An ultrasound investigation into the morphology of the human abdominal wall uncovers complex deformation patterns during contraction.

The abdominal wall components, specifically muscle and connective tissue, must meet and accommodate a wide range of force demands for torso movement, spine stabilization, and respiration. It has a composite laminate nature that may lend itself to facilitating the required tissue responses. The purpose of this exploratory study was to examine the deformations of the abdominal wall connective tissues, with a special focus on both the internal oblique aponeurosis and the tendinous intersections of the rectus abdominis, using ultrasound imaging, during relatively simple contractions of the abdominal musculature. There were two main findings of this study: (1) deformations occurred in nearly 50% of contractions that would be characterized by a simultaneous expansion in multiple planes; (2) the laterally generated forces of the oblique and transverse muscles transfer a great deal of force across the rectus abdominis muscle and sheath, leading to a lateral movement of the rectus muscle during abdominal contraction.