Figure 2. Half-sarcomere stiffness during a stretch.

A, force and average motor distortion in response to a step stretch imposed during isometric contraction. Upper trace, force (T) relative to isometric force (T₀); middle trace, length change (ΔL, nm hs⁻¹); lower trace, axial distortion of myosin motors (Δz, nm). B, relations of T₁/T₀ (filled circles) and e/e₀ (open circles) versusΔL for one fibre. The continuous line is the linear fit to T₁/T₀ data for ΔL=±1 nm hs⁻¹, the slope (e₀) is 0.26 T₀ nm⁻¹. C, average T₁/T₀ and e/e₀ relations for 9 fibres (mean ±s.e.m.); the continuous line is calculated as in B, the slope is 0.263 ± 0.001 T₀ nm⁻¹. T₀ in these experiments was 139 ± 7 kPa (mean ±s.e.m.).