Fig. 4. (A) Maximum power output (solid lines) and efficiency (broken lines) with changes in the amplitude of stretch/shortening at a low stiffness (blue) and high stiffness (red). (B) Maximum power output and efficiency and the duty cycle, phase of activation and amplitude of stretch/shortening that achieve that power output with varying relative stiffness. Solid lines represent the values obtained for maximum power output and broken lines those obtained for maximum efficiency.