Fig. 3. Principle component weightings from the intensity spectra from the ramped isometric contractions. The components were calculated from 2160 intensity spectra from the rectus femoris, vastus lateralis, vastus medialis, lateral gastrocnemius, medial gastrocnemius and soleus muscles from 10 subjects and over a force range from 5 to 95% max. voluntary contraction (MVC). The first four principle components (PC) are shown, with the relative proportion of the total signal that they describe.