Figure 5. Force transients during length changes in fibres treated with MgADP.

(A) Superimposed contractions showing the force increase during stretch (top) when the fibre was activated in pCa²⁺4.5 (solid line) and treated with MgADP (dashed line). The corresponding length changes are show in the bottom panels. 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 in presence of MgADP are shown in blue and red, respectively. (B) Superimposed contractions showing the force decrease during shortening (top) when a fibre was activated at pCa²⁺4.5 (solid line) and treated with MgADP (dashed line). The corresponding changes in fibre length are shown in the bottom. (C) Closer view from the initial shortening phase showing that MgADP activation induced an increase in L₁. All forces were normalized by the isometric forces (P_o) before the shortening. The regression lines for the contractions produced in pCa²⁺4.5 before and after MgADP treatment are shown in blue and red, respectively. MgADP treatment increased L₁ significantly, while it did not change the other variables.