Elastic- and viscous-like property of the upper arm estimated by the pushing method

The purpose of this study is to estimate the elastic- and viscous-like properties of the human upper arm using the pushing method. Healthy male subjects put their upper arms horizontally on a table. Their arms were fixed to the table with tapes. An indenter was placed 1-2 mm over the upper arm. When the indenter was moved vertically with a robot arm, the displacement y of the indenter and the force f was measured. The relationship between the displacement y and the force f was modeled with an elastic component, a viscous component and the friction of the indenter using the simplex method. In our model, an elastic coefficient k and a viscous coefficient d are expressed with a polynomials of the indentation depth x. The elastic coefficient and the viscous coefficient were well modeled with the third and the first order polynomials of the depth, respectively. The relationship between the elastic coefficient and the depth were independent of the indentation velocity. However, the viscous coefficient decreased with increasing indentation velocity.