Fig. 4. (A–C) Stress–strain response in time from a 1 Hz sinusoidal elongation of vocal ligament. Note that the amplitude of strain remains constant (A) while stress (B) decreases over time. The decrease in stress is a result of tissue hysteresis, a phenomenon resulting from viscous properties of the tissue. (C) Stress–strain relationship for the same data set. The upper part of the `banana-shaped' curve is the loading phase (stretching). The lower part is the unloading phase (relaxation). The difference between both curves is due to hysteresis of the tissue, i.e. lower stress in the tissue during the unloading phase. The low strain region of the loading phase was fitted with a linear regression line, while the high-strain region was modeled with an exponential function. (D) The limit of the linear region (`Linear strain limit') determined by maximizing the sum of the two regression coefficients (`sum of r²'). The maximum linear strain limit (₁) in this example is approx. 0.09.