How Do Muscles Grow?

The specifics of muscles growth are not well understood yet.

Yesterdays discussion brought up some questions about the specifics of muscle growth. It seems there is some confusion on what muscle growth even is.

To understand muscle growth we have to first understand what a muscle is made up of.

Skeletal muscles are somewhere in the neighborhood of 80-85% water, this is the fluid that makes up the cytoplasm of each cell. The rest of the structure is a mix of protein and lipids and some carbohydrates.

Glycogen is stored in the muscles as well as some amount of amino acid pool that is in a constant state of flux.

Glycogen is stored in approx a 1-2 ratio with water; for ever gram of glycogen the muscle can store it also needs to store two grams of water. Each gram of muscle protein also seems to require approx 2 grams of water.

The transient states of exercise, or even day to day activity are what determine if your muscles will grow or atrophy. In other words, it’s incomplete to assume your muscles have a standard size.

A more accurate view would be say: How big are you muscles when they are:

A) complete inactive in a cast

B) active from day to day activity but no purposeful weight training

C) stimulated from regular weight training

D) stimulated from drug use (testosterone and GH etc)

E) stimulated from supplement use (creatine, BCAA’s etc)

F) Some combination of the above

Each one of these stimulus (or lack thereof) combined with your genetic predisposition for a baseline of muscle fibers will determine how ‘big’ your muscles are given the state they are in.

The specifics of what even makes a muscle bigger and smaller is still unclear. Some research points to sarcolemma growth while other research suggest sarcomere growth, and still others are assuming both happen along with some degree of hyperplasia and potential fiber splitting.

In any case the size of a muscle is dependent upon a transient state of stimulus. Take the stimulus away and the muscle will atrophy, add more stimulus in and it will hypertrophy, but there are always limits to both ends of the spectrum.