Muscle Activation Series – Part I

What It Means When Your Muscles are Switched Off and Why You Should Care

If you’ve been to an appointment with us before, you’ve probably heard us talking about muscle activation or muscle recruitment.

It’s a big issue that affects most of our clients one way or the other, and we’ve found there are three main muscles/areas that tend to be underactive and the underlying cause of a lot of our clients’ problems.

 

In today’s post, we look at what muscle activation/recruitment is, in broad terms, and why we think it happens, etc.

In the next three posts (released every two weeks) we’ll look at the three most common muscles that seem to be underrecruited and how we notice they create problems or affect movement elsewhere.

By the end of this series, you’ll have a good understanding of what muscle activation is, what happens when muscles aren’t recruited when they should be, and what you can do about it.

What Is Muscle Activation?

Quite simply, a muscle is activated or recruited when the brain sends a signal, via a nerve, to the muscle for it to contract.

It isn’t a question of strength, or even endurance.

It’s just a question – if you need to contract, or ‘turn on’ a muscle, can you do it?

Almost everyone can activate their biceps…

*the pool is this way…* (sorry if you don’t get this reference… you can also substitute ‘check out my guns’)

Bend your elbow, squeeze your forearm close to you, and boom – your bicep should get a little harder…

This indicates that the connection between your brain and your bicep is good.

There are two considerations with activation/recruitment.

One is: Can you switch the muscle on (like you just did with your biceps)?

Two is: Does your brain switch the muscle on at the right time during a movement (does it recruit it for the right movements)?

It does you no good to be able to turn your biceps on if your brain doesn’t switch on, or recruit it when you’re doing a push up or picking up your suitcase.

What Is an Underactive/Under-recruited Muscle?

Luckily, most people don’t have an issue with activating or recruiting their bicep.

But there are various other muscles that people DO have trouble turning on.

That’s when we call that muscle ‘underactive’ or ‘underrecruited’.

This means either that a person can’t contract the muscle at all (like, their brain says ‘contract, goshdarnit!’ and nothing happens) or it can contract that muscle specifically, but it doesn’t when that muscle should be contributing to a movement.

This is also called ‘muscle amnesia’ by some practitioners, because it’s like the muscle forgets how to turn on (I do not like the term personally, because my literal brain says ‘muscles can’t forget things!’ and ‘it’s not forgotten – it’s the message isn’t effectively getting from brain to muscle!’… one of the many joys of being… well, we’ll call it detail-oriented).

Why Do Muscles Get Under-Active or Under-Recruited?

First of all, I did a search for ‘muscles switched off’ or ‘muscle amnesia’ to try and find you some good other source material (which I’m including at the bottom for other links), and I am not impressed with the results.

It looks like, like me, most practitioners are relying on their own observations and clinical experience vs any sort of long-term, large-scale study (which is fair, because muscle recruitment and activation isn’t going to be a research priority for many institutions/companies).

(side note: in that quick search, I’ve also come to the conclusion that another post detailing why muscle amnesia is misleading needs to be written, especially when another term for it, at least in the case of the glutes, is dead butt syndrome. WTH? who thought that was a good idea for a syndrome name?)

Here’s what’s observable/what we know:

Our brain is efficient. It doesn’t want to waste energy on stuff it doesn’t have to. So, if you aren’t using a muscle for an extended period of time, it makes sense that it wants to turn those muscles off.

Our brain also has a principle called ‘use it or lose it’, also called ‘competitive plasticity’. If you don’t use a particular skill or set of neuronal connections, our brain will re-purpose them to be used for something you are using. (source: The Brain that Changes Itself, Norman Doidge, p. 59-61)

There appears to be a mechanism where if you hurt yourself (like, sprain your ankle), the brain tries to stop using that muscle to allow it to heal. It seems to do that by not sending messages down the whole pathway (which is why rehab is so important to regain normal function after surgery or an injury).

Put that all together and you have a few different scenarios in which it makes sense that your brain stops sending signals to turn on your muscles.

The Switchboard Analogy

switchboard for muscle activation analogy
just replace ‘wheel house’ and ‘life boat’ with ‘gluteus maximus’ and ‘hamstrings’

You know I love my analogies.

This is the analogy I use to explain how muscle recruitment seems to work with our muscles.

(disclaimer: this is not how the brain is actually put together. in case that wasn’t clear)

Imagine that there’s a switch board in our brain (like with little old styles which is with labels on them – see picture).

That switch would have a wire attached to it. The wire is our nerve, going from the switch, i.e., the control in our brain, to the muscle.

When we’re observing muscle activation problems, it seems like three different things can happen.

One, it’s almost like the wiring gets frayed or poorly insulated so a message is getting through and we’re getting like a tiny, tiny bit of activity or contraction, but it’s really faint or really weak. In those cases, it seems like the brain can sense that muscle isn’t capable of supporting the movement, so it uses another muscle instead. 

poor signal for muscle activation
it’s like the wiring is frayed when relaying the message from brain to muscle and the message doesn’t get through

Two, that switch has one ‘label’ on it, but the wire goes to a different muscle. I’ve had clients on my table and we’re trying to contract their glute, for example. They’re sitting there thinking ‘contract glute, contract glute,  contract glute’.

Meanwhile the glute isn’t moving, it’s not doing anything, but their hamstring is getting tighter and tighter and tighter.

Three: Sometimes there’s just no activation at all – like there’s no movement. You ask somebody to, say, contract their lower abdominals and they just lay there and nothing happens.

There’s no contraction, no movement, and it’s almost like the wire’s been cut completely (but obviously that’s not what’s happened because we can get it back and if a nerve is severed you’re not getting a message through that again).

Again, this isn’t what’s actually happening, as in, there’s not an actual switchboard in your brain with a tiny little octopus switching switches on and off.

But, when you’re trying to get your muscles to be reactivated it’s a useful analogy to draw on, because as we all know our brain loves pictures.

What Happens if Muscles Are Underactive/Under-recruited?

Our body is an amazing system.

If everything is working well, if nothing is too tight, if nothing is underused, movement feels so much easier.

If you have a muscle that’s not doing it’s job, because for whatever reason the brain isn’t using it, isn’t asking it to work in a movement that it should be, then all the other muscles around it have to compensate.

You can imagine what happens when a muscle is asked to take on 20% more work because the muscle that’s supposed to be doing its job, isn’t.

That’s right – excess muscle tension.

The Most Common Muscles that Need Help

Generally speaking, there are 3 common muscles/muscle areas that get underactive.

Glutes

The glutes (gluteus maximus, medius, and minimus) don’t tend to kick in or do the job that they’re supposed to do often.

Lower Abdominals

The lower abdominals are another one. They can very easily be switched off for various reasons (*ahem*, sitting all day slouched at a computer, in a car or on the tube, and on the sofa watching TV *ahem*)

Mid & Lower Traps

The middle and lower traps are the third. They’re important for your posture and sitting up properly.

In this series, we’ll go through each one of these individually to talk about what happens when they become deactivated, what common compensation patterns you’ll see.

 

 

 

 

https://www.self.com/story/what-is-gluteal-amnesia

https://www.newscientist.com/article/dn6322-unused-back-muscles-switch-themselves-off/

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