Muscular development and physical activity as major determinants of femoral bone mass acquisition during growth

[EN] OBJECTIVES: To investigate to what extent bone mass accrual is determined by physical activity and changes in lean, fat, and total body mass during growth. METHODS: Twenty six physically active and 16 age matched control boys were followed up for three years. All subjects were prepubertal at the start of the survey (mean (SEM) age 9.4 (0.3) years). The weekly physical activity of the active boys included compulsory physical education sessions (80-90 minutes a week), three hours a week of extracurricular sports participation, and occasional sports competitions at weekends. The physical activity of the control group was limited to the compulsory physical education curriculum. Bone mineral content (BMC) and areal density (BMD), lean mass, and fat mass were measured by dual energy x ray absorptiometry. RESULTS: The effect of sports participation on femoral bone mass accrual was remarkable. Femoral BMC and BMD increased twice as much in the active group as in the controls over the three year period (p < 0.05). The greatest correlation was found between the increment in femoral bone mass and the increment in lean mass (BMC r = 0.67 and BMD r = 0.69, both p < 0.001). Multiple regression analysis revealed enhancement in lean mass as the best predictor of the increment in femoral bone BMC (R = 0.65) and BMD (R = 0.69). CONCLUSIONS: Long term sports participation during early adolescence results in greater accrual of bone mass. Enhancement of lean mass seems to be the best predictor of this bone mass accumulation. However, for a given muscle mass, a greater level of physical activity is associated with greater bone mass and density in peripubertal boys.

Engineering knowledge-based variance-reduction simulation and G-dominance for structural frame robust optimization

[EN] This paper proposes the incorporation of engineering knowledge through both (a) advanced state-of-the-art preference handling decision-making tools integrated in multiobjective evolutionary algorithms and (b) engineering knowledge-based variance reduction simulation as enhancing tools for the robust optimum design of structural frames taking uncertainties into consideration in the design variables.The simultaneous minimization of the constrained weight (adding structuralweight and average distribution of constraint violations) on the one hand and the standard deviation of the distribution of constraint violation on the other are handled with multiobjective optimization-based evolutionary computation in two different multiobjective algorithms. The optimum design values of the deterministic structural problem in question are proposed as a reference point (the aspiration level) in reference-point-based evolutionary multiobjective algorithms (here g-dominance is used). Results including