Triceps brachii muscle

The Triceps brachii muscle, more commonly referred to as the Triceps is a large muscle located on the rear of the upper arm between the elbow and the shoulder.

The function of the Triceps are the extension of the elbow joint, this means that they straighten the arm. This means the Triceps complete the opposite function to the Biceps.

The word Triceps means three headed muscle (Tri meaning three). These three heads are:

• The long head running from the shoulder blade (Scapula at the infraglenoid tubercle)
  
• The lateral head runs down the posterior shaft of the humerus, lateral and superior to the radial (spiral) groove (finishing half way down the upper arm).
  
• The medial head runs down the posterior shaft of the humerus, medial and inferior to the radial (spiral) groove (finishes at the elbow).
  

The Triceps account for about sixty percent of the muscle mass in the upper arm. Because of this you will find many bodybuilders working the Triceps just as much, if not more than the Biceps to add size and width to the arm.