Fig. 6. Analysis of isometric Ca2+back-titration experiment (part 3 of 3). Summary of the analysis of the Ca2+back-titration experiment of figure 4. The solid lines in this diagram correspond to the lines of minima of each of the two three-dimensional diagrams of figure 5projected in the x–y plane. The intersection of the lines (myoplasmic Ca2+delivery = 109.5%, myofibrillar Ca2+sensitivity variable B = 63 s−1) (see eq. 4in appendix) defines the conditions for a least-squares fit to the aequorin signal of the Ca2+back-titrated twitch and a same peak [Ca.T] as in the control twitch.