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Torso Strength – Dynamic and Static Loading



Yo Smitty,
I got a question that I want to see if you can clear up for me on a scientific level.

With your last video of the straight leg situps with chains you talked about loading them dynamic and static. What is the science behind it and why it helps improve it, for some reason I still have the hardest time understanding the two. Its like I get it working out but I am just trying to understand the science behind it all.


The science behind it is all about motor unit recruitment and tension.  Of course we need to brace the core statically to protect the spine under compression and for force transfer during all other movement (rotation, extension, flexion, lateral flexion, etc.).

We also need to develop strength of the torso dynamically, because movement is dynamic and random, in our case we’re talking about athletics.  The chains created a dynamic loading because they are always adjusting.   And if they are always adjusting, our motor units are rapidly firing to transfer, counteract and balance the load.  The more dynamic and intense the loading, the higher the threshold of motor unit is excited.  If we can control and forcibly lift the weight, then we can become efficient at firing the HTMU’s quicker.  This improves reaction time.

Hope this helps…



Here is the video in question:

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9 Responses to “Torso Strength – Dynamic and Static Loading”

  1. Matt Holmes Says:

    You rock bro, thanks for breaking that one down.

  2. zach even - esh Says:

    dude, great answer and this makes greater sense now, thanks smitty.

    i will be hitting you up on core and torse training advice to make me stronger and healthier,

    thanks bruddah!


  3. RiseAboveStrength Says:

    Awesome core exercise!
    2 Questions:

    1)Advantages w/ straight leg over bent knees, more ab/core muscle recruitment?

    2) What brand of handles do you like to use for exercises like that?

    Thanks guys

  4. Jim Smith Says:

    Thanks everyone.

    1) greater range of motion
    2) I believe they are called “D” handles, Elite sells them.

    I believe it is very important to explain complicated concepts in a simple, easy to understand way.

  5. Frank Says:

    Good stuff as always!

  6. D-Rock Says:

    So if the chains act as a dynamic load, where is the static load? Or are chain sit-ups used as the dynamically loaded movement in a more comprehensive program that would include other, statically loaded core movements?

  7. Jim Smith Says:

    1. The torso (as a whole) is braced statically (isometrically) to protect the spine and engage movement

    1. The torso (which includes the anterior and posterior musculature) contracts dynamically to control the chains
    2. Chains act dynamically due to their swinging

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