Here's what A former national weightlifting champion Keith Wassung has to say about deep squats:
From
http://www.riverhorsepubl.com/Lifting.html
Full Squats for Strength & Development:
When you hear the word “SQUATS” do you think of an early eighties Dutch punk rock band, or of one of the most demanding, resulting producing exercises known to man? Hopefully you associate with the latter, but in any case the full squat is one of the best overall movements for producing both strength and development not only in the legs, but for the overall body.
Full Squats are something that you must learn to do with the mind as well as the body. A proper combination of mental and physical energies will ensure that you will be able to squat using a total effort and nothing less. I often look back at my training log of 27 years and I observe an exact correlation between squat progress and overall progress, meaning that I made the best overall gains in strength and development when my squat was progressing the most. Another thing I have always found to be true about squats is that you can almost always make increases, for example, I have often gone into the gym, totally confident and ready for my session--and I load the bar to do upper body work, such as bench presses--and there are some days, when no matter how hard I try, no matter how hard I push, the reps that I am attempting to make just wont happen. But with the squat the desired reps almost always came. I think that is because the legs are so much stronger than we even imagine and there is always some reserve strength to get another repetition.
Squats and Systemic Growth
You may be wondering, "Just exactly how do squats promote growth throughout the body?" To begin with, the squat involves multiple joints and muscles which in turn increase the level at which the nervous system must coordinate movement in conjunction with the lifter's muscle-skeletal system. In the squat there are numerous muscles of the body working simultaneously to provide the stability and mobility needed for this exercise. It has been estimated that there are up to 200 muscles involved in the squat.
The hormonal or endocrine system combined with the nervous system makes up what is known as "neuroendocrinology". This term describes the relationship of chemical substances that have both neural and hormonal functions. The endocrine glands are stimulated to release hormones by a chemical signal received by the receptors on the gland or by neural stimulation, which is what occurs during weight training. Ever wonder why you feel particularly upbeat and euphoric after a hard workout, even if you are physically drained? It’s because of the increased presence of hormones in your body, hormones that also influence our moods. This is similar to the “runner’s high” experienced by long distance runners.
The increase in anabolic hormone levels observed after a hard workout can increase hormonal interactions with various cellular mechanisms and enhance the development of muscle protein contractile units. On neural stimulation from an alpha motor neuron to initiate a muscle action, various signals (electrical, chemical, and hormonal) are sent from the brain and from activated muscles to a number of endocrine glands. Hormones are secreted during and after the workout in response to the physiological stress of resistance exercise. This simply means that the nervous, muscle-skeletal, and hormonal systems are responsible for the effects promoted by exercises like the squat.
There are various hormones, which produce this effect, and the one that most people are familiar with is testosterone. It's been demonstrated that testosterone serum concentrations can increase with exercises such as the squat.
Squats can increase growth throughout the entire body because they use numerous muscles and this means they stimulate more muscle fibers than say an exercise such as a leg extension or a leg press. The greater the fiber recruitment, the greater the process for potential growth and development in the muscle. Only muscle fibers that are recruited by resistance training are subject to adaptation and the more muscles used in an exercise like the squat the more the muscle fibers are stimulated.
Preparations
Your squat workout should begin about an hour after the completion of your most recent squat workout. Take the time to sit down with your training log and some good post workout nutrition, and enter your last workout’s sets and reps into the log, along with any particular training notes for that day. Then, begin outlining some training goals for the next workout. You have to set specific goals and have a game plan to achieve them. Once your next workout outline is done, write it on a post-it note, stick it on your day planner or your bathroom mirror, any place where you can glance at it a couple of times each day and by the time your next workout arrives, you will be mentally prepared to complete the required sets and reps. Try to eat a high complex carbohydrate meal the night before a squat workout—whole-wheat pasta with a ground turkey and marinara sauce works very well. Take the time to properly warm-up, which can consist of some stretching and mobility exercises such as five minutes on a stationary bike pedaling at a moderate pace.
Equipment
If you are going to make decent progress in the squat, you have to be properly equipped and probably the most important gear is a decent set of shoes. I often see people lifting in shoes that provide little in the way of support for the foot and ankle, in fact most “running shoes” are mushy and cause the ankles to buckle slightly inward as the lifter is descending with the bar. Buy a pair of high-topped training shoes, preferably with the ability to tighten the lace around the ankle. If you use the shoes only for your training, they should last for years. Using a lifting belt is a personal decision, though it should be used sparingly and mostly with heavy weights/low rep type sets. The last vital piece of lifting equipment is a strong abdominal region. Having a strong, well-developed trunk region will do wonders for your overall strength. Train the abs in order to make them functionally stronger by doing exercises such as weighted crunches, side bends and frog kicks.
SQUAT TECHNIQUE
Squatting is a very natural movement; In most of the world—especially Asia and Africa—people squat to rest, to eliminate, and to perform many tasks including giving birth. I was in the gym last week and a guy approached me and told me he was frustrated with his lifting, etc. I asked him about squats and he told me that he was unable to squat. I told him that must be really tough when you have to have a bowel movement! Human bodies are designed to squat! Having said that, there is a certain learning curve associated with the full squat and it’s very important to learn and implement the technique correctly. There is an abundance of squatting technique information available in books, videotapes and websites, but the best way to learn is in person. If you need to improve your squat form, find an experienced lifter somewhere near you and ask them for help and advice. You may have to drive several hours to find someone, but it will be time well spent. The experienced lifter does not have to be a world-class athlete to give you quality instruction. You will find that the majority of experienced lifters are very generous with their time and will gladly help someone who truly has the desire to learn. Be sure you listen and take notes on the instruction you receive. You may even want to offer to pay for a steak dinner afterwards.
I advocate the full barbell squat as one of the core exercises in most any weight-training program. If you are an aspiring powerlifter, then you will need to spend some time performing squats in a powerlifting style in order to prepare for competition. I believe that the full squat will be of tremendous value in laying down a proper strength foundation. There are individuals who may have structural problems (knees, back, etc) which prevent them from squatting at the present time. If this is the case, then those problems need to be properly evaluated and some type of corrective or rehabilitative action taken. When it comes to your health, don’t be afraid to get a second or even third opinion. I don’t have a whole lot of confidence in health care professionals whose only advice is to avoid exercise or activities as I fail to see the positive benefits of physical atrophy of the human body.
Many fitness experts warn against performing squats past the point of parallel for fear of potentially damaging the knees. As a general rule I disagree with those experts though there are certainly individual exceptions. When the full squat is performed correctly and with total control through a complete range of motion, the knees are strengthened, not weakened. According to the American Academy of Orthopedic Surgeons, an estimated 50 million North Americans have suffered or are suffering knee pain or injuries and six million of them will visit a doctor for knee problems each year. The majority of these problems are degenerative in nature and are the result of disuse of the knee joint. Squatting keeps the knee joints mobile and free of pain. Several joint facets on the inside of the kneecap are used only when an individual performs a complete squat.