The Signal for Growth

Muscle growth doesn’t happen by accident.

Muscle tissue is very expensive for the body. Humans beings are “perfect” systems. You only build this tissue when there’s environmental need.

I don’t think anyone needed to be told that you don’t grow muscle sitting on the coach… naturally 🙄

Here’s an experiment you shouldn’t try.

Don’t leave your bed for a month and see how much of your gains you lose.

Then take a walk around the block and boom. You’ve built muscle. This was because you added back the growth signal for normal environmental function.

You’re an efficient machine, you’ve evolved to have a system governed by demand.

This stops you from scaling your energy expenses up to the point you’re in energy debt.

However, here’s some observations you might have

• You have to challenge a muscle for it to grow, thus growth doesn’t happen globally

• You can preferentially grow parts of the chest/other muscles thus muscle growth doesn’t happen on a whole muscle level

• The growth signal can only he experienced on the fibres level

All of this is to prevent unnecessary energy expenses, after all why would you grow all muscle fibres when only some had a demand?

We’ll speak more about how muscle fibres are recruited soon, this will be all about the signal itself.

Remember growth only occurs on active fibres which means there has to be something which detects this resistance, and something we can manipulate.

Enter costameres and titin.

These are the mechanoreceptors in the muscle fibre.  These detect external environments 🕵️‍♂️

These two have different mechanisms of growth, different stimulus, and different ways we can manipulate it.

It’s now that you need to split mechanical tension into active, and passive.

1. Active mechanical tension is resistance that occurs whilst you try and contract a fibre

2. Passive mechanical tensions is resistance that occurs whilst a fibre is being stretched

Passive Mechanical Tension (Titin)

This adaptation is quite honestly one you can ignore.

It’s not that you won’t grow through this, it’s just not entirely worth your time.

Keep reading if you’re interested in what this is otherwise follow this guidance and skip to active mechanical tension:

• Have a controlled eccentric for injury prevention

• Use stretched position if the muscle has good leverage there (sparingly)

• Don’t worry about maximising passive MT ever.

Now for those left who are serious about learning.

Titin is like a big spring in your muscle.

When you force a muscle to have a controlled eccentric, or you’re in a big stretch, Titin helps out by being a spring (I assume you know how those work).

When Titin gets challenged, it sends a growth signal.

This growth signal adds sarcomeres in series in the muscle fibre which makes it longer.

It’s not that this growth is bad or doesn’t work but there’s a few reasons why we don’t focus on it.

1. It has a very low adaptive ceiling which change reached in a matter of weeks (you can only stretch your muscles so far)

2. The adaption leaves very quickly which means you have to keep using the same stretch positions to keep the adaptation

3. It only happens to active muscle fibres

You might be wondering why I included number 3, it’s obvious…

Here’s the problem.

You are about 2x as strong in an eccentric as a concentric, this means you’re not using many of your muscle fibres and won’t grow as well.

“But…” I hear you thinking.

“What if you just do eccentric only work?”

You’re right.

If we wanted to get more of this adaptation, we could do some exercises that only work the eccentric to use as many muscle fibres as possible but there’s a BIG problem with that.

• Eccentrics generate the most muscle damage, and thus fatigue, by far.

• You’d have to keep doing the eccentric only training on the exercises forever or you’d lose the adaption

• The adaptive ceiling is still low.

Now I’m sure you get why you ignore passive tension almost entirely.

In truth although this adaptation results in growth, what you’re really seeing is a protective mechanism.

The lengthening of the muscle is to prevent injury.

By controlling your eccentrics we meet that very same need.

Trying to get more of this just means we get huge interference in the actual growth we’re seeking, due to all the fatigue…

Active Mechanical Tension (Costameres)

Let’s talk about real growth.

Talking to costameres are worth your time.

You talk to these through the concentric.

Here’s why they matter so much

• Bigger muscle fibres

• Very high adaptive ceiling

• Is actually the adaptation we care about

It’s very easy to explain the simple side of what’s going on here.

Inside each and every muscle fibre are a LOT of motors.

These motors are what perform a contraction and make everything all well and good!

The costameres are able to detect how many motors are used, when we reach a certain threshold it signals growth.

When a muscle is challenged in a concentric it starts to experience involuntary concentric slowdown.

As a movement starts to reach failure (roughly the 5 reps prior) it needs to turn on more motors to recruit more motors to perform the movement, as the reps get slower more motors are brought on.

These are the reps that our costameres sense and ask the body for bigger, stronger muscles.

But here’s what this means for your training

• If a set isn’t within roughly 5 reps of failure you cannot grow.

• If there’s something inhibiting motors from being recruited, growth will be limited.

• You can’t stop a set because we start to notice slowdown/difficulty to keep your desired speed

That makes a lot of sense to all of you.

I will on this one be telling you how we can manipulate this to get better growth.

There’s two major things at play which will limit this signal for growth outside of motor unit recruitment

1. Glycogen stores

2. Muscle temperature

I’ve wrote all about glycogen stores over and over and over, if you want a proper read check this out.

TL:DR low glycogen stores means 1) less motors 2) less muscle fibres

Outside of that the recommendation is easy, get a good amount of carbs.

For muscle temperature you’ll have to play this one by ear partially.

If it’s winter it’s going to be a bit harder to do, if it’s summer it’s probably going to be super easy.

When muscle temperature is low we can’t switch on as many motors.

Here’s the fix warmup.

This isn’t a warmup to practice a motor pattern, it’s for our actual muscle.

• 15-20m of Zone 1 cardio and some dynamic stretches

This will get that heart pumping and the muscle warming.

This is pretty much all there is to it.

This is a foundational lesson of muscle growth, the signal is arguably the most important part.

If you know this, and motor unit recruitment, the rest can be guesswork.

GO GET THAT SIGNAL!

Your Hypertrophy Hero,
Fletcher

P.S. Don’t make the warmup intense or it’ll hurt your training itself.