I recently found this passage in a book review online. I don't have the knowledge to determine if the comment has any merit. Can anyone comment?
"Our muscles grow in response to injury - it is the destruction of the outer member of muscle cells. We are literally "killing" muscle cells and injuring our bodies (on purpose mind you). The damaged muscle cell will receive help from a stem cell, called a satellite cell, which will adopt itself into the muscle cell and make it grow in size. This is why muscle grows with intense exercise/intentional injury.
Since muscles grow from stem cells, this raises the question as to the role of supplementation and nutrition in skeletal muscle growth. In his book, the author mentions the enzyme myostatin, which is a natural inhibitor of stem cell production. The people with this mutation are able to lift weights and injure muscle cells, but their body naturally produces so many stem cells that their muscles rapidly increase in size soon thereafter. Professional bodybuilders are known to have these mutations.
There is an evolutionary advantage to not having this mutation and that is that individuals with large muscles require a higher metabolism, and this can be a detriment to living in an environment with limited food resources.
There is no evidence that amino acids, proteins, and other supplements increase the natural amount of stem cells (called satellite cells) in skeletal muscle - This means they may have no effect in muscle regeneration. The reader should keep in mind that mice and cows with the myostatin mutations grow huge from simply grazing or running on mouse wheels - they do not chug protein shakes and waste money on supplements like so many aspiring but misinformed bodybuilders do.