August 18


What makes muscles grow? Your introduction to hypertrophy

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Whether you're interested in competitive bodybuilding or not, almost everyone who enters the gym is keen to build muscle. At least grow some areas of their body, and perhaps shrink others. What makes our muscles grow though? In a process called hypertrophy, our muscles grow bigger and stronger. But how does this process work, and how can we use it to our advantage?


Ultimately, what determines how our muscles grow is how we use them on a day to day basis.

How our body uses its muscles

Have you ever gone to lift a box that was much lighter than expected? Or how about you've opened a door that was nowhere near as heavy as you thought it was?

Often caught by surprise, you usually jerk and react to the lighter load.

Let's look at what happens using the door as an example.

Imagine you're standing in front of a door, ready to open it. Experience teaches us which muscles to use and what force they need to apply. Your brain has been learning this sort of thing since you learned to crawl and walk. When you're ready to open the door, you're brain (and muscles) are primed ready for the task at hand.

Firstly, your brain signals motor neurones in your arm and shoulder. Next, your muscles respond to the message by contracting and relaxing. These contractions pull on the bones in your arm and skeleton and generate movement.

Now, the heavier the object, the greater the force required to shift it. Your brain sends more signals to more muscle fibres to contract.

These extra signals cause stronger muscle contractions, allowing you to generate more force.

Now, what happens if the door is stuck?

It's unlikely your arm muscles will be strong enough to open it on their own. Your brain, somewhat instantaneously, signals other muscles to recruit their help. Your feet plant themselves into the floor and your abdominals and back muscles tense.

You manage to yank the door open.

The stimulus makes muscles grow

Your brain and nervous system have just used the available muscles to meet the task at hand.

However, in the background, your muscles are subjected to a different signal. Cellular stress.

When muscles lift, particularly something that is a little too heavy for what they are capable of, they undergo minute damage.

In the context of making our muscles grow, this is a good thing and something that we want.

Essentially, our muscle cells have become damaged and need to be repaired and rebuilt.

The immune system steps in to help grow and build muscle tissue

The injured muscle cells release cytokines. These are chemical messengers that signal to the immune system there's a problem and it needs to react. In this case, repair the damage.

This is when muscle growth starts to happen.

Now it makes sense that the more damage to the muscles, the more your body will have to repair and rebuild.

You'll know this if you've ever perhaps went a little too hard during a workout and regretted it the next day or so where you struggle to walk, or lift your arms!

What makes muscles grow bigger and stronger?

Regular exposure to tasks your muscles can't quite cope with will make them adapt so ultimately they are able to cope.

Say for example you can't lift a 70kg barbell. You do however keep trying. Each attempt will microscopically damage the muscle fibres. Your immune system will leap into action to repair them. It will figure out that building them to the previous standard will do no good, they'll only get damaged again.

Instead, it will use extra resources to build them a little bigger and a little stronger. So that you will eventually be able to lift that 70kg barbell.

It's this constant cycle of damage and repair that ultimately makes our muscles grow.

Why don't our muscles always stay big and strong then?

Building muscle, and keeping it around for no good reason is metabolically expensive.

Nature designs our bodies around efficiency and longevity.

Generally speaking, our bodies adapt to most day-to-day activities that take place. Our muscles have already been built strong enough to cope. As a result, these general daily activities no longer cause enough stress or damage to stimulate new growth.

So if we're looking to build muscle, a.k.a. achieve hypertrophy, we need to expose our muscles to heavier workloads than they currently are.

And that my friends, is 'progressive overload' in action.

Furthermore, if you don't regularly challenge your muscle fibres to some resistance, they will indeed shrink. Muscular atrophy occurs where your body, in an attempt to effectively manage its resources, reabsorbs some of the protein strands it isn't using.

Is growing muscles really that simple?

Ultimately, yes. While the process is simple, other factors have a big effect on how our bodies respond and adapt.

Our muscles need more than just regular activity to encourage them to grow.

Remember, growth comes from your immune system repairing damaged muscle fibres. As a result, adequate nutrition, hormone levels, rest and quality sleep become important.

Put simply, your body responds to the demands you ask from it. If you train your muscles properly, easy well and rest appropriately, you'll create the perfect conditions for muscle growth.

Just remember, much in the same way as life - if you want meaningful growth, you'll need appropriate challenges and the right kind of stress.

About the author

Paul Stokes

Paul Stokes BSc (Hons) is a Certified Personal Trainer, Accredited Sports Nutritionist, qualified Exercise to Music Instructor, Precision Nutrition coach, Massage Therapist and teaches 8 of the Les Mills Group Exercise programs.

He currently works in the Oil & Gas industry as a Wellness Coach, imparting his vast knowledge and experience to improve the quality of life of several hundred offshore workers.

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