ABSTRACT
Elasticity is important for maintaining the normal physiological functions of tissues, especially load-bearing tissues, such as the articular cartilage and musculoskeletal tissues. Macroscopically, the tissue components are maintained in an equilibrated metabolic state at an appropriate level of new cell growth and apoptosis so that the mechanical properties of tissues are optimised for performing their normal physiological functions. Microscopically, it has been demonstrated that the biomechanical microenvironment is very essential for the stem cell lineage specication (Engler et al. 2006). So extracellular matrix (ECM) leads to neurogenic dierentiation. ECM with moderate elasticity is advantageous for myogenic dierentiation, while a sti ECM is osteogenic. Special aspects of elasticity related to physiology include the normal ageing eect, diurnal or menstrual change and variation of elasticity associated with muscle contraction. For example, skin elasticity is known to change with age, and the elderly usually have stier skin than young people. e suction method has been used to study the eect of ageing on the skin’s mechanical properties (Ohshima et al. 2013). On the other hand, short-term physiological changes due to hormonal uctuation such as the menstrual cycle have also been demonstrated to induce a change of elasticity to so tissues such as the breast parenchyma (Lorenzen et al. 2003). e variation of breast elasticity in dierent quadrants and also the relationship between the breast elasticity and other factors such as body mass index (BMI) and breast size were investigated in another study, which is useful for a better understanding of the breast physiology (Li 2009). Circadian change of the tissue stiness has also been investigated, although it failed to demonstrate a signicant dierence in arterial tissues (Kollias et al. 2009; Drager et al. 2011). Further study is needed to investigate how dierent parts of the human body such as lower and upper extremities will be aected diurnally in terms of elasticity change.
