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Ask Dave: Why is core strength so important?

Updated: Jan 10, 2021

This post was originally written in Feb 2013, but as the “Water Bottle Speech” still gets rolled out, and came up in a recent Facebook discussion, I figured it’s worth the repost.

Enjoy, Dave


Over the weekend I was over in Galway as a guest of the inimitable Sarah Smith, owner of Galway Kettlebells, where I taught my bodyweight training workshop.

The workshop is always a blast to teach, each time I run it I’m more than impressed by the level of questions that get asked. On this one though I got a doozy.

A 17 yr old martial artist was on the course, a bright wee lad who is relatively new to the whole fitness / strength & conditioning world. So often the best questions come from those with the least knowledge, and like I said, this was a corker. He asked,

“So why exactly is core strength so important?”

Usually I am asked about developing core strength, this is the first time I’ve been asked one of the most important of all questions, “Why?”

To really answer, first of all we all need to be on the same page as to what exactly the “core” is, I personally use three definitions dependent on the context I’m working from.

Lets go over these three definitions:

Definition 1 – The Water Bottle Concept

This idea came to me while teaching seminar on Kettlebells to group one day. I asked the group, who were mainly young fitness instructors for their opinions on how to define the “core” Needless to say I got a lot of blank looks followed by stumbling descriptions and a lot of pointing at the stomach.

At that moment I grabbed my water bottle and used it to illustrate a simple view of the core as a singular unit as opposed to a jumble of parts. Here’s a short version how the speech goes

A plastic water bottle, even an empty one, can support a good portion of my bodyweight without any issue. Assuming I can balance on it, it can support my entire bodyweight with a degree of deformity occurring.

A sealed empty plastic bottle supporting a 10kg plate

A sealed empty plastic bottle supporting a 10kg plate

Now if put the tiniest hole in the bottle, or simply unseal the lid, it will collapse under a fraction of that weight.

But if we remove the lid....

But if we remove the lid….

How does the sealed bottle hold me up where an open one collapses? It is after all the same bottle made of the same thin plastic.

It’s the internal air pressure that supports my weight. The walls of plastic merely present the air escaping so that there is sufficient pressure to support me. As soon as the air finds a way out, through a weak spot in the plastic, the bottle collapses.

This is almost exactly how our abdomen works when we are generating high levels of force. The air pressure in the torso stiffens the body so that the hips and shoulders can use it as a platform to push from.

The water bottle even helps us with the anatomy:

  • The front side is our Rectus Abdominis, or “6 pack.”

  • Directly opposite this on the back of the body is the Erector Spinea. The sides represent our obliques.

  • The label illustrates the Transverse Abdominis nicely as it goes around the bottle, albeit on the outside rather than the inside.

  • The base of the bottle is the Pelvic Floor

  • and the lid represents the Diaphragm.

When all of these elements are working together, we are strong. Individually they are pretty much useless.

How does this help us? It shows us how the core works as a unit, stiffening to both protect the body and also to transfer force from one end of the body to another. For our martial artist, that means when his fist lands, the core stiffens so that the force is transferred not just into, but through his opponent with minimal recoil reverberating back through himself.


Definition 2 – From the Hips to the Shoulders

I don’t use this one as much as the water bottle idea, but I find it useful for getting the contact athletes and fighters to reconsider their training needs.

It’s a simplified version of the next definition that follows this:

The way I like to illustrate this is with 2 pens and an elastic band. Put a pen through the band and hold it steady, now put the other pen through it and start twisting. After a few twists hold the top pen steady and release the bottom one.

What happens?

That’s right, the bottom pen spins as the band unwinds. That’s exactly how a Thai boxer throws a kick, wind the top so that the bottom whips around.



If the bottom pen is our hip and the top pen is our shoulder, then the band is our core. What connects the hip to the shoulder? A whole host of muscles, including everything talked about in the Water Bottle idea and adding in the Glutes, Lats, Rhomboids, Traps and so on and so forth.

Look at thrower, be it shot put or baseball, doesn’t matter. See how they get their hip all the way around so the torso is twisted like our elastic band visual.  Then, as the torso teaches its maximal stretch it snaps the shoulder through, whipping the arm out and propelling the ball at rocket speed towards the target.

Every muscle that was involved in that stretch can be construed as the core. It’s not just your abs, it’s the entire connection between the hips and shoulders.

Definition 3 – The Spine

This is the "real" core. It is a series of 33 bones, 24 of which are able to articulate against the bone above and below it. The spine can flex, extend and rotate, essentially moving in each and every plane. It also protects our spinal cord and acts as an anchor point for a huge amount of muscle.


Let’s use throwing a punch as an example: A punch starts in the ground, we extend our rearmost ankle and knee which pushes our rear side hip forwards. This all happens fairly fast with each joint accelerating the next.

Now assuming our abdominal muscles have enough elasticity and strength, the hip turning while the shoulder is stationary will torque the midsection, the spine will become twisted and many the muscles the attach to the spine will either become lengthened (stretched) or shortened (contracted).

The spine then will unwind, releasing that stretch and literally slingshotting the shoulder forward throwing out the arm and knocking out the person opposite you.

If you get nothing from that other than the word “slingshotting” I’m cool with that, just as long as you use that word at something today in conversation. Drop me a comment letting me know how you get on….

Cue one of my favorite self defence coaches, Mick Coup, talking about the punch:

The flexion / extension of the spine in the sagittal plane (front to back) is used by strongman and Kettlebell lifters during presses and jerks to propel weight efficiently overhead with a whip or wave like action. Combine the forward flexion with rotation and you have a tennis serve, reverse it and you have a suplex throw.

Really, the spine is the core. Muscles are designed to move joints and the spine has 24 articulating vertebrae, as well as the sacroilliac, the atlas and others. That’s a lot of joints, all of which needs to be controlled by muscular contraction.

Now, does the core need to be strong?


It also needs to be mobile, or “elastic” as I prefer to think of it. So don’t just do your strength work, be sure to do some mobilisation work too.

I hope this offers some food for thought, I’d be fascinated to hear your opinions on the topic. I’ll talk about strengthening the core in another post.


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