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PostPosted: Sun Jan 30, 2011 10:48 pm 
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Does anybody know how much the force(s) at different knee angle varies while we are squatting? Is there any article/journal discussing about this matter that I could read? Once I read an article that says actually thighs above parallel exert greater pulling/forward force on the patella/knee because of quad pull > hamstring pull on the tibia.

I recently acquired a knee problem on my right knee and I'm trying to minimize further damage (I know I should rest/stop but I'd like to keep training). As my main sport is olympic weightlifting (beginner), I'd like to know if doing power version of the lifts (thighs above parallel) would be better for my knee.

Thanks for the help!


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PostPosted: Mon Jan 31, 2011 4:53 am 
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Sorry, I can't answer your question directly, but I had a couple of comments.

Part of the problem of squatting above parallel is that the stabilizing ligaments of the knee are at their most lax at perpendicular, so there is more play for the femur to move forward on the tibia at the time of reversing the movement.

I suspect (I don't really know, but this seems reasonable to me) that the forces involved in the squat, where the legs are carrying the weight down, reversing direction and then taking the weight up are different than what happens with the O lifts, where you drop into the squat essentially with loading being BW, then catching the weight and driving it back up.


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PostPosted: Mon Jan 31, 2011 8:46 am 
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Jungledoc wrote:
Part of the problem of squatting above parallel is that the stabilizing ligaments of the knee are at their most lax at perpendicular, so there is more play for the femur to move forward on the tibia at the time of reversing the movement.


Interesting, Doc. So as long we avoid perpendicular (I think it's about the tibia and the femur?) where the ligaments are most lax, it's okay? This includes greater or less than perpendicular.

BTW could you please elaborate further why are the ligaments most lax at perpendicular?

Jungledoc wrote:
I suspect (I don't really know, but this seems reasonable to me) that the forces involved in the squat, where the legs are carrying the weight down, reversing direction and then taking the weight up are different than what happens with the O lifts, where you drop into the squat essentially with loading being BW, then catching the weight and driving it back up.


It didn't cross my mind and I think you're right!


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PostPosted: Mon Jan 31, 2011 9:31 am 
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Here's the answer to your original question.
http://www.myoquip.com.au/Biomechanical ... rticle.htm

For further reading:
http://www.pponline.co.uk/encyc/squats- ... ercise-319
http://www.nsca-lift.org/HotTopic/downl ... 0Depth.pdf
http://www.apec-s.com/Deep%20Squats.pdf


From Starting Strength:
"In a partial squat, which fails to provide a full stretch for the hamstrings, most of the force against the tibia is upward and forward, from the quardirceps and their attachment to the front of the tibia below the knee. This produces an anterior shear, a forward-directed sliding force, on the knee, with the tiba being pulled forward from the patellar tendon and without a balancing pull from the opposing hamstrings. This shearing force--and the resulting unbalanced strain on the prepatellar area--may be the biggest problem with partial squats. Many spectacular cases of tendinitis have been produced this way, with "squats" getting the blame."


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PostPosted: Mon Jan 31, 2011 10:02 am 
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Thank you for being so kind and providing me with all those links, stu! Actually that statement by Rippetoe is what I wrote on the original post (quad pull > hamstring pull on partial squats), but I've also read (maybe it's Cressey?) that the hamstring only contracts isometrically during squatting movements (constant pull).

I'll read those and perhaps will get back here with something.


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PostPosted: Tue Feb 01, 2011 10:42 am 
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stuward wrote:


After reading all of the articles, this one seems to be the least useful because it only discusses the amount of torque on the hip/knee at various angles and doesn't include the amount of strain on the various ligaments of the knees. Also they are selling products....

I don't get this bit about what they are concluding:
Quote:
This study has demonstrated that throughout a deep squat movement with heavy loading the moments of force experienced at the hip and knee joints typically vary from excessive to inconsequential. Because of this the leg extensor muscles are likely to be effectively activated for only a minor part of the exercise movement.

It therefore seems appropriate to question the efficacy of the squat as a general exercise for developing leg strength.


I think they are referring to this:
Quote:
...it can be expected that the leg extensor muscles function most efficiently in the mid range of the exercise movement. The conjunction of such a muscle strength profile with the torque curves shown above means that a heavy load would place the exerciser in a biomechanically disadvantageous position in the deep range of the movement. At the same time there would be inadequate effective activation of the leg extensor muscles through the top range.


So basically the majority of resistance training with free weight are not effective? I think I've read similar statements about Arthur Jones and his Nautilus machines.

>>>
stuward wrote:


This one is loaded with a lot of valuable info. I like it when they are discussing about the forces acting on ACL, PCL, and patella when squatting, which cannot be assessed correctly just based on limbs and moments of force model like on the preceding article.

>>>
stuward wrote:


Another good info on knee ligaments and forces acting on them when squatting. This one also mentions that the hamstrings contract isometrically in the majority of their ROM.

>>>
stuward wrote:


Interesting tidbits by Starr and Rippetoe about the controversial Dr. Klein's research. Also this article mentions about joint laxity and running, which also interests me because I'm a beginner runner. Actually I have a guess that my knee problem might be caused by running downhill and my lack of experience. One thing though that while this article appears to make running as somewhat dangerous, the second article above also mentions that long distance runners' joints are stronger compared to the sedentary population (though I know an ex marathon runner with meniscus/cartilage degeneration and patella problems).

>>>
It's not as easy as I thought it to be and furthermore I don't know the details of my "injury" but at least I got some good info. Thanks again, stu!


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