Figure 3.

(a,b) Sarcomere length and stress (force/cross-sectional area) as a function of time for two exemplar myofibrils stretched from an initial sarcomere length on the descending limb or (c,d) near the plateau of the force–length relationship. Sarcomere lengths are non-uniform for the isometric contraction prior to stretch and remain non-uniform following stretch. Stresses increase during stretch dramatically and remain greater after stretch (for at least 25 s) than the forces prior to stretch, and greater than the expected forces (based on myofilament overlap for the average sarcomere length) at optimal length (e_o) and final length achieved after the stretch (e_f).