Answer:
Flexion of lumber spinae.
Explanation:
Rectus abdominis is also known as abs. These muscles are present on the anterior side of the human abdomen. This muscle extend from the pubic symphysis.
The main function of the rectus abdominis muscle is to flex the lumbar spinae and helps in crunch and sit ups. This is a type of postural muscle. This muscle also plays an important role in respiration.
Thus, the answer is the flexion of the lumber spinae.
