What do training theories tell us?

We will discuss training theories to understand the perspective from which you should view the process of muscle hypertrophy.

There are currently a couple of well-researched training theories that attempt to explain what is involved in the process that results in muscle hypertrophy.

The first is called the muscle damage theory; this theory states that when muscles are damaged by exercise.

• The resulting damage becomes a sequence of cascading signals that result in muscle hypertrophy.
• Although this appears to be the most widely supported theory, it does not seem to be the only one in sports science.

The other theory is called the substrate accumulation theory; the basis of this theory is that during exercise, various substances accumulate that can activate the muscle growth mechanism through the direct or indirect stimulation of anabolic hormone release.

Although both training theories have merit, one without the other leaves us with an incomplete explanation of the subject.

It is important to examine each of these theories and their possible stimuli in order to better understand them and use their principles to produce greater muscle growth.

Explanation and Understanding

In the usual scenario, it is possible to damage muscles; this can happen in different ways; muscle damage can occur through trauma and result in an injury such as a strain, separation, or muscle tear.

• This type of damage is, of course, harmful to the muscle and can result in weak points in the long term if it is not allowed to heal properly.

However, there is also trauma that induces microtears in muscle fibers, specifically during resistance training, which produces soreness or pain for a couple of days afterward, right?

Within the training theories, it was not long ago that we thought soreness was the result of a buildup of lactic acid in the muscle, but we now know that this is not the case.

Lactic acid causes the muscle contraction process to signal a stop in order to protect the muscle from damage.

The liver, heart, and slow-twitch fibers (red fibers) act as processors to metabolize lactic acid so that it can be quickly eliminated from our system.

The resulting soreness we feel is actually the result of the muscle damage that occurred during exercise.

More on training theories

Several studies have taken muscle biopsies before and after exercise and examined them with an electron microscope.

The myofibrils before exercise have a normal arrangement, but the myofibrils after exercise show a completely altered pattern.

This disruption is known as a “microlesion” or “microtears”; these tears appear to affect only a small percentage of the fibers in the muscle. Clearly, considerable force is required to cause these tears, such as that involved in moderate- to high-intensity resistance training (weights, cables, bands, etc.).

Within the training theories, it is established that these injuries also occur as a result of the eccentric contraction phase.

This explains why stimulating growth through maximum fiber recruitment requires:

• Those last two repetitions.
• Making a concentrated effort to lower the weight slowly.

Now, it is extremely important to visualize what is happening in the muscle in order to fully understand how it is functioning during the performance of resistance exercises.

Muscle damage occurs in two different phases; the first phase begins immediately after the exercise is completed.

Remember that the key points for progressing or achieving hypertrophy are time under tension (mechanical tension), metabolic stress, and muscle inflammation.

Phase 1 of muscle damage

In this phase, as stated in the training theories, the tension experienced by the muscle during contractions causes channels to open in the muscle fibers.

Especially during the eccentric part of the exercise, when the muscles lengthen, these channels allow calcium to flow into the muscle cell.

As a result of this influx, structures known as lysosomes are activated; the job of these “little guys” is to specialize in digesting proteins, and this results in the beginning of muscle breakdown.

Calcium also activates other types called phospholipase A2; the job of these enzymes is to make small holes in the muscle membrane.

The result of their work also causes an increase in the number of free radicals; basically, what is happening here is that once calcium enters the muscle cells, it activates a self-destruct mechanism within the muscle.

Phase 2 of muscle damage

It begins after three or four hours have passed; as a result of the damage from the first phase, the job of this second phase is to begin mounting an attack on the damaged area to clear away the remaining debris.

The release of inflammatory chemicals induces swelling in the damaged area, resulting in more pain. In addition, an increase in pain known as “next-day DOMS” is noticeable.

The result of all this cell membrane destruction is the opening of microscopic holes that allow other substances, such as growth factors, to escape from the cell.

Within the training theories it is predicted that through the release of these substances, growth factors affect protein synthesis in surrounding cells, and this process in turn may result in satellite cell proliferation.

Satellite cell proliferation

Satellite cells consist of only one nucleus, and protein synthesis takes place inside the cell’s nucleus.

Growth factors can cause satellite cells to combine with damaged cells and help damaged cells synthesize proteins more efficiently.

Satellite cells can fuse with one another and create new muscle cells in a process known as hyperplasia.

What all this means is that when cells are damaged by exercise, several processes take place to release growth factors, and this results in satellite cells combining with other cells to create new muscle cells.

They can also fuse with existing muscle fibers to promote the repair process by improving protein synthesis.

The muscle damage theory is very popular and has many supporters among those who discuss training theories; it is fair to point out that it is not without weaknesses.

• One point that seems to stand out is the assumption that the signal for muscle growth is muscle damage;
• Under this hypothesis, anything that reduces the amount of muscle damage should also reduce the corresponding muscle hypertrophy.