Relationship between CI, ΔSL, and diastolic or systolic SL. (A) Plots of ΔSL (diastolic SL minus systolic SL) versus CI. A significant linear relationship was observed (R = 0.66; P < 0.001). Diastolic and systolic SLs were obtained for 30 sarcomeres in M1 (Fig. 1, A and B) at which average SL became maximal and minimal, respectively, during each of six consecutive cardiac cycles. Resultant ΔSL values, as well as diastolic and systolic SL values, were averaged for six cardiac cycles; CI was quantified from Fig. 1 E, top (Fig. 1 F, bottom). (B) Plots of diastolic SL versus CI revealed a significant linear relationship (R = 0.41; P < 0.05). (C) Plots of systolic SL versus CI showed no significant correlation (n.s.). (D) Plots of ΔSL versus diastolic SL, using values in A and B, revealed a significant linear relationship (R = 0.71; P < 0.001). (E) Plots of ΔSL versus systolic SL, using values in A and C, showed no significant relationship (n.s.). In A–E, dashed lines indicate 0 values.