Extraction of quasi-linear viscoelastic parameters for lower limb soft tissues from manual indentation experiment

A manual indentation protocol was established to assess the quasi-linear vi scoelastic (QLV) properties of lower-limb soft tissues. The QLV parameters were extracted using a curve-fitting procedure on the experimental indentat ion data. The load-indentation responses were obtained using an ultrasound indentation apparatus with a hand-held pen-sized probe. Limb soft tissues a t four sites of eight normal young subjects were tested in three body postu res. Four QLV model parameters were extracted from the experimental data. T he initial modulus E-0 ranged from 0.22 kPa to 58.4 kPa. The nonlinear fact or E-1 ranged from 21.7 kPa to 547 kPa. The time constant tau ranged from 0 .05 s to 8.93 s. The time-dependent material parameter alpha ranged from 0. 029 to 0.277. Large variations of the parameters were noted among subjects, sites, and postures.