Fig. 11. (A) Variability of the force–velocity characteristic (Hill hyperbola, see Materials and methods for details) of the extensor muscle (see values in Table 4). Different symbols represent different animals. (B) Deviation of the force–velocity curve from hyperbolic shape in the region of P/P₀ between 0.6 and 1 for one typical experiment (open circles). In the region P/P₀>1, force–velocity measurements are shown under stretch (filled circles, data from six experiments) to demonstrate the sigmoid zero crossing of the Hill hyperbola. The force axis was normalised to the maximum isometric contraction force P₀. See text for details.