Skeletal muscles are the only voluntary muscles in the body. To contract, skeletal muscles must receive instructions from the nerves. If the nerve is damaged, muscles are unable to contract, and the result is atrophy. Muscles of the body are given names based on their location, function, size and structure. Most muscles of the arm are attached at some point to either the scapula, humerus, radius or ulna and allow activities important to daily living and muscle strengthening.
Biceps Brachii
The biceps brachii muscle is known simply as the biceps. The two heads of the biceps brachii are the short head and long head. This two-headed muscle is located on the front of the upper arm, originates in the scapula and inserts at the radius. The biceps brachii muscle is responsible for flexing the elbow. Exercises that isolate the biceps brachii muscle are preacher curls, hammer curls and barbell curls.
Triceps Brachii
The triceps brachii is known as the triceps. The three heads of the triceps brachii are the medial, long and lateral head. This three-headed muscle is located in the back of the upper arm. The lateral and medial heads of the triceps muscle originate at the humerus. The long head originates at the scapula, and all three heads insert at the elbow. The triceps brachii muscle is responsible for elbow extension or straightening the arm. Exercises that isolate the tricep muscles are tricep dips, tricep kickbacks and seated triceps extension.
Brachialis
The brachialis muscle is located on the inside of the upper arm near the elbow. The brachialis muscle originates on the lower front half of the humerus, arm bone, and inserts at the elbow. The brachialis is the strongest flexor of the elbow. According to ExRx.net, the brachialis muscle is activated during static elbow flexion. All exercises involving the biceps brachii incorporate the brachialis.
Brachioradialis
The brachioradialis muscle is located on the outside of the upper arm near the elbow. The brachioradialis is another flexor of the elbow, and dependent on the position of the forearm, it plays an active role in rotating the palm up and down. This muscle originates on the outside portion of the forearm near the elbow and runs from the elbow halfway down the forearm. According to Frederic Delavier, author of Strength Training Anatomy, hammer curls are the best exercise for developing the brachioradialis.
Coracobrachialis
The coracobrachialis muscle originates on the scapulae and inserts halfway down the upper arm. The muscle is located in the upper inside portion of the arm near the armpit. The coracobrachialis is responsible for raising the arm away from the body and bringing the arm down toward the body. The coracobrachialis muscle is activated during shoulder raises to the front and out to the sides.
References
- Strength Training Anatomy, 2nd edition; Frederic Delavier; 2006
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