Fig. 5.
A sample eccentric contraction at a very slow lengthening velocity. (A) This contraction depicts the potential for high gear ratios when forces are just above maximum isometric force (Po). The three phases of the contraction are the same as those described in Fig. 2. In this contraction, MTU lengthening during a period of constant force is achieved with little or no stretch of the fascicle. This contraction suggests that small, slow stretches of the MTU can be accommodated by changes in muscle pennation angle and do not require the fascicles to be stretched. (B) A schematic diagram of how architectural changes of the muscle can limit fascicle stretch during eccentric contractions. The muscle before the contraction is shown with dashed fascicles. A decrease in the muscle thickness (t) and a decrease in pennation angle (red) can allow the MTU to be stretched without any length change in the fascicle.