Table A1.

Main biomechanical parameters and common formulas.

Biomechanical Terminology	Explanation	Common Formula or Law	Reference
Elasticity	Elasticity refers to the property that an object can recover its original size and shape after deformation.	△F = −k·△x, when the object deforms, the elasticity is directly proportional to the elongation. (Hooke’s law)	[14,19,39,40,43]
Viscosity	The resistance of fluid to deformation under shear stress is measured.	τ = µ$\frac{du}{dy}$refers to the velocity gradient along the Y direction, μ is the viscosity coefficient.	[14,54,55,56,58,61,65,69,82,83,109,110,123,143,151,155]
Viscoelasticity	The comprehensive properties of viscosity and elasticity of fluid	${\mathsf{\gamma }=\mathsf{\gamma }}_{\mathrm{E}}{+\mathsf{\gamma }}_{\mathrm{H}}{+\mathsf{\gamma }}_{\mathrm{Y}}$ $\gamma$: total deformation; ${\gamma }_E$: ordinary deformation; ${\gamma }_H$: the delayed high elastic deformation;${\gamma }_Y$: viscous deformation.	[6,18,19,63,112,113,143]
Stress (σ)	Internal force per unit area	σ = P/A, ratio of load to section area.	[15,34]
Shear stress	The interaction force between two sides of any section (shear plane)	τ = $\frac{F_S}{A},$ load $F_S$ is parallel to the section.	[13,17,43]
Strain (ε)	The local relative deformation of the object under the action of external force and non-uniform temperature field.	$\mathsf{\epsilon }=\underset{\mathrm{L}\to 0}{\lim }\left(\frac{\mathsf{\Delta }\mathrm{L}}{L}\right)$, L is the original length and ΔL is the elongation.	[42]
Shear strain	The relative shape variable produced by the object during shearing	γ $=\tan \theta$, $\theta$is the skew angle; when the shear strain is infinitely small, γ = $\theta$.	[44,85]
Elongational strain	The ratio of the change of the line length to the original line length.	The strain produced by an object in tension or compression.	[42,68,84,124,125,148]
Young’s modulus (E)	A physical quantity describing the ability of solid materials to resist deformation.	E = σ/ε, the ratio of stress to strain.	[7,17,18,38,39,43,48,69,70,105,106,107,123,125,126,133,134,139,140,141,142,143,149,152,155]
Shear modulus (G)	Shear stress characterizes the material’s ability to resist shear strain.	G = τ/γ, the ratio of shear stress to shear strain.	[48,104,110]
Poisson’s ratio($v$)	The ratio of the absolute value of the transverse positive strain to the axial positive strain.	Load in elastic range:${\epsilon }_x=-v{\epsilon }_y$, $v$ is a constant, beyond the elastic range, $v$ increases with the increase of stress until 0.5; Relations between E, G, $v$:$\mathrm{G}=\mathrm{E}\backslash \left[2*\left(1+v\right)\right]$	[15,16,55]
Dynamic viscoelasticity	The viscoelasticity of objects in vibration.	It describes the ratio of stress to strain of an object under dynamic load	[51,52,61]
Storage modulus (G’)	The measurement of energy storage in the process of strain cycling and is usually expressed as the real part of the complex modulus.	Complex modulus: $\mathrm{G}$ =$G^{\prime }$+ j$\mathsf{\omega }G”$ Storage modulus: $G^{\prime }=G*\cos \left(\delta \right)=\left({\sigma }_0/{\gamma }_0\right)*\cos \left(\delta \right)$	[88,151]
Loss modulus (G’’)	The degree of energy loss when the material deforms; usually expressed as the imaginary part of the complex modulus.	Loss modulus: $G”=G*\sin \left(\delta \right)=\left({\sigma }_0/{\gamma }_0\right)*\sin \left(\delta \right)$	[88,151]
Loss tangent(tan$\delta$)	Reflect the ratio of viscosity and elasticity of material	Loss tangent: tan$\delta$ = $G”/G^{\prime }$	[88,151]