Figure 7.

The relationship between critical force (F_c), critical average sarcomere length (SL_c) and velocity of stretch (n=17). Each mean value is a result of four to five experiments. Circles, control myofibrils; squares, BDM-treated myofibrils. (a) In control myofibrils, F_c increased significantly with increasing velocities to reach a plateau at 1.5 μm s⁻¹ SL⁻¹, after which it did not change significantly. BDM-treated myofibrils show a continuous increase in force in long lengths, and a plateau in the F_c-velocity curve was not obtained in the present experiments, although force increase seems to be levelling off at approximately 3.5–3.6 P₀. The horizontal line shows isometric reference force (F_c/P₀=1). Data for BDM and control experiments were fitted by an exponential equation (y=a(1−bx), where a and b are constants). (b) Velocity of stretch did not affect the SL_c, with the exception of BDM-treated myofibrils that showed a sudden increase in SL_c when velocity was changed from 0.6 μm s⁻¹ SL⁻¹ to faster stretches. Data for BDM experiments were fitted by an exponential equation (y=a(1−bx), where a and b are constants) and data for control experiments were fitted by linear regression.