Triceps

Triceps is the main muscle located at the back/posterior compartment of the arm. The name 'Tri' is derived from the presence of three 'heads': long, medial and lateral. The tricep composes of 2/3 of your arm therefore it is a key muscle to concentrate on when building arm strength and size. Each muscle starts at a different point on the body, but all of the muscles attach to the same place on the elbow. It is responsible for elbow extension, that is extending your arm out from the elbow in any pressing or pushing movement. The long head is the only part that crosses over the shoulder joint, so the long head can actually assist at pulling the shoulder backwards (shoulder extension).

Anatomy

• Long head
• Lateral head
• Medial head

The Triceps Brachii also assists Latissimus Dorsi in extending the shoulder joint. It contracts strongly during the up phase of a push up, to straighten the arm. The long head starts on the infraglenoid tubercle of the shoulder blade which means that is crosses the shoulder joint.The lateral head starts on the posterior part of the arm. It is situated towards the top outside part of the arm. The medial head starts on the posterior part of the arm also but it is situated on the lower inside part of the humerus.

Recommended Exercise 

Obviously, any exercise that focuses on straightening the elbow will work all heads of this muscle and there are many good isolation exercises and compound exercises. Examples of isolation exercises are things like kick backs, push downs, or overhead extensions.
 

• Long head responsible for the arm looking bulging at the back of the arm, workout that puts the elbow away from the body will provide better stretch towards the long head such as dumbbell triceps overhead extension and french curl.
• Cable or isolation would be best to bring out the triceps striation