For the past few months I have been working on a small theory with the triceps muscles. I see a lot of shoulder type injuries in my office here in Grand Rapids. Everything from frozen shoulder, rotator cuff inhibition, labral surgeries and impingement's. One thing I've started to notice is that the long head of the triceps is weak and under developed and that the medial head has adhesion's.
Let's review a little anatomy. The triceps brachii has three parts, hence the tri. The bicep has two parts, hence bi. Want bigger arms, do triceps work, 2/3 of your arm is triceps. The triceps is made up of the lateral, medial and long head. The lateral head, most outward portion, gives the famous horseshoe shape seen on people. The medial portion is in the middle, and lies underneath the other two. These two portions attach from the humerus into the ulna. The last portion is the long head, you guessed it, the longest of the triceps. It's the most medial. What makes this muscle different is that its origin is actually into the scapulae. All three will extend the elbow, but the long head will actually adduct the arm in a similar fashion as the latissimus dorsi.
So back to my observations. After doing soft tissue work to the medial head, it usually brings a feeling of lightness to the shoulder or elbow joint. I am starting to view this muscle as an upper body shock absorber, in the same fashion the vastus lateralis is a shock absorber for the lower body. (This is why triceps strength is big time important for mountain bikers!)
Now in people that don't have shoulder issues, but do lots of overhead work, pressing, or throwing or the patients/athletes that bounce back quicker, the long head seems more well developed. The long head may have fascial anatomy with the teres minor muscle. It is considered part of the deep arm line in anatomy trains research. Having strong connections with the rhomboid muscle. Functionally, the long head works to keep the under part of the shoulder joint stable. It works to prevent displacement of the humeral head down and back.
The long head will not work in simple pressing exercises. It is actually pretty dormant in standard pressing and overhead work. The long head needs to be stretched to get a full workout. Its secondary function as a humeral adductor allows it to get good work in with doing back work. To isolate the long head, doing an exercise such as a skull crusher with combined pullover type movement, has proven to be effective.
Here is Arnold doing a famous bodybuilder pose. The under hang is the development of the long head. I would bet that Arnold didn't have many shoulder problems!