GENERAL INFORMATION
These muscles are a pair of muscles located in the upper back region. Specifically, they consist of the serratus posterior superior and serratus posterior inferior muscles. These muscles are involved in the movements of the ribcage and assist in respiration. Consequently, they play a crucial role in breathing and thoracic mobility.
ORIGIN
- Serratus Posterior Superior: Originates from the spinous processes of the upper thoracic vertebrae (C7 to T3).
- Serratus Posterior Inferior: Originates from the spinous processes of the lower thoracic vertebrae (T11 to L2). Therefore, these origin points are well-positioned to support their respective functions in rib movement.
INSERTION POINT
- Serratus Posterior Superior: Inserts into the upper borders of the second to fifth ribs.
- Serratus Posterior Inferior: Inserts into the lower borders of the ninth to twelfth ribs. Thus, these insertion points are essential for facilitating rib movement during respiration.
MAJOR ARTERIES
These muscles receive their blood supply from various arteries, including the intercostal arteries, which are branches of the thoracic aorta. Consequently, these arteries ensure that the muscles receive adequate blood flow to perform their functions effectively.
NEURAL INNERVATION
The serratus posterior superior is innervated by the second to fifth intercostal nerves, while its inferior is innervated by the ninth to twelfth intercostal nerves. Therefore, proper nerve function is crucial for the activation and control of these muscles.
TRIGGER POINT
Trigger points can develop in the serratus posterior muscles, causing localised pain and tenderness. These trigger points can be caused by overuse, poor posture, or muscle imbalances. Addressing these trigger points through massage or other therapies can alleviate discomfort and improve muscle function.
CONCENTRIC FUNCTION
Contraction of the serratus posterior muscles results in the elevation and lateral movement of the ribs. They also expand the thoracic cavity during inhalation, making them essential for adequate breathing.
ECCENTRIC FUNCTION
These muscles have a limited eccentric function during exhalation. They control the descent of the ribs and assist in forced exhalation, helping maintain stability during this process.
ISOMETRIC FUNCTION
When these muscles contract isometrically, they stabilise and support the ribs and contribute to maintaining proper posture. Therefore, they provide essential support during various physical activities.
RELATED MUSCLES (SCIENTIFIC NAMES)
- Serratus Posterior Superior: Elevates the upper ribs to aid in deep inhalation, increasing lung capacity.
- Serratus Posterior Inferior: Depresses the lower ribs to aid in forceful exhalation, crucial during vigorous activities or respiratory distress.
- External Intercostal Muscles: These synergistic muscles help lift the ribs during inhalation, increasing the thoracic volume.
- Internal Intercostal Muscles: Oppose the external intercostals by helping to lower the ribs and compress the thoracic cavity during exhalation.
- Diaphragm: The primary muscle of respiration; contracts to pull the thoracic cavity downward, expanding lung volume and working in coordination with the serratus posterior for efficient breathing.
ANTAGONIST MUSCLES
- External Intercostal Muscles: Function during inhalation, making them antagonistic to the serratus posterior inferior during expiration.
- Diaphragm: Its contraction during inhalation opposes the serratus posterior inferior’s action, which is more active during forced exhalation.
COMMON INJURIES
- Muscle Strains: These occur from overexertion or improper lifting techniques, leading to pain and dysfunction in upper body movement.
- Thoracic Outlet Syndrome: Compression at the thoracic outlet can affect nerves and blood vessels, potentially implicating the serratus posterior muscles in discomfort and reduced mobility.
- Chronic Postural Strain: Poor posture can lead to chronic stress on these muscles, resulting in persistent pain and susceptibility to further injury.
EXERCISES
- Controlled Breathing Drills: Practicing controlled inhalation and exhalation to engage and strengthen the serratus posterior muscles specifically.
- Reverse Snow Angels: Lying face down and moving arms in a reverse snow angel motion to engage and strengthen the upper back, including the serratus posterior.
- Wall Slides: Standing against a wall and sliding arms up and down to improve mobility and strength in the upper back and shoulder blades.
- Elastic Band Pull-Aparts: Using a resistance band to perform pull-parts that target the serratus posterior and improve scapular mobility and strength.
- Swimming: Freestyle or backstroke can particularly help strengthen these muscles due to the rib and scapular movements involved.
STRETCHES
- Extended Child’s Pose: Deepens the stretch in the lower back and engages the serratus posterior inferior by elongating the spine.
- Supine Thoracic Extensions: Lying on the back with a foam roller placed under the thoracic spine to gently stretch and mobilise the back.
- Seated Twists: Engaging in gentle seated twists to mobilise the thoracic spine and stretch the muscles.
- Dynamic Yoga Poses: Incorporating movements such as the Cat-Cow stretch and dynamic yoga sequences that encourage flexibility and strength in the back.
- Pectoral Stretches: Using a doorway or a wall to stretch the pectorals, which indirectly benefits the serratus posterior muscles by promoting overall shoulder girdle flexibility.
These additional details provide a more comprehensive insight into the functional roles, injury risks, and preventive measures for maintaining the health of these muscles, emphasising their significance in respiratory mechanics and upper body mobility.