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.