Sarcomeric and sarcoplasmic hypertrophy
The subject of sarcomeric or sarcoplasmic hypertrophy has been and continues to be a subject of debate and confusion. The ratio of myofibrillar to sarcoplasmic protein is constant and proportional. Sarcoplasmic hypertrophy does not occur without myofibrillar hypertrophy, i.e., there are not two types of hypertrophy. When muscle size increases, it does so in the same proportion of myofibrillar tissue (approximately 80% of the muscle volume) and sarcoplasm increase (20% of the volume) so that there are no substantial differences in terms of the type of training that favors one or the other.

Furthermore, although there is an increase in the myonuclear domain, this will always occur in proportion to the myofibrillar increase, that is to say, if for example the myofibers/sarcoplasm ratio is 80%/20%, when the cross section of the muscle increases, both will increase in the same proportion and if anything, the myofibrillar portion will slightly decrease, but only in the case of substantial hypertrophy such as for example a bodybuilder (let us say 70%-30% at the most).

It is true that you can get some increases in sarcoplasmic volume by taking creatine, carbohydrate loading, doing blood flow restriction training, or causing muscle damage, but none of them cause a very large increase in muscle volume in the first place, and they are all transient. Stop taking creatine or carbohydrate loading, and the water disappears. Fluid retention in the muscles after a blood flow restriction session or a training session that causes a lot of muscle damage dissipates within 72 hours, and the effect progressively diminishes over time. Average skeletal muscle glycogen concentrations are closer to 1.5-2 grams of glycogen per 100 grams of muscle. In other words, glycogen would account for an increase in total muscle volume by approximately 6-8%, and that increase would be sarcoplasmic hypertrophy, but nothing significant.

In fact, if the sarcoplasm were to increase greatly in relation to the myofibers, that is, if there were an increase in the myonuclear domain without an accompanying increase in myofibrillar proteins, it would be a complete mess because the distances for chemical reactions would increase, since the myonuclear domain would increase too much for proper physiological functioning to occur and the biochemical reactions would lose efficiency, even without being able to occur to a certain extent. It would be cellular chaos. In fact, there is only one context where this ratio is altered, which is in the case of sedentary/aging. The degradation of sarcomeric proteins proceeds at a faster rate in elderly, sedentary and/or pathological subjects, and sarcoplasmic proteins are degraded at a slower rate in these cases. In addition, the synthesis of sarcoplasmic proteins decreases less with age than the synthesis of myofibrillar proteins. In other words, if you are sedentary and do not move, you will increasingly have a myofibrillar-sarcoplasmic protein ratio more in favor of the latter, with the consequent loss of functionality and muscle strength.

If I remember correctly, this concept came from Vladimir Zatsiorsky. However, Vladimir himself accepts that he does not remember the studies and references that determined this concept in the 50’s. However, authors such as Poliquin have mentioned this concept in their publications, articles and books. Even so, like everything else, it is neither black nor white, nor can it be concluded that it DOES exist (at least in the popular concept of people and also to attribute to it the difference in strength between power lifters and bodybuilders, which is absurd) nor confirm that it does NOT exist categorically.

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