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It's known that squeezing the abs is one of the most important rule of (to my knowledge) all workout exercises, especially with weights

The reason of this is the ability of ths abs to stabilize the back preventing it from overarching (anterior pelvic tilt) to get momentum and make the exercise easier (let's think at pull-ups, overhead press etc).

This is very useful because in such exercises there is high risk of anterior pelvic tilt. I can understand the importance of abs in such situations since they their shortening may tilt the pelvi backwards and counteract the anterior pelvic tilt. For the same reason, in many exercises it's advised to squeeze the glutes.

What I don't understand is why squeezing the abs is a must even in all exercises where there is high risk of posterior pelvic tilt. I'm thinking for instance at squat (butt wink), deadlift and barbell roa. In such exercises I find it more difficult not to go in posterior pelvic tilt. Why should abs shortening help me?

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    This has already been answered but yes you squeeze your abs during squats, etc. but you also arch your lower back to prevent the issue you're having. squeezing your abs and tilting your pelvis posteriorly are two different things, usually I've only seen pos. tilting pelvis as a benefit to core exercises
    – Ace Cabbie
    Mar 24, 2021 at 19:45
  • @Ace Cabbie But isn't abs squeezing a possible cause of posterior pelvic tilt?
    – Kinka-Byo
    Mar 24, 2021 at 21:07
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    you can tense your abs and squeeze them without posteriorly tilting your pelvis, but to posteriorly tilt your pelvis you have to tense your abs, if that makes sense. if youre referring to the chronic condition "posterior pelvic tilt" and not just the act of tilting your pelvis, Ive only seen this with people who sit in an office all day or have bad posture and the overly tight abs are more a 'result' of the condition, rather than a cause.
    – Ace Cabbie
    Mar 26, 2021 at 20:41

2 Answers 2

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Control

If you were to use only your spinal extensors to counteract the bending force that a deadlift, squat, or row applies to your torso, then those muscles would need to perfectly counteract the continuously changing bending moments exerted by the external load at each of the 17 joints throughout the thoracic and lumbar vertebrae. Whereas if instead all the muscles of the trunk contract together, so that the abs and the spinal extensors are fighting against each other, this creates an overall stiffness throughout the torso that is capable of resisting these bending forces.

Imagine you're trying to secure a crate being transported in a car trailer. What has a higher likelihood of success; just cranking down several straps over the crate, so it's locked in place, or instead using a single strap running from the crate to only one side of the trailer, and attempting to angle the strap so that it can apply force in the direction that you anticipate will be needed for the next corner you will be turning?

It's important to note though that the cue is tensing all the muscles of your core, not just the abs. If you only tense the abs and neglect the lumbar extensors, then yes, you're pretty likely to inadvertently go into lumbar flexion.

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  • Thank you very much, that's really a complete answer. Just a question: how can we activate the lumbar extensors to balance the abs squeezing? I've been told that back extension is performed by pushing the hips forwards thanks to glutes squeezing. Does it happen also in the situation we are speaking about?
    – Kinka-Byo
    Mar 24, 2021 at 7:00
  • Do lumbar extensors shorten or lengthen to perform back extension (to balance abs squeezing)?
    – Kinka-Byo
    Mar 24, 2021 at 7:01
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    Lumbar extensors shorten during back extension, i.e. exercises like the superman. These are the muscles running up you back on either side of your spine. You should be able to reach around and place a hand on your lower back and feel them tighten up as you brace. (Although they may already be a little tight even before you brace, just from the normal demands of holding your torso upright.) Mar 24, 2021 at 7:13
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    Correct, hip extension occurs between the pelvis and femurs, whereas back extension occurs above the pelvis. The hip extensors and back extensors pull on the pelvis in opposite directions. You can have back extension with hip extension, such as in a superman exercise, back extension without hip movement, as in a yoga cobra pose, or back extension with hip flexion, as in sticking your butt out. Mar 24, 2021 at 7:30
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    Yes, but it's more commonly referred to as "hyperextension". Mar 25, 2021 at 12:18
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What you're calling "squeezing your abs" is usually referred to as "bracing".

Don't think of bracing as squeezing your abs inward. It's actually more of a push outward, together with your breath and your whole core musculature including your obliques, lower back and the inner core, creating a rigid and stable torso. Get your breathing right and push out with your breath through your stomach. Tense like you're preparing for someone to punch you in the abs, then push out with your breath forward and out the the sides.

This kind of bracing doesn't affect the pelvis tilt, you can move it back and forth while braced.

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  • Thanks for you answer. What is still not clear for me is how can we be sure that our abs squeezing doesn't lead to posterior pelvic tilt? Should we think to extend our back in the meanwhile?
    – Kinka-Byo
    Mar 25, 2021 at 5:42
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    Again, don't squeeze your abs, brace your whole core outward, including your back. You can practice this with a weightlifting belt. Try pushing out against the belt like you're trying to break it. Do what you normally do with your pelvis, set it in place before starting the lift and keep it in that position.
    – Curiosity
    Mar 25, 2021 at 8:26

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