Upper Arm Muscles: Anatomy & Function (Explained)

✔ Evidence-Based. Scientifically Reviewed by Michael Sharpe, MSc.

Your upper arm, forearm, and hand make up each of your arms. The upper arm is from your shoulder to your elbow. Your forearm is from your elbow to your wrist and then your hand.

In this article, I'll discuss the anatomy and function of the upper arm muscles.

What Do Muscles Do?

Many muscles in your arms work together to enable you to execute a variety of movements and activities. The four movements muscles allow are as follows.

• Flexion: This action pulls two body parts, such as your forearm and upper arm, closer together.

• Extension: This action widens the gap between two body parts. Straightening your arm is one example of this.

• Abduction: This is when you move a body part away from your body's centre, such as when you raise your arm out and away from your body.

• Adduction: This refers to returning a body part back towards your body, such as your arm resting along your torso.

Anterior Compartment

The biceps brachii, coracobrachialis, and brachialis are the three muscles that make up the anterior compartment of the upper arm. The musculocutaneous nerve innervates them all.

Biceps Brachii

The biceps brachii muscle has two heads. Despite the fact that the bulk of the muscle mass is found anterior to the humerus, it is not attached to the bone.

A connective tissue layer called the bicipital aponeurosis is released when the biceps brachii tendon reaches the forearm.

This connects to the deep fascia of the anterior forearm to create the ceiling of the cubital fossa.

• Origin of short head: Coracoid processof the scapula

• Origin of long head: Supraglenoid tubercle

• Insertion: Radial tuberosity and bicipital aponeurosis into deep fascia on medial part of forearm

• Artery: Brachial artery

• Nerve: Musculocutaneous nerve (C5-C7)

• Actions: Flexes elbow, flexes and abducts shoulder, supinates radioulnar joint in the forearm

• Antagonist: Triceps brachii muscle

Coracobrachialis

In the arm, the coracobrachialis muscle is found deep below the biceps brachii.

The coracobrachialis is the smallest of the three muscles that connect to the scapula's coracoid process, the pectoralis minor and the short head of the biceps brachii are the other two muscles.

• Origin: Coracoid process of scapula

• Insertion: Anteromedial surface of humerus distal to crest of lesser tubercle

• Artery: Brachial artery

• Nerve: Musculocutaneous nerve (C5, C6, and C7)

• Actions: Adducts humerus, flexes the arm at glenohumeral joint

Brachialis

The brachialis muscle is located deeper in the arm than the biceps brachii and further away than the other arm muscles. It forms the floor of the cubital fossa.

• Origin: Anterior surface of the humerus, particularly the distal half of this bone

• Insertion: Coronoid process and the tuberosity of the ulna

• Artery: Radial recurrent artery, brachial artery

• Nerve: Musculocutaneous nerve (C5-C7) and radial nerve (C5, C6)

• Actions: Flexion at elbow joint

How to Train the Bicep Muscle

For elbow flexion, dumbbell curls and cable curls are effective for exercising both heads of the bicep; for shoulder flexion and abduction, utilise dumbbell press and flys as an extra exercise because the bicep is an auxiliary muscle and other muscles take over in this activity.

Weighted forearm supination is effective for forearm supination.

Your bicep muscle training technique should be determined by your aim, however given their fibre type makeup, which appears to be primarily type 2, you may choose to train for these specific fibre types.

Posterior Compartment

The triceps brachii muscle, which has three heads, is located in the upper arm's posterior compartment. The medial head is deeper than the other two that it is surrounded by.

Triceps Brachii

• Origin of long head: infraglenoid tubercle of scapula.

• Origin of lateral head: above the radial groove. Medial head: below the radial groove

• Insertion: Olecranon process of ulna

• Fibre Type: The tricep group seems to be Type 2 dominant

• Artery: Deep brachial artery, posterior circumflex humeral artery (long head only)

• Nerve: Radial nerve and Axillary nerve

• Actions: Extends forearm, extends and adducts arm, extends shoulder

• Antagonist: Biceps brachii muscle

How to Train the Tricep Muscle

For forearm extension, exercises such as tricep pushdowns, cable pushdowns work well. For arm extension and adduction (the long head only), reverse flys and side raises work well as an assistance movement.

Another assistance exercise for shoulder extension is the shoulder press, which also utilises the tricep muscle group.

Your training style for the tricep muscles should depend on your goal, based on their fibre type composition, which seems to be predominantly type 2, you may want to train for these specific fibre types.

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