Fig. 3. Proximo-distal differences in muscle architecture within the hindlimb of a cursorial animal (similar patterns occur in the forelimb and in the limbs of other running birds and mammals). Representative fascicle strain (red) and myoelectric (EMG) patterns (black) recorded in vivo from muscles of various animals are shown in relation to proximo-distal differences in muscle–tendon architecture. For fascicle strain traces, the tick on the scale bar indicates zero strain (the estimated resting length of the fascicles, based on the average length during quiet standing). In vivo forces (gray) are also shown for the two distal muscles. Fascicle strain and time scales are the same for all muscle recordings shown. Duration of stance phase is shaded gray.