Metabolic Stress: Definition, Causes And Consequences

Does the concept of metabolic stress sound familiar to you? Do you relate it to physical exercise? This concept refers to an organic process and, at the same time, to a factor that allows you to gain muscle mass (that is, increase the size of the muscle). Thus, it is a process that leads to muscle hypertrophy.

Muscle hypertrophy is the growth of the muscle, that is, an increase in its size, the number of myofibrils (made up of actin and myosin filaments) that make up the muscle, or both variables. But what else do we know about metabolic stress? Why does it appear and what are its consequences? Is it enough to increase muscle mass? Can we resort to other processes? 

Metabolic stress and muscle hypertrophy

As we have seen in the introduction, metabolic stress is an organic process that facilitates muscle hypertrophy. We could say that hypertrophy is what bodybuilders or people who work to increase their muscle mass are looking for. As a summary, we could achieve this effect through:

• Muscle damage
• Metabolic stress
• Mechanical stress.

Mechanical tension produces muscle damage and an inflammatory response, which would be the one that would enhance the release of muscle growth factors. Thus, the muscle would enlarge.

On the other hand, according to studies, the maximum gain in muscle mass is achieved through metabolic stress without losing mechanical tension.

How does metabolic stress arise?

Metabolic stress appears when we increase the workloads on a muscle or a certain group of muscles. This causes a progressive increase in muscle growth. 

At the chemical level …

That is, we load the muscle and generate a process called anaerobic glycolysis, which produces adenosine triphosphate (ATP). ATP is the energy you need to train. This process is what allows us to obtain the energy necessary to perform muscle contractions from glucose molecules, in a state of oxygen deprivation or insufficiency.

Why does all this occur? Because the speed with which we need this energy is greater than the rate at which glucose is oxidized with oxygen; thus, it is a fundamentally anaerobic process.

Accumulation of metabolites

Specifically, the metabolic stress that we attribute to exercise appears as a consequence of the accumulation of metabolites. Metabolites are compounds that are produced by the breakdown of nutrients.

Its function is to provide the body with the type of energy it needs, especially during resistance training. All of this would cause the muscle hypertrophy response. 

The main metabolite that accumulates thanks to the metabolite stress process is lactate, a glucose metabolite produced by body tissues under conditions of insufficient oxygen supply. Other metabolites that we find in this process are: phosphate, hydrogen and the glucose metabolite (anaerobic glycolysis), among others.

Consequences

What happens when these products accumulate in the body? According to a study by Takarada et al. (2000), this could increase the secretion of several anabolic hormones. The anabolic hormones are: testosterone, somatotropin or growth hormone (STH or GH) and insulin.

On the other hand, according to a study by Ebbeling et al. (1989), the increase in waste products together with a deficiency of energy substrates (ATP), can cause muscle damage. 

The importance of doing repetitions

One of the recurring practices of athletes in their training and, especially of bodybuilders, is the performance of repetitions in their exercises, in addition to attending an intense level of training. But what happens when we train at very intense levels? That the oxygen demand exceeds the supply.

In fact, it is believed that the lack of oxygen, also called hypoxia, in certain muscle cells, is a key factor that would explain why certain intervals of repetition of exercises when we train lead to greater muscle growth or muscle hypertrophy. 

Therefore, performing repetitions during exercises, as well as reducing breaks (to a few minutes) can be interesting if we want that accumulation of metabolites to be much greater and, as a consequence, the anabolic response is also so. In this way, the hypertrophy achieved would also be greater.

Final thoughts

As we have seen, when it comes to gaining muscle mass or achieving muscle hypertrophy, not only metabolic stress is used, but also other processes. These include: exerting muscle tension and causing muscle damage intense enough to stimulate muscle growth.

Metabolic stress is an organic process that would explain, in part, why the increase in muscle size occurs. In this article we have been able to learn a little more about the operation of this process, although if you want to train in the healthiest and most effective way possible, it is best that you go to a professional specialized in the matter.