Knowing the anatomy of the arm is the first step to increasing their size. By knowing where the muscles are located in the arm and what they do, each of them can be targeted with specific exercises. There are three major muscles groups in the arm:
The bicep is composed of two muscles. One muscle has two heads or connection points on one end (the long head and short head), hence the term “bi” meaning two. Located on the front part of the upper arm between the elbow and shoulder, both heads attach on one end to the shoulder blade, run along the front of the humerus, and terminate at the other end to the radius bone just below the elbow. The bicep allows you to bend your arm upward at the pivot point (elbow) in a curling motion.The second muscle is the brachialis. It is a small muscle under the bicep brachii. It connects the humerus bone in the upper arm to the ulna, the longer bone in the forearm, and is the strongest flexor muscle of the elbow.
The forearm muscle group is composed of two major muscles also – the pronator teres and brachiodradoalis. With your palm facing up, the pronator teres is located on the inside of the elbow joint. This muscle allows you to turn your hand from a palm up to a palm down position. The brachioradialis connects at the lower end of the humerus in the upper arm to the radius bone in the lower arm just above the wrist. It too functions to help bend the arm at the elbow.
Just as the “bi” in biceps indicates two, the “tri” in tricep means it has three heads – the lateral, long and medial. While the biceps are on the front part of the arm and allow you to bend your arm at the elbow (flex), the triceps brachii are located on the back of the arm and function to bring your arm back down to straight (extend).
This muscle is located along the outside of the back of the arm and connects the humerus and shoulder blade (scapula) to the ulna in the forearm.
The long head is located on the inside on the back of the arm and connects the same as the lateral head. It too assists in helping the elbow extend, but it also provides some stabilization to the shoulder joint.
While the long and lateral head are located on the outside and inside back of the arm respectively, the medial head is located midway between the other two muscles. Connectivity is the same as the other two heads, however the function is more closely related to the lateral head.
Building Arm Muscle
Here are some exercises that target each of the arm muscles:
Biceps – Barbell and dumbbell curls
Brachialis – Hammer curls and reverse grip barbell curls
Forearms – Palm up barbell wrist curls over a bench
Brachioradialis - Palm down barbell wrist curls over a bench
Triceps – Lying tricep press and close grip bench press
We know exercise builds muscles, but the mistake many people new to bodybuilding make is they focus on working just the biceps to get big looking arms. Because all of the muscles in the arm have to work together when flexing and extending, all have to be of similar size and strength.