Figure 3 (a) Abdominal wall curvatures change in sagittal and transverse planes during the inflation process (b) The displacement vs. pressure of the central marker (c) Abdominal cavity volume change during the inflation process (d) Stress—strain relationship of the abdominal wall showing the male wall to be stiffer than the female wall. Fig. 2. (a) The travel paths of infrared markers on half abdominal wall, O is the origin of the coordinate system (b) Simulation of the abdominal wal motion during the inflation process.