity can increase and maintain bone mineral density (BMD) in premenopausal women, optimal exercise dosing remains unclear. Heterogeneous interventions, poor reporting of key intervention characteristics, non-bone-specific intensity prescriptions, and inconsistent skeletal site selection have hindered translation into practice. This systematic review and meta-regression synthesised the impact of Physical activity interventions framed by the FITT principle (frequency, intensity, time, type) on BMD at the femoral neck, hip, lumbar spine, and total body.

Methods: Eight databases were searched (October 2025) for randomised controlled trials (RCTs) ≥3 months examining PA effects on BMD in premenopausal women. A synthesis and meta-analysis were performed to determine the effects of PA interventions on BMD at four skeletal sites. Meta-analysis and univariate/bivariate meta-regression to determine whether intervention effects on BMD differed according to FITT characteristics.

Results: Thirty-one RCTs were eligible. PA interventions led to small to moderate improvements in bone mineral density at all four sites (femoral neck: g0.37; hip: g0.33; lumbar spine: g0.31; total body: g0.33; all P ≤0.01). Meta-regression showed that these effects differed significantly by one or more of the FITT principles: High frequency (≥4days/week) interventions led to greater improvements than those of low frequency (≤3days/week) at the femoral neck (g0.77 vs 0.27, P 0.002), hip (g0.78 vs 0.21, P 0.003) and total body (g0.79 vs 0.21, P 0.013). The effects of moderate and high-intensity activity on BMD were similar across all sites, except for total body, where high-intensity activity led to greater improvements (g0.58 vs 0.13, P 0.019). Short sessions (30 mins) outperformed longer sessions (≥60 mins) at the femoral neck (g0.59 vs 0.25, P 0.021) and total body (g0.71 vs 0.16, P 0.027). Weight-bearing interventions led to greater improvements in BMD than resistance training at the femoral neck (g0.49 vs 0.08, P 0.003), the hip (g0.47 vs 0.08, borderline P 0.059) and total body (g0.49 vs 0.01, P 0.034).

Conclusion: The greatest BMD gains occur with frequent (≥4 day/week), short (30 mins), weight-bearing activity of at least moderate impact, supporting an evidence-based FITT prescription that may offer a time-efficient and scalable strategy to optimise peak bone mass and strengthen early prevention of osteoporosis.