Artículo: Hipertrofia sarcoplasmática

[Hiperius]

Bueno, aquí os dejo un artículo de Dan Moore sobre el Sarcoplasma y varios estudios que demuestran que ambas hipertrofias, miofibrilar y sarcoplasmáticas, no se pueden separar. Aqui os dejo la traducción hasta donde tenía ganas y después el texto original completo:

¿Que es el Sarcoplasma?

Dentro del sarcoplasma existen componentes solubles (o acuosos), que forman el 80 por ciento del mismo; éste está compuesto de iones y macromoléculas solubles como enzimas, hidratos de carbono, sales diferentes y proteínas, así como una gran proporción de ARN. Este componente acuoso puede ser más o menos parecido a un gel o líquido dependiendo de la condición y las fases de actividad de la célula. En general, las regiones del margen de la célula son parecidas a un gel y el interior de la célula es el líquido.

Los componentes insolubles del sarcoplasma son orgánulos (como las mitocondrias, cloroplastos, lysosomas, peroxisomas, ribosomas), varios vacuolas, cytoesqueletos así como estructuras complejas de la membrana (p.ej. el reticulo sarcoplásmatico).

La fracción de la proteína del músculo que compone el citoplasma (sarcoplasma en una célula del músculo) se compone sobre todo de las enzimas que participan en metabolismo de la célula, como la conversión de energía anaerobica de glucógeno a ATP, el transporte intracelular, y varias otras funciones de enzima. Esta fracción forma aproximadamente el 25 o el 30 % de la proteína total del músculo frente a la más grande y más hablada proteína estructural (la proteína miofibrilar), que forma aproximadamente el 40 %.

Proteína de músculo esquelético

Hablando de síntesis de proteína una de las cosas que primero deben ser identificadas es de que fracción de proteína hablamos.

La síntesis de proteína corporal es un promedio de las tarifas de síntesis de varias proteínas en los tejidos diferentes del cuerpo, la piel, el músculo, órganos, y el plasma.

La proteína muscular mixta es un promedio de las tarifas de síntesis de proteínas de músculo totales e incluye mitochondrial, sarcoplasmica, componentes estructurales y proteínas de tejido conectivo.

La proteina Myofibrillar es un comprendido de proteínas individuales como myosina, actina, titina, tropomyosina, troponina, la proteína C, y algunos componentes de proteínas mitochondrial.

Las proteínas sarcoplasmáticas son sobre todo enzimas que participan en el metabolismo de célula. Sin embargo, si los orgánulos dentro de las células de músculo se rompen, ésta fracción de proteína también puede contener las enzimas metabólicas localizadas dentro del reticulo sarcoplasmático, mitocondrias y lysosomas.

La Síntesis de Proteína Fraccionaria

Ahora sé desde hace algún tiempo que la elevación crónica en la síntesis de proteína por encima de la de degradación de proteina tiene suma importancia en la hipertrofia del músculo esquelético (1,2). Esto es la razón por la que comenzamos este artículo, para examinar como la alimentación y el ejercicio afectan al volumen de sintesis/degradación de la proteina muscular.

El entrenamiento de resistencia ha mostrado cambios muy fuertes en el volumen de sintesis/degradación de proteína (4,5) y la mayor parte de los estudios han usado la proteína de músculo mixta como la medida de eficacia. Lamentablemente este método no demuestra como la resistencia o el ejercicio dinámico que se entrena de manera diferente afectan cada fracción.

En un estudio que mira si la edad afecta a la Síntesis de Proteína (6) fue notado que hacia el final de 2 semanas de ejercicio de levantamiento de pesos, MHC y tarifas de síntesis de proteína mixtas aumentó tanto en participantes más jóvenes como en más viejos. La tarifa de síntesis de proteína actina fue aumentada después del ejercicio en sólo el grupo más jóven. La magnitud del aumento inducido por ejercicio de MHC y tarifas de síntesis de proteína mixtas era similar en los grupos más jóvenes y más viejos. En el grupo más jóven, el MHC y la tarifa de síntesis de proteína Actina (contráctil) aumentaron el 83 % y el 78 % respectivamente mientras la tarifa de síntesis de proteína de músculo mixta aumentó (el 102 %).

