What does it take to build muscle? We often hear about hypertrophy and building mass, but what does that actually mean?What part of the muscle cell is responsible for increases in strength and muscle size? Well here is the answer. Sarcoplasmic hypertrophy and myofibrillar hypertrophy. I will try to explain it in the easiest way I can.
The muscle cell is made up of fibers, that are comprised of myofibrals, which are comprised of myofillaments actin and myosin. However, there are other components to the cell that help make up the contractile machinery of the muscle fiber volume. A muscle cell has organelles (tiny structures that work synergistically to metabolize metabolites). In order to produce more volume of the cell it is important to develop the sacoplasmic machinery that produces greater energy. The mitochondria is the powerhouse of the cell and is where ATP is manufactured. Aerobic and anaerobic enzymes play a part in the breakdown of triglycerides and glucose. Depending on the type of training and the intensity triglycerides and glucose can be broken down and transported to the mitochondria through a process known as oxidative phosphorylation. These enzymes can grow over time as a result of training. As the enzymes grow, glycogen storage inside the muscle cell also increases. The mitochondria can increase in number and size making it more efficient at metabolizing and producing greater amounts of ATP. The sarcoplasmic fluid concentrations increase in and between cells. This process is known as sarcoplasmic hypertrophy. Sarcoplasmic hypertrophy is simply the increase in the oxidative and glycolytic processes and machinery of the cell. Though this hypertrophy produces some increase in cell size it isn’t the main factor in developing overall strength and size. Improving the cellular mechanisms of metabolism is the first step in creating greater muscle size because as the enzymes and oxidative properties improve, so is the ability to produce greater energy to help with the neural drive of the contraction. Performing 12 repetitions against a sub-maximal load produces more sarcoplasmic hypertrophy than performing fewer reps at maximal loads.
The true increase in muscle size depends on myofibrallar hypertrophy. The myofibral houses myofillaments; actin and myosin. Actin and myosin are also known as sarcomeres. Sacromeres are responsible for increased size and strength. When a load is presented to the muscle the actin and myosin crossbridges are influenced. If the intensity or trauma is great enough the crossbridges become damaged. This damaging effect causes structural damage to the plasma membrane allowing calcium ions to infiltrate into the muscle cell disrupting the intracellular balance. When calcium ions are higher than normal inside the cell, enzymes known as calpains are activated to remove fragments of easily releaseable myofilaments. Also, to help with the removal of fragments is a protein known as ubiquitin. This episode attracts granulocytes known as neutrophils (phagocytes). Neutrophils are the most abundant type of white blood cells. They show up when tissue or cells become inflammed or damaged. During this event of de-fragmentation within the cell, neutrophils increase in number. They help clear up free radicals and debris released by calcium-mediated release developed by ingulfing them. Monocytes also attract to cell trauma and are there to help support the immune system once neutrophils demise after a day or two. Monocytes release macrophages and dendritic cells from the spleen. Monocytes help release the toxins that have built up in the cell.
Once the phagocytic stage runs its course the cell is more vulnerable. Lysosomal proteases, free radicals, and other by products breakdown the damaged fibers. Macrophages are important in rebuilding the interior matrix of a muscle fiber. Without proper involvement of macrophages the repair of muscle is compromised.
Now proper nutrient exchange is needed to re-establish the configuration of the muscle cell. During the recovery process muscle cell regenerates and becomes more stronger and enduring, depending on the activity, to allow for greater effort during the next exercise bout.
Here is how the growth cycle works.
As mentioned previously the muscle cell is a network of organelles that work to sustain energy and protein production. These organelles are supported by a nuclei that helps with protein synthesis. Muscle cells have many nuclei to help support growth. If muscle cells didn’t have the ability to increase the number of nuclei then the cell would be small and growth would be limited. The more nuclei available the greater the amount of protein produced. Actin and myosin are proteins and when they are broken down they must be regenerated. How do nuclei increase in muscle cells?
There are cells outside the muscle cells known as myogenic stem cells or myoblasts. When the need arises these myoblasts will donate their nuclei to the involved active muscle fiber. This process increases the number of nuclei giving rise to the myonuclei number. This process is not as simple as you may think. In order for this event to occur three things must take place, 1. myoblasts have to increase. When myoblasts increase this is known as proliferation. 2. They must configure into “similar” muscle cells. This is known as differentiation. 3. They must fuse with active muscle cells that need additional support.
During the recovery phase the muscle cell is in need of repair. The cells are weakened and in order to rebuild the tissue growth factors must be released to begin building the stronger matrix of the cell. Since all the micro work of cleaning the debris and fragments from the cell via phagocytize process is done, now it is time for greater help from growth factors and hormones to re-establish protein synthesis and nutrients exchange into the cell.
