The development of the skeletal system in children and the influence of muscular strength

In a study on 14 healthy children aged from 6 to 13 years, the volumetric spongiosa bone density (SBD), cortical bone density (CBD), bone cross-sectional area (BCSA), cortical area (CA), and bone strength index (BSI) at the distal radius were analyzed using peripheral quantitative computer tomography (pQCT Bone Scanner XCT-900, Stratec, Pforzheim, Germany). BSI values were calculated on the basis of the moment of resistance and cortical density using system integrated software. These parameters were correlated with grip strength measurements obtained using a grip dynamometer. There were age-dependent increases in BCSA (r = 0.68), CA (r = 0.78), BSI (r = 0.79). SBD and CBD, however, did not show an increase with age. Grip strength correlates strongly with the parameters of bone geometry BCSA (r = 0.8), CA (r = 0.86), and BSI (r = 0.9) at p < 0.01. SBD and CBD showed no significant correlation to grip strength. The results of this study suggest that an increase in cortical thickness and cross-sectional area represent the most important adaptation mechanisms of the growing bones in response to biomechanical usage. These parameters represent the most important factors of bone strength. Volumetric bone density (material characteristic) of spongiosa and cortical bone is an age-independent parameter which does not change significantly with increasing muscular strength in healthy subjects. These relationships must be considered when selecting parameters to be used as success criteria in studies on the influence of physical exercise on bone status.