Este estudio indica la identificación que, como con la alimentación, todas las proteínas aumentan regulado con el ejercicio de resistencia. Ahora el punto interesante era que el protocolo de ejercicio usó siete ejercicios de levantamiento de pesos (Nautilus el equipo) que incluyó la prensa de pecho, la prensa de pecho inclinada, jalones dorsales (el agarre amplio y estrecho), la prensa de pierna, la extensión de rodilla, la flexión de rodilla, y dos ejercicios de levantamiento de pesos libres que incluyeron press tras nuca y la extensión de tríceps por encima de la cabeza. Cada participante completó diez sesiones de ejercicio de levantamiento de pesos: 2-3 series/día de los nueve ejercicios mencionados arriba, 8-12 repeticiones/serie, el 60-90 % de fuerza de músculo máxima voluntaria. Esto era una amplia gama de intensidad y fácilmente indica que la gama de repeticiones en sí mismo no es un factor determinante.

Para más lejos ilustrar esto la intensidad o la gama de rep utilizada no cambian esta proporción todo demasiado dramáticamente que podemos mirar el trabajo más reciente que examina las tarifas sintéticas de proteínas fraccionarias con dinámico o el ejercicio de tipo de resistencia.

Atherton et al. (7) usó el estímulo eléctrico con la alta frecuencia (HFS; 6x10 las repeticiones de 3 explosiones de s en 100 Hz para imitar el entrenamiento de resistencia) para identificar la presencia de señales durante el aumento de la síntesis de proteína. Lo que él notó, significativamente a este artículo y discusión, era que HFS aumentó considerablemente la síntesis de proteína miofibrilar y sarcoplasmatica 3 h después del estímulo, 5.3 y 2.7 pliegues, respectivamente.

De modo interesante Bowtell (8) encontró que cuando la misma cantidad total de ATP es usada, el ejercicio en 60, 75 y el 90 % de la fuerza "en una repetición máxima " causa exactamente el mismo estímulo de síntesis de proteína de músculo, sugiriendo que una vez que todas las fibras de músculo son reclutadas, aumentando la tensión encima del 65 %, no causa ningún estímulo diferente en la síntesis de proteína de músculo. Incluso aunque yo no sea consciente si las fracciones específicas fueran medidas en el estudio de Bowtell, yo estoy segudo que a la luz de lo anterior, ambas fracciones aumentarían de manera similar.

En otro estudio, Louis (9) los sujetos realizaron 20 series de 10 repeticiones (con un descanso de 80 seg después de cada serie) sobre un isokinetic dynometer para evaluar si la Creatina tiene un impacto sobre la señalización anabólica y la síntesis de proteína. Otra vez, en el reino de este artículo, fue encontrado interesante que este ejercicio aumentó las tarifas sintesis myofibrillar y sarcoplasmçatica por 2-3 pliegue.

Mirando el ejercicio dinámico (extension de cuadriceps), el Molinero (10) vio que las tarifas de síntesis de proteína en la pierna ejercida aumentaron considerablemente en 6 h y alcanzaron su punto máximo dentro de 24 h tanto en myofibrillar como en fracciones sarcoplasmaticas, p. ej. los aumentos de 2.8 y de 2 pliegues, respectivamente. Las tarifas de myofibrillar y la síntesis de proteína sarcoplasmatica en el músculo ejercido se habían caído ligeramente en 48 h, pero eran todavía considerablemente encima de las tarifas en la pierna descansada. Por 72 h, las tarifas de ambas fracciones se habían disminuido.

Nuestro último estudio que observa aumentos de sintesis fraccionarias, mirará si realmente hay una dependencia de tipo de fibra. En muchos animales la tarifa de síntesis de proteína es más alta en fibras lentas/oxidativas que en fibras rápidas/glycolyticas. Encontrar si esto era verdadero se hizo un estudio reciente en el cuerpo humano (11). Se reclutó nueve jóvenes sanos y con una infusión constante miraron tarifas sintéticas en el soleo, vasto lateral y triceps. Las fibras tipo I contribuyó 83 +/-el 4 % de las fibras totales en soleus, 59 +/-el 3 % en vastus lateralis y 22 +/-el 2 % en tríceps. Las tarifas de síntesis de proteinas Myofibrillar y proteínas sarcoplasmatias (FSR, la h de % (-1)) eran 0.034 +/-0.001 y 0.064 +/-0.001 (soleus), 0.031 +/-0.001 y 0.060 +/-0.001 (vastus), y 0.027 +/-0.001 y 0.055 +/-0.001 (el tríceps). Durante infusión de aminoácido, la proteina myofibrillar FSR aumentó 3 pliegues, y la sarcoplasmatica 2 pliegues encima de valores basales (P <0.001), otra vez mostrando que no existen diferencias entre ambos tipos de tejido muscular.

What is the Sarcoplasm?

