Muscle Growth: How Hypertrophy Works


Muscle growth, or hypertrophy, is one of the most sought after goals of the average lifter in the gym.  Every single time I talk to an old buddy from college, they always ask for tips on how to get bigger.  Not that there is anything wrong with that, however, I felt compelled to write a post about the specifics of muscle growth.  I have written previous posts about muscle hypertrophy.  I have even given some simple programs to follow.  Despite all of this, I still feel that it is better for lifters to understand the science behind muscle growth.  When ever you want to succeed at any endeavor, you must first lean all that you can about it. 


What Causes Muscle Growth?

Here is where things get fuzzy.  The unfortunate truth is that nobody really knows the exact mechanism that causes muscle growth.  It is all mostly theories and hypothesis.  The main proposal for the mechanisms of muscle growth is the energy replenishment theory.  When exercising, your muscles burn energy (glycogen) for fuel to do mechanical work.  At the same time, your muscles are being mechanically damaged from the stress of exercise.  Your body is trying to counteract this by initiating the repair process, known as protein synthesis. 

Herein lies the problem, both of these processes require energy.  During exercise the body is spending most of that energy on exercising.  At the same time it is trying to initiate protein synthesis to undo some of the damage.  After exercise almost all of the energy in the body is now going to protein synthesis.  So here is where the magic is supposed to happen.  After exercise the body tries to make up for all of the energy lost in the muscle.  It tries to cram as much glycogen into the muscle as possible.  This is believed to cause the infamous super-compensation.

Super-compensation is when the body react to a stressor in a more immediate and intense way.  This favorable training effect is the holy grail of any athlete.  In fact, most training programs out there are trying to recreate this effect for long term training cycles.  It is this super-compensation after exercise that is believed to stimulate muscle growth.      


Different Types Of Muscle Growth

Ok so we now understand the general theory behind muscle growth.  Now we have to take a look at the different types of muscle growth.  There are two distinct types of muscle growth, or hypertrophy.  They are sarcomere hypertrophy and sarcoplasmic hypertrophy. 

Sarcomere hypertrophy is a type of hypertrophy in which the myofibrils within the muscle cell grow bigger.  If we recall, the little myofibrils in the muscle cell are actin and myosin.  These myofibrils bind to each other and slide across each other in order to cause a muscle contraction.  The more myofibrils there are and the bigger and stronger they are, the more tension the muscle will be able to generate.  When strength and conditioning coaches write strength programs for athletes and they have a phase for hypertrophy, this is the hypertrophy they are referring to. 

Sarcoplasmic hypertrophy, on the other hand, functions by a different mechanism.  This type of muscle hypertrophy is where the myofibrils don’t get bigger and instead the fluid medium and the outer layer (sarcoplasm) get bigger.  The sarcoplasm is to a muscle as the skin is to the human body.  It is what encases the muscle and helps to hold everything in place.  This type of growth occurs when the volume placed on the muscles is too great that the myofibrils cannot keep up.  As a result the muscle cell swells up and grows as a means to try to add some sort of mechanical leverage to the working muscle.  Unfortunately, this doesn’t work out too well and maximal strength is not increased too much.  This type of hypertrophy is good for bodybuilders and wrestlers.       


Training Programs For Muscle Growth

Both of the above types of muscle growth are completely trainable.  The only question is do you know which type you are training for or not.  When I see both high school athletes and college athletes using bodybuilding programs in magazines, it literally kills me.  These kids are buying modern advertising propaganda hook, line and sinker.  As long as you understand what these two types of muscle growth are and which one you desire, all is well. 

To train for sarcomere hypertrophy, you want to keep the overall volume of any given lift down to 20-30 repetitions for each exercise.  This will ensure that the myofibrils are forced to grow and get stronger.  To train for sarcoplasmic hypertrophy, you want to do much more volume for a given exercise in your workouts.  You want to do anywhere from 50-100 repetitions with a given exercise with a moderate amount of weight. 

Of course you could perform this kind of volume with any kind of exercise you want.  To get the best results, you should use this kind of volume with bigger multi-joint exercises.  This will create a larger response on the body.  Additionally these exercises tend to be based off of real world movement patterns.  Using this type of training with isolation exercises could cause imbalances.     



Most lifters don’t understand that training programs are like tools in a carpenters tool kit.  If you know any carpenter you will know that carpenters use way more than one tool.  Likewise as a lifter you should always have more than one training program.  Most lifters only use one type of program for any and all exercises that they perform.  That follows the saying “if the only tool you have is a hammer, every problem has to look like a nail.” In the end it just simply will not work. 

You have to know how things work in order to modify them.  That is what I hoped to accomplish with this post.  If you truly want to get bigger then you have to know the exact mechanisms on how to get big.  I have given you a good start, but now the rest is up to you.      

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