Muscle Fibre Type I, Type IIa and Type IIb (Which type of muscle defined hypertrophy?)

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If you’ve been on my blog for a while, you might probably be into hypertrophy training.

But is there any definition of a true effective hypertrophy training really means? Besides of you need to train with weight?

Does it mean that bodyweight exercise isn’t hypertrophy and you should not ever consider it?

In this post, I will explain the only distinction between hypertrophy vs non-hypertrophy training– distinction between muscle type I (slow twitch muscle fibre) and type II (fast twitch muscle fibre).

What really defines hypertrophy?

Let’s start off with the official definition of the muscle hypertrophy means, here’s what I found:

Hypertrophy training focuses mostly on developing your muscles. You’ll focus on increasing the size of your muscle fibres, developing large muscles in areas that you work out the most.

As we sees most of the fitness enthusuast will say that in order to achieve hyperthrophy, you need to lift heavy, start goingto the weight section of the gym instead of running on the treadmill.

This often causes a misconception that as long as we are training with weight, we are training with hypertrophy. However, although this is partially true, the equipment that you use and which type of workout you did isn’t directly determine muscle hypertrophy.

To understand why did we always wish to hit the hyperthrophy effect of the training, you need to know the difference of muscle type I and muscle type II.

Every Muscle is Different

Most of the time when we think of a muscular person with muscular, those body building person often come to mind.

And when we talk of a person with lean muscle, we often think of a marathon runner.

Ever wonder why did the marathon runner did not have the same muscle size as abodybuilder? Although we can assume that the training of the sprinter was no less intense than a bodybuilder.

Because both of them have different type of muscle.

A bodybuilder has more type 2 muscle fibre. While a marathon runner has more type I musclefibre.

As we said, we use muscle all the time in every type of exercise, but how you train your muscle and the end product of muscle will define what it looks like in the end.

To have more muscle definition, you need to increase muscle fibre type II. If you wish to look lean and more cardiovascular efficient, then you might need to work on getting more muscle type I.

The type I and Type II Muscles, Big difference

Muscle growth is determined by an increase in muscle fiber number (hyperplasia) as well as an increase in muscle fiber size (hypertrophy).

Jinzeng Yang, in Progress in Molecular Biology and Translational Science, 2014.

Everyone is born with the same amount of muscle fibre. Based on how we use the muscle in our daily living, a person might have one dominant muscle fibre type than other. Most of us consists of three muscle fibre types in our body varies on different proportions.

Some might have more type I muscle fibre than the other, while someone might have more type II fibre. However, note that muscle type isn’t fixed throughout your life. Based on your training condition, it is possible to you convert your muscle type over time.

Here’s different type of muscle fibre type with description:

Slow Twitch Muscle Fibre

Type I

Type I muscle fibre is smaller compared with type II fibre. Often time people with more muscle types I will found them more easily in doing steady-state activities for a long time. The explosiveness and intensity aren’t as much as activities in type II.

This type of muscle supports most of the aerobic exercise and is more effective in resistance to fatigue.

We use type I muscle fibre most of the time in our daily life such as maintaining posture and resisting gravity, the muscle is able to contract over a long time.

Type I muscle look lean and did not add much visual impact on appearance.

Type I muscle is NON-Hyperthrophy.

Fast Twitch Muscle Fibre

Type IIa

Type IIa muscle have characteristics between muscle types I and IIb. This type of muscle still considered under muscle type II because of its explosiveness and higher output. However, it isn’t as easily fatigue then muscle fibre type IIb. This type of muscle fibre supports provide strength and moderate fatigue resistance.

Think of a sprinter, the work that the muscle does is mostly explosive, but unsustainable in a long time.

In this case, the appearance of muscle fibre type IIa will appear to be bigger than type I, but still smaller than muscle type IIb.

When we lift weight in the rep range of 8-12, we are miostly using muscle fibre type IIa.

Type IIa is the most hypethrophic muscle.

Type IIb (Also called as IIx)

This type of muscle fibre supports even more explosiveness and is unable to resist fatigue than type IIa.

For the average person, this type of muscle is only used when there is an emergency circumference that you need to escape or lifting up heavy objects than you usually did.

This type of muscle usually work in a way that we required an extreme strength in a short duration of time.

Most of the power lifting used muscle type IIb.

It is inefficient to sustain therefore the rep range that effective to activate type IIbmuscle is 5 RM(Repetition Maximum) below.

This type of muscle supports maximal strength.

Customizing your workout to work three type of muscle

Notice how the difference between different type of muscle works and develop in a different scenario? When we are training one type of muscle more, then it will results in more amount of that type of muscle in our skelectal.

For hypertrophy wise, most of us want more definition, in this case, integrating more weight lifting is efficient in activate more muscle fibre type IIa. And this type of muscle tends to have higher metabolism compared to muscle type I.

If you wish to have a balanced amount of muscle type, then integrating three types of training is best of optimising the benefits of the three type muscle. You can have a better endurance in physical activity as well as strength.

A better way to arrange your session if you wish to work three type of muscle in one single session:

One set of powerlifting (muscle fibre type IIb) > moderate intensity weight lifting(muscle type IIa) > cardio (muscle type I)

Final thought

As I said, it is important to have a clear goal in your fitness journey because differnt goal required different approach.

By learning the differentiation between different type of muscle will give you better understanding of how to really optimized your training to get the results that you want.

I hope you’ll get some insight from this. Next week, I’ll talk about how carbs work to maintain our health and reevaluate why did most of us had misunderstood about carbs (in fact carbs isn’t as bad as we think).

Stay tuned and thanks for reading!

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