Within the sarcoplasm there are soluble (or aqueous) components (making up 80 percent of it); composed of ions and soluble macromolecules like enzymes, carbohydrates, different salts and proteins, as well as a great proportion of RNA. This watery component can be more or less gel-like or liquid depending on the condition and the activity phases of the cell. In general, margin regions of the cell are gel-like and the cell's interior is liquid.

The insoluble constituents of the sarcoplasm are organelles (such as the mitochondria, the chloroplast, lysosomes, peroxysomes, ribosomes), several vacuoles, cytoskeletons as well as complex membrane structures (e.g. sarcoplasmic reticulum).

The muscle protein fraction that makes up the cytoplasm (sarcoplasm in a muscle cell) is made up of mostly enzymes participating in cell metabolism, such as the anaerobic energy conversion from glycogen to ATP, intracellular transport, and several other enzyme functions. This fraction adds up to about 25 or 30% of the total muscle protein versus the larger and more talked about structural protein (myofibril protein) makes up about 40%.

Skeletal muscle protein

When speaking of protein synthesis one of the things that first must be identified is which fraction of protein we are talking about.

Whole body protein synthesis is an average of the synthesis rates of various proteins in different tissues of the body, skin, muscle, organs, and plasma.

Mixed muscle protein is an average of the synthesis rates of total muscle proteins and includes mitochondrial, sarcoplasmic, structural components and connective tissue proteins.

Myofibrillar protein is comprised of individual proteins such as myosin, actin, titin, tropomyosin, troponin, protein C, and some components of mitochondrial proteins.

Sarcoplasmic proteins are mostly enzymes participating in cell metabolism. However, if the organelles within the muscle cells are broken, this protein fraction may also contain the metabolic enzymes localized inside the sarcoplasmic reticulum, mitochondria and lysosomes.

Fractional Protein Synthesis
It has now been known for some time that chronic elevation in protein synthesis above that of breakdown is of prime importance in skeletal muscle hypertrophy (1,2). It is this basis of understanding that we start this article off by looking into how feeding and exercise impacts fractional protein turnover.

Years ago David Millward and Peter Bates identified that protein synthesis had a direct relationship to both feeding and fasting (3). They also noted that during tissue growth (from feeding) the maintenance of a constant composition necessitates the same absolute increase in synthesis for all proteins, both contractile (myofibril) and soluble (sarcoplasmic). This would mean that the increase in the synthesis rate for each protein will be an increasing proportion of the overall rate for the slower-turning-over proteins or in more simpler terms, the increase of both fractions are held within a ratio.

Resistance training has shown very strong shifts in protein turnover (4,5) and most of the studies have used mixed muscle protein turnover as the gauge of effectiveness. Unfortunately this method does not show how resistance or dynamic exercise training differently affects each fraction.

In a study looking at age affects of Protein Synthesis (6) it was noted that by the end of 2 weeks of weight-lifting exercise, MHC and mixed protein synthesis rates increased in both younger and older participants. The actin protein synthesis rate was increased after exercise in only the younger group. The magnitude of the exercise-induced increase in MHC and mixed protein synthesis rates was similar in the younger and older groups. In the younger group, the MHC and Actin (contractile) protein synthesis rate increased 83% and 78% respectively while the mixed muscle protein synthesis rate increased (102%). This study points to the identification that, as with feeding, all proteins are up regulated with resistance exercise. Now the interesting point was that the exercise protocol used seven weight-lifting exercises (Nautilus equipment) that included the chest press, inclined chest press, latissimus pull-down (wide and narrow grip), leg press, knee extension, knee flexion, and two free weight-lifting exercises that included seated overhead press and overhead triceps extension. Each participant completed ten weight-lifting exercise sessions: 2–3 sets/day of the nine exercises listed above, 8–12 repetitions/set, 60–90% of maximum voluntary muscle strength. This was a pretty broad range of intensity and easily points out that the rep range itself isn’t the determining factor.

To further illustrate that the intensity or rep range utilized does not change this ratio all too dramatically we can look at more recent work looking into the synthetic rates of fractional proteins with dynamic or resistance type exercise.

Atherton et al. (7) used electrical stimulation with high frequency (HFS; 6x10 repetitions of 3 s-bursts at 100 Hz to mimic resistance training) to identify signalling present during increased protein synthesis. What he noted, significant to this article and discussion, was that HFS significantly increased myofibrillar and sarcoplasmic protein synthesis 3 h after stimulation 5.3 and 2.7 fold, respectively.

Interestingly Bowtell (8) found that when the same total amount of ATP is turned over, exercise at 60, 75 and 90% of the one-repetition-maximum force results in exactly the same stimulation of muscle protein synthesis, suggesting that once all muscle fibers are recruited increases in tension above 65% cause no further stimulation in muscle protein synthesis. Even though I am not aware if the specific fractions were measured in the Bowtell study it would stand to reason that in light of the previous both fractions would be up regulated.

