Figure 1: Force due to myosin crossbridges. (a) A unitary force, , is generated over a finite time of attachment, (also called time-on), when the myosin power stroke swings the lever arm a net unitary displacement, . The time of detachment, , refers to the time period between a crossbridge detaching from actin and before reattaching. (b) An additional crossbridge-dependent force is transmitted through the half sarcomere when an elastic element in series with the crossbridge and with stiffness undergoes a length change due to an externally applied perturbation of the half sarcomere, . The force recorded at any time , , due to the perturbation reflects the displacement of the elastic element since the initial time of crossbridge attachment, .