Situps (flexion of trunk) would be accomplished by contraction of the: SELECT ANY ACCURATE ANSWERS. O latissimus dorsi O deltoid trapezius O diaphragm O rectus abdominis Solution Rectus abdominis causes the flexion of trunk. It is a longitudinal muscle which is situated at the anterior of abdomen. Originates from pubic bone and inserts into 5,6 ,7 ribs, xiphoid process of sternum.