reticular arrangement of collagen/elastin fibrous walls that create compartments that surround and retain adipose tissue (Hsu et al., 2007; Jahss et al., 1992). Based on the size of these compartments, they can be categorised into two layers; superficial (attached to the plantar epidermis), and deep (attached to the calcaneus). The superficial layer contains micro-chambers while the deep layer consists of larger, macro-chambers (Blechschmidt, 1982). The material and structural behaviour of the heel fat pad regulates the amount of load that is transmitted to the bones and joints of the lower limb across a range of loading scenarios; from low rate activities such as standing and running, to high rate incidents that can cause injury such as sport and vehicular accidents. Therefore, the characterisation of the tissue across a range of strain rates can be used for a variety of applications such as understanding the pathophysiology of related diseases (Kinoshita et al., 1996; Tong et al., 2003), shoe and insole design (Jørgensen and Bojsen-Møller, 1989), reconstruction of degenerated tissue (Wang et al., 1999), design of biomimetic materials for treatment of injuries and diseases of the plantar foot (Balkin and Kaplan, 1991; Mulder, 2012), development of accurate FE models (Fontanella et al., 2013), or prediction of and protection from injury in road traffic accidents and underbody blast (Dong et al., 2013; Shin et al., 2012). The heel fat pad is inhomogeneous and anisotropic while it is reported to exhibit viscoelastic behaviour due to its biphasic nature (Rome, 1998). studies have used In vivo imaging (Gefen et al., 2001; Prichasuk, 1994), indentation (Erdemir et al., 2006; Rome et al., 2001), or both techniques (Tong et al., 2003) to quantify the material properties of the tissue. Indentation, however, cannot be utilised to obtain material properties as the captured behaviour depends on the diameter of the indenter and is localised (Spears and Miller-Young, 2006).
reticular arrangement of collagen/elastin fibrous walls that create compartments that surround and retain adipose tissue (Hsu et al., 2007; Jahss et al., 1992). Based on the size of these compartments, they can be categorised into two layers; superficial (attached to the plantar epidermis), and deep (attached to the calcaneus). The superficial layer contains micro-chambers while the deep layer consists of larger, macro-chambers (Blechschmidt, 1982). The material and structural behaviour of the heel fat pad regulates the amount of load that is transmitted to the bones and joints of the lower limb across a range of loading scenarios; from low rate activities such as standing and running, to high rate incidents that can cause injury such as sport and vehicular accidents. Therefore, the characterisation of the tissue across a range of strain rates can be used for a variety of applications such as understanding the pathophysiology of related diseases (Kinoshita et al., 1996; Tong et al., 2003), shoe and insole design (Jørgensen and Bojsen-Møller, 1989), reconstruction of degenerated tissue (Wang et al., 1999), design of biomimetic materials for treatment of injuries and diseases of the plantar foot (Balkin and Kaplan, 1991; Mulder, 2012), development of accurate FE models (Fontanella et al., 2013), or prediction of and protection from injury in road traffic accidents and underbody blast (Dong et al., 2013; Shin et al., 2012). The heel fat pad is inhomogeneous and anisotropic while it is reported to exhibit viscoelastic behaviour due to its biphasic nature (Rome, 1998). In vivo studies have used imaging (Gefen et al., 2001; Prichasuk, 1994), indentation (Erdemir et al., 2006; Rome et al., 2001), or both techniques (Tong et al., 2003) to quantify the material properties of the tissue. Indentation, however, cannot be utilised to obtain material properties as the captured behaviour depends on the diameter of the indenter and is localised (Spears and Miller-Young, 2006).