In another study, Louis (9) subjects carried out 20 series of 10 repetitions (with a rest of 80 s after each series) on an isokinetic dynometer to evaluate if Creatine has an impact on anabolic signalling and protein synthesis. Again, in the realm of this article, what was found interesting was that this exercise increased the synthetic rates of myofibrillar and sarcoplasmic proteins by 2- 3 fold.

Looking at dynamic exercise (one legged kicking), Miller (10) saw that the rates of protein synthesis in the exercised leg increased substantially by 6 h and peaked within 24 h in both myofibrillar and sarcoplasmic fractions, i.e. increases of 2.8 and 2-fold, respectively. The rates of myofibrillar and sarcoplasmic protein synthesis in the exercised muscle had fallen slightly by 48 h but were still significantly above the rates in the rested leg. By 72 h, the rates of both fractions had decreased.

Our last look at fractional elevations will look at whether or not there is a fiber type dependency. In many animals the rate of protein synthesis is higher in slow-twitch, oxidative than fast-twitch, glycolytic muscles. To find if this held true for muscles in the human body a recent study (11) recruited nine healthy, young men and with a constant infusion looked at synthetic rates in the soleus, vastus lateralis and tricep. Type-1 fibers contributed 83 +/- 4% (mean +/-s.e.m.) of total fibers in soleus, 59 +/- 3% in vastus lateralis and 22 +/- 2% in triceps. The basal myofibrillar and sarcoplasmic protein fractional synthetic rates (FSR, % h(-1)) were 0.034 +/- 0.001 and 0.064 +/- 0.001 (soleus), 0.031 +/- 0.001 and 0.060 +/- 0.001 (vastus), and 0.027 +/- 0.001 and 0.055 +/- 0.001 (triceps). During amino acid infusion, myofibrillar protein FSR increased to 3-fold, and sarcoplasmic to 2-fold above basal values (P < 0.001), again showing that even within differing types of muscle tissue the ratio remains.

What can be seen when reviewing these and many other papers on the subject is the response to resistance training of fractional elevation remains in line with the results of feeding, both are elevated but the slower turnover proteins (myofibrillar) generally show a larger magnitude in increase. Since these studies show that this holds true with resistance training, dynamic exercise and HFES, all utilizing differing intensities and work output, it seems unlikely that the rep range is the sole cause of any increase in sarcoplasmic fraction up-regulation.


Nuclear Domains
It is well established that satellite cell contribution is a very important factor in muscle hypertrophy (12,13). As a cell grows and increases it’s cytoplasmic volume the nucleus must maintain mRNA production for the entire area of increased size of cytoplasm (14). Since muscle cells are multi-nucleic, each nucleus controls mRNA over a finite area or its domain (14,15), hence the term nuclear domain.

Skeletal muscle hypertrophy has shown to induce increases in myonuclei and or increases in domain size (16). Resistance training has reported a very broad range of increases in fiber hypertrophy (17). In several hypertrophy studies it appears that there is a limit that needs to be reached before domain size increases necessitates increased nuclei donation. Studies that have shown significant increase in hypertrophy, above 26%, also showed large additions of myonuclei in animals (18-20) and in humans (21).

Work in humans is rather limited but what can be seen in this smaller body of work is very interesting. Acutely, resistance training and resistance type training do not exert the same magnitude of response in humans as what is seen in smaller animals.

A recent study (22) examining the acute effect of training showed less significant changes in donated nuclei and in fact after an acute bout of (a) fifty one legged ‘drop down’ jumps were performed from a stable platform of 45 cm, (b) eight sets of ten maximal eccentric knee extensions at –30 degree/s using an isokinetic dynamometer and (c) eight sets of ten maximal eccentric knee extensions at –180 degree/s using an isokinetic dynamometer, satellite cell proliferation did occur but there was no increased satellite cell donation. Apparently a single bout in humans is not enough to induce the same changes seen in smaller animals.

