Knees buckling

Discussion in 'Fitness & Nutrition' started by y1997, Mar 8, 2007.

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  1. y1997

    y1997 Made in the U.S.S.R.

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    My knees start to buckle in on heavy squats/legpress. What is the cause of this? Weak glutes and tight hips?
     
  2. Ceaze

    Ceaze https://hearthis.at/DoYouEvenUplift Moderator

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    Posted by Bill Hartman:


    One concept within the book [Starting Strength] that I question is Mark’s contention that the reason that an athlete has difficulty keeping his knees out during a the performance of a squat is due to weak adductors.

    Certainly a small technicality because Mark goes on to give coaching cues to resolve this training error as well as for all the other basic exercises many of which I use myself.

    However, I found myself lying awake at night trying to rationalize why he felt that it was weak adductors that caused the knees to cave in during a squat. So I looked around a bit to try to either support or refute his contention.

    For the sake of discussion, I’m eliminating poor technique as a cause. It’ll just get in the way because even well-trained lifters will at times cave at the knee during very heavy lifts.

    On to it.

    The first common belief is that it is due to weak hip abductors. Mark doesn’t feel that this is correct.

    I agree.

    In fact, there’s evidence that shows that adduction of the femur in a single leg squat was independent of hip abductor strength (this may cause many to rethink their position on anterior knee pain and weak glute medius, huh?). I think we’re safe here in extrapolating this information to a bilateral squat situation.

    Myth debunked perhaps?

    My gut reaction was that the adduction in the squat (knees caving in) was simply the body moving into a position of strength. The body will tend to select movement pattern that are safest based on your current abilities. We agree on that point, however, Mark states that the hip adducts to allow the stronger quadriceps to do more of the work. I think it may be something else.

    Comparisons of different stance widths of squatting show that there’s no significant affect on the involvement on the quads in general. Using this as a guideline, I’m going to say that quad involvement doesn’t change because of the knees moving inward.

    Sumo deadlifts (wide stance thus wide knee position) have also been shown to have greater quad EMG activity compared to traditional deadlifts (narrower knee position). Again, I’m taking some liberty here but if bringing the knees inward is supposed to increase quad involvement, I’m not finding it.

    So I can’t bring myself to agree that it’s an attempt to bring the stronger quads into a more advantageous position.

    If you look at squat mechanics, on the descent there is a natural abduction and internal rotation of the femur. At the bottom of the squat, there’s a big jump in adductor and glute electrical activity. This is followed by a natural adduction and external rotation of the femur on the ascent.

    A wider knee position can certainly magnify the degree of adduction at the bottom and on the ascent from the squat if whatever should be holding the knee outward isn’t strong enough.

    So what holds the knee outward?

    Could it be gluteus maximus?

    Maybe, but I doubt it. In a hip flexed position, like in the squat, the glute max is a lousy hip external rotator and a better hip extender.

    But here’s something else to consider.

    In a wide knee position, the ends of the glute max are closer together which may make it actively insufficient. By adducting the hip, it may realign the glute max and allow it to produce more force into hip extension. Even so, the glute max has a poor moment arm for hip extension in the bottom of a squat which improves as the ascent continues. The EMG for the glutes increases dramatically, but my guess is that it’s simply working harder due to a lesser mechanical advantage.

    So what does have a great hip extension moment arm in the bottom of a squat?

    Adductor magnus and the biceps femoris.

    Let’s look at the adductors first.

    We kind of know that adductors are involved because of the hip adduction (knees caving in or rather pulled in) in question. But you need to look at how the adductors work.

    They’re not one muscle nor do they have one function.

    Adductor longus is a great hip adductor regardless of hip position. So the wider the knee position in the squat the more active the adductor longus becomes. Remember the natural adduction of the hip on the ascent from the squat.

    Adductor magnus can be divided into 3 sections: anterior, middle, and posterior. The anterior portion is a good hip adductor regardless of the measure of hip flexion. The middle and posterior portions are weak adductors but great hip extenders. So much so that it’s frequently referred to as another hamstring muscle.

    How much does the biceps femoris/hamstrings contribute to the hip extension from a squatting position?

    They actually produce as much as 50% of the hip extension strength. In trained powerlifters and weightlifters, biceps femoris (the lateral hamstring) showed an increase in activity by 50% from the descent to the ascent.

    So what happens if the biceps femoris is relatively weak?

    First here’s a bit of information. The biceps femoris has a direct attachment to the lateral aspect of the femur, the lateral knee ligament, and it’s well-known attachment to the fibula. The makes the biceps femoris a good lateral knee stabilizer as well as producing an external rotation force at the tibia.

    If the biceps is unable to do its job as in the case of too heavy a load or simply relative weakness compared to the other hip extensors, the knee will cave inward (actually a combination of adduction at the hip and internal rotation of the tibia).

    The result and my best guess is that your brain will want to move into a position of strength and emphasize the muscle with the greatest leverage and muscle mass…the adductor magnus.

    So in my estimation it’s a biceps femoris weakness and not the adductors.
     
  3. jokka

    jokka OT Supporter

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    i have a problem with my foot placing. I have to constantly adjust my feet b/c for some reason my right foot seems to be more forward than my left. It feels akward when they are in the correct position.
     
  4. y1997

    y1997 Made in the U.S.S.R.

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    :bowdown:

    Thanks Ceaze.

    So what should I do to improving my "inside hamstrings" or biceps femoris?
     
  5. Ceaze

    Ceaze https://hearthis.at/DoYouEvenUplift Moderator

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    lateral = outside
    medial = inside
     
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