Figure 6.

The dependence of stretch velocity on the force produced by myofibrils. (a) Activated myofibrils stretched at three constant velocities. The increase in force during stretch is more accentuated at higher velocities. In this example, the transition on force rise could be defined when stretches were performed at 2.8 and 0.6 μm s⁻¹ SL⁻¹, while it was not detectable when stretch was performed at 0.4 μm s⁻¹ SL⁻¹. Peak forces in these examples were 1.84, 1.58 and 1.42 P₀ (from faster to slower stretches), and F_c were 1.80 and 1.40 P₀ (not detected when stretched was performed at 0.4 s⁻¹ SL⁻¹). Bars depict values 20 per cent above isometric forces. (b,c) Force traces and superimposed length records for individual sarcomeres when stretch was performed at 2.8 and 0.6 μm s⁻¹ SL⁻¹, respectively.