Fraction of OFF motors at rest and of motors attached in isometric contraction. (A) Fraction of motors in the OFF (ordered) conformation, fOFF, at rest as a function of temperature, calculated from the intensity of the M3 (circles, from six muscles) and ML1 (triangles, from three muscles). (B) Fraction of motors attached at the plateau of the isometric tetanus, fA, calculated from the intensity of the M3 (circles, from six muscles) and AL1 (triangles, from three muscles), as described in the text. On the left ordinate axis, fA has been normalized to its value at 30°C for a direct comparison with fOFF in A. (C) Duty ratio (r), calculated as explained in the text. Values in A–C are mean ± SEM.