ABSTRACT:The development of the musculoskeletal system in children and adolescents became an important topic in the field of pediatric research when the connections between muscle force and bone diseases were revealed. The present study focused on reference values of ground reaction forces, which derive from muscle forces of the lower limbs. Specifically, the study investigated the relationship between anthropometric characteristics and peak jump force (PJF), and peak jump power (PJP). The parameters were assessed by jumping mechanography using the Leonardo Jumping Platform. The entire study group was comprised of 135 school boys (ages 7-21 y) and 177 girls (ages 6 -19 y), who were enrolled in a German primary school and a German high school. The analysis of the parameters revealed that forces deriving from the motor performance of jumping follow an exponential relationship to body size parameters. Therefore, with consideration of anthropometric characteristics, the assessment of ground reaction forces might provide a novel, inexpensive, and accurate approach for the assessment motor performance in children and adolescents.
Previously published data (J Bone Miner Res (2005); 20: 471) did not give evidence that the administration of the nitric oxide precursor L-arginine increases bone formation and decreases bone resorption in postmenopausal women. Data of this trial were reanalysed for putative effects of L-arginine on muscle mass and muscular function. Therefore, 11 females of the former study group (n=15; age 54.5+/-4.1 years; daily oral administration of 18 g L-arginine hydrochloride (equivalent of 14.2 g L-arginine) over 6 months) and 12 females of the control group (n=15; age 55.3+/-4.4 years; daily administration of 18 g dextrose over 6 months) were analysed for biomechanical parameters (MIGF, maximal isometric grip force; PJF, peak jump force; PJP, peak jump power) and for the cross-sectional muscle area (MA) and fat area (FA) at forearm and leg (calf) measured by peripheral quantitative computed tomography. The study was performed in a double-blind design. The assessment of muscular and biomechanical parameters was undertaken before and after 6 months of L-arginine versus placebo administration. L-arginine-supplemented females had a significant increase of PJF/kg in comparison with the control group. PJP/kg, MIGF, MA and FA were not significantly influenced by the administration of L-arginine. In conclusion, the administration of L-arginine increased maximal force in mechanographic analyses and may prevent a decline of muscle force in postmenopausal women.
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