How Hypertrophy Works

So with all that in mind, you should be going into this chapter with a good idea of what it is you want to accomplish. Only that way, will you be able to take the relevant information from this and ignore all the rest.

So hypertrophy. What is it? When your muscles grow, what actually causes them to grow? What is actually happening? As you probably had already guessed, there’s actually multiple things going on, which is where all the confusion comes in.

Generally though, we can split hypertrophy down into two main processes. These are ‘sarcoplasmic’ and ‘myofibrillar’ hypertrophy. Actually though, even this is contested somewhat – some experts actually believe that these terms are merely pseudoscience and that they aren’t actually based on any concrete evidence.

But whether or not the precise principles of myofibrillar and sarcoplasmic hypertrophy are accurate, the reality is that these two types of training do result in two different types of muscle. This is how strength athletes have been training for decades, with a lot of success, so it’s safe for us to take this understanding and apply it. These terms and the description will simply serve as a somewhat useful ‘crutch’ for understanding what’s going on here...

Myofibrillar Hypertrophy

So on the one hand, we have myofibrillar hypertrophy, which is the predominant form of hypertrophy used for building strength. This is also sometimes referred to more simply as ‘muscle damage’. And that’s an apt name because it really does describe what is going on here – you are damaging the muscle.

Or more specifically, you’re actually tearing the muscle. By lifting heavy enough weights, you’re actually causing tiny rips in the fibers that make up the muscle, known as muscle fibers (the tears themselves are called ‘microtears’).

Muscle fibers work just like any other cell in the human body, except that they can have multiple mitochondria and mitochondria can also increase as you train more frequently and in higher volumes. Right now though, we’re interested in tearing the muscle fiber, which then causes it to be marked for repair. Once we’re sleeping or resting, these tears are then repaired by the body using protein and amino acids to restore the muscle and build the muscle fibers to be thicker and stronger.

It’s generally agreed that it’s impossible to increase the number of muscle fibers (a process that is known as ‘hyperplasia’) through conventional training. However, you can increase the thickness of the fibers through this process which makes them stronger and increases your ability to throw heavy weights around.

What’s the best way to cause these microtears? That would be to train with heavier weights, which in turn will allow you to cause more damage more quickly, triggering more growth. That’s why powerlifters – who are predominantly interested in pure power – will train using weights close to their one rep maxes and lift only a few times.

Sarcoplasmic Hypertrophy

Then you have sarcoplasmic hypertrophy, which is also sometimes known as ‘metabolic stress’. Here, the objective is not to create micro tears but rather to swell the muscles with metabolites, metabolites being hormones and other compounds that stimulate more growth and hypertrophy. The obvious examples of these are testosterone and growth hormone, both of which are ‘anabolic’ in nature.

So how do you trigger this kind of change in your body? This time, the aim is to occlude the muscle and allow blood to build up there – right up until the point here you have too much lactic acid in your muscles to continue and you start to feel a lot of discomfort. You do this by using higher repetitions, as this allows you to increase that all-important ‘time under tension’ – the amount of time that your muscle spends contracting during any given workout.

While the precise mechanism of action isn’t fully understood, this appears to increase the amount of sarcoplasm in the muscle cells – their ability to retain fluid and to store glycogen. This in turn then allows the lifter to continue lifting for longer and to see more growth.

 
While myofibrillar hypertrophy does lead to some increase in size as well as strength, sarcoplasmic hypertrophy appears to be the fastest way to increase size. A bodybuilder trains with significantly lighter weights but uses higher rep ranges, often reaching into the 10s, 12s and 15s before they reach failure.

This is why a considerably smaller powerlifter will often be able to lift more than a much larger bodybuilder. But that is not to say that a bodybuilder’s muscle isn’t as ‘strong’ or that one type of lifting is better than the other. 

All of this information is available in the Hypertrophy Manual