We are back with another anatomy session. This time we’ll be looking at the lower half of the leg.
The leg is a bit trickier than the arm. There are simply more muscles in the leg which means there is a lot of ground to cover.
And we are back with another anatomy study! This time we will be focusing on the forearm.
We are going to talk about the upper arm in this section. Including the deltoid!
Andrew Loomis is pretty cool for two reasons: 1. He has these awesome diagrams of arms and 2. He is pretty much fair use! Unfortunately I can’t say the same for Jack Hamm, who I repeat for the thousandth time, has some of the best explanation on anatomy.
Let’s move on shall we?
The important thing to understand about the deltoid muscle is that it’s a shoulder muscle. It has three fibers; anterior fibers, middle fibers and posterior fibers. That basically means there is a front, side and back.
Anterior is in red, middle is in blue and posterior is in yellow.
Muscles work together. They are not isolated bulges. The deltoid as a whole works with the shoulder, chest and back muscles. The deltoid helps to rotate the humerus bone with the help of the pectorals, subscapularis and latissimus dorsi. That basically means that it receives help from the chest and the back.
The front deltoid(anterior) basically assists in rotating and pushing the arm away from the centre of the body. The middle deltoid assists in lateral rotation and hyper extension. The back deltoid(posterior) assists in rotating towards the centre body and pushing away from the body.
What this all means is that the positioning of the arm is very important when considering where the deltoid is and how it is positioned. A good rule to consider is that the bicep and tricep never pass the brachialis.