Moments in Squat Stance Moments in Squat Stance

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Thread: Moments in Squat Stance

  1. #1
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    Default Moments in Squat Stance

    From Reynolds article, "The Difference Between Starting Strength and Powerlifting," it's written,

    "The total moment on the body of the powerlifter isnít actually reduced in their version of the squat [ultra wide stance, toes angle out], but rather transferred from the sagittal (side) plane to the frontal plane, redirected off the back and moved primarily to the thighs Ė and thus the equipment (the suit and knee wraps) that the rules of the sport permits."

    My question is about the moment being transferred from the sagittal plane to the frontal, and thus being placed on the thighs. In the frontal plane, we have the center of mass of the barbell on the middle of the upper back. And there is a moment between that COM and the right thigh. But that moment is also on the left thigh as well, balancing the weight as a kind of Class I Lever.

    So since the weight is being countered equally by the left and right thighs of the body, is the body really having to overcome a moment as it is in the SS Squat (from the sagittal plane) with the torso leaned over, creating a moment at the hip joint?

    It seems to me that the total moment is greater in the SS Squat. Or maybe it's not. Is it ultimately the same in either case?

    At the very least, can we safely say that the total moment that must be overcome is greater in the SS Squat, but that the total moment is the same in either situation?

  2. #2
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    The point is to throw the moment force onto the levers in such a way as to maximize the amount of muscle mass available to operate the moment. I don't see how the moment is split between the thighs.

  3. #3
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    Default

    Quote Originally Posted by Scott Beall View Post
    From Reynolds article, "The Difference Between Starting Strength and Powerlifting," it's written,

    "The total moment on the body of the powerlifter isn’t actually reduced in their version of the squat [ultra wide stance, toes angle out], but rather transferred from the sagittal (side) plane to the frontal plane, redirected off the back and moved primarily to the thighs – and thus the equipment (the suit and knee wraps) that the rules of the sport permits."

    My question is about the moment being transferred from the sagittal plane to the frontal, and thus being placed on the thighs. In the frontal plane, we have the center of mass of the barbell on the middle of the upper back. And there is a moment between that COM and the right thigh. But that moment is also on the left thigh as well, balancing the weight as a kind of Class I Lever.

    So since the weight is being countered equally by the left and right thighs of the body, is the body really having to overcome a moment as it is in the SS Squat (from the sagittal plane) with the torso leaned over, creating a moment at the hip joint?

    It seems to me that the total moment is greater in the SS Squat. Or maybe it's not. Is it ultimately the same in either case?

    At the very least, can we safely say that the total moment that must be overcome is greater in the SS Squat, but that the total moment is the same in either situation?
    The moment does not cancel from side to side. The right and left legs act independently from a structural standpoint, not as a rigid Class I lever that transfers force or moment from one side to the other.

    Also, the total moment at the joints is not necessarily the same in one squat configuration vs the next. We can look at a low bar squat vs a high bar squat vs a front squat and compare the moment arm lengths in the sagittal plane and note how the MA length shifts between the hip and knee (to the bar) from one version to the other. This a notional comparison that assumes that stance and angle of thigh external rotation remain the same. Once the stance changes - as it does with an ultra wide stance PL squat - you must look at the 3-d sum of the moments (easiest viewed in the transverse plane, since moment about the z-axis will always be 0), and not just the sagittal plane. The total moment at the hips/knees will be slightly different in a PL squat vs a low bar squat vs a toes-forward, knees-forward high bar squat.

  4. #4
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    It's a good question and a fun thing to think about, but in a normal SS squat, the hamstrings and glutes on each leg are both working together to overcome the moment forces on the hip from the barbell (and actually using their own moment force to extend the hip). In a very wide squat (where the torso is much more vertical) at the bottom, the femurs are still parallel to the ground (or better yet, perpendicular to the gravity vector), and thus they still work together to overcome all that moment (because at parallel they aren't in compression or tension at all....at least in relation to gravity).

    It's clear that moment operates in a 360 degree system, not a 2D single plane system.

    It's much easier to understand the moment forces operating on the body the way Rip explained them in the 3rd ed of SS;BBT, but we all understand that moment doesn't care what plane you are looking at.

    Are the upper arms in less moment at the bottom of the bench press? This would be nearly the exact same scenario you posed about the thighs in the squat. It "looks" like a little bit of moment from the side, but looks like a whole bunch of moment from the front. And we can abduct/adduct or internally/externally rotate the humerus to apply the amount of moment forces on different muscle groups...same as in the squat.

    The real thing that taking a super wide stance squat (or a super wide grip bench press) does is that is reduces the total amount of WORK done by reducing the ROM, which is opposite of what we are trying to do to get generally strong.

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