Cómo se produce la hipertrofia muscular

How does muscle hypertrophy occur?

When we combine science and reality to understand how muscle hypertrophy occurs, we need to clarify things, as Roberto Castellano does.

Muscle hypertrophy refers to an increase in the cross-sectional diameter of muscle fibers, which means a greater number of contractile actin and myosin filaments, generated to a greater extent through protein synthesis.

By definition, muscle hypertrophy is an increase and growth of muscle cells, achieved through exercise.

To recap, there are two types:

  • Myofibrillar / Sarcomeric: growth of muscle contractile components.
  • Sarcoplasmic: increased muscle glycogen storage.

Which type you should focus on depends on your fitness goals, as sarcomeric training will help with strength and speed, while sarcoplasmic growth helps give your body more sustained energy for athletic endurance events.

The way you lift a weight or exercise with a resistance-producing accessory (including your body weight) will determine how your muscles grow and change; obviously, achieving muscle hypertrophy requires knowledge.

For example, you can develop muscle tone with a lighter weight, but it will require a large number of repetitions to improve the efficiency of the muscle fibers.

Unless you perform a set of repetitions to the point of fatigue or technical/muscular failure, you will not achieve much muscle definition with this training style.

On the other hand, using a heavy weight is an effective way to stimulate the growth and definition of muscle fibers. It is also a more efficient way to train, but, obviously, periodization comes into play here, requiring periodic changes in volume or intensity.

Muscle hypertrophy: how can you develop it?

To build muscle through weightlifting or the use of accessories, you need both mechanical damage and metabolic fatigue.

When you lift a heavy weight, the contractile proteins in your muscles must generate force to overcome the resistance provided by the weight.

In turn, this can result in structural damage to the muscles.

  • Mechanical damage to muscle proteins stimulates a repair response in the body.
  • Damage to the proteins in muscle fibers results in increased muscle size.

Mechanical fatigue occurs when muscle fibers deplete the available supply of ATP, an energy component that helps muscles contract. When you can no longer fuel muscle contractions or lift the weight correctly, this also leads to muscle hypertrophy or an increase in lean mass.

Both mechanical damage and metabolic fatigue are important for achieving muscle hypertrophy.

You do not need to train your muscles to the point of what is called “failure,” which means being unable to complete another repetition to achieve the results you want.

On the other hand, a 2010 study found that to achieve maximum gains, significant metabolic stress on the muscles is necessary, in addition to a moderate degree of muscle tension (1).

In this study, the researchers found that exercises involving shortening movements (concentric) at fast to moderate speeds for 1–3 seconds and lengthening movements (eccentric) at slower speeds (2–4 seconds) are highly effective.

An example of a concentric movement is lifting the weight toward the shoulder during a biceps curl; returning to the starting position would be eccentric, but this concept is very clear among both beginners and advanced athletes.

Muscle hypertrophy: how often should you train?

How often you need to exercise to achieve muscle hypertrophy also depends on your goals, and biological individuality plays a key role in this, because every body is different.

However, there are splits you can use:

  • Train (especially with heavy weights) three days a week: this allows a day between sessions for your muscles to recover. Here, recovery is essential for muscle growth.
  • Train each muscle group only two days a week, depending on your current fitness level.
  • Alternatively, you can alternate upper-body and lower-body training on different days. This allows you to work different muscles while giving yourself time to rest and recover.

Regarding training frequency, let us recap briefly. Here we show you a video by Raúl Carrasco, who provided us with a summary of this topic, which, in addition to being controversial, is crucial for achieving results.

Now, regardless of everything that can be generated depending on each training program, let us delve a little deeper into muscle hypertrophy.

Sarcomeric muscle hypertrophy

Myofibrils are essentially bundles of myofilaments (the contractile parts of a muscle, the parts that pull); they are found in every skeletal muscle fiber.

Each muscle cell contains many myofibrils. Myofibrillar or sarcomeric hypertrophy occurs due to an overload stimulus (lifting more than your body is accustomed to) that causes trauma to individual muscle fibers.

Your body treats this as an injury and, as such, overcompensates during the recovery process by increasing the volume and density of the myofibrils so that the “injury” does not happen again.

This is one of the reasons why you must maintain progressive overload to continue making gains.

Sarcomeric hypertrophy generally occurs in the range of 6 to 8 repetitions (using a weight that allows you to complete only 6 to 8 repetitions per set).

This type of muscle hypertrophy occurs when myofibrils increase (an increase in muscle fiber size and muscle fiber count).

This type of muscle is extremely dense and hard; a muscle consisting mainly of sarcomeric hypertrophy feels as hard as a rock in a contracted state. This increases your strength exponentially as the amount of muscle fiber increases and the size of the muscle fibers increases.

