Muscle Hypertrophy: How do Muscles Grow?


What makes the muscles grow (muscle hypertrophy)? Simply stated, when the human body is brought up against something heavy that causes a struggle in the muscles involved, it lends to develop stronger and bigger muscles the next time. This is so that lesser effort will be required the next time the same challenge comes up.

Hypertrophy is just a medical term that is synonymous for enlargement or growth of various areas in the body that may be muscles, organs, skins etc. But, a person only trains for the enlargement of his/her muscles and that is exactly the subject of this article. Call it muscle hypertrophy, call it muscle growth; it is a process that is adaptive in nature and needs to be stimulated for proper growth. The demands are necessary for every person on the planet and no one can naturally induce hypertrophy without meeting them.

What is the definition of muscular hypertrophy?

From a physiological point of view it is generally accepted that muscles increase in size through a process known as hypertrophy. This is an increase in the size of muscle fibers and you should not confuse this process with muscle hyperplasia, an increase in the number of muscle fibers. Muscular hypertrophy occurs when we work at high intensities, causing muscular fatigue and damage. It is this fatigue (reduction in energy stores such as ATP and glycogen, along with metabolic stress) and damage (microtrauma to individual muscle fibers) that stimulate the repair process that results in muscle growth.

The intensity of effort dictates the level of muscle tissue breakdown and determines the recovery time necessary for optimum muscle repair and growth. Therefore, there must be an appropriate period of recovery for the muscle tissue to completely heal and repair itself. This recovery is known as supercompensation.

muscle fiber growth

If an athlete allows an adequate to optimal amount of time for recovery and takes in proper nourishment, the “dam­aged” muscle tissue will respond by getting stronger and larger. This is what we call the adaptation principle or, more explicitly, the specific adaptation to imposed demand (SAID) principle.

Virtually all muscle hypertrophy results from an increase in the number of actin and myosin filaments in each muscle fiber, causing enlargement of the individual muscle fibers; this condition is called simply fiber hyper­trophy. Programmes designed to encourage hypertrophy have to maximize both load, to cause muscle damage, and volume, to stimulate muscular fatigue.

The three phases of muscle growth

For muscular mass to increase, three distinct phases must take place.

1) Adequate muscle stimulation

First, growth must be stimulated within the body. As we’ve learned, this can only he accomplished through subjecting your muscles (and, more specifically, your nervous system) to a high level of muscular output – a great amount of work in a unit of time. This is what we call the concept of progressive overload.

The progressive overload principle slates that to induce muscle growth (muscular hypertrophy), you must exercise at a level beyond the point to which your muscles are accustomed. In other words, your training session should challenge you physically. You should struggle with the weights. You will need to consistently boost the training stimulus or load at a rate that is compatible with the training-induced adaptations that are occurring. Following the principle of progressive overload requires that you provide your muscles with a new stimulus when they have adapted to the current overload. You can do this in a variety of ways. You’re free to increase the resistance, increase the number of repetitions, or increase the number of sets for a given muscle group.

When providing an overload, select one of these options at a time. Although you want to provide a new stress on the muscle, you do not want to overtax the muscle or supporting structures to the point of injury.

Although every training session does not have to be more intense than the last ses­sion, the principle of progressive overload states that the training program needs to be increased gradually over time to realize gains. For example, if you have been able to easily complete a given workout for a couple of exercise sessions, it may be time to make changes to provide an overload once again in order to keep the resistance training program fresh, challenging, and effective.

2) Phase of recovery

The second phase is that of recovery. Both the body and the systems that feed the body must be given time to clean up the metabolic waste products of the workout and to replenish their energy reserves after a very draining maximum-overload workout. In fact, we’ve recently learned that completing this process can take anywhere from two or three days to six weeks or more, depending upon the level of muscular output employed during the training session and the subject’s innate adaptability to exercise.

3) Growth process itself

The third and final phase is the growth process itself. This process will take place only after the recovery process has run its course. At least one study indicated that the actual growth of muscle may occur in as little as fifteen minutes during deep. However, you must remember that in no case will muscle growth occur until adequate stimu­lation has been achieved and total recovery is complete. There is no way to force your body to skip steps one and two. It’s always stimulate, recover, grow. Stimulate, recover, grow.

muscle hypertrophy explainedWhat are the necessary conditions for muscle hypertrophy to occur?

