If you’re a guy in the gym working with weights, not only are you probably trying to lose some fat, but also gain some muscle. This article discusses the mechanisms of how muscles grow, plus why most women won’t gain large amounts of muscle when working with weights. Although there are different types of muscles, such as cardiac muscle (your heart), for our concerns, we will talk exclusively about skeletal muscles.
The 650 skeletal muscles in the human body contract when they receive signals from motor neurons, which are triggered from a part of the cell called the sarcoplasmic reticulum.
When someone like a powerlifter is able to lift very heavy weight despite not looking very muscular, it’s due to their ability to activate those motor neurons and contract their muscles better.
After you workout, your body repairs or replaces damaged muscle fibers through a cellular process where it fuses muscle fibers together to form new muscle protein strands or myofibrils.
In one of the most interesting studies in the past 5 years, researchers showed that those who were “extreme responders” to muscle growth, with an incredible 58% myofiber hypertrophy from an exercise, had 23% activation of their satellite cells. Underlying all progression of natural muscle growth is the ability to continually put more stress on the muscles. In order to produce muscle growth, you have to apply a load of stress greater than what your body or muscles had previously adapted too. Muscular tension also most dramatically effects the connection of the motor units with the muscle cells. If you’ve ever felt sore after a workout, you have experienced the localized muscle damage from working out. Metabolic stress causes cell swelling around the muscle, which helps to contribute to muscle growth without necessarily increasing the size of the muscle cells.
Hormones are another component largely responsible for muscle growth and repair because of their role in regulating satellite cell activity. The IGF regulates the amount of muscle mass growth by enhancing protein synthesis, facilitating glucose uptake, repartitioning the uptake of amino acids (the building blocks of protein) into skeletal muscles and once again, activates satellite cells to increase muscle growth. In addition to that, different people have different genetics, which range from hormonal output, muscle fiber type and number, along with satellite cell activation, that can all limit muscle growth.


For muscle breakdown and growth to occur you must force your muscles to adapt by creating stress that is different than the previous threshold your body has already adapted to. I understand, muscle cells breaks down during work out and they rebuild later, ensuring muscle growth. Sometimes though a week off can help the body’s response to exercise as it not only rests your muscles but nervous system. Muscle loss though is based on different factors and is usually associated with how much muscle you have (if you have a lot, it might be harder to maintain it), your diet while not working out (the higher the protein and carbs, usually the less you’ll lose), your baseline hormonal levels and overall stress on your body. Skeletal muscle is composed of thread-like myofibrils and sarcomeres that form a muscle fiber and are the basic units of contraction. Motor neurons tell your muscles to contract and the better you become at having those signals tell your muscles to contract, the stronger you can get. These repaired myofibrils increase in thickness and number to create muscle hypertrophy (growth).1 Muscle growth occurs whenever the rate of muscle protein synthesis is greater than the rate of muscle protein breakdown.
This stress is a major component involved in the growth of a muscle and disrupts homeostasis within your body. This local muscle damage causes a release of inflammatory molecules and immune system cells that activate satellite cells to jump into action. Scientists used to question bodybuilders when they said the “pump” caused their muscles to become larger.
This is from the addition of muscle glycogen, which helps to swell the muscle along with connective tissue growth. Although most testosterone is bound in the body and therefore not available to use (up to 98%), strength training seems to help not only release more testosterone, but also make the receptors of your muscle cells more sensitive to your free testosterone. People will generally not see visible growth for several weeks or months as most initial changes are due to the ability of your nervous system to activate your muscles. To ensure you’re doing your best to grow muscle, muscle protein synthesis must exceed muscle protein breakdown. This is can be done by lifting heavier weights, continually changing your exercises so that you can damage more total muscle fibers and pushing your muscles to fatigue while getting a “pump.” After the workout is completed, the most important part begins which is adequate rest and providing ample fuel to your muscles so they can regenerate and grow.


When activated, they help to add more nuclie to the muscle cells and therefore contribute directly to the growth of myofibrils (muscle cells). What is interesting to note, though, is that some people known as “non-responders” in the study had 0% growth and had a concurrent 0% activation of their satellite cells. The stress and subsequent disruption in homeostasis causes three main mechanisms that spur on muscle growth. This doesn’t mean that you have to feel sore in order for this to happen, but instead that the damage from the workout has to be present in your muscle cells.
This type of growth is known as sarcoplasmic hypertrophy and is one of the ways that people can get the appearance of larger muscles without increases in strength. Testosterone can also stimulate growth hormone responses by increasing the presence of neurotransmitters at the damaged fiber site, which can help to activate tissue growth. For instance, men have more testosterone than women, which allows them to build bigger and stronger muscles. This requires that you take in an adequate source of protein (especially essential amino acids) and carbohydrates to help facilitate the cellular process of rebuilding broken down muscle tissue. That is, I feel that normal ache during the sets with freeweights and when reaching failure I feel the muscles burn. Muscle growth tends to occur more steadily after this initial period of strength gain because you are more easily able to activate the muscles. Therefore, it seems the more you can activate these satellite cells, the more you’ll be able to grow.
Visible muscle growth and evident physical changes in your body’s muscle structure can be highly motivational which is why understanding the science behind how muscles actually grow is important. I usually do all the sets until failure, but while a friend next day cannot move his worked out muscles, I feel absolutely nothing.



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