I was watching a video and they were saying how when squatting with a vertical tibia, stress is funneled to the hip joint much more than the knee. Can anyone help explain the difference between keeping the tibia vertical vs angled? Is it basically keeping your lower leg vertical while squatting? Basically sitting straight back into a chair with a vertical lower leg? Like a box squat?
Squatting with a completely vertical tibia exponentially increases the low back load, as well as increasing the hip load. Squatting with excessive tibia angulation/dorsiflexion, increases the shear force at the knee.
I'm not sure I agree with, or maybe I don't understand, the first sentence of your reply. I don't understand how the vertical tibia "exponentially increases the low back load." I think low back stress has much more to do with forward lean than tibia angle. The weight (or load) on your low back is whatever is on the bar, unless you get forward. This forward lean would then act as a lever, increasing stress on the low back.
I agree 100% with your second sentence, and I would submit that that is a great reason to strive to keep the shin as perpendicular to the floor as possible - to protect the knee. I believe the OP's description of sitting straight back into a chair, like a box squat is right on.
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I think it depends on your lever lengths. For long limbed lifters you gotta put your knees somewhere (if your torso is upright as in a front squat) so there are two options: to the sides (degree dictated by stance width) and to the front. I once saw a guy with freaky squatting levers squat with an upright torso with pretty vertical shins. I can't do that with my relatively long femurs or I'd tip over. To keep my shins upright would need to involve my either squatting sumo stance and / or sitting my butt back with a forwards lean as in a back squat.
Oly lifters often have their toes well in front of their knees in the deep squat position (with an upright torso). Apparently they don't have knee issues... But anecdotally... They do. Dunno.
Here's an article from Cosgrove from awhile back, he cites a study that states squatting with a vertical shin increases low back load 1070% (I actually read the source article bc I cited it in a presentation, don't have it on this comp, but you can pubmed search the authors from the Cosgrove article)
And X2 to what BBB said
OK, I see the point BBB and Face are making about vertical shins leading to forward lean and resultant low back stress. I'm not trying to be purposefully argumentative, but do you guys think the same caution applies if a person is able to keep the upright shin and also keep the back relatively straight? I squat with a fairly high bar placement, and I don't lean forward very much. I know a few other guys with this same style.
Like Alexus said, levers are going to be different on everyone, so you might be able to squat with more vertical tibia, and a more vertical back if you can keep the bar over your COG. You may see other lifters doing the same, but if you actually measured/observed carefully, I would imagine that these people have a greater degree of dorsiflexion and/or spinal flexion then you are recalling.
Or maybe the population you mention all have similar leverage to allow for a more vertical tibia/spine. Or they squat with a very wide base. Or they aren't going to depth. A lot of variables to consider,and it could be any one or a combo of these factors and more.
IMO...they have a very wide base(almost what we used to call a 'duck' squat)and rarely reach a point where the hip joint falls below the knee. They 'arch' the bar out of the rack and the combination usually results in a shorter range of motion as well. Lifters that squat like this usually have more hip problems that issues with their knees, that is why groove-briefs and power pants were developed.
Really informative post. Not my thread, but cheers BBB.