The arm’s curved shape comes from its major exterior muscles. These bulky muscles also give the arm its strength.

The muscles of the arm that can be seen easily on the surface include:

  • Biceps: This large muscle of the upper arm is formally known as the biceps brachii muscle, and rests on top of the humerus bone. It rotates the forearm and also flexes the elbow.
  • Triceps: This large muscle in the back of the upper arm helps straighten the arm. It is formally known as the triceps brachii muscle.
  • Brachioradialis: This muscle, located at the top of the forearm near the elbow, helps rotate the forearm both outwardly and inwardly. It also flexes the forearm at the elbow.
  • Extensor carpi radialis longus: This muscle next to the brachioradialis is one of five major muscles that help to move the wrist in multiple directions. When you clench your fist, this muscle bulges out from the skin.
  • Deltoid: Although technically part of the shoulder, the deltoid muscle controls the majority of the shoulder’s movements and thus enables the arm to have increased range of motion.

Strength training exercises are common ways to increase the size and overall strength of the major muscles in the arms. Common exercises to build up arm muscles include curls, presses, pushdowns, and extensions using weights.

Pain can occur anywhere in the arm. The most common cause of arm pain is overexertion of a muscle or injury to it. Twisting, pulling, or falling are common ways muscles in the arms become painful. Although repetitive injuries affect the deep muscles more often, pulled muscles from lifting something too heavy or overexerting can also create pain and soreness, but this usually subsides in a few days.

Arm muscle pain can usually be easily treated with resting the affected muscle and icing, elevating, and compressing the area.