Bone Abstracts

Background: Relationships between muscle function and bone have been examined using a range of techniques, with conflicting results. We aimed to determine these associations within an adult population comprising individuals with high bone mass and family controls.

Methods: Recruitment was from four UK sites within the high bone mass (HBM) study; cases and unaffected family controls were pooled. Peak ground reaction force and peak power, during a multiple one-leg jump and single two-leg jump respectively, were recorded using a Leonardo Mechanography Ground Reaction Force Platform, and hip BMD by DXA scanning. A subgroup underwent mid-tibial pQCT (Stratec XCT2000L). Linear regression analysis adjusted for age, gender, height and weight. Force and power were log transformed.

Results: 189 participants had matching jump plate and hip DXA data (70 males (mean age 58 years), 119 females (mean age 56 years)). Median jump power was 2.25 kW (IQR 1.78, 2.93) and force 1.95 kN (1.68, 2.39). Jump power was positively related to hip BMD (standardised β (95% CI) 0.29 (0.07, 0.51), P=0.01), but jump force was not (0.03 (−0.16, 0.22), P=0.74). In 113 participants with force and pQCT data, power was positively associated with tibial SSI (0.26 (0.09, 0.44), P<0.01) and with cortical thickness (0.33 (0.06, 0.60), P=0.02) but not with total bone area (0.10 (−0.10, 0.30), P=0.33). Force was also positively associated with SSI (0.24 (0.07, 0.42), P=0.01), but in contrast to power was associated with total bone area (0.22 (0.03, 0.42), P=0.02) but not cortical thickness (0.05 (−0.22, 0.32), P=0.72).

Conclusion: Muscle power and force are both positively associated with cortical bone strength. However, distinct mechanisms appear to be involved, since power was primarily associated with reduced endosteal expansion (reflected by cortical thickness and hip BMD), whereas force was associated with increased periosteal expansion (reflected by total bone area). Based on these findings, interventions targeting both muscle force and power may have the greatest benefit for cortical bone strength.