Rotator Cuff Muscle Performance
Enhancing your rotator cuff muscle performance involves understanding how your rotator cuff muscle works. What exactly happens during rotator cuff exercise and rotator cuff rehab?
Have you ever wondered what is going on inside the muscles of rotator cuff when you are doing some rotator cuff training?
In this section I want to give you some basic muscle science facts.
I will focus on skeletal muscle as that is what a rotator cuff muscle is.
The basic action of any muscle is contraction; indeed all that any muscle can do is create contraction force.
For example, when you think about moving your arm using your biceps muscle, your brain sends a signal down a nerve cell telling your biceps muscle to contract.
The amount of force that the muscle creates varies; the muscle can either contract a little or a lot depending on the signal that the nerve sends. That is why skeletal muscles are said to be under conscious control.
How does a rotator cuff muscle contract?
A muscle is actually a bundle of many cells called fibers. You can think of muscle fibers as long cylinders, and compared to other cells in your body, muscle fibers are quite big.
A muscle fiber contains many myofibrils. Myofibrils are cylinders of muscle proteins. These proteins allow a muscle cell to contract.
Myofibrils contain two types of filaments that run along the long axis of the muscle fiber, and these filaments are arranged in hexagonal patterns.
There are both thick and thin filaments present in each skeletal muscle. Each thick filament is surrounded by six thin filaments. This is shown in the diagram below.
Thick and thin filaments are attached to another structure called the Z-line.
As you can see the Z-line runs perpendicular to the long axis of the fiber.
The myofibril that extends from one Z-line to another is called a sarcomere.
It is the thick and thin filaments do the actual work of a muscle; and the way they do this is pretty cool.
Thick filaments are made of a protein called myosin.
At the molecular level, a thick filament is a shaft of myosin molecules arranged in a cylinder. Thin filaments are made of another protein called actin. The thin filaments look like two strands of pearls twisted around each other.
During muscle contraction, the myosin thick filaments grab on to the actin thin filaments by forming what are known as crossbridges.
The thick filaments pull the thin filaments past them, making the sarcomere shorter.
This shortening of the sacromere results in the shortening or contraction of the whole muscle.
This dynamic forms the basis of your rotator cuff muscle performance.
Types of rotator cuff muscle contractions
There are two distinct types of rotator cuff muscle contraction; Isotonic and Isometric. The contraction or shortening of the muscle fibres creates a mechanical force, or muscle tension that affects rotator cuff muscle performance.
Whether the muscle itself changes length, which is known as same-force or isotonic contraction, or not, which is known as same-length or isometric contraction depends upon what we want the muscle to do.
Here is a great example to demonstrate this. Your bicep muscle is attached to your shoulder blade at one end and to the ulna in your forearm at the other end.
When the bicep muscle contracts, it shortens and pulls the ulna up towards the shoulder blade. This movement allows you to lift your forearm and any given load - Isotonic contraction.
In contrast, if you are carrying a really heavy load, such as a full suitcase, that makes you unable to lift your forearm, then the biceps does not shorten significantly. But the force generated by the rotator cuff muscle performance is still helping you carry the suitcase - Isometric contraction.
In just the same way as all muscles are different, for example the rotator cuff muscle is vastly different to your bicep; all skeletal muscle fibres are similarly not alike. There are large variations in both the structure and function of muscle fibres.
For example, skeletal muscle fibres vary in colour depending on their content of myoglobin. There are other differences related to such things as the amount of mitochondria present; this is described below.
Myoglobin is a protein and has oxygen bound to it, thus providing an extra reserve of oxygen so that the muscle can maintain a high level of activity for a longer period of time.
Mitochondria are known as the powerhouses of the cell. They act like a digestive system that takes in nutrients, breaks them down, and creates energy for the cell.
Skeletal muscle fibres also contract with different velocities, depending on their ability to split Adenosine Triphosphate (ATP). ATP - Adenosine Triphosphate is a complex chemical compound formed with the energy released from food and is stored in all cells, particularly in muscle cells.
Based on various structural and functional characteristics, skeletal muscle fibres are classified into three different types: Type I fibres, Type II B fibres and type II A fibres.
In the section titled "how rotator cuff muscle exercises work" I explain why these different muscle fibre types are very important to us. I also explain how the ability of each rotator cuff muscle performance to adapt is so important when considering rotator cuff training or rotator cuff exercise and why rotator cuff rehab really works.
Hopefully in this section I have given you an insight into how a rotator cuff muscle actually works to better explain yur rotator cuff muscle performance. Don't worry there will not be a test!