[Episode 76] How Do Muscles Grow

by | Nov 22, 2021

In this episode we will be continuing on with our look at important things you need to know about the body. Next in this mini-series, we talk about the question, ‘how do muscles grow?’



Because one of the most common things I hear folks say when they start training is that they don’t want to “get bulky”. So I’m gonna be breaking down how muscle growth works and why weight training doesn’t actually mean you’re gonna build muscle mass.

Now full disclosure, I’m geeking out a little with the body stuff this week!


Sponge Bob with glasses flipping through a book



Before i get stuck in, this is why I’m bringing it up!

The reason that I wanna share about muscle growth this week is because how often people share with me that they wanna train but don’t wanna get bulky.

So I’m breaking down muscle growth for you this week.

When we are able to understand our bodies and how they work, not only are we able to look after them better, we can also build our confidence in the way we train to help us reach our goals.

And this is super important. Our ability to understand our bodies can be really motivating. I can’t tell you how many folks I train or have trained, that always want to know why they are doing specific movements, using specific weights or doing a certain number of reps during their training.

So much of the time the answer I give is because to gain a particular response from our muscles, we need to do specific things.

Now I’ve shared a bit about this in earlier episodes. These are episode 22, episode 24 and episode 26. These episodes looked at how to gain muscle mass, strength and endurance.

But I wanted to go deeper in explaining what training actually does to your muscles.


Alexis from Schitts Creek saying "There is more to this storey"



Now that’s out of the way, lets talk about muscles!

Muscles are pretty complex. They aren’t just made up of single long strands of muscle tissue, well they kind of are.

But I want you to imagine that every muscle is actually made up of tiny little sections of muscle fibres that are all bundled together and connected end on end for the entire length of every muscle. These little fibres bundled together are called myofibrils.

And each little myofibril section is encased in what is called a Sarcolemma. These Sarcolemmas are all held together within tissue called Endomysium which is connective muscle tissue that surrounds muscles fibres.

Each individual little strand of bundled Sarcolemmas and connective tissue are referred to as Fascicles.

Now these fascicles are encased in the Perimysium. Which is connective tissue that connects muscle bundles together.

Finally all these muscles fibres and bundles are surrounded by connective tissue called Epimysium. Which holds all the muscle tissues together and helps keep each muscle in its appropriate form.


Muscle fibres structure


It’s kind of like if you imagined that each of your fingers was a little bundle of myofibrils aka muscle cells.

Now take your myofibril fingers and stick them in mittens. The mitten is just like the Sarcolemma tissue.

Then take your hands and put them together and place an even bigger mitten over the top of both of them. This big mitten now bundles your Sarcolemma hands together into a Fascicle.

Finally imagine if you placed your Fascicle hands into an even bigger mitten again, and there were other people all placing their own mitten bound hands into this giant mitten, all parallel to each other.

This final giant mitten would act just like the Epimysium which hold all our muscle bundles together. That’s about it!

Just having an idea of how muscles are constructed, it can help us get an understanding of how they move the way they move.

See because our muscles are made up of so many bundles, we can begin to see why they are so strong. When we contract a muscle, meaning we make our muscle shorten, what we are doing is getting our little myofibrils to slide over each other (within their own little bundles) which in turn generates force.



There are three types of muscle fibres


Type I slow twitch muscle fibres

Slow twitch muscles produce the least amount of muscle force, are the most fatigue resistant and are used during endurance activities. These muscle fibres have the smallest diameter.


Type II-A, Fast twitch muscle fibres

Fast twitch muscle fibres generate more force than type I muscle fibres. These muscle fibres can sustain their force for a reasonable amount of time. Type IIa fibres allow us to work at a high intensity for longer.

These muscles fibres are the second biggest of our muscle fibres.


Type II-B fast twitch fibres

Fast twitch fibres produce the most amount of force but fatigue the quickest due to the force of muscle contraction. This fibre type is used for explosive force activities like jumping, sprinting or weightlifting.

