GENERAL INFORMATION
The serratus posterior inferior is a muscle in the chest region. It is part of the serratus posterior muscle group, which also includes the serratus posterior superior. The serratus posterior inferior assists in the movements of the ribcage and plays a role in respiration. Consequently, it is essential for proper breathing mechanics and rib movement.
ORIGIN
This muscle originates from the spinous processes of the lower thoracic vertebrae, specifically from T11 to L2. Therefore, its origin points are well-positioned to support its function in rib depression.
INSERTION POINT
The muscle inserts into the lower borders of the ninth to twelfth ribs. Thus, its insertion points are crucial for facilitating rib movement during breathing.
MAJOR ARTERIES
This muscle receives its blood supply primarily from the intercostal arteries, which are branches of the thoracic aorta. Consequently, these arteries ensure that the muscle gets adequate blood flow to perform its functions effectively.
NEURAL INNERVATION
The muscle is innervated by the ninth to twelfth intercostal nerves. Therefore, proper nerve function is essential for the activation and control of the serratus posterior inferior muscle.
TRIGGER POINT
Trigger points can develop in this muscle, causing localised pain and tenderness. These trigger points can be attributed to muscle overuse, poor posture, or muscle imbalances. Addressing these trigger points through massage or other therapies can alleviate discomfort and improve muscle function.
CONCENTRIC FUNCTION
The contraction of the serratus posterior inferior muscle contributes to the depression and lateral movement of the lower ribs. It aids in exhalation by compressing the thoracic cavity, thus playing a vital role in the breathing process.
ECCENTRIC FUNCTION
This muscle has a limited eccentric function during inhalation, as it controls the ascent and expansion of the lower ribs. Consequently, it helps maintain stability during the inhalation process.
ISOMETRIC FUNCTION
Isometric contraction of this muscle provides stability and support to the lower ribs and assists in maintaining proper posture. Therefore, it offers essential support during various physical activities.
RELATED MUSCLES (SCIENTIFIC NAMES)
- Serratus posterior inferior: This muscle is crucial for the movement and stability of the lower ribs during respiration.
ANTAGONIST MUSCLES
- External intercostal muscles: These muscles assist in the elevation of the ribs during inhalation, opposing the action of the serratus posterior inferior.
- Diaphragm: As the primary muscle of respiration, it contracts to increase thoracic volume, working antagonistically to the rib-depressing action of the serratus posterior inferior.
COMMON INJURIES
- Strains or sprains: Sudden or excessive twisting or bending movements can cause this type of injury, leading to sharp or dull pain in the lower back.
- Trigger points: Localised pain and discomfort due to muscle overuse or imbalances often manifest as tender spots that can radiate pain.
- Muscle imbalances: Weakness or tightness in surrounding muscles can lead to postural issues and pain, especially in the lower back and ribs.
EXERCISES
- Rows: Strengthen back muscles and indirectly engage the serratus posterior inferior by promoting scapular retraction and stability.
- Lat pulldowns: Enhance overall back strength and support proper muscle function, especially targeting the latissimus dorsi and indirectly benefiting the serratus posterior inferior.
- Planks: Maintaining a stable trunk and engaging the back muscles improves core stability and indirectly works the serratus posterior inferior.
- Deadlifts: Promote lower back strength and stability by engaging multiple muscle groups, including the serratus posterior inferior, to maintain proper form.
- Face pulls: Target upper back muscles and improves posture by promoting shoulder retraction and stability, indirectly engaging the serratus posterior inferior.
STRETCHES
- Thoracic rotations: Rotating the upper body and increasing flexibility in the thoracic spine enhances thoracic mobility and indirectly stretches it.
- Chest stretches against a wall: These stretches promote flexibility in the chest and back, indirectly stretching the serratus posterior inferior and improving posture.
- Foam roller exercises: Target the lower back and release tension in the muscle by applying pressure along the spine and muscle groups.
- Cat-Cow stretch: This exercise improves spine flexibility and reduces muscle tension by moving the spine through flexion and extension, indirectly stretching the serratus posterior inferior.
- Seated twists: Rotating the spine and enhancing flexibility in the thoracic and lumbar regions increases thoracic mobility. It also help stretches the lower back muscles.
