Welcome back to the series that loves to talk about muscle, and is therefore aptly named Muscle Talk. We have been working our way through the many muscles of the upper body of late, and soon we will be revisiting the lower body. The arms have been on the agenda the past couple of weeks beginning with the shoulder muscles, as well as the muscles of the upper arm. It makes sense that we continue on our journey down the arm to the muscles of the forearms. While these muscles may not get the attention as some of the other glamorous ones, they are incredibly necessary for maximum lifting function, as without a strong grip everything from deadlifts to pull-ups will be compromised. Aesthetically, they are impressive on their own when developed to their full capacity. So let’s look at the muscle that make up the forearm, and see what’s going on when we grip a barbell or dumbbell.
The muscles within the forearm are many, and help to perform numerous functions. Theses functions include; moving the hand at the wrist, moving the fingers, while other muscles supinate and pronate the forearm. Most of these muscles are fleshy proximally, and have long tendons distally that insert in the hand. These tendons are anchored by fascia known as flexor/extensor retinacula, which help to keep the tendons from jumping outward when tensed. Within the wrist, they are surrounded by tendon sheaths to reduce friction. Most of these muscles originate at the humerus, and even though they cross the elbow joint they produce no direct action on the elbow. At the wrist the muscles of the forearm help to flex, extend, abduct, and adduct the hand. At the finger joints however, these muscles only help to extend and flex. The sheaths of the fascia divide the muscles in the forearm into two compartments; the anterior flexor compartment, and a posterior extensor compartment. These compartments are then divided into superficial and deep layers.
Beginning with the anterior and superficial muscles of the forearm, we have the pronator teres. This two-headed muscle is visible between the proximal margins of brachioradialus and flexor carpi radialis. It forms the medial boundry of cubital fossa. It pronates the forearm, and is a weak flexor of the elbow. The flexor carpi radialis runs diagonally across forearm. Midway, its fleshy belly is replaced by a flat tendon that becomes cordlike at the wrist. It is a powerful flexor of the wrist, as well as abducts hand, and is a weak synergist of elbow flexion. The palmaris longus is a small fleshy muscle with a long insertion tendon that is often absent. It may be used as a guide to find the median nerve that lies lateral to the wrist. It’s action is that it tenses skin and fascia of the palm during hand movement. It is a weak wrist flexor, and a weak synergist for elbow flexion. The flexor carpi ulnaris is the most medial muscle of this group. It’s a two-headed muscle. The ulnar nerve lies lateral to its tendon. It is a powerful flexor of the wrist, and it also adducts the hand in concert with extensor carpi ulnaris. It stabilizes the wrist during finger extension. The flexor digitorum superficialis is a two-headed muscle that is more deeply placed. It is overlain by muscles above it, but is visible at the distal end of the forearm. It flexes the wrist and middle phalanges of fingers two through five. It is the important finger flexor when speed and flexion against resistance are required.
The next on the list are the deep muscles of the anterior department. The flexor pollicis longus is partly covered by the flexor digitorum superficialis. It lies lateral and parallel to flexor digitorum profundus, and flexes the distal phalanx of the thumb. The flexor digitorum profundus is overlain entirely by the digitorum superficialis. It flexes distal interphalangeal joints, and is a slow acting flexor of any or all fingers, as well as assisting in flexing the wrist. The pronator quadratus if the deepest muscle of the distal forearm. It passes downward laterally, and is the only muscle the arises solely from ulna and inserts solely into the radius. It is the prime mover of forearm pronation, and acts with pronator teres. It also helps hold the ulna and the radius together.
This next group are the superficial muscles of the posterior compartment. The brachioradialis is a superficial muscle of the lateral forearm. It forms the lateral boundry of cubital fossa, extends from the distal humerus and distal forearm. It’s a synergist in forearm flexion, acts to its best advantage when the forearm is partially flexed and semipronated, and also stabilizes the elbow during rapid flexion and extension. The extensor carpi radialis longus runs parallel to the brachioradialis on the lateral forearm, and may blend with it to a degree. It extends the wrist in conjunction with the extensor carpi ulnaris, and abducts the wrist in conjunction with the flexor carpi radialis. The extensor carpi radialis brevis is somewhat shorter than the extensor carpi radialis longus, and lies deep to it. It extends and abducts the wrist, and it acts synergistically with extensor carpi radialis longus to steady the wrist during finger flexion. Extensor digitorum lies medial to the extensor carpi radialis. A detached portion of this muscle, extensor digiti minimi, extends the little finger. The extensor carpi ulnaris is the most medial of the superficial posterior muscles. It’s a long slender muscle that extends the wrist in conjunction with the extensor carpi radialis. It also adducts the wrist in conjunction with flexor carpi ulnaris.
The following are the deep muscles of the posterior compartment. The supinator is a deep muscle at the posterior aspect of elbow. It is largely concealed by the superficial muscles. It assists the biceps brachii to forcibly supinate the forearm, and works alone in slow supination. It also is an antagonist of the pronator muscles. The abductor pollicis longus runs lateral and parallel to the extensor pollicis longus, and just distal to the supinator. It abducts and extends the thumb. The extensor pollicis brevis and longus are a deep muscle pair with a common origin and action. They are overlain by the extensor carpi ulnaris. The extensor indicis is a tiny muscle arising close the wrist. It extends index the fingers, and assists in wrist extension.
The forearm is a seriously complicated muscle group as a whole. It makes sense that it would be due to the large number of functions our forearms and fingers have. I applaud those of you that made an effort to understand what all of the muscles do, as when we know what it is our body does, we are one step closer to being able to control the destiny of our physical selves. Leaving any aspect of our training up to fate makes little sense to me, so the grasping of the more detailed groups of muscles is still a necessary step in removing chance from our training equation.
As always, following the first Muscle Talk edition of the week is Super Foods. These amazing ingredients are just as valuable to understand, as within their simple forms lies a complex network of nutrients that can enhance our physical selves even further. Join me here tomorrow, and let the journey of learning continue. I look forward to seeing you then,