These muscle fibres have the biggest diameter of all the muscles fibres.



So that’s the low-down on what muscles are! How do they grow then?

Now we have a bit more of an understanding of our muscles. Next, let’s have a look at how they grow from training.



Depending on the type of training that you do, will have an influence on the type of muscle fibres you have. Remember these are our Type I, IIa and IIb muscle fibres.

Now when we train, in whatever style we’re training in it causes tiny little microscopic tears in our myofibrils.

Our body repairs these tears with new muscle tissue through protein synthesis. Which increases the thickness as well as the volume of myofibrils we have. This process over time is how our muscles grow.


How does this translate in your workouts?

What this means in regards to gaining muscle mass is that if you are training your body with a focus on muscle endurance, you’re gonna be developing/maintaining a higher volume of type I slow twitch muscles.

Aesthetically it means that you’re likely to stay pretty lean and toned muscle wise.

If you train a combination of endurance, aerobic (cardio) and moderate to high intensity resistance training, you’re more likely to develop type IIa fast twitch muscles.

Training like this is going to build muscle mass. But it’s likely to be leaner muscle mass as it’ll have a combination of type I and type IIa muscle fibre types.

While if you train for 1 max reps and focus on just heavy lifts and power movements, you’re gonna develop those bigger type IIb muscle fibres. This is where folks develop that really bulky muscle that you see.

So as you can see, lifting weights and doing resistance training in general are not going to build bulk.

And when we look at building muscle mass we can see how developing those type IIb slow twitch muscle fibres are targeted with those heavier loads, and lower rep ranges that make up a mass gain program.


An image of Spock saying "Logical"



Ok, that’s a lot! Where to from here though?

Now there are some things to take into consideration when it comes to building muscle. And the biggest one is your hormone levels.

The higher your testosterone levels, the more muscle mass you are likely to build. This is because research suggests that higher levels of testosterone increase protein synthesis. Which is the process that occurs to repair muscle damage caused by training.

But, this does not mean that you’re just going to gain a whole bunch of muscle. You still have to train in those particular ways I’ve mentioned to achieve significant gains in muscle mass.



Closing Recap

That’s it for this segment in the mini-series! To sum thing up just now, we covered:

  • What muscles are and how they are made up in our bodies. Being little bundles of myofibrils, encased in connective tissues.
  • The different types of muscle fibres we have in our bodies which are;
    • Type I slow twitch muscles which are our endurance muscles.
    • Type IIa fast twitch muscle. Which are our muscle fibres that form the bridge for our bodies to be able to perform aerobic and high intensity activities as they produce a reasonable amount of for and sustained endurance.
    • Type IIb fast twitch muscle fibres which produce the highest amount of power and have the lowest endurance capabilities.
  • And finally we had a look at how different types of resistance training develop each of these different types of muscles fibres.

All that said, we now have a pretty thorough understanding of why resistance training in general, is not going to make you bulky.

Until next week remember that our bodies are amazingly complex. And each of our bodies respond differently to the activities we practice. It can be easy to get caught up generalising physical responses to training. But in reality it’s not that simple. So feel good about exploring how to move and don’t be scared off by fitness myths.

Have a rad as day pals.

Newsom-Davis, J. M. , Warshaw, . David M. , Crompton, . Robin Huw , Alpert, . Norman R. , Curtin, . Nancy A. , Wood, . Bernard , Gergely, . John , Davies, . Robert E. , Walker, . Warren F. and Alexander, . Robert McNeill (2020, June 2). muscleEncyclopedia Britannica. https://www.britannica.com/science/muscle

Bowie Stover Thinking Pose

Bowie Stover

Pronouns: they/them

My passion to help others through developing an active and healthy lifestyle, along with my desire to contribute as much as I can back to our queer community, has led me to co-found Non Gendered Fitness. To be a small part of your day that makes a HUGE impact on your life would be one of the most gratifying and rewarding experiences that I could hope to have.

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