Hello, I'm checking the FLV Curve in MuJoCo muscle dynamics by re-implement them + the force generation calculation part. When I calculate the value of LT of "EF" muscles in the default arm26.xml model, it was -0.51, which were negative value. It this value acceptable? Here are some values of arm26.xml model: (for EF) scale = 200 range_min = 0.75 range_max = 1.05 lengthrange_min = 0.01 lengthrange_max = 0.21 lmin = 0.5 lmax = 1.6 vmax = 1.5 fpmax = 1.3 fvmax = 1.2 peak_force (derived) = 126.92 Calculation of LT and L0: (0.01 - LT) / L0 = 0.75 (0.21 - LT) / L0 = 1.05 LT (derived) = -0.51 L0 (derived) = 0.68 It makes value of L as: L = LM / L0 = (actuator_length - LT) / L0 = (actuator_length + 0.51) / 0.68 Therefore, normalized L might have a value larger than (max value of LM) / L0. === I tried to calculate the FP (Passive force of muscle) same as FLV.m (apologize for python) FP = np.zeros(self.n_tendons) cond1 = L <= 1 cond2 = np.invert(cond1) & (L <= b) cond3 = np.invert(cond1 | cond2) FP[cond1] = 0 FP[cond2] = 0.25 * self.muscle_fpmax[cond2] * np.power((L[cond2] - 1) / (b[cond2] - 1), 3) FP[cond3] = 0.25 * self.muscle_fpmax[cond3] * (1 + 3*(L[cond3] - b[cond3]) / (b[cond3] - 1)) f_active = 0 self.fiber_force = (f_active + f_passive) * self.muscle_peak_force FP and mjData.actuator_force, with the setting of mjModel.actuator_dyntype = mjDYN_NONE and ctrl = 0, was different. Please let me know if any calculation was wrong. Thanks.