Sarcoplasmic muscle hypertrophy

The sarcoplasm consists of the energy sources and fluids surrounding the myofibrils in the muscle; it includes elements such as ATP, glycogen, creatine phosphate, and water.

An increase in the size of the blood vessels that supply blood to the muscles can also be included in sarcoplasmic hypertrophy and is commonly known as capillarization.

This occurs in the same way as myofibrillar hypertrophy, through your body overcompensating during the recovery phase after your energy sources have been depleted during a workout.

At this stage, you must increase your energy stores, such as ATP and glycogen, to prevent exhaustion during training.

In this type of muscle hypertrophy, the muscles’ sarcoplasm (fluid inside the cell membrane) increases.

There is no increase in myofibril (muscle fiber) size, and no new myofibrils are created; the only increase is in the volume of sarcoplasm (fluid inside the cell) per cell, and this occurs in a range of 9/10 to 15 repetitions per set.

Any repetition range above 15 repetitions per set will begin to work on your muscles’ endurance capacity and will begin to become an aerobic rather than anaerobic exercise.

It should also be noted that any repetition range between 1 and 5 per set increases one-repetition maximum strength (or power) as your body adapts to the greater amount of weight used.

Here, you can recruit nearly all the available muscle fibers, which puts you into a state of neuromuscular efficiency. However, there are no gains in size or endurance within the very-low-repetition range.

Sarcomeric training

Strength training with more than 80% of your 1RM, repetitions in the 3–8 range, and 2–4 minutes of rest produces the greatest changes in myofibrillar/sarcomeric volume and density.

Therefore, if you want to achieve sarcomeric muscle hypertrophy, you must lift heavy weights.

  • The heavier the weights you lift, the more muscle fibers are recruited and, in turn, damaged
  • However, it is recommended to keep repetitions at a minimum of 3–5, as it is primarily neuromuscular adaptations that improve strength (2) (Zatsiorsky, 1995).

In fact, doing few repetitions is essential for achieving maximum growth, as you reach the adaptations every bodybuilder desires. (3) (Charles Poliquin 1997).

Sarcoplasmic training

Sarcoplasmic muscle hypertrophy is achieved through what is known as fatigue training.

Fatigue training consists of training at an intensity of approximately 75% of your 1RM, with repetitions in the 9/10–15 range and short rest periods of 45–90 seconds.

It is known as fatigue training because it rapidly and directly uses up much of the energy stored in muscle cells and fatigues the muscles.

In this scenario, you should consider time under tension when choosing the number of sets for your workouts.

  • A minimum amount of time under tension is required for muscle hypertrophy to occur.
  • Because of this, you generally need to complete more total sets for a strength-training routine than for a higher-repetition fatigue-training routine.

In fatigue training to achieve muscle hypertrophy, the time under tension must be longer than the immediately available energy.

In this case, the most immediate energy source for short-term anaerobic exercise is the ATP and creatine phosphate stores; however, these are very short-term and, as such, will be depleted in 7–10 seconds.

After this, your body will break down glycogen for energy, producing lactic acid (which causes the burn you feel).

Therefore, you should maintain a time under tension of more than 10 seconds per set during fatigue training, and you can achieve this by including slower repetitions; methods such as supersets targeting the same muscles are an excellent way to do so.

To explore this fascinating topic further, take a look at this introductory video developed by Roberto Castellano, which also discusses satellite cells.

Repetitions and types of hypertrophy

There is a spectrum through which muscle hypertrophy of the myofibrils and sarcoplasmic hypertrophy, which we have already discussed, occur, but in summary:

  • 1–5 repetitions: leads to a maximum increase in relative strength and myofibril recruitment.
  • 6–8 repetitions: produces the best middle ground between myofibrillar and sarcoplasmic hypertrophy.
  • 9–12 repetitions: maximizes sarcoplasmic hypertrophy.
  • More than 15 repetitions: moves into the muscular endurance range, where hypertrophy is gained slowly.

Myofibrillar damage will not stop occurring above 12 repetitions; it will simply occur to a lesser degree, with less muscle fiber recruited than at lower repetitions.

Put another way, why would you want to train in a repetition range in which you do not achieve maximum gains in sarcoplasmic or sarcomeric hypertrophy?

The point is that when you can train both to their maximum potential without diminishing the gains of the other type of muscle hypertrophy, you would achieve efficiency.

Well, then sarcomeric hypertrophy is best achieved through strength training and sarcoplasmic hypertrophy through fatigue training. What is the best way to achieve both?

To answer the question, you can seek advice from one of two bodybuilding giants, and it depends on the individual.

References

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