Associations between muscle mass and strength and bone microarchitecture in Caucasian postmenopausal women

This study examines associations between muscle mass, strength, and bone microarchitecture in 160 postmenopausal women from the OsteoPreP Study. Findings reveal that greater appendicular lean mass index (ALMI) and hand grip strength correlate with increased cortical area and trabecular vBMD, although ALMI was associated with lower cortical bone density, explained by physical activity.

To investigate associations between muscle mass, strength, and bone microarchitecture in postmenopausal women.

Postmenopausal women (n = 160) (mean ± standard deviation: 55.9 ± 2.6 years) were included as part of the baseline examination from the OsteoPreP Study. Appendicular lean mass (ALM) was calculated as the sum of lean mass in the upper and lower limbs obtained using dual-energy X-ray absorptiometry. Participants completed hand grip strength testing using a dynamometer. Bone microarchitecture parameters including cortical and trabecular volumetric bone mineral density (vBMD), trabecular thickness, cortical area, and porosity were analyzed by using high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal tibia and radius. Metabolic equivalents (METs) were objectively determined by accelerometer. Linear regression (unstandardised β-coefficients; p-values) analyses were performed with adjustments for confounders.

Higher appendicular lean mass index (ALMI; ALM/height² in kg/m²) was significantly associated with greater cortical area (2.55 mm² per 1 kg/m² increase in ALMI, p < 0.001) and greater trabecular vBMD (9.44 mg/cm³ per 1 kg/m², p = 0.013), but with lower cortical vBMD (- 11.37 mg/cm³ per 1 kg/m², p = 0.039) at the radius, after adjustment. Higher hand grip strength (kg) was also significantly associated with greater cortical area at the radius (0.67 mm² per 1 kg, p = 0.001), with similar associations at the tibia. Additionally, physical activity levels (MET-hours/week) partially mediated the association between ALMI and cortical vBMD (- 2.01 mg/cm³, 95% CI: - 5.25 to - 0.03).

In summary, greater ALMI and hand grip strength are associated with increased cortical area and trabecular vBMD, but lower cortical vBMD, which is partially explained by physical activity levels. Although greater muscle mass is correlated with larger bones, it comes at the expense of cortical vBMD in postmenopausal women.