[b said:
Quote[/b] ]how do u hypertrophy?
Good question. I will try to keep this brief.
When you lift a weight, the muscle tissue experiences tension. This tension triggers chemical signals within each muscle cell. This process is called “mechanotransduction.” Mechanotransduction is the process by which cells convert mechanical stimuli into biochemical signals. In our case the “mechanical stimuli” is lifting, holding, and lowering the weights.
Muscle cells are called “mechanocytes”. This is sort of a general term applied to any cell which responds to mechanical stimuli. As a mechanocyte, you can take a muscle cell out of a muscle and put it in a dish. If you then tie each end to something that can stretch it, you will find that this alone will make it grow. All it needs is amino acids. It doesn’t need the rest of the body or even any other cells in order to grow when you stretch it.
When muscle cells are stretched (either passively or actively) it triggers protein synthesis inside of the cell. This increase in protein synthesis will lead to a net gain of protein if protein breakdown doesn’t keep pace with it. If protein synthesis is greater than protein breakdown you are in an “anabolic” state.
Now true hypertrophy (i.e. muscle growth) requires more than just an increase in protein synthesis. After all, you will get an increase in protein synthesis just from eating a big protein meal.
In addition to an increase in protein synthesis inside the cell, there must also be a remodeling of the cell in order to accommodate more contractile proteins. These are the proteins that produce muscle contraction.
A muscle cell’s size (i.e. volume) is limited by the number of nuclei that it has. Luckily, a muscle cell can get more nuclei from “satellite cells” (think of them as muscle stem cells) that sit quietly around the muscle cells until they are called into action.
What calls satellite cells into action? Muscle damage from high levels of mechanical tension. When a muscle cell experiences “microtrauma” from tension levels that it is unaccustomed to, it will release (they ooze out really) growth factors that cause satellite cells to donate their nuclei to the traumatized muscle cell. With these additional nuclei, the muscle cell can then grow larger than it could before in order to accommodate these new high levels of tension.
So, in summary, hypertrophy involves:
1) Tipping the scales of protein synthesis and protein breakdown to favor protein synthesis.
2) Cellular microtrauma that leads to the activation of satellite cells and the donation of their nuclei to damaged cells.
Of course this leaves unadressed many many variables that might also play a role, such as training methods, nutrition (substrate availability), hormones, supplements, and genes.