Figure 7

A muscle deformation example. The pennation angle in the Soleus muscle was measured over time by using speckle tracking, as illustrated in (a). A representative pennation angle measurement is plotted together with the (negated) first PCA score vector in (b). Note how similar the score vector and the pennation angle are; this means that the muscle deformation that is measured as pennation angle changes in the image sequence is also captured by the first score vector. The second score vector is plotted together with the representative pennation angle in (c). It can be seen that the isometric phase of the movements begins and ends when there are swift changes in the second score vector and only small changes in the first score vector. The isometric phase is thus mainly captured by the second score vector.