Rock Climbing

A Guide to the Forearm Muscles

You know the forearm, between the wrist and the elbow. And you know the forearm muscles, like the flexor digitorum superficialis. Everyone’s favorite, right?

Most bodybuilders have an above-average understanding of anatomy, talking about muscles like the pecs, delts, abs, lats, glutes, quads, biceps and triceps. However, few are able to banter about their favorite exercise for the extensor carpi radialis brevis. You’re about to join that number with this article all about forearm muscles.

Human Body Anatomy Bones and Muscles

A Quick Walk through Nomenclature

For most of history between the dark age and the modern age, Latin was a nearly universal language. As a result, scientists – and anyone else who was educated – was educated in Latin and anything worth reading was published in Latin.

Even though the world has become multilingual, the names that we use for muscles are still the latin names that they were given. We’re not here to learn latin, but knowing a couple of prefixes and suffixes will help you navigate unfamiliar muscle names when you hear them. That’s handy because we’re probably not going to get around to all of the forearm muscles here.

First, it helps to know the names of bones. Muscles span bones, originating on one and inserting on another. Sometimes, almost the whole name for a muscle is composed of the bones that it connects to, as in the case of the flexor carpi ulnaris – with the carpals and the ulna being the bones in question.

Next, muscle names often relate to what they do. Looking back at the flexor carpi ulnaris, it flexes. That means that when this muscle activates, it brings the bones that it’s connected to closer together. We’ll also see “extensors” – when they activate, it moves the bones that they’re connected to farther apart as does the extensor carpi radialis longus. 

“Longus,” by the way, just means “long” and “brevis” means short. “Medial” means that it’s in the middle, “super – ” means that it’s closest to the skin. “Abductors” move things away from the body and “adductors” move them towards the body.

Finally “cep” means head and refers to the big part of a muscle. It’s almost always used with a latin prefix denoting how many heads the muscle has “bicep” meaning “two heads.” 

Got all that?

An Even Quicker Walk Through Muscle Action

We’ve already touched on a few other quick notes to have in mind but they should be firmly in mind before we continue.

Muscles “originate” on one bone and “insert” on another. When they “flex” – that’s “contract” – they bring the insertion closer to the origin. Most of the time this is how we work out a muscle but, with something called “reverse muscle action” you can work out most muscles by using that muscle to move the origin away from the insertion against resistance.

Finally, each muscle tends to have one job with respect to a movement. That means that completing a motion requires at least two muscles that work in opposite capacities. That means that, while most exercises target a specific muscle, being smart about it can allow you to work out two at a time by doing an exercise as you would, and then gradually and deliberately doing it backwards to complete the rep.

That was a very around-the-bush way to get started but now when you hear just about any muscle name you can quickly determine where it is and what it does – more than enough to figure out how to work it out. Further inspiration, pick up an anatomy book. We’re using Tortora and Derickson’s “Principles of Anatomy and Physiology.”

Anterior Forearm Muscles

Muscles of the Forearm, and How to Work Them Out

The forearm is made up of an aggravatingly high number of aggravatingly small muscles that do aggravatingly specific things. The end result is that the forearm muscles are notoriously difficult to bulk up. In fact, most workout guides will admit that forearm muscles exist in an image, and then kindly never mention them again.

Thankfully, anatomists have divided the forearm into “compartments” of muscles that do similar things. With a little thought, we can use this information to design a forearm muscle-targeted workout routine.

The Superficial Anterior Compartment

This part of the forearm consists of four forearm muscles – the Flexor Carpi Radialis, the palmaris Longus, our old friends the flexor carpi ulnaris and the flexor digitorum superficialis. These muscles bring the hand toward the forearm. 

To workout these forearm muscles, hold weights in each hand, with your arms at your sides but not tightly held against the body. Then, move the weight away from your body by moving your wrist and keeping the forearm still.

They also flex the fingers closer where they meet the palm, but there are special exercises for this area that we’ll talk about in the next section.

The Deep Anterior Compartment of the Forearm

This part of the forearm consists of only two muscles, the flexor pollicis Longus (“pollicis” refers to the thumb) and the flexor digitorum profundus (“profundus” means “deep” as in closer to the bone). These forearm muscles flex the thumb and the fingers toward their tips.

Exercising these forearm muscles involves flexing the fingers against resistance. There’s a specific tool for this called a “grip exerciser.” Plug that into your favorite search engine or mention it to the staff at your favorite sporting goods shop, and they’ll get you the connection. Hold the gripper close to your palm and squeeze to exercise the superficial compartment, or move it out farther and squeeze it with your fingertips to exercise the anterior compartment.

Or, just get a stress ball and squeeze that.

Forearm Muscle Anatomy

The Superficial Posterior Compartment

This part of the forearm consists of the extensor carpi radialis longus and the extensor carpi radialis brevis, the extensor digitorum, the extensor digitorum minimi, and the extensor carpi ulnaris. 

These forearm muscles extend the wrist and the fingers closer to the palm. As for the exercises, we’ll stick with the pattern from the first two compartments: We’ll focus here on exercising with wrist movement and keep the fingers all together by describing their exercises in the next subsection.

Now, remember the exercise we started with, holding weights? This exercise is the reverse of that one. Instead of moving those weights away from the body, we’re going to bring the weights in towards the body, again, by moving your hands at the wrist, not by moving your forearms.

The Deep Posterior Compartment

This compartment includes the abductor pollicis longus and brevis, the extensor pollicis longus and the extensor indicis. These forearm muscles extend the thumb and the fingers toward the tips.

If you follow that search engine thread from earlier or follow the shop attendant at your sporting goods store, you’ll see that there are some zany exercise tools for working these muscles too that involve putting your fingers through elastic bands to provide resistance. The coolest ones include a stress ball in the middle so that you can do all of the finger and thumb exercises that we’ve covered in this article.

Tight on cash? Don’t want to go out? Already have a stress ball and don’t want to get some crazy mechanism? That’s fine – just get a rubber band. Stretch the rubber band around your thumb and index finger and move them apart, stretching the rubber band. Then, keeping one end of the rubber band around the thumb, move the other end to the next finger and on down.

The only problem? After a while it becomes really hard to find high-gauge rubber bands that provide enough resistance to be worth the trouble. The most industrial rubber bands that most people have casual access to come around the bottoms of heads of broccoli.

Who Says Exercises Have to Be Exercises?

Weights, rubber bands, and stress balls are all great ways to deliberately work out your forearm muscles. However, there are a couple of neat hobbies that do the trick too.

Anything that uses grip will do. Easy examples include rock climbing and playing guitar. But that doesn’t mean that those are the only two things that do. Think about your hobbies and wonder of any of them work out the muscles we’ve been learning about.

Further reading

Tortora, Jerry and Derrickson, Bryan. “Principles of Anatomy and Physiology.” Ed. 14. Wiley Publishing. 2017.