Figure 3. Force-time and angle-time histories during electrically induced contractions.

For shortening contractions, the minimum forces during the shortening phase (F_Shortening), steady-state isometric forces (F_ISO) and muscle stiffness were measured for comparisons with the corresponding values obtained from isometric reference contractions. The effects of shortening conditions were tested by systematically changing amplitudes (A) and speeds (B) of shortening. The inset shows a schematic illustration of the stiffness measurement used in this study.