Muscle Fibers Posted on 30 Mar 23:02 , 0 comments

IMG_1415By Todd Lee M.D.


Most people don't know the difference between muscle cells and muscle fibers. That's because there really isn't one; muscle cells are shaped like fibers.  Myocyte is Greek for muscle cell: myo- muscle, -cyte cell. Collections of cells form muscle tissue. There are 3 types of muscle tissue: Cardiac, Smooth, and Skeletal.

Since this is a bodybuilding site, I'm going to focus on skeletal muscle fibers.

Skeletal Muscle Fiber Nomenclature

First and foremost, a lot of the organelles in a muscle cell are different than any other cell. A sarcoplasmic reticulum is the muscle cell or MYO name for an endoplasmic reticulum. A sarcolemma is the cell membrane,  a sarcosome is a mitochondria, sarcoplasm is cytoplasm etc. For you veterans of molecular biochemistry this is old hat but for those of you who don't have a working model of a functional cell in your mind don't worry, I have pictures!

Neuromuscular Junction

Sarcoplasmic_Reticulum_PicMuscle fibers are the bundles of cells that form the muscle. Skeletal muscle is actually very complex and has a large neural component. The signal comes from the brain or spinal cord to the muscle and causes acetylcholine to be ejected from the motor neuron to the nicotinic receptors on the muscle cell. This causes the sarcoplasmic reticulum which traverses the entire length of the cell to depolarize it's calcium supply into the sarcoplasm. This causes a electrochemical change that causes the muscle fiber proteins to contract!

The muscle proteins that contract are the protein fibers actin and myosin. They slide along each other and release, kind of like a caterpillar type writer, the actin slides along the myosin till its maximally contracted then an ATP must be spent to release. It costs energy to do this, ATP is converted to ADP and another ATP is necessary to release. Thus, creating rigor mortis and cramping where the muscle contracts, but won't release is from an energy deficiency; either water, carbohydrates, oxygen or fat depending on the fiber type and electrolyte balance for proper electrical conductivity.

Hail Hydra!

[caption id="attachment_517" align="alignleft" width="150"]Hydra_Pic The Hydra, coolest monster ever is the anipamorphic avatar of Operation Ragnarok![/caption]

The Hydra was a reptile in Greek Mythology with multiple heads and you couldn't kill it without destroying all the heads. As soon as you killed a head however, two grew back... What a badass!  In Norse Mythology, Thor fights it in the final battle of Ragnarok, in which it's called, The World Eater or the World Serpent.

In a lot of ways a muscle cell is like the hydra of the body. It has tons of nucleuses which is the brain of the cell. Each nucleus was at one point donated by a satellite cell: a supporting cell that surrounds the muscle which is also called a myoblast. These are like stem cells, they haven't differentiated into a specific type of muscle cell yet.

[caption id="attachment_518" align="alignleft" width="342"]Call me crazy but this looks like a hydra to me. Destroy one nucleus , no big deal there are HUNDREDS! unlike any other cell. Call me crazy but this looks like a hydra to me. Destroy one nucleus, no big deal there are HUNDREDS! Unlike any other cell.[/caption]

The satellite cell donates a nucleus to a muscle cell after it is recruited through IGF-1ec or MGF. IGF-1ec is created in the muscle cell by drop sets and other heavy training by the hormones estrogen, testosterone or the anabolic steroid called Trenbolone. The more nucleuses a myocyte has, the more mitochondria, glycogen, actin and myosin the muscle cell can handle and subsequently the bigger it gets!

Betaine increases IGF-1 receptors, so using Wyked 2.1 or Nocturnus makes your workouts more effective since you're releasing IGF-1 mid workout.  The best time to have a IGF-1 receptor upregulation would be pre workout; so you get the most satellite cell activation and the most nucleus donation and subsequently the capacity to make more muscle protein, thus more strength and size.

It's a Fixer Upper

If you lose a lot of muscle mass cutting for a show, you're not losing your nucleuses, only the fuel and contractile proteins. This means it’s way easier to get back lost size than it is to grow bigger than you have ever been. It’s like a shelled out house is easier to fix then it is to build a house from scratch. It’s just a matter of filling up the muscle with glycogen and giving the cell the amino acids it needs to lay down more muscle proteins. The signal for muscle growth from testosterone, estrogen and IGF-1ea is still necessary of course.

There are Two Basic Types of Skeletal Muscle

Skeletal_Muscle_Type1_PicType 1 is small and red. It is red because of the presence of myoglobin, which has a heme group. Like hemoglobin, myoglobin's heme group is an Fe++ (ferrous Iron) bound to an oxygen. This combination is what creates the red or rust color of blood and red or type 1 muscle cells!

Why oxygen? Because type 1 cells are endurance fibers. They are used for aerobic respiration, using mitochondrial (sarcoma) to oxidative phosphorylate ATP with oxygen and fat for fuel in the krebs cycle. T2 reduces the efficiency of this, as it is an uncoupler. It basically puts holes in the mitochondria allowing protons to leak out, allowing less calorie energy generated per gram of fat. Thus increasing fat burning. Since it accelerates this reaction, it depletes the Type 1 muscle cells of their energy sources, in this case fat!

T3 increases the rate of the mitochondrial energy production but is not an uncoupler like T2, so the 2 together are way better than separate.

L-Carnitine transports the fat to the mitochondria. So by using T2 with Rise and swell, Wyked 2.1 and Nocturnus when you're supposed to, you burn more fat throughout the day since all the products have L-carnitine. L-carnitine is transporting fat from your adipocytes to your mitochondria for energy production all day long and the T2 decreases the amount of energy produced so you have to burn more fat to get the same calories per hour.

Type 2 muscle cells are white since they have no heme groups or mitochondria. Since they are power or, fast twitch fibers, they don't need fat for fuel and thus don't have as many mitochondria since they don't use that as their fuel source. Likewise, the lack of a need for oxygen means no myoglobin.

What white fibers do have is size and strength.

A larger motor unit causes a greater depolarization effect and a more forceful contraction. The greater cross sectional area of the white fiber means more hydraulic pressure for contraction. The glycogen (starch) fuel source causes a lot of water to fill the muscle cell with it. This causes a internal hydraulic pressure which helps with force of contraction.

Type 2 fibers come in 2 types; A and B. Type 2B is how I described type 2 above, where as Type 2A is an intermediary fiber and can act like 1 or act like 2B depending on how you train. Your body adapts to what it needs by altering the function of these transitional (2A) fibers.

T2 switches fibers from Type 1 to Type 2. By depleting fat from Type 1 and increasing fuel in Type 2, it drives the change of having the Type 2A fibers behave more like Type 2B then Type 1.


Nothing in this article or on this site should be considered medical advice or as an endorsement to violate any law of the country in which you reside.  The information given is for fun and entertainment purposes only.  All claims are 100% dependent upon proper diet and exercise.  Please consult a medical practitioner prior to any diet and exercise program.