Relative force decrease (%) in contractions produced in the different experimental conditions, when compared to contractions produced at pCa2+ 4.5.

Legend: (i) first set of experiment, with fibers activated at four Ca2+ concentrations, (ii) second set of experiments, with fibers activated in presence or absence of blebbistatin, and (iii) third set of experiments, with fibers activated in pCa2+ 4.5 (with and without blebbistatin) and pCa2+ 6.0. The three sets of experiments correspond to the description given in Methods.*Significantly different from contractions produced at pCa2+ 4.5 (p≤0.05).