Triceps Brachii Muscle
The Triceps Brachii is the big muscle on the back side of your upper arm and has 3 heads. That's where the name "Tri - Ceps" (tri = 3) comes from. Its function is to extend the arm. The biceps flexes the arm. The triceps brachii muscle is often simply called triceps. The word brachii means "arm" and triceps just means muscle with 3 heads. So if you are talking about the triceps, you could also mean another muscle with 3 heads. However, everybody associates "Triceps" with the Arm Triceps (triceps brachii). The triceps makes up about 70 percent of the upper arm size. The rear delts cover the upper part of the triceps. Find exercises and information about other muscles at weight training main.