How Do Muscles Grow? The Science Of Muscle Growth - BuiltLean (2023)

How Do Muscles Grow? The Science Of Muscle Growth - BuiltLean (1)

If you’re the typical guy in the gym working with weights, not only do you want 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. Skeletal muscle is composed of thread-like myofibrils and sarcomeres that form a muscle fiber and are the basic units of contraction.

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. 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.

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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. This is why some powerlifters can be relatively smaller compared to bodybuilders, but can lift significantly more weight. Motor Unit recruitment also helps to explain why, after practice, certain movements become easier to perform and most of the initial strength gains will be when you first start to lift weights. Muscle growth tends to occur more steadily after this initial period of strength gain because you are more easily able to activate the muscles.

The Physiology Of Muscle Growth

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. 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 adaption, however, does not happen while you actually lift the weights. Instead, it occurs while you rest.

So how do you actually add muscle to your muscle cells? This is where Satellite cells come in and act like stem cells for your muscles. When activated, they help to add more nuclei to the muscle cells and therefore contribute directly to the growth of myofibrils (muscle cells). Activating these satellite cells may be the difference between what allows certain “genetic freaks” to grow massive muscles and what makes other people “hard-gainers.2

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. Modest responders, who had a 28% growth, had 19% activation of their satellite 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. Therefore, it seems the more you can activate these satellite cells, the more you’ll be able to grow. So then the question becomes, how do you activate these satellite cells to increase muscle growth?

3 Mechanisms That Make Muscles Grow

Underlying all progression of natural muscle growth is the ability to continually put more stress on the muscles. This stress is a major component involved in the growth of a muscle and disrupts homeostasis within your body. The stress and subsequent disruption in homeostasis causes three main mechanisms that spur on muscle growth.

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1. Muscle Tension

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. How do you do this? The main way is to lift progressively heavier weights. This additional tension on the muscle helps to cause changes in the chemistry of the muscle, allowing for growth factors that include mTOR activation and satellite cell activation.3

Muscular tension also most dramatically effects the connection of the motor units with the muscle cells. Two other factors help to explain why some people can be stronger, but not as big as other people.

2. Muscle Damage

If you’ve ever felt sore after a workout, you have experienced the localized muscle damage from working out. This local muscle damage causes a release of inflammatory molecules and immune system cells that activate satellite cells to jump into action. 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. Typically soreness is attenuated over time by other mechanisms.

3. Metabolic Stress

If you’ve ever felt the burn of an exercise or had the “pump” in the gym, then you’ve felt the effects of metabolic stress. Scientists used to question bodybuilders when they said the “pump” caused their muscles to become larger. After more investigation, it seems as though they were onto something.

Metabolic stress causes cell swelling around the muscle, which helps to contribute to muscle growth without necessarily increasing the size of the muscle cells. This is from the addition of muscle glycogen, which helps to swell the muscle along with connective tissue growth. 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.

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So now that you know the three main mechanisms of muscle growth, the next question is: how do hormones affect muscle growth?

How Do Hormones Affect How Muscles Grow?

Hormones are another component largely responsible for muscle growth and repair because of their role in regulating satellite cell activity. Insulin Growth Factor (IGF)-1, in particular Mecho-Growth Factor (MGF) and testosterone are the two most vital mechanisms that promote muscle growth.4

Testosterone is the main hormone that most people think about when working out with weights, and there seems to be some validity to the thought that testosterone increases protein synthesis, inhibits protein breakdown, activates satellite cells, and stimulates other anabolic hormones. 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. 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.

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.

Why Muscles Need Rest To Grow

If you do not provide your body with adequate rest or nutrition, you can actually reverse the anabolic process and put your body into a catabolic or destructive state. The response of muscle protein metabolism to a resistance exercise bout lasts for 24-48 hours; thus, the interaction between protein metabolism and any meals consumed in this period will determine the impact of the diet on muscle hypertrophy.5 Keep in mind there is a certain limit on how much your muscles can actually grow dependent on gender, age, and genetics. For instance, men have more testosterone than women, which allows them to build bigger and stronger muscles.

