Developing a DYNAMIC core- Part 2- Why?

Posted: December 25, 2011 in Training Articles

In my last two posts, I’ve talked about training the core.  First, I explained what core stability means and showed you a video of one of the most basic yet effective core stability exercises: the forearm plank.  In the next post, I went over the difference between static stability and dynamic stability and how this can have an enormous effect on sports and life in general.  I also showed you this video of a core reaction exercise:

You might be asking yourself: What makes this an exercise for the core?

That’s a good question, and the answer(s) to that question is the basis for my entire integrated dynamic core training system.

First of all, look at the direction that the resistance is going:

It’s a little bit hard to read, but essentially the resistant force from the band is pulling diagonally down and to the left (in this picture) while the triceps are only exerting a vertical force, directly overhead.  Since the band is not only pulling in vertical plane, but also (and in this instance to a greater degree) in a horizontal one, there must be some stabilization involved, and any time the resistance is placed above the waist, this stabilization is going to come from the core.  Conversely, a typical overhead triceps extension as shown below does not have a diagonal component to it.  The resistance from the weight pulls directly down with gravity, while the triceps exert a force directly overhead:

(Image from

Without the diagonal component, this exercise involves very minimal core stabilization.

In addition to this diagonal force vector that actively engages the core, the use of the band also creates VARIABLE resistance.  As the band is stretched, the amount of resistance goes up, and is at it’s peak at the final stage of the exercise.  This means that when the arms are completely extended overhead, the abs must engage the strongest in order to keep the spine in a neutral position.  It’s this variable resistance that creates the DYNAMIC nature of the exercise– a resistance that constantly changes through the range of motion.

That’s all for now.  Let me know what you think of these exercises as I continue to post them!

Adam Reeder, cPT
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