Everything you need to know about muscle fibre

Maybe you’ve started a new fitness regime and looking to tone up. Maybe you’re looking to work different muscles, or maybe you’re just interested in the human body.

Whatever your reason, we’ve got you covered.

In this article, we’ll be looking at muscle fibres, the different types and the role they play in your body.

We’ll do this by looking at lifestyle choices, diet and any supplements that may help you support your muscle fibre so you can get the most out of your body.

What are muscle fibres?

The human body has more than 600 muscles.

Each of those muscles has an elastic-like tissue that consists of thousands, or even tens of thousands, of tiny muscle fibres.

Each one is made up of many tiny strands which are known as fibrils.

Your nerve cells control the contraction of each muscle fibre with impulsive movements.

The strength of your muscle is dependent on how many fibres are in each muscle.¹

To help do this, your body makes adenosine triphosphate (ATP), which helps your muscle cells change into mechanical energy.²

What are the three different types of muscle fibres?

There are three types of muscle tissue in your body. They are made up by:

• Skeletal muscle
• Smooth muscle
• Cardiac muscle

Each type of muscle has muscle fibres. Below we’ll go into what muscle fibres you can expect to find in each.

1. Skeletal muscle

Your skeletal muscles are made up of hundreds and thousands of muscle fibres, which are tightly bound together by your connective tissue.  

Each of your muscle fibres contains a smaller unit, which is made up of different sized stands. The thick and thin strands give your muscle tissue a striped like appearance.

Your skeletal muscle fibres are placed into two types – helpfully they are titled Type 1 and Type 2, while type 2 is broken into two subtypes:

• Type 1

Type 1 is known as ‘slow twitch’ as it uses muscle fibres that use oxygen to build energy to help your muscles move. This means your muscle slowly contract.³

Type 1 fibres also have a higher density of energy-generating cells which are called mitochondria, which makes them dark in colour.

• Type 2A

Much like type 1 muscle fibres, type 2A fibres can also use oxygen to build energy for movement.

However, this is known as ‘fast twitch’ and they contain fewer mitochondria, which makes them lighter in colour.⁴

• Type 2B

Type 2B fibres are different as they don’t use oxygen to generate energy.

Instead, they store energy within them so they can be used for short bursts of movement. They contain even fewer mitochondria than type 2A fibres, so they appear white.⁵

2. Smooth muscle

Different to skeletal muscles, smooth muscles don’t have the same striped effect as skeletal muscles.

Instead, their smooth looking appearance gives them their name.

Smooth muscle fibres are also much shorter than skeletal muscle fibres. They have an oblong shape to them, much like a rugby ball.

3. Cardiac muscle

Similar to skeletal muscles, cardiac muscles actually have the same striped effect, but instead they’re only found in the heart and have a number of unique features.

Cardiac muscles have their own rhythm.

They also have special cells, which are known as pacemaker cells that help the cardiac muscles to contract.

Typically, they work at a constant, steady pace, but they are also capable of speeding up and slowing down when required.

Cardiac muscle fibres also help the beating of your heart.

They do this as they are all connected internally. So, when your pacemaker cells generate an impulse, the impulse spreads in a wavelike pattern, which in turn helps your heartbeat.

What do the different types of muscle fibre do?

Each of these different types of muscle fibre plays different functions within your body, which include

Skeletal muscle

Skeletal muscles are attached to your skeleton by tendons. They help control the voluntary movements your body makes.

This includes walking, bending over, moving your arms and legs.

Smooth muscle 

On the other side of that coin, smooth muscles are responsible for involuntary movements. This means that you’re unable to control them.

This includes moving digested food through your digestive tract and even changing the size of your pupils.⁶

Cardiac muscle

As you’ll know by now, cardiac muscle is found in your heart and is what allows your heart to beat.

Like smooth muscle, cardiac muscle is also involuntary but in a more coordinated way so your heart beats how it’s supposed to.

Why do we need muscle fibres?

Basically, without muscle fibres your body would not be able to operate to its full capacity, or even at all.