(Video) How muscles grow

Why Rapid Muscle Growth Is Unlikely

Muscle hypertrophy takes time and is relatively slow for the majority of people. 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.

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. To ensure you’re doing your best to grow muscle, muscle protein synthesis must exceed muscle protein breakdown. 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. 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.

How Muscles Grow: Conclusion

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. 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.

Have any questions about how to get muscles to grow? Leave a comment below.

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(Video) The Scientific Secret of Strength and Muscle Growth

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FAQs

How do you force muscle growth 5 science based methods? ›

Find out how to force muscle growth with these 5 science-based methods.
...
Sometimes, one way to overload is not as good as the other, depending on the exercise.
  1. Load. If you are a beginner, this is the best answer on how to force muscle growth: by adding more weight to your lifts. ...
  2. Reps. ...
  3. Sets. ...
  4. Tempo. ...
  5. Form.
Feb 16, 2022

What stimulates muscle growth the most? ›

Resistance training (RT) is a primary exercise intervention used to develop strength and stimulate muscle hypertrophy. Increases in muscle mass constitute key components of conditioning in various sports due to the correlation between muscle cross-sectional area and muscle strength [1,2].

What are the 3 main factors needed for muscle growth? ›

According to the exercise physiologist Brad Schoenfeld, there are three primary mechanisms of muscle growth: Muscle tension, metabolic stress and muscle damage. Oftentimes all of these factors are correlated with the amount of weight you lift.

What is the main ingredient for muscle growth? ›

Protein is the main nutrient involved in muscle building. It's also involved in muscle repair after a workout and almost all regular body functions.

What chemical helps build muscle? ›

The most common muscle-building supplement there is can be found right in your fridge. It's called protein. When you eat protein, your body breaks the protein down into amino acids. Those amino acids are then used to repair and grow new muscle fibers.

How quickly can you gain muscle stronger by science? ›

How fast can I build muscle at first? In a huge analysis of over 200 studies (conducted primarily on untrained people), the average rate of increase in muscle cross-sectional area was roughly 0.1-0.2% per day.

Can you force your body to build muscle? ›

You can make incredible muscle gains by doing the same proven, mass-building exercises every week, steadily increasing weight and reps (overload).

What are 5 steps you should take to build muscle mass? ›

The 5 Essentials of Muscle Building
  1. Take in more calories than you burn.
  2. Lift progressively more weight.
  3. Give your body sufficient recovery time.
  4. Here are five actionable tips for building muscle, whether you are a veteran of the iron or a newcomer to the gym:
  5. Lift more weight.
  6. Add more protein to your diet.
  7. Get enough rest.

What actually grows muscle? ›

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. These repaired myofibrils increase in thickness and number to create muscle hypertrophy (growth).

What really grows muscle? ›

Muscle hypertrophy occurs when the fibers of the muscles sustain damage or injury. The body repairs damaged fibers by fusing them, which increases the mass and size of the muscles. Certain hormones, including testosterone, human growth hormone, and insulin growth factor, also play a role in muscle growth and repair.

What is the most important nutrient for muscle growth? ›

Protein. Protein is one of the most essential macronutrients for muscle growth and repair because it's packed with amino acids that your body does and doesn't produce. That's why it's important to have protein post-workout to restore these muscle-building macronutrients.

What causes the most muscle growth? ›

Muscular hypertrophy involves increasing muscle size, typically through strength training. Putting strain on the muscles through working out causes the body to repair them, resulting in an increase in muscle fibers. Having more muscle fibers will lead to greater strength and muscle size.

Do sore muscles mean growth? ›

Muscle soreness is related to muscle damage, which can promote, but is not required for, muscle growth. In a nutshell, unless your goal is to feel sore, then you don't need to be sore after every workout.

Which vitamins build muscle? ›

Vitamin B6, folate and B12 are arguably the most important B vitamins when it comes to muscle growth and recovery! Both vitamins B6 and B12 have a direct role in protein metabolism.

