Figure 4.

Regional differences in muscle fascicles

A, change in fascicle length. B, true fascicle strain (100 × ln [l_f/l_f(FSL) − 1]). C, pennation. D, fascicle alignment (the angle fascicles make with the long axis of the muscle). In each panel there are 14 curves, each of which is the average, across all subjects, from one site in the muscle (Fig.1) as a function of muscle–tendon length (repeated measurements were not included). Muscle–tendon length has been expressed as a percentage of the in vivo range of lengths. In C and D, continuous lines are sites in the medial gastrocnemius and dashed lines are sites in the lateral gastrocnemius.