a-b: Isotonic contractions: optimum shortening and optimum work in relation to stretching length. Fig. 3a shows four experiment units (1, 2, 4, 10) from a sequence of ten units with rising stretching forces (top fields) and stretching lengths (bottom field). With each stretching force and length of the muscle, a single supra-maximal stimulus was applied for 0.1 ms (vertical line with zigzag arrow), achieving an isotonic shortening that reached its highest value in experiment unit 2 (see red arrow). In the graph Fig. 3b, the stretching curve is shown, with isotonic length contractions plotted as red lines for each measuring point. In the graph Fig. 3c the shortening in relation to muscle length (red line), and the contraction work in relation to muscle lengths (blue line) are shown.