The in vivo mechanical properties of muscular bulk tissue.

The aim of this study was to characterize the bulk modulus properties of the upper arm under relaxed and controlled contraction which is defined as 25% of the maximum voluntary contraction. A new testing machine was designed to generate a continually increasing load on the upper arm and measure the load over time. The machine consists of a device which is effectively a cuff that applies controllable pressure on a 47 mm wide band of the upper arm. A set of four different constant strain rates was used to test the stiffness of the arm bulk tissue. The stress-strain test consisted of 0.5, 1, 2, and 4 mm.s(-1) constant strain rates. The stress-strain curves obtained show strongly non-linear response of the bulk tissue. The nonlinearity is evident that the stress-strain curve for bulk tissue is time dependent.