Training with relatively heavy weights

Only training with relatively heavy weights leads to microscopic damage in the fibers of the working muscles and according to the theory of progressive overload and adaptation, it’s the body’s natural repair and regeneration process which leads to the increase in muscle mass.

Rest between training sessions

Nothing is worse for muscle growth than working them out before they have recovered from the previous work out. This can actually hinder their ability to grow, which will make the next work out pointless.

A rest period of at least 48 hours between weight training sessions which target the same muscle groups is crucial. This is the minimum amount of time it takes for the body to repair the damage. It is for this reason that the majority of training programs designed specifically for the purposes of muscle gain favor a split training approach, targeting a different group of muscles in each session.

Increasing intensity gradually over time

Asking a muscle group to lift or move an increasing amount of weight on a regular basis creates the need for your body to adapt by gaining the strength needed to cope with the new demands being placed upon it. The gain in strength is often the gain in size as stronger muscle fibers are “bigger” muscle fibers. This is why gaining muscle takes time. It takes regular, repeated overload to initiate an adaptation response, and it takes adequate rest and recovery between training sessions to generate the maximum gains in terms of strength and mass.

That’s why it’s important over time to increase the repetitions or weights of an exercise. This increase forces the muscles to rebuild even stronger. If you keep the same number of reps or the same amount of weight for too long a period, the muscles become complacent and no new growth occurs. That’s why you have to increase intensity as your training continues.

Providing building blocks for the muscles to be rebuilt from

What does the body need as those building blocks? The answer is simple: Protein. Growth can only occur if the muscle protein synthesis outranks the muscle protein breakdown. We don’t mean that you need to start drinking massive amounts of protein shakes. However, it’s vital that you eat more protein than your normally would.

Otherwise, no matter how many reps you do, your muscles have nothing to rebuild with.

You don’t need to go crazy and start counting portions. As a general rule, increase your protein intake whenever you are exercising. It will ensure that your muscles grow back quickly. Thus, if you want to grow muscle, you must accomplish this task.

Getting enough sleep

Sleep, time off working out those muscles, and food are vital when it comes to muscle recovery; use them effectively and you will be ready for the next time that you go to the gym.

muscular hypertrophy processWhat is muscle atrophy?

Muscle atrophy and muscle hypertrophy are scientific terms which basically refer to muscle wastage (atrophy) and muscle growth (hypertrophy).

Muscle hypertrophy will not continue indefinitely. If muscle stimulation does not progress, then the body has no reason to adapt and so it will remain at that level. It is often the reason why people get frustrated at their attempts to get fit; the body will always strive for homeostasis.

Conversely, inactivity will lead to atrophy. As we age, our bodies naturally go through this process and this is especially prevalent in the elderly, who will generally exhibit low levels of muscle mass in the limbs and a predisposition to brittle bones. However, muscular atrophy can occur at any age where inactivity means that there is little reason for the body to maintain muscle tissue. The saying “use it or lose it” is a very true one!

Putting it together: Muscle hypertrophy

Building muscle is the goal of many individuals embarking on an exercise routine. Men generally ask to build muscle, often in the upper body for a better physique and in some instances to increase strength and gain weight to enhance sports performance.

Muscular hypertrophy is the process of increasing muscle size. The process itself isn’t as complicated as some authors may have led you to believe. It occurs as a direct result of demands placed upon a muscle and the nervous system that is attached to it. The signal for hypertrophy is overload, that is, making the muscle work harder than it is normally accustomed to. To overload a muscle, you need to apply a load or a resistance for the muscle to contract against. That resistance must be progressive from one workout to the next.

The process the body goes through is that of compensation. It will remodel its bone, connective tissue, and muscle size in anticipation of a similar bout of effort in the future, thereby safeguarding itself from future discomfort or possible injury.

That’s it. The bottom line in the quest for bigger and stronger muscles is progressive resistance. If you’re able to increase your resistance by your next workout, it’s because your muscles have overcompensated from your previous training session by getting bigger and stronger.

About Author

Hey! My name is Kruno, and I'm the owner and author of Bodybuilding Wizard. I started this website back in late 2014, and it has been my pet project ever since. My goal is to help you learn proper weight training and nutrition principles so that you can get strong and build the physique of your dreams!

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