An example of the force-length relation (A) observed in the experiments conducted at 35°C. Each pair of points (prestaircase, solid line vs. poststaircase, dashed line) was obtained at the start (Pt) and end (Pt*) of 10 s of 10 Hz stimulation at a given sarcomere length. In the lower panel (B), the relative force (Pt*/Pt) is presented as a function of sarcomere length. Data from 4 muscles are shown. Regression analysis gave r2 = 0.74 and Pt*/Pt = -0.59·SL +3.27 (where SL is sarcomere length).