Biomechanics 1
Subject and importance of biomechanics. Rheology of the solid materials. Viscoelastic properties of bones and muscles
Biomechanics is the study of the structure and function of biological systems such as humans, animals,cells etc by means of the methods of mechanics (behaviour of physical bodies when subjected to forces).
Mechanical properties are important for
- Orthopedy
- Cosmetic surgery
The type of mechanical properties are:
- 1. Active; muscle motion, mechanoreceptors, ATP-synthase, growth (motion in cell and cell substructure).
- 2. Passive; external force reaction of biological structure.
There are two types of biological material by phases:
- 1. Solid; bones, muscle, vascular, skin
- 2. Liquid; blood, lymph, synovial fluid
[Rheology is the study of flow and deformation of materials under applied forces]
Deformation (strain); change in shape and/or size of an object due to an applied force. Force = F can be a result of tensile, compressive, shear forces, bending & torsion.
Stress = Force / Area !!
Elasticity: When stress is applied → instantaneous stretch. When stress is removed → return to original shape.
Viscosity: measure of the resistance of a fluid which is being deformed.
Viscoelastic materials exhibit time-dependent strain. Viscoelasticity is the result of the movement of structures (molecules) inside of a material.
Bones experience certain viscoelasticity due to the following components and structures:
- 1. Hydroxyapatite; is a mineral that makes up about 65% of bone by weight. It gives bones their hardness.
- 2. Collagen; the bone elasticity is mainly due to the protein collagen.
Muscle viscoelasticity: components causing muscle viscoelasticity are; collagen and elastin.
- Collagen; stress when strong stretching
- Elastin; stress when moderate stretching.
The model for smooth muscles is Maxwell model and the model for skeletal muscles is the Voigt model.