The transverse abdominis is the innermost of the flat muscles of the abdomen, being placed immediately beneath the internal oblique muscle.

Origin

The transversus abdominis muscle has 4 points of origin running from the inner surface of the 7th to 12th costal cartilages, the thoracolumbar fascia, the iliac crest horizontally, and the inguinal ligament.

Insertion

It has its insertion on the linea alba.

Function

In the respiratory system, the transverse abdominis is an expiratory muscle.

Most often the respiratory system, more specifically, the inspiratory and expiratory muscles, are not thought to be trainable except through aerobic type activities.
This, however, is only partially true. The respiratory system muscles can also be strengthened with specific strength training exercises.

Volume 12 - The Respiratory System of our Kinesiology of Exercise Ebooks is a first for a book on strength training for the respiratory system.