Figure 2.

A, schematic representation of the fibre mounted between the force (T) and length (P_M) transducers. The S_M and S_T boundaries of the segment are selected for measuring the half-sarcomere length changes (L). B, left panel shows responses of force (T/T₀, upper trace) and hs length (L, lower trace), respectively, to 4 kHz oscillations (P_M, middle trace) imposed during the rise of isometric contraction. Electrical stimulation starts at 0 ms. B, right panel shows responses to oscillations at three different times (a–c, as marked by the vertical lines next to the force trace in the left panel) on an expanded time scale. C, dependence on the isometric force level of the hs length change in response to an oscillation amplitude of ∼0.15% of the fibre length at 2.15 μm sarcomere length (l₀).D, dependence on the isometric force level of the phase shift (Δφ) between T and L (filled circles), and between T and P_M (open circles). E, dependence on isometric force of Δφ between the signals from the force-transducer spot (S_T) and from the motor spot (S_M; filled circles), and between S_M and P_M (open circles).