Your Muscles Don’t Stretch! They Literally Grow Longer!

Did you know that skeletal muscle can grow in more than one way?

Most people are aware of their muscles’ potential to get bigger and thicker in diameter – like the way you build muscle with strength training in the gym.

However, few people are aware of their muscles’ potential to grow longer in length and get more supple as a result.

This ability of your muscles to grow in length will be referred to as the Flexibility Growth Factor (FGF). Let’s now turn your attention to how it works and why you should be aiming for it.

Muscle Growth – The Other Way!

Studies by Vander, Sherman, and Luciano show that a muscle can be contracted up to 70% of its normal resting length or stretched up to 130% of its normal resting length. This naturally puts a limit on how far a muscle can be stretched and also produce force.


Muscles are made up of muscle fibres that are arranged in bundles parallel to each other. It’s well established that muscles can grow in diameter by increasing the number of myofibrils and hence increase thickness (e.g. bodybuilding). However, it is a lesser-known fact that muscles can also add more sarcomeres and grow in length.

When you stretch properly, your body actually adds new sarcomeres to increase the length of your muscles.

Now this part is really important – most people view their muscles and flexibility work as synonymous to a rubber band that is maximally stretched and eventually breaks and tears (the often propagated view).

This paradigm is only a half-truth – your muscles stretch but they do so in a manner that is more resemblant of your muscles being like antennas that extend in and out, rather than a rubber band.

Viewing your muscles as extendable and retractable antennas is also a better mental visualisation while you’re actually performing stretching exercises.

But how do you stretch past the 130% limit and start adding new sarcomeres (antenna pieces) to your muscles? Well, your typical static stretching for a few minutes before or after a workout is not the answer.

You need to perform exercises or stretches in which your muscles tense as they are being stretched. For instance, eccentric tension exercises and contract-relax stretches (performed effectively) will increase the length of your muscle fibres by adding new sarcomeres (Fridén 1984; Handel et al. 1997; Lieber and Fridén 2000).

To give you a taste of this in practice, watch this >>video using the example of the contract-relax stretching method for the hamstrings.

The FGF also empathises the importance of strengthening any new range of motion you are requiring your body to move through. This is why it is best to not always view stretching as a passive, mindless activity – you need to be engaged in it and actively strengthening the new ranges of motion you are developing.

If the upside of trying to add sarcomeres and lengthen your muscles isn’t appealing enough, the downside should definitely get your attention.

NOT understanding the FGF factor, can leave you feeling frustrated at best injured at worst. It can hamper your future performance, stagnate (and even regress) your recovery, reduce your flexibility, increase your chances of injury, and ultimately make your stretching a futile and counterproductive activity that turns into a big waste of time!

Stay tuned for the next piece where we will go over the drawbacks or ineffective flexibility work and why muscle length is even more important with increased muscular size.

Before then, be sure to reach out for practical advice on how you can individually alter your muscular length safely and effectively with your own stretching practices.

If you’re serious and ready right now to implement some changes to make your stretching an effective activity (rather than stagnating ritual that gets you nowhere!), then simply fill out your details below and one of our expert coaches will get in touch with you:


What kind of fitness animal are you?