I think forward knee displacement (the amount of forward knee travel) is one of the most misunderstood aspects of squatting technique. But obviously, knee extension is a primary squatting mechanic, so it's one of the most important things to understand if you're going to move some heavy f*&%ing weights.
Here's the deal: it can be tricky to figure out how far forward your knees should travel during the squat, because it's HIGHLY dependent on individual biomechanics and muscular strengths and weaknesses. If you just look at top-level lifters, you'll see a wide variety of techniques, and no clear connection between what they do and what you SHOULD do.
However, you really need to find what works for you, because the amount of forward knee displacement in the squat largely determines the balance of load between the quads and posterior chain. If you're a posterior-dominant lifter, you're probably biased towards keeping your shins pretty upright, but that might not be ideal. The opposite is true for quad-dominant lifters: you might actually not want to bust out those squat shoes and push your knees so far forward, because you're somewhat limiting your ability to recruit the low back and hamstrings.
Forward knee displacement also influences your ability to hit depth, at least to a degree. Too little forward knee displacement, and your hip mobility might keep you from getting all the way down into the hole. Too much, and your ankles become the stopping point.
Here's my rule of thumb: the right amount of forward knee displacement for you is that which creates a straight bar path. Obviously, this is a bit of a simplification, but if you follow this rule, you'll at least get close to your ideal squatting technique.
Next month, we'll take a look at ankle mobility, how it relates to squatting strength, and what you can do to improve it!
