Muscle Breakdown: Supinator
Table of Contents
What is the Supinator Muscle
The Supinator is a muscle located in the forearm that is responsible for, you guessed it, supination! Supination is a type of movement produced by the forearm that is responsible for turning your palm towards the sky. The Supinator is a very important muscle for many sports such as Tennis and Baseball, and every day activities such as washing and combing our hair. Keep reading to learn all about the Supinator!
Supinator Muscle Cadaver
Supinator Origin
The Supinator originates from both the Ulna and the Humerus. On the Ulna, the Supinator originates from the Supinator Crest. On the Humerus, the Supinator originates from the Lateral Epicondyle and both the Radial Collateral Ligament and Annular Radial Ligament. The Supinator also has some superficial fibers that originate from the Radius.
Supinator Insertion
The Supinator inserts into the proximal third of the Radius. The is the lateral bone in the forearm
Supinator Attachments
The attachment of a muscle to bone is the same as the muscle’s origin. This area is where the muscle does not move during a contraction. For the supinator, the attachment site is Supinator Crest, Radial Collateral Ligament and Annular Radial Ligament from the Lateral Epicondyle of the Humerus.
Supinator Crest
The Supinator Crest is part of the origin of the Supinator Muscle. The Supinator Crest is located on the upper shaft of the Ulna, and is the bony ridge where the muscle connects to the bone.
Supinator Innervation
The Supinator is innervated by the Radial Nerve which turns into the Posterior Interosseous Nerve when it exits the muscle.
Radial Nerve Supinator
The Supinator muscle is innervated by a deep branch of the Radial Nerve, that becomes the Posterior Interosseous Nerve when it exits the muscle.
Supinator Function
The primary function of the Supinator is to supinate the forearm. An easy way to remember the movement of supination is to imagine that you are holding a cup of soup. Your palm is always facing the ceiling.
We experience the most powerful supination of the forearm when the elbow is flexed at 90 degrees. This is because the Biceps Brachii will assist in supination at this angle. This is why it is easier to open a bottle of wine when it is closer to the body as compared to when the arm is fully extended.
Supinator Fossa
The Supinator is a deep muscle in the forearm. Since the Supinator is only superior to the Radius and the Ulna, it is the Supinator which in combination with the Brachialis muscle forms the floor of the Cubital Fossa. The Cubital Fossa is a small triangle shaped depression near the anterior elbow.
The medial border of the Cubital Fossa is the Pronator Teres, the lateral border is the Brachioradialis, and the superior border is in between the medial epicondyles of the Humerus. The function of the Cubital Fossa is to act as a passageway from nerves, tendons and arteries to travel between the upper arm and the forearm.
Wrist Supinator
The Supinator is one of two muscles that are involved in supination of the wrist. The Biceps Brachii also helps to perform the supination movement, however the primary function of the Biceps is elbow flexion.
Supinator Action
You might be curious as to what movements require us to supinate the forearm. Many everyday movements involve supination such as clapping, grasping a handful of snacks from a bowl, turning the pages of a book, playing cards and carrying plates and cups. Sports such as Tennis and Hockey also require supination of the forearm.
Supinator Trees
There is no Supinator Teres, however the Supinator performs the opposite function of the Pronator Teres muscle. Although the function of both muscles is right in each name, many people still get confused as to which muscle performs each function!
Supinator and Pronator
The Supinator’s antagonist muscle is the Pronator Quadratus. The primary function of the Pronator Quadratus is to pronate the forearm. Pronation occurs when the palm of the hand is rotated downwards so that it is facing the floor. Pronation is the opposite movement to supination.
Supinator Stretches
You can stretch the Supinator muscle by performing a simple movement. In a seated position begin with the palm facing downwards. Use the opposite hand to grasp the forearm that is being stretched at the outer wrist and pull upwards. Use the base of the hand to press downwards at the inner wrist.
You can also passively stretch the Supinator muscle by using the opposite hand to slowly take the wrist through supination.
Supinator Exercises
You can strengthen your Supinator at home using a light dumbbell! We recommend starting with the lightest dumbbell you have (1-2lbs) and increasing the weight as you progress.
In a seated position, rest the elbow of the arm you are looking to strengthen just above the knee. Hold the head of the dumbbell vertically in your hand and gently let its weight rotate the arm inwards and outwards to perform supination. Repeat this movement for 3 sets of 10 reps.
