Triceps Brachii Muscle

Triceps Brachii Muscle

This is the Triceps Brachii PDF for you to download

Triceps Brachii is the key functional muscle of the canine forelimb (thoracic limb).

As an intrinsic muscle found in the caudal brachial region, it occupies the space between the scapula - humerus - olecranon of the ulna (point of elbow).

Intrinsic = muscle origin + insertion are within the thoracic limb

The canine Triceps Brachii is a very important antigravity muscle in natural balanced stance, postures and motion in dogs of all ages, breeds and size. This canine muscle has 4 heads;

  • Lateral Head; is important as a joint stabiliser and is active when the joint is weight bearing and maintaining a rigid limb. It's also important in natural balanced motion
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Clinical Tip: This is why It's crucial for canine therapists to include static work in natural balanced stance in their treatment plan.

  • Medial Head; is largely composed of Type I slow twitch muscle fibres (red fibres - aerobic - fatigue resistant) and is important in maintaining posture and natural balanced stance
  • Accessory Head; lies deep between the other 3 heads and has a significant postural role, as it has a high percentage of Type I (red) slow twitch muscle fibres
  • Long Head; spans two joints and is an elbow extensor and shoulder flexor. It has 70% fast twitch muscle fibres (Type IIA - X) as it is involved in burst activity of short durations (high force production) and is very important in canine motion

This shows palpation of the
This shows palpation of the fascial guttering between the long head + lateral head, which is a common site for canine trigger points.
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Clinical Tip: For accurate and relevant information, it's very useful to palpate the dog in different postures as the dog's natural fascial tension changes depending on the posture the dog is in. Muscle tension also alters with different postures. We also know muscle tension is highly influenced by the emotional status of each dog in the clinical environment and during the therapeutic palpation experience.

This shows palpation of the origin of the long head on the caudal border of the scapula.
This shows palpation of the origin of the long head on the caudal border of the scapula.

This shows the location and palpation of the lateral head of Triceps Brachii.
This shows the location and palpation of the lateral head of Triceps Brachii.

The long head passes over two joints, whereas the other 3 heads only pass over one joint.

Muscles have the greatest force exerted at their origin and insertion (attachments), so these are the more common sites for muscle injury.

Muscles that pass over two joints will have an action at both joints and are much more prone to injury, compared to muscles that pass over one joint.

Triceps Brachii key action is as an antigravity muscle and elbow extensor, with the long head also being a shoulder flexor due to its attachments. Understanding the arrangement of the different heads with its surrounding fascia will empower your assessment accuracy and efficacy of your selected treatment techniques.

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The long head of Triceps Brachii is a common site for muscle injuries in the athletic dog.

Innervation of Triceps

Triceps Brachii is innervated by the radial nerve, which is the largest nerve in the brachial plexus and very important in relation to canine movement.

As a rule if a nerve passes through a muscle, it tends to innervate it.

Nerve route: The radial nerve arises from C7 - T2 spinal nerves and exits the axillary space passing into the Triceps Brachii and then piggybacks the Brachialis muscle as it spirals distally around the humerus. As it passes into contact with the lateral head of Triceps Brachii, the radial nerve drops distally passing into the extensors of the antebrachium (forearm).

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Clinical Tip: Injuries to the radial nerve leads to an inability of the forelimb to support the dogs weight, as the Triceps Brachii is a very important antigravity muscle. It's essential to reinstate the extensor pattern of support in these cases using a multi modal treatment approach.

Lily modelling a "well fitted Y shaped harness" optimising her natural balanced stance, postures and motion.
Lily modelling a "well fitted Y shaped harness" optimising her natural balanced stance, postures and motion.
A "well fitted Y shaped harness" maximises efficient and natural balanced motion.
A "well fitted Y shaped harness" maximises efficient and natural balanced motion.

This poorly fitting harness clearly shows how it will hinder forelimb protraction and
This poorly fitting harness clearly shows how it will hinder forelimb protraction and negatively influence natural balance stance and motion in the dog.

Close up of a poor fitting harness impeding the movement sequence of the dog.
Close up of a poor fitting harness impeding the movement sequence of the dog.

Anti-pull harnesses take the dog out of balance and are not therapeutically helpful.

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Clinical Tip: Always carefully check the Y shaped harness is the best fit and does not impinge on the long head of Triceps Brachii, as this will negatively impact the dogs natural balanced stance and motion. Breed variation across this amazing species means you need a selection of different Y shaped harnesses to choose from for each dog in your professional care.

This Bitesize Canine Resource was produced for you and is owned by K9HS Courses.