03/24/2026
Muscle(s) Monday Serratus Posterior Superior & Serratus Posterior Inferior.
The serratus posterior superior is a thin, often overlooked muscle located in the upper back beneath the rhomboids and trapezius. It originates from the spinous processes of the lower cervical and upper thoracic vertebrae and travels outward to attach along the upper ribs (typically ribs 2–5).
From a massage therapy perspective, this muscle often becomes involved when the upper back feels tight, restricted, or fatigued, especially in people who spend long periods sitting, typing, or holding tension through the shoulders. Because it sits underneath larger muscles, it can quietly contribute to that familiar feeling of stiffness between the shoulder blades.
Functionally, the serratus posterior superior assists in elevating the ribs during inhalation. When we take a deep breath in, this muscle helps lift the ribs upward and outward, allowing the lungs to expand more fully.
This is one reason why full, intentional breathing can make such a difference in how the upper back feels. When the ribs move freely, the muscles that support them can do their job with much less strain.
Further down the back sits its partner muscle: the serratus posterior inferior.
Like the superior portion, it also runs from the spine outward to the ribs, but it lives lower in the body. It originates from the lower thoracic and upper lumbar vertebrae and attaches to the lower ribs (typically ribs 9–12).
While the serratus posterior superior helps lift the ribs during inhalation, the serratus posterior inferior helps depress the ribs during exhalation. Together, these muscles help coordinate the rhythm of breathing — one assisting the ribs to rise, the other helping them settle back down.
From a therapeutic perspective, this lower muscle can sometimes contribute to tightness through the thoracolumbar region, the area where the rib cage meets the low back. When breathing becomes shallow or restricted, these muscles may not move through their full range of motion.
To support these muscles well, the key is surprisingly simple: big, full breathing.
📷: The Trail Guide to the Body
