Fig.7. Strain levels in the biceps femoris and vastus lateralis during different portions of the stance and swing phases. Generalized fascicle strain patterns (based on average strain levels during trotting) for the biceps and vastus are shown in A and C, respectively, as are the five subdivisions of the step cycle for the two muscles (four stance and one swing). Average strain levels for walking, trotting, galloping trailing limb (TL) and galloping leading limb (LL) are shown for each of the phases in the biceps (B) and vastus (D) (N=4 individuals per muscle). Methods used for obtaining these fascicle strain levels are described under ‘Data analysis’ in the Materials and methods section. Negative values for muscle strain indicate fascicle shortening, whereas positive values reflect fascicle lengthening. If both shortening and lengthening occur during one of the intervals, both positive and negative columns are present for that interval. Error bars are standard deviations. Dark gray shading represents strain occurring during the stance phase, and light gray shading represents strain occurring during the swing phase.