This morning I was scanning Youtube over a cup of coffee and come across this video: https://youtu.be/Fob2wWEC72s
This is pretty well in line with how we teach squats at Karma. I teach the squat from the ground up, so feet first with 8 "rules" most of which are negotiable.
The first 3 address the feet:
1. Feet about hip width apart -- (totally negotiable). Depending on what feels comfortable and natural. I personally squat pretty narrow. Coach Nicole tends to squat fairly wide. Katy (while re-taking a CrossFit course) actually had her knee tweak while being made to squat into the "cookie cutter" squat idea in this video.
2. Toes about 15 degrees out -- (totally negotiable). This falls in line with number 1, it may just feel a little better to toe-out more, but I will tie that to another point in a moment.
3. Weight in your heels/mid-foot -- (not negotiable). This has to do with how the muscles recruit how the knee gets loaded while squatting. The idea that squatting is bad for the knees isn't correct but squatting too far forward on your foot can be rough on the knees and needs to be avoided.
The next 2 address the knees:
4. The knee shouldn't extend past the toes -- (totally negotiable). This is a really common misconception with squatting, but it relates to #3 above. For many people the knee goes out past the toes because the are too far forward in their feet. And we already said that is a non-negotiable point, your weight needs to stay heel/mid-foot. If you have flexible ankles or are wearing weightlifting shoes or both your knee might well extend past your toes while keeping your weight back in your foot. If that's the case you're fine!
5. The knee tracks inline with the toes/point of shoe -- (not negotiable). So, many people might say "Well the Chinese lifters..." and yeah, I know. Basically the knee is a hinge, and hinges are not really meant to twist. If that doesn't make sense take the top hinge off of any door in your house and see how the bottom hinge holds up. In this video the doc refers to this as the joints being stacked. For long term knee health this matters.
The next 2 address the hip:
6. The hip should drop below the knee or "below parallel" depth -- (negotiable). This is really negotiable for new lifters mostly, eventually everyone should be working to that depth as it takes the hip through a full range of motion and will help keep the joint healthy. Besides that, how else our you going to poop while camping? If you're a new lifter and you can't get to that depth without breaking one of the non-negotiable rules above or without keeping your spine in a good position (more on that in a second) then chasing that depth might do more bad then good.
7. The hip should start the movement back and down (semi-negotiable). So this is really based on proximity to the spine. The brain communicates with the body though the spine so body parts closer to the spine get the information first and should move first. This is really what is meant by "core" it has nothing to do with having a six-pack set of abs! The reason I say semi-negotiable is in part because nerve impulses are electricity and that moves fast enough that the time from your hip to knee is basically irrelivant and a good squat often looks like the movement is happening simultaneously. However, and especially in CrossFit, most people come in squatting pretty badly so if you exagerate the movement of your hips back you are less likely to break the non-negotiable rule about weight distribution in your foot from above. It is an over-correction to teach it this way, but as long as it is smoothed out as the squatting motion matures that's fine.
The last one addresses the lumbar spine:
8. Keep your back straight (non-negotiable). First off, staight isn't the same as vertical. Second, the spine has some natural curve to it anyway, that's what we want to maintain. This is a problem when you load the spine in an excessive arch, the weight bearing discs in the spine don't like that. What this looks like is often confused with starting the motion from the hip. Starting from the hip is "hinging" and the butt moves back. Starting from the lumbar is "arching" and the butt moves back. One is good, the other isn't. Then of course there is the butt rounding under in the bottom position or the "butt wink". There is a lot that can be addressed here that I will save for another time, but basically the spine loaded out of the normal curves is not a good idea. In the video you'll see that talked about as it relates to the range of motion of the hip joint and why different positions are needed for different lifters. Sometimes it's just poor motor control. At any rate it should be avoided.