The serratus posterior inferior is a muscle located deep in your back, underneath the larger and more superficial back muscles. It plays an important role in the movement and stabilization of your rib cage, although it is not as prominent as other muscles when it comes to movement.
This muscle originates from the spinal vertebrae—specifically, the lower thoracic and upper lumbar vertebrae. From there, it extends outward and upward to attach to the lower four ribs. Its primary function is to assist in pulling these ribs down during movements that involve exhaling forcefully, such as blowing out candles or during heavy lifting where you forcefully expel air. This action helps in stabilizing the rib cage and the lower back, providing a solid base for other muscles to act upon during various activities.
In terms of your goal of achieving visible six pack abs, the serratus posterior inferior is indirectly related. While it does not directly contribute to the aesthetic appearance of your abs, it supports the overall structure of your core. A strong and stable core can enhance your ability to perform exercises that target the abdominal muscles more effectively and safely. Exercises that strengthen this muscle along with other core muscles can improve your posture and reduce the risk of injuries, particularly in the lower back. This makes your core workout routine more effective, potentially leading to better definition and visibility of your six pack abs as you reduce body fat and build muscle in that region.
Strengthening the serratus posterior inferior involves exercises that focus on the movement of the ribs and lower back, such as certain types of pull-downs or rowing movements where you focus on controlling the extension and contraction of your back muscles. Integrating these exercises into a balanced workout routine can contribute to a stronger, more stable core, supporting your quest for defined abs.