Sarcomere model is based on lattice geometry, filament compliance, and transition rates. (A) A simplified schematic of the thick filament (red) and binding sites on the thin filament (blue) in a hexagonal pattern. (B) Myosin is modeled as a system of linear (k_R) and torsional (k_θ) springs with a defined myosin rest angle (θ) globular domain length (R). (C) The sarcomere is modeled as an array of springs of different stiffness. During contraction, the myosin heads cycle and the distance between the Z-line (blue, right) and the M-line (red, left) decreases. (D) The model cycles through a coupled thin filament (TF) state transitions and myosin motor head (XB) state transition, where myosin is unable to leave the unbound state (XB1) until it is in range with an actin site that has reached an open state (TF4).