GENERAL INFORMATION
The infrahyoid muscles, commonly referred to as strap muscles, consist of four individual muscles located beneath the hyoid bone in the neck. These muscles play pivotal roles in the mechanical aspects of swallowing and the positioning and stabilisation of the larynx. Which is essential for speech and breathing.
ORIGIN
- Omohyoid: Originates from the upper border of the scapula near the scapular notch.
- Sternohyoid: Emerges from the posterior surface of the manubrium of the sternum.
- Sternothyroid: Begins at the posterior surface of the manubrium and extends to the first costal cartilage.
- Thyrohyoid: Starts from the oblique line on the thyroid cartilage of the larynx.
INSERTION POINT
- Omohyoid: Inserts into the intermediate tendon and lower border of the hyoid bone.
- Sternohyoid: Attaches to the body of the hyoid bone.
- Sternothyroid: Inserts into the thyroid cartilage.
- Thyrohyoid: Attaches to the base of the hyoid bone, specifically its greater horn.
MAJOR ARTERIES
- Omohyoid: Receives blood supply primarily from the superior thyroid and occasionally from the lingual arteries.
- Sternohyoid: Supplied by the superior thyroid artery and small branches from the thyrocervical trunk.
- Sternothyroid: It also receives its blood supply from the superior thyroid artery.
- Thyrohyoid: Primarily supplied by the superior thyroid artery.
NEURAL INNERVATION
The infrahyoid muscles are mostly innervated by the ansa cervicalis, a loop of nerves formed from the cervical plexus, except for the thyrohyoid muscle. Which is uniquely innervated by fibres from the hypoglossal nerve (CN XII).
TRIGGER POINT
Trigger points in the infrahyoid muscles often manifest with symptoms such as a sensation of a lump in the throat, difficulty swallowing, and localised neck pain. Which can be triggered by stress or poor posture.
CONCENTRIC FUNCTION
Concentric contraction of the infrahyoid muscles results in the depression of the hyoid bone and larynx, facilitating the swallowing process and aiding in speech by modifying the position of the voice box.
ECCENTRIC FUNCTION
Eccentric contraction allows these muscles to control the ascent of the hyoid and larynx. Which is crucial after they have been depressed during activities like swallowing or speaking.
ISOMETRIC FUNCTION
Isometric contractions of the infrahyoid muscles provide essential stabilisation and support to the hyoid bone and larynx during head and neck movements, preventing undue stress and maintaining alignment.
RELATED MUSCLE-SCIENTIFIC NAMES
- Omohyoid: Consists of two bellies, the inferior and superior, connected by an intermediate tendon.
- Sternohyoid: A simple, narrow muscle directly covering the anterior surface of the neck.
- Sternothyroid: Lies deep to the sternohyoid and parallel to it.
- Thyrohyoid: Short muscle that adjusts the position of the larynx relative to the hyoid.
ANTAGONIST
- Geniohyoid: Elevates and pulls the hyoid bone forward.
- Mylohyoid: Elevates the floor of the mouth during the early phase of swallowing.
- Stylohyoid: Elevates and retracts the hyoid bone.
- Digastric: Elevates the hyoid and assists in opening the jaw against resistance.
COMMON INJURIES
- Muscle strain: This can occur from abrupt movements or excessive strain during activities like heavy lifting or abrupt neck movements, causing sharp pain and difficulty in neck movements.
- Overuse injuries: Frequently seen in vocal professionals and athletes, resulting from repetitive use and leading to chronic pain as well as functional limitations.
EXERCISES
- Neck flexion: Slowly bend the head forward, pressing the chin toward the chest to engage the infrahyoid muscles, helping to improve muscle tone and aid in swallowing.
- Neck extension: Gently tilt the head back to look upwards, stretching the infrahyoid muscles. Which can not only relieve tension but also strengthen these muscles.
- Resistance swallowing: Practice swallowing while gently pressing on the throat; this resistance helps strengthen the infrahyoid muscles, improving both tone and function.
- Head lifts: While lying on your back, slightly lift the head off the ground, focusing on using the neck muscles to enhance strength in the infrahyoid.
- Chin tucks: Draw the chin straight back to create a “double chin,” which not only helps strengthen the infrahyoid but also improves the postural alignment of the neck.
STRETCHES
- Towel stretch: Utilise a towel to gently pull the head forward, which intensifies the stretch across the infrahyoid muscles, promoting flexibility as well as relieving tension.
- Side neck stretch: Tilt the head to one side, stretching the infrahyoids on the opposite side. Which can alleviate tightness and aid in neck mobility.
- Diagonal neck stretch: Combine a gentle tilt and slight rotation of the head to stretch the infrahyoid muscles diagonally, enhancing flexibility.
- Yoga neck rolls: Execute slow, circular movements with the head and neck to stretch the infrahyoids thoroughly. Which not only helps reduce stress but also improves blood flow.
- Manual neck stretch: Using hands, apply gentle pressure on different areas of the head and neck to target the infrahyoid muscles specifically for a deep stretch.
