GENERAL INFORMATION
The sternocleidomastoid (SCM) is one of the most prominent muscles of the neck and is responsible for a wide range of head movements. The muscle has two heads: the clavicular head and the sternal head. The clavicular portion of the SCM originates from the clavicle and plays a significant role in head rotation, flexion, and lateral movement. This muscle also contributes to stabilising the head during posture and helps in breathing by lifting the sternum and clavicle during forced inhalation.
ORIGIN
The clavicular head of the sternocleidomastoid originates from the medial third of the clavicle.
INSERTION POINT
The clavicular head, along with the sternal head, inserts into the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone.
MAJOR ARTERIES
- Superior Thyroid Artery: Provides blood supply to the sternocleidomastoid muscle.
- Occipital Artery: Contributes additional blood flow to the SCM.
- Suprascapular Artery: Assists in supplying the muscle with nutrients and oxygen.
NEURAL INNERVATION
- Accessory Nerve (Cranial Nerve XI): The primary nerve innervating the SCM, allowing control over head and neck movements.
- Branches Of The Cervical Plexus (C2-C3): Provide additional motor and sensory input to the clavicular part of the sternocleidomastoid.
TRIGGER POINT
Trigger points in the clavicular part of the SCM can cause pain that radiates to the front of the head, behind the ear, or around the eye. This can lead to tension headaches, dizziness, or neck stiffness, particularly when the muscle is overused or strained.
CONCENTRIC FUNCTION
During concentric contraction, the clavicular part of the SCM shortens, contributing to head flexion and lateral rotation. It helps tilt the head to the same side while turning the face to the opposite side.
ECCENTRIC FUNCTION
In eccentric contraction, the clavicular portion lengthens while controlling the head’s return to a neutral position after rotation or flexion. This function helps stabilise the head during movement and prevents sudden jerking motions.
ISOMETRIC FUNCTION
The clavicular SCM can maintain tension without shortening or lengthening, keeping the head in a stable, fixed position. This function is essential for posture control, particularly when holding the head steady during prolonged activities like reading or typing.
RELATED MUSCLES – SCIENTIFIC NAMES
- Trapezius Muscle: Assists with head and neck extension and movement.
- Scalenes: Help with neck flexion and lateral movements.
- Levator Scapulae: Elevates the scapula and contributes to neck lateral flexion.
- Splenius Capitis: Aids in extending and rotating the head.
ANTAGONIST
- Splenius Capitis: Opposes the SCM by extending and rotating the head in the opposite direction.
- Trapezius (Upper Fibres): Works against the SCM during head extension.
COMMON INJURIES
- Scm Strain: Overstretching or overuse of the clavicular portion of the SCM can cause pain, stiffness, and limited range of motion in the neck.
- Torticollis (Wry Neck): Spasms or contractures in the SCM can lead to an abnormal, tilted head position, often causing discomfort and restricted movement.
- Tension Headaches: Trigger points in the clavicular SCM may lead to referred pain in the head, particularly around the eye and temple, resulting in headaches.
- Neck Whiplash Injury: Sudden neck movement, such as during car accidents, can overstretch or tear the clavicular SCM, causing pain and inflammation.
- Postural Imbalance: Poor posture can strain the clavicular SCM, leading to chronic neck pain and headaches.
EXERCISES
- Chin Tucks: Tuck your chin gently towards your chest while maintaining a straight back. This exercise strengthens the SCM by engaging the clavicular part, improving posture and neck stability.
- Neck Flexion Resistance: Place your hand on your forehead and gently push against it while flexing your neck. This exercise helps strengthen the clavicular head of the SCM, building resistance.
- Neck Rotations: Slowly rotate your head from side to side, improving flexibility and strengthening the SCM for better movement control.
- Isometric Neck Hold: Place your hand against the side of your head and push gently while resisting the motion. This exercise strengthens the clavicular part of the SCM by working it in an isometric fashion.
- SCM Activation Exercise: Lie on your back and lift your head slightly off the ground while keeping your shoulders down. This exercise activates and strengthens the SCM, particularly the clavicular portion.
STRETCHES
- Sternocleidomastoid Stretch: Tilt your head towards one shoulder and gently rotate it in the opposite direction, holding the position to stretch the clavicular part of the SCM.
- Upper Trapezius Stretch: While sitting, pull your head gently to one side, feeling the stretch along the side of the neck. This stretch helps relieve tension in the SCM.
- Neck Extension Stretch: Look upwards and slightly backwards, holding for 10-15 seconds. This stretches the SCM and helps reduce stiffness.
- Levator Scapulae Stretch: Sit with your hand behind your head and pull your chin towards your chest and opposite knee, releasing tension in both the SCM and levator scapulae.
Shoulder Shrugs: Slowly raise and lower your shoulders to release tension in the trapezius and clavicular SCM, promoting relaxation and flexibility.
