A funny thing happens when you walk into a weight room with an NCAA Division III athlete. It's kind of like witnessing a "Best of Bro-science" compilation, and by "best of" I really mean stuff so awful that you pray for short-term amnesia.
It isn't that what's happening is so aesthetically upsetting that you'd rather watch someone mop up a paint spill with facial tissue. Yes, a lot of it is hard to watch, but what really makes it uncomfortable is that many of them are 100% certain that they know what they're doing.
One of the freshmen said, "I think, by now, everyone pretty much knows how to lift." The irony gave me concussion-like symptoms.
During my year coaching NCAA baseball players, I saw countless problems. Among them were some ugly rows, a shocking lack of pull-ups, the improper use of unstable surfaces, and a neglect of soft tissue work. The biggest problem, of course, was -- with the exception of a few athletes -- extremely poor barbell work.
For the most part, if anyone was doing barbell work, he wasn't doing anything but back squats, and calling them "half squats" would have been more accurate. Depth is easily the most prevalent problem with squats.
Poor depth results in quad dominance because of poor activation of the abductors, adductors, hamstrings, and glutes. Because no one wants to back off to a load that their weak posterior chains can handle, poor depth is the toughest problem to correct.
On top of that, poor depth is typically accompanied by excessive ankle dorsiflexion. Instead of bending at the hips, the athlete's knees track forward to allow for more knee flexion. This action moves the barbell closer to the ground, but does not improve the depth of a squat. In this position -- above parallel with ankle dorsiflexion -- the anterior part of the knee faces unnecessary sheer force which may cause pain and may eventually lead to injury.
Next to depth, the most common issue with squats is knee position. Apparently, someone is out there teaching young athletes to squat with a wide stance and feet facing forward. (I have a vague recollection of being taught that myself while in high school.) As the legs bend into the squat and approach 90° of knee flexion, this stance creates unnecessary valgus stress on the medial collateral ligament, which is really good if you're also into grinding your lateral menisci. Such a position suffers many of the same muscle activation problems as poor depth and causes a great deal more pain. (This is true for any flat-footed, standing position where the knees wind up medial to the feet.)
On top of these issues there are chunks of bro-science to deal with: counting that quarter-depth squat as a completed rep so you can tell people "I squatted 400 lbs", coaching cues like "look at the ceiling", and thinking that the Smith Machine is just as good as a barbell.
It takes about 10 minutes to teach someone the correct way to squat, but it takes quite a bit of practice to get it right. Anyone willing to do the work in the first place should be willing to do the work correctly. I'm not going to re-invent the wheel here by breaking the squat down piece by piece and telling you how to do it, but I'm also not going to leave you hanging.
Mark Rippetoe and Lon Kilgore collaborated on one of the most popular strength training books of all time. It's called Starting Strength. You may have heard of it.
This book is the strength training bible for anyone that hasn't mastered the basic barbell lifts (squat, deadlift, press, clean). It tells you everything you need to know to do these exercises the right way.
If you're serious about strength training, you owe it to yourself to make sure you know what you're doing, and if you're a competitive athlete, there's no reason you shouldn't be serious about strength training.