Fig. 3

Force enhancement property of skeletal muscle as experimentally observed in a whole, intact muscle a and in a single, mechanically isolated sarcomere b. Note that the steady-state isometric force following an active stretch is substantially greater than the corresponding steady-state force for a purely isometric reference contraction at the same length and with the same amount of activation (indicated as FE in both figures). Furthermore, the force enhancement often also contains a passive component, indicated by PFE in fig. (a). Note also, the increase in force above that observed at optimal sarcomere length following active stretching of a single sarcomere (O-FE in Fig. b). Finally, note that the amount of force enhancement is increased with increasing stretch magnitude (in Fig. a)