Figure 3. Force transients during length changes in different Ca²⁺ concentrations.

(A) Superimposed contractions showing the force increase during stretch while the fibre was activated in pCa²⁺4.5 (solid line) and pCa²⁺6.0 (dashed line) (top), with corresponding changes in fibre length (bottom). All forces were normalized by the isometric forces (P_o) before the stretch. The regression lines for the contractions produced in pCa²⁺4.5 and pCa²⁺6.0 are shown in blue and red, respectively. (B) Superimposed contractions showing the force decrease during shortening when a fibre was activated in pCa²⁺4.5 (solid line) and pCa²⁺6.0 (dashed line) (top), with the corresponding length changes (bottom). (C) Closer view from the initial shortening phase, showing that decreasing Ca²⁺ concentration induced an increase in L₁ and P₁ amplitudes. All forces were normalized by the isometric forces (P_o) before the shortening. The regression lines for the contractions produced in pCa²⁺4.5 and pCa²⁺6.0 are shown in blue and red, respectively. Decreasing Ca²⁺ concentration increased L₁ and P₁ amplitude.