Fig. 1.

Typical stress-strain curve of bone material and tendon (left) and definitions of stiffness, strength and toughness (right). Stiffness is the resistance against (small) deformation and corresponds to the slope (a). Material stiffness is often measured by the elastic modulus (or Young’s modulus). Strength is the maximum stress the material can sustain before failure (b), and a rough measure for toughness is the energy to failure [shaded area under the curve (c)]. Clearly, bone is stiffer but tendon is tougher (left panel). Figure adapted and reprinted from [7] with permission from Springer Science and Business Media