The TVA is the deepest muscle, lying deep beneath the rectus abdominis and its fibres wrap horizontally around the sides of the torso between the lower ribs and pelvis. The TVA’s exact origin is the inguinal ligament, iliac crest, lower 6 ribs and the thoracolumbar fascia. The insertion is the pubis, linea alba and the xiphoid process. It has a nickname of The Corset due to the fibres running horizontally around the torso.
The TVA is a stabiliser muscle and its job, along with other stabiliser muscles, is to support the relevant body parts while the mobiliser muscles are working. Stabiliser muscles are usually deep muscles and they tend to work 20-30% of the maximum and consist of a high percentage of slow twitch muscle fibres. The fibres are short in length compared with mobiliser muscle fibres and need to work for long periods of time, hence they only work to 20-30% of their maximum.
If we look at the Abdominal Curl exercise, the rectus abdominis is the mobiliser muscle during this exercise and provides the forward flexion movement. The TVA, along with the internal obliques (also stabilisers) will assist with stabilising the torso throughout. Also, when day-to-day activities or exercises are performed such as walking and shopping, the stabilisers are working constantly to support areas of the spine during such movements as bending forward to pick up bags. During actions such as this, ‘pulling the abs in’ will assist in the activation of the stabiliser muscles within the torso, such as the TVA, pelvic floor muscles and lumbar multifidus, to compress the abdomen increasing the intra-abdominal pressure which maintains spinal alignment. This increased pressure takes the pressure off the intervertebral discs within the spine.
If stabiliser muscles stop performing their role correctly, the mobiliser muscles take on the role of being stabilisers as well as mobilisers which can result in a decrease in efficiency and increased risk of injury to vulnerable areas such as the lower back.