Muscle fibers can hypertrophy by increasing their cross section, that is, getting thicker. The mechanisms through which hypertrophy occurs are complex but what we are clear is that muscle fibers need a mechanical stimulus to grow. This stimulus is detected by mechanoreceptors adjacent to the muscle cell, which are involved in the large cascade of cell signaling events that induce muscle hypertrophy.
But do these events occur only by stimuli of a mechanical nature? Are there other stimuli to induce muscle hypertrophy? We are going to talk about this in this article, of how events of a chemical nature such as metabolic stress can also explain muscle hypertrophy.
What is metabolic stress?
Metabolic stress is defined as an accumulation of metabolites and by-products of glucose metabolism from anaerobic glycolysis and related to muscle contraction. We refer to metabolites such as lactate, hydrogen ions, inorganic phosphorus or creatine.
This circumstance in combination or not with muscular ischemia (reduction in blood flow) causes a high degree of metabolic stress, which has been theorized that it can mediate the hypertrophic response by causing alterations in the hormonal environment, cellular swelling (cell swelling), free radical production and increased transcription factors in cell signaling pathways involved in growth such as Akt / mTOR, MAPK or calcium dependent.
What happens at the cellular level?
As we mentioned, all the previous events can produce a high degree of cellular swelling which, although it still requires more research, can cause positive adaptations of the ultrastructure of the cell membrane. These improvements in the cell membrane would be explained through an increase in the internal pressure of the cell against it.
In this way, It is known that proper cell hydration prior to training is related to better responses at the level of protein synthesis and even with an optimization of amino acid transport.
How to apply metabolic stress to my training?
According to current research, maximum muscle mass gains are produced through training that produces significant metabolic stress without loss of mechanical stress during it.
This can be achieved through a program that covers a wide range of repetitions (6-20) and a multitude of series, generally between 7 and 11 per session and muscle group and between 10 and 20 throughout the week. Breaks between sets should ensure the most complete recovery possible to dissipate central fatigue and avoid unwanted reductions in the volume of training to accumulate or the load to be used.
As for the cadence of the repetitions to be executed, concentric contractions performed at the maximum intentional speed are recommended and more controlled eccentrics, preferably between two and four seconds long.
By last, microcycles or training weeks can be periodized where muscle failure is reached In some of the latest series of muscle groups to work. However, current research suggests that in most cases reaching muscle failure may be as effective as staying close to it, that is, one, two or three repetitions of it.
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