I was going to write about a specific muscle today (Quadratus Lumborum), but when I started working I realized that in order to get a grasp on the muscle - what and how it moves - it’s important to know some basic muscle anatomy medical vocabulary. This serves two purposes: 1) for you to be visualize, sense, and become aware of your musculature and what may be causing you problems; 2) to make you sound really smart when you’re talking to your friends.
A muscle has to start somewhere (its origin) and end somewhere (insertion). Since a muscle’s function is to provide movement (action), each is attached to a particular bone in your body. Most muscles have a proximal (closer to your trunk) origin and a distal (farther from your trunk) insertion. Understanding the origin and insertion points will give you a pretty good idea of what action that muscle is intended to perform. I like to visualize muscles as rubber bands comfortably stretched between two points in the body. Let’s take a look at the anatomy of a fairly familiar muscle, the biceps, and illustrate its origin, insertion, and action.
As you can see, the biceps muscle (also known as biceps brachii) is a two-headed muscle with two origins and one insertion point. You can also see that the muscle itself is not directly attached to the bone, rather tendons connect the muscle to bone.
Without worrying about the Latin names of the bones and bony landmarks, you can see that - very generally speaking - the biceps originates on the shoulder and inserts on the inside of your forearm. Again, think of a rubber band comfortably stretched from your shoulder to the front of your forearm. When the biceps contracts, it shortens, providing an action. So what happens when you contract your biceps? Your elbow bends and your forearm moves toward your shoulder.
We often think of the biceps as a powerful muscle, but in fact it only provides weak arm flexion. One of the reasons for this is because the muscle crosses more than one joint - the elbow and the shoulder. As a rule, a muscle that crosses more than one joint is not the prime mover of a particular motion because its action is spread across multiple joints providing more than one joint movement.
With all of that, we can now see and hopefully understand this:
You’ll also notice “innervation” on the muscle chart. This just lets us know which nerve complex innervates that particular muscle. This is important in recognizing pain patterns and effectively treating a patient. In this case, the musculocutaneous nerve which runs through the fifth and sixth cervical vertebrae.
I really hope if you took the time to read this that it did more to educate than confuse! As a therapist, these are the things I need to know to effectively treat my clients, but just as importantly, the more you the client know the more tuned in with your body you will be. It really isn’t brain surgery - a muscle has an origin and insertion to produce some movement in the skeletal system. Now that we know this, we can focus on and truly understand those muscles that cause us the most discomfort…next time.