How does weight training cause muscle growth?

September 14th, 2007 by Paul Johnson

One of the most core questions for every bodybuilder, is what are the mechanisms that cause muscle growth? Perhaps if we knew exactly the mechanisms, we could gear a diet and training routine around it. Let's discuss some of the major theories out there and the merit of them.

Muscle Damage Theory:

This theory will make a lot of sense to the novice bodybuilder, who is so sore they can barely walk after their first squat workout. Originally people thought lactic acid was the cause of muscle soreness and damage. It wasn't until they actually took a electron microscopic biopsy of the muscle tissue, that they could see what really happened.

They discovered that a small portion of the fibers had a disorderly pattern. They coined the term to describe this "micro tears". Upon further research they found that eccentric(the negative portion of a rep), did better than the positive in inducing this micro tear. The negative portion is therefore probably more important for muscle growth.

Muscle growth and hormone involvement:

We have been just focusing at the muscle aspect, but the whole body is involved in muscle growth and recovery through the
release of hormones. Muscle damage theory doesn't really answer a lot of questions. That is where another theory comes into play called, substrate accumulation theory. The theory basically believes, that muscle growth is a result of the release of the cascade of anabolic hormones post-workout.

We know the body releases and regulates levels of growth hormone, IGF-1, cortisol, adrenaline, testosterone, during and for many hours post-workout. The most important hormone involved during the muscle building process seems to be testosterone. Testosterone levels will dip low and not reach their peak again until somewhere around 48 hours after weight training.

The longest time protein synthesis lasts post workout for a muscle, is about 48 hours, but often lasts far less than that. Excessive cortisol levels, that start to increase post-workout, must go to a low level quickly again or else overtraining happens.

Which muscle growth theory is correct?

Both theories have flaws when looked at them independantly. For example, if you believed in substrate accumulation theory exclusively, then you would believe that taking a bunch of steroids without weight training could cause muscle growth.   You need muscles to be stimulated plus the hormonal response.  Both theories however, work well together. When they are put together, it seems to be the most plausible explanation.

Muscle Hyperplasia theory:

Unfortunately, it doesn't stop with those two theories. Another major theory is based on hyperplasia, which is a very controversial. Due to the complexity of this theory I wrote my own exclusive article on it: Does Hyperplasia Cause Growth in Human Skeletal Muscles?. It provides some interesting insight, including how to possibly stimulate hyperplasia, that you won't find anywhere else.

  1. Muscle Builders on December 28th, 2009

    Great article this is very informative and useful thank you.

  2. ahmed on March 30th, 2010

    smartwhey is amazing i love it.32g of protein each scoop perfect.ive been taking it for 7 months and im very happy with it.i gained alot of muscle and i lost fat.

  3. Dinesh on July 27th, 2010

    sir, please tell me some fast trick to grow body i m too skiny pls pls

  4. paul sin on December 16th, 2010

    what food do i eat

  5. Isac on February 3rd, 2011

    so is it the best to take alot of beef aminos and intake alot of anabolic protein after my evening work out then eat a good high protein meal then go to bed?