היפרטרופיה סרקופלזמית, מאמר מעניין.

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המאמר הבא מדבר על השפעות של טווחי חזרות שונים על התכווציות חלבונים שונים וכתוצאה היפרטרופיות שונות, כידוע לכם תא בשריר מכיל בתוכו מיופיברילים שמהווים כ-40 אחוז מתא השריר, המיופיברילים מורכבים ממספר חלבונים כגון, אקטין, מיוזין, טיטין, טרופומיוזין, טרופונין, חלבון C, וכנראה שעוד כמה...
תא השריר מכיל גם את החלק הסרקופלזמי שמהווה כחלק גדול יותר מהמיופיברלים ומכיל בתוכו בעיקר אנזימים שאחראים על תהליכים מטבוליים בתא כגון הפקות אנרגיה וכדומה, הרבה אנשים מדברים על ההשפעה שיש לטווחי חזרות מסוימים על היפרטרופיה סרקופלזמית, המאמר הבא מדבר בדיוק על הנושא הזה תוך כדי צירוף מחקרים, הסברים מעניינים ומסקנות

תהנו :

Sarcoplasmic Hypertrophy and Rep Range
By Dan Moore

One of the issues I still see when reading training articles is how the rep range dictates whether any hypertrophic response predominantly influences changes in size of the contractile components of muscle cells or the sarcoplasmic volume. The intent of this article is not to dispute that sarcoplasmic hypertrophy exists but to clarify if the rep range used will dictate which protein fraction will increase and whether or not the rep range specifically induces different changes to the nuclear domain of muscle fibers.
There may very well be other factors such as metabolite accumulation and osmolality shifts within the cell that would give temporary changes to the muscle cell volume and size but since these are mostly temporary I did not feel they should be included in this article.

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.