Fig. 3. Torsion control during terrestrial locomotion in salamanders. During walking, the ground reaction forces directed through the diagonally opposed limbs cause the pectoral and pelvic girdles to rotate (curved arrows over the trunk). The oblique orientations of the lateral hypaxial muscles are hypothesized to prevent torsion caused by the limbs. In this example, the medial muscles (open arrow, m. obliquus internus and m. transversus abdominis) on the salamander’s right side are active to counteract torsion caused by the hindlimb, while the lateral pair (filled arrow, m. obliquus externus superficialis and m. obliquus externus profundus) of hypaxial muscles on the left side of the trunk is active to counteract the torsion caused by the forelimb (figure modified from Carrier, 1993).