Your muscle fibres and your muscle work hard to bring movement to your body.

But how does this work?

While the method behind each type of muscle fibre may be different, the basic process is still very much the same.

When you move, one of the first things that occur in your body is something known as depolarisation.  

Depolarisation is the change in electric charge. This can be started by a stimulating input such as a nerve impulse, or in your heart, by a pacemaker cell.  

This leads to a chain reaction within your muscle fibres, which eventually leads to a burst of energy, which results in your muscle contracting.

When your muscles stop receiving the stimulatory input, they stop and relax.

Muscle fibres are responsible for many movements and help control physical forces within your body.

Without them, you wouldn’t be able to move, and your heart wouldn’t beat.

How do you know if your muscle fibres are healthy?

There is no specific way to tell if your muscle fibres are healthy.

However, there is a test you can try to test your strength to find out which are the more dominant fibres in your body.

Muscle fibre test

When training with weights, choose strength exercises such as a bench press.

This is where you lie on your back and lift the weight vertically.

You should load the weight bar to around 80% of what you may usually do, or what you think is possible.

Try and do as many reps as possible, the below will illustrate how your muscle fibres work in your body:

•    Less than 7 reps: fast-twitch dominant
•    7 to 9 reps: balanced between slow- and fast-twitch fibres 
•    More than 9 reps: slow-twitch dominant⁷

How can you look after your muscle fibres?

Much of the advice that is provided on looking after your muscle fibres come from looking after your muscles post-workout.

This is important because it allows you to fuel the muscles and help them recover properly, which helps them build and stay healthy.

Five tips for looking after your muscle fibres

Below are our top five tips for looking after your muscle fibres.

1. Fuel up after exercise

It’s thought that you should try and eat at least a snack within half an hour of completing an exercise.⁸

Food groups like carbs and protein are a great choice as they can help your muscles to repair and rebuild.

You can try something like a simple smoothie or milkshake as they’re packed with protein. You could even try a banana or handful of nuts.

You should also remember that hydration is important for your recovery too.

It’s recommended that you drink a pint of water for every hour of exercise you do to keep your fluid levels topped up.

2. Stretch after exercise

Making sure that you do 5-10 minutes of stretching after exercise can help repair your muscles and reduce the risk of injury.

If you are exercising regularly, you may want to try a monthly sports massage.

3. Maybe try an ice bath?

Ice baths aren’t for everyone but taking a nice cool soak in the tub can help your muscles relax and recover after an intensive workout or long run.

4. Make sure you get enough sleep

Getting the right amount of sleep is as important as any other area of looking after your muscle fibres.

According to the NHS, the right amount of sleep for recovery is between 6 and 8 hours a night.⁹

This will allow your muscles time to rest and reach their full potential.

5. Take rest days

While sleep is important, taking rest days is equally as important to allow your body to recuperate.

This will allow your muscles and your muscle fibres times to recover and rebuild as necessary.

You should look to allow for 1 or 2 rest days every week to ten days.

This doesn’t mean you should do nothing, but you can always go for a walk or swim which will allow your muscles to stretch and relax.

A summary of muscle fibres

Muscle fibres are single muscle cells that are found in all muscle tissue in your body.

They help your body complete many functions, including generating movement and even helping your heartbeat.

There are three types of muscle tissue:

1. Skeletal muscle fibre
2. Smooth muscle fibre
3. Cardiac muscle fibre

Each of these types has different characteristics and qualities to help complete different roles within your body.

It’s important to look after your muscle fibres in order to keep your body functioning in the way it should.

Muscle fibre can get damaged due to injury, a nerve condition or an underlying health condition.

If you have any concerns about your muscle fibre health, you should contact your GP or a health professional.

In the meantime, you can obtain a good standard of muscle fibre health by following a healthy, well-balanced diet that includes meat, dairy and fish – however, those following a vegetarian or vegan diet may be interested in looking at supplements to help gain their desired muscle strength.

The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Last updated: 15 December 2021