Figure 1.

Schematic representation of myosin S1 and S2 segments behavior during different contractions and at different respective portions of the F-V curve. (A) During fast shortening muscle actions, S2 complex will not fully stretch, hence myosin will apply lower pulling force onto actin (i.e., the thinner straight line in the figure). (B) During slower shortening contractions, up to when the shortening velocity would be equal to 0 (i.e., isometric contractions), the S2 segment will be fully stretched and therefore myosin will be able to apply greater pulling force onto the thin filament. (C) During lengthening actions, myosin S2 complex will be able to stretch even further (figure adapted from Jones et al., 2004).