Association of Jumping Mechanography-Derived Indices of Muscle Function with Tibial Cortical Bone Geometry

Jumping mechanography has been developed to estimate maximum voluntary muscle forces. This study assessed associations of jumping mechanography-derived force and power measurements with tibial cortical bone geometry, compared to other estimates of muscle mass, size, and function. Healthy men (n = 181; 25-45 years) were recruited in a cross-sectional, population-based sibling-pair study. Muscle parameters include isokinetic peak torque of the quadriceps, DXA-derived leg lean mass, mechanography-derived peak jump force and power, and pQCT-derived mid-tibial (66 %) muscle cross-sectional area (CSA). Mid-tibial cortical bone parameters were assessed by pQCT. In age, height, and weight-adjusted analyses, jump force and power correlated positively with cortical bone area, cortical thickness, and polar strength-strain index (SSIp) (β = 0.23-0.34, p ≤ 0.001 for force; β = 0.25-0.30, p ≤ 0.007 for power) and inversely with endosteal circumference adjusted for periosteal circumference (ECPC) (β = -0.16, p < 0.001 for force; β = -0.13, p = 0.007 for power). Force but not power correlated with cortical over total bone area ratio (β = 0.25, p = 0.002). Whereas leg lean mass correlated with all cortical parameters except cortical over total bone area ratio (β = 0.25-0.62, p ≤ 0.004), muscle CSA only correlated with cortical bone area, periosteal circumference, and SSIp (β = 0.21-0.26, p ≤ 0.001), and quadriceps torque showed no significant correlations with the bone parameters. Multivariate models indicated that leg lean mass was independently associated with overall bone size and strength reflected by periosteal and endosteal circumference and SSIp (β = 0.32-0.55, p ≤ 0.004), whereas jump force was independently associated with cortical bone size reflected by ECPC, cortical thickness, and cortical over total bone area ratio (β = 0.13-0.28; p ≤ 0.002). These data indicate that jumping mechanography provides relevant information about the relationship of muscle with bone geometry.