Insulin-like growth factor 1 (IGF-1), fibroblast growth factor (FGF), and transforming growth factor- (TGF-Beta) are used to help the myoblasts proliferate (FGF), differentiate (IGF-1), and mediate (TGF). Growth factors can leave the intercellular level and permeate out into the surrounding area because of the increased permeability of the cell as a result of the damage. The end product is myoblasts fuse with other muscle cells and donate their nuclei, giving rise to muscle cell growth.
In order to sustain the protein synthesis of the muscle cell and to cause growth their must be enough IGF-1, growth hormone, testosterone and some prostaglandins present. Protein synthesis is directly linked to messenger RNA. Messenger RNA (mRNA) is a genetic coded substance that determines how much protein is to be synthesized. The nucleus of a cell, the control center, releases mRNA to the ribosome (an organelle that makes up proteins from amino acids). Under traumatic cellular damage the nucleus is believed to send additional mRNA in response to damage to the actin and myosin crossbridges. Amino acids are then released and begin to rebuild the protein. Seeing the amino acids are the building blocks of protein this only seems appropriate.
To help increase amino acid uptake are the following; 1. IGF-1, 2. Growth Hormone 3. Testosterone.
IGF-1: Acts similar to insulin promote anabolic effects in the human body. There are 2 types of IGF-1. 1. Paracrine IGF-1 produced in the liver and autocrine IGF-1 made in cells other than the liver. Paracrine travels throughout the body because it is released from the liver, whereas, autocrine remains localized and is only influence by cells in the surrounding area. Paracrine must be influenced by cell receptors outside the muscle cell in order to enter the muscle cell. Autocrine IGF-1 on the other hand doesn’t have to wait for a receptor to signal its release, because it is already in the muscle cell. Autocrine IGF -1 responds to increased tensile forces. When both forms of IGF-1 are in the cell they interact with calcium-activated enzymes allowing for protein synthesis. One way to increase the production of IGF-1 to enter the muscle cell is to ingest fast acting glucose polymers after working out. The glucose will illicit an insulin charge. Insulin is an anabolic hormone that helps send fat, sugar and growth factors (IGF-1) into the cells.
During training the anterior pituitary gland secretes growth hormone. Growth hormone helps with the release of IGF-1 from the liver and muscle during recovery. Allowing for more protein synthesis. Prostaglandins also play a role in protein synthesis. During a contraction certain prostaglandins are released. PGE2 and PGF2-alpha are the two prostaglandins that are involved in the growth process of cell repair. PGE2 increases protein degradaton and cell proliferation and PGF2-Alpha increases protein synthesis.
The last growth component is testosterone. Everyone talks about testosterone but not everyone knows what testosterone actually helps muscle growth. I will now explain to you how testosterone works. Inside the muscle cell there are androgen receptors. These receptors will attract to free floating testosterone (not attached to protein) that enter through the muscle cell Bound testosterone, attached to a protein, is controlled by receptors outside of the muscle cell. The number of receptors dictate the amount of bounding testosterone. Once inside the cell testosterone goes to the nucleus and the protein synthesis cycle occurs. Testosterone is the greatest anabolic agent in the human body. It increases protein syntheses dramatically. it also helps increase myoblast sensitivity to IGF-1 and FGF. Ultimately, increasing myoblast proliferation and differentiation. Growth hormone and IGF-1 systemic output is also influence by testosterone. Seeing the testosterone is apparently the driving force for protein synthesis you can understand why bodybuilders and athletes are addicted to taking steroids to grow. When taking a synthetic form of testosterone protein synthesis can lasts hours during the day leading to greater muscle growth. Natural athletes and bodybuilders have only a small opportunity to create an anabolic effect allowing testosterone to boost protein synthesis. The body can only manufacture so much testosterone naturally. Guys that take testosterone, growth hormone and insulin have a tremendous advantage on the natural athlete. Protein synthesis stays on almost around the clock. The muscle tissue grows beyond natural levels. However, the side effects of taking these compounds is not worth it.
Resistance training boosts testosterone and growth hormone levels. To develop bigger muscles it is important to activate more of the fast twitch fibers. The fast twitch have more actin/myosin filaments and generate the greatest tensile forces. Due to the damage that intense training provides the rebuilding process at the cellular level can take from 36-48 hours.
By knowing how to train correctly using the right amount of intensity will boost testosterone and growth hormone levels. Knowing how to do this separates the weekend certified personal trainer and the college degreed professional personal trainer.
If you need help designing a muscle building program please contact me at www.darylconant.com. I would be glad to help you.
Daryl Conant, M.Ed