What drinks make your muscles stronger? ›

What drinks are good for muscles and joints?
  • Balance Mineral Drink.
  • Plain water.
  • Green tea.
  • Smoothies.
  • Tomato juice.
  • Cherry juice.
Jul 23, 2019

What can I drink to rebuild muscle? ›

The 10 Best Muscle Recovery Foods and Drinks
  • Tart cherry juice. Drinking tart cherry juice may benefit both trained athletes and novice gym-goers alike. ...
  • Watermelon and watermelon juice. Watermelon is sweet, hydrating, and loaded with nutrients. ...
  • Fatty fish. ...
  • Pomegranate juice. ...
  • Beet juice. ...
  • Whey protein shakes. ...
  • Eggs. ...
  • Dairy.
Aug 19, 2021

How long does it take to build 1 pound of muscle? ›

Most beginners will see noticeable muscle growth within eight weeks, while more experienced lifters will see changes in three to four weeks. Most individuals gain one to two pounds of lean muscle per month with the right strength training and nutrition plan.

Should you lift weights everyday? ›

You might find it hard to recover from workouts if you lift every day. Inhibited recovery: Perhaps the biggest downfall to daily strength training is that your body doesn't get a real chance to recover. This can lead to muscle overuse injuries or issues with muscle imbalances if you don't carefully plan your workouts.

How many reps to build muscle? ›

Reps for muscle growth

In order to get bigger and stronger, you must ensure your muscles work harder than they are used to. Generally, between 6-12 reps for 3-6 sets will help to build overall muscle size.

What muscle is harder to build? ›

Calves. Calf muscles are also considered as one of the most difficult to grow in the gym, to the point where many people give up trying. It turns out that the lower leg muscles are not that significantly different from other skeletal muscles.

Is built muscle permanent? ›

Your muscles will always be able to shrink and grow depending on your lifestyle, but some of the adaptations you make while building muscle will improve your musculature forever. If you can accumulate enough of those changes, you'll find that your new set point is far more lean and muscular than it was before.

Can muscles get bigger without getting stronger? ›

During this honeymoon period, even the most poorly designed workout programs can produce noticeable changes in your physique. That's why research shows that when you're new to resistance training, getting stronger does produce muscle growth, but you don't have to gain much strength to gain size.

What exercises build muscle faster? ›

Perform compound exercises

To maximize your muscle-building capability, perform multi-joint compound lifts, suggests Williams. “These lifts include chest press, overhead press, row, deadlift, and squats,” she says. “They recruit more muscle groups and the most muscle fibers, giving you the biggest bang for your buck.

What is the secret to big muscles? ›

Protein with Each Meal Helps Boost Muscle Mass

You need protein to build and maintain muscle mass. To achieve this, you should be looking to eat at least 1g per 454g of body-weight. That's 200g/day if you weigh 91kg. The easiest way to get this amount is to eat a whole protein source with each meal.

What foods to avoid when building muscle? ›

Avoid or limit alcohol, foods with added sugars and deep-fried foods. In addition to your diet, whey protein, creatine and caffeine can be useful supplements.

Why is peanut butter good for building muscle? ›

Just one tablespoon of peanut butter has four grams of protein, making it a good source of protein for building muscle. Peanut butter is also a good source of monounsaturated fat and antioxidants as well as vitamins and minerals that will help your body stay healthy and function properly.

What chemical causes muscles to contract? ›

When the nervous system signal reaches the neuromuscular junction a chemical message is released by the motor neuron. The chemical message, a neurotransmitter called acetylcholine, binds to receptors on the outside of the muscle fiber. That starts a chemical reaction within the muscle.

What forces cause muscles to grow? ›

Lifting weights applies three types of stress to muscle fibers that signal for them to grow: mechanical tension (which you may have heard called “volume”), metabolic stress (think: “the burn” which comes from decreasing the pH in working muscles), and muscle damage [6].

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1. how muscles grow
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2. Muscle Regeneration
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3. How To Build Muscle (Explained In 5 Levels)
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4. Science of Bodybuilding and Muscle growth
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5. What Happens to Your Body When You Start Exercising?
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