Representative data showing the time course of changes in individual versus average SLs in an LV myocyte of a mouse with normal systolic function. (A) Time course of changes in an individual SL versus average SL showing a positive correlation during six cardiac cycles. Cardiac cycle number is shown on top of each graph. Black circles, individual SL; blue squares, average SL. Sarcomere nos. 3, 25, 30, 23, 26, and 4 are shown for cycles 1, 2, 3, 4, 5, and 6, respectively. (B) Same as in A, showing a negative correlation during six cardiac cycles. Cardiac cycle number is shown on top of each graph. Black circles, individual SL; blue squares, average SL. Sarcomere nos. 25, 18, 12, 13, 6, and 7 are shown for cycles 1, 2, 3, 4, 5, and 6, respectively. In A and B, data were obtained from M1 in Fig. 1 A. Number in each graph indicates CI.