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The bones are the rigid structure of the musculoskeletal system. In sports biomechanics they are modeled as beams subjected to compression, traction, flexion, torsion loads and combinations of these. Cortical bone has Young's modulus E 1720 GPa and compressive strength of ~170 MPa. Trabecular bone is more porous and soft (E 0.15 GPa). Under cyclic sports load, bones adapt by remodeling (Wolff's Law): the bone structure is oriented according to the lines of main tension. Stress fractures occur when cyclic loading exceeds the microscopic repair capacity. The second moment of area (I) of the cross section of the bone determines its bending strength and torsional rigidity. The length of the bone defines the lever arms of the muscular forces. The Euler-Bernoulli beam model describes the deflection and stress distribution under transverse loading; Saint-Venant theory describes torsion. In sports impacts, the stress wave propagates at speeds of ~3,000 m/s in cortical bone.

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ID:('ky', 447)

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ID:(0, 447)