Dr. Andy Galpin

So that's really what we mean.

Isolated doesn't necessarily mean isometric and not moving.

It just means you're targeting

And I'll explain really quickly here why that actually matters and why those don't work as well as those bigger exercises because of my very next point, which is the one thing you'll see really consistent here.

The key driving principle in effective ab or core exercises is contraction intensity.

So if you can contract your abs really hard with a body weight movement or an external load or a machine, it's clearly telling you those things were not the variables that mattered.

What mattered is you simply got yourself in a position where you were safe, you didn't get hurt, and you were able to contract really, really hard.

That's the key differentiator, and it is clear as day once you go through all the literature.

That is the thing that always has to be there to work.

If it's not there, it doesn't work.

And how you choose to get to high intensity is really up to you.

What we're talking about here is a great example of what's called the size principle.

So the size principle says that you have these motor units.

So this is all the motor neurons in your body and then the motor units in the muscle that they activate.

When you start to produce a human movement, you will always start with what are called low threshold motor units.

These tend to, but are not always slow twitch motor units.

They tend to, but not always are smaller, but they are the ones that are more energetically efficient.

And when you need more force demands, the way that your body increases force output is that you turn more of these motor units on.

You may be actually surprised, but you don't have the ability to regulate force production at the level of muscle, such as to say at the individual muscle fiber itself, you can't contract it at 60% or 70%.

When a muscle fiber contracts, it contracts at full force.