- The biceps brachii -- the hill-shaped muscles on the front of the upper arms
- The triceps brachii -- the horseshoe-shaped muscles on the back of the upper arm
- The forearm flexors -- the muscles found on the palm side of the forearm
- The forearm extensors -- the muscles on the watch face side of the forearm.
The triceps actually take up approximately two-thirds of the real estate on the upper arm [source: Schlosberg, Neporent]. If you do nothing but exercises that isolate the biceps -- such as curls -- you're cheating yourself. Exercises like tricep kickbacks and tricep presses are also important to overall arm growth [source: Frisch].