Kadi looked at chronic application in a very interesting and telling look at training and detraining. (23). In this study he subjected 15 subjects to 3 months of progressive resistance training using a 6-12 RM. The various exercises were conducted in 4–5 sets, in the first weeks (training sessions 0–5) exercises involved 10–12 RM loads, followed by 10 RM loads in early weeks (training sessions 6–15), heavier loads of 6–10 RM in the later weeks (training sessions 16–30), and very heavy loads of 6–8 RM in the final weeks (training sessions 31–38). The subjects then detrained for 3 months. Satellite cell activity increased significantly over the entire training period. Reaching significance at around 30 and again at the 90-day marks. Hypertrophy of fiber increased at 30 days and 90 days, 6.7% and 17% respectively. Interestingly though was the observation that the area controlled by each nuclei was virtually unchanged over the entire training period. This clearly illustrates that the rep range was not the primary inducer of hypertrophy or domain volume changes since the fiber size and satellite cell count increased no matter the rep range. It also clearly indicates that the duration of chronic training is a key element in both hypertrophy and satellite cell activity.

An earlier study by the same researcher (24) saw a concomitant increase in satellite cell count and an increase in myonuclei donation over a 10-week training protocol in female athletes. The muscle examined in this study was the trapezius so it could be that the increase could be muscle specific, as it’s been shown that the trapezius has a higher androgen receptor content (25). This may have also been another reason why the previously cited work by Kadi showed such a difference as the biopsies were taken from the vastus lateralis.

In summary it is very common to see studies reflecting both increased protein synthesis and hypertrophy with a myriad of rep ranges and resistance training protocols. The extent of hypertrophy may be a direct reflection in increased translational efficiency or an increase in pre-translational abundance of mRNA. The differences may be owing to the training status of the individual and not necessarily the rep range used in the resistance training routine. Although it appears that the rep range will have an impact on metabolic shifts in isoform content this does not change the sarcoplasmic vs. contractile protein synthesis ratio but merely dictates which fiber type will experience the greater amount of hypertrophy.

As stated in Rennie’s 2004 review (26), it may take 20 weeks of resistance training to increase hypertrophy by 20%. This coincides very well with the research presented in this article, as it appears that the change in fiber size has a direct correlation to when satellite cells donate their nuclei for continued domain regulation. Therefore moderate increases in nuclear domain are very possible without the aided donation of nuclei from satellite cells and this does not appear to be rep range dependant. A statement can also be made that the results seen in small animals and humans may be very different. This may be owing to the extent of damage that is seen and how hypertrophy and necrotic damage stimulate the satellite pool differently but that is beyond the scope of this article.

[KaS]

Gracias Hiperius!
Tengo entendido que no se puede separar la sarcoplasmatica de la sarcomerica, lo que si puede incidir mas en una que en otra.
Repeticiones entre un rango de 8-12 mas sarcoplasmatica
Repeticiones entre un rango de 2-6 mas sarcomerica
Quizas seria mejor enfocar los entrenamientos a rutinas de fuerza...

[Lights Out]

Quizas seria mejor enfocar los entrenamientos a rutinas de fuerza...

¿Sí? no me digas!!!

Ahora en serio, las rutinas de fuerza (3-5 series de 3-5 repeticiones, centrándose en ejercicios compuestos) provocan aumento de la musculatura en los levantadores principiantes, en los intermedios y en menor medida en los avanzados.

Hasta que no eres intermedio tirando a avanzado, las rutinas de volumen no son realmente necesarias.

[KaS]

¿y? Yo no hablo de rutinas de volumen...
Lo que yo he comentado es que para "enfocar" mas a la sarcomerica que digamos que es la util quiza deberiamos "en general" a hacer rutinas de fuerza, ni hablo de volumen ni del nivel, ni mio ni de otro

[Týr]

Lo que yo he comentado es que para "enfocar" mas a la sarcomerica que digamos que es la util quiza deberiamos "en general" a hacer rutinas de fuerza, ni hablo de volumen ni del nivel, ni mio ni de otro

Todo el mundo debería comenzar a hacer rutinas de fuerza hasta ser capaz de mover más de su peso corporal en la mayor parte de ejercicios básicos. Y solamente llegados a este punto debería uno decantarse por un entrenamiento especializado (culturismo, rugby, artes marciales, atletismo...).

Sin una sólida base de fuerza es muy complicado construir un físico adecuado para destacar en el resto de deportes.

[Lights Out]

¿y? Yo no hablo de rutinas de volumen...
Lo que yo he comentado es que para "enfocar" mas a la sarcomerica que digamos que es la util quiza deberiamos "en general" a hacer rutinas de fuerza, ni hablo de volumen ni del nivel, ni mio ni de otro

Básicamente, suscribo lo que ha dicho Týr.

Las rutinas de fuerza pura y dura dan muy buenos resultados, generalmente mejores, incluso, en la mayoría de la gente que no lleva un porrón de años entrenando correctamente que las rutinas de volumen.

A título personal, las rutinas de fuerza me han dado más masa que las rutinas de masa.