Thread: How To Squat
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Old 02-14-2006, 06:38 PM
Darkhorse Darkhorse is offline
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part 1: debunking the myths

The squat is, perhaps, the single best exercise for leg strength and development. Squatting significantly strengthens the muscles responsible for knee and hip extension: quadriceps, hamstrings, and glutes, as well as the smaller stabilizing muscles such as the torso musculature. The squatting motion and position is also the foundation for many other exercises, such as deadlifts, Olympic lifts, and even every day lifting tasks. I think it is a very worthwhile task to learn how to squat, and anyone who can get out of a chair can do it. It has benefits not just for your strength, but for balance, confidence, daily-life strength, cardiovascular capacity, and active flexibility.

Problem is, the squat is often taught incorrectly, and it's stigmatized as difficult and dangerous. People warn that it is bad for your knees and back, inappropriate for beginners (or anyone not a male collegiate athlete), too hard to learn, blah blah the sky is falling, etc. So, let's go through all the scary things we've heard about squatting, to debunk them one by one.

myth #1: squatting must not be done with a full range of motion or you will hurt your knees.

This is probably the worst myth of all. It's one of those "well known facts" which is mysteriously unsupported in the research (it's a well known fact that as soon as you say "it's a well known fact", you won't be able to back it up). According to this myth, full squats (a squat in which the knee joint is taken through a full range of motion, so that at the bottom the hamstrings make contact with the calves) are inherently dangerous, particularly to the knee joint.

While biomechanical research does support the fact that forces on the connective tissues of the knee increase with the knee angle, particularly on the posterior cruciate ligament, there is no evidence that these increased forces actually lead to injury. There is no direct evidence that full squatting causes or even exacerbates knee pain nor damage. I do not know of a single documented case where full squatting led directly to knee injury. Not one! Which is pretty amazing, considering that the clinical literature is positively littered with injury narratives. You'd think we'd see some evidence, but there is nothing, nada, zero. Studies of Olympic weightlifters and powerlifters, both of whom squat with heavy loads, show no increased risk of knee damage in either population. Olympic lifters, in particular, regularly drop to full depth under hundreds of pounds, perhaps as often a hundred times a week or more, for years, and yet their knees are healthier than those of people such as skiiers, jumpers, or runners. No study, short or long term, has ever shown an increase in knee laxity from deep squatting.

In fact, there is strong evidence that full squatting actually improves knee stability! The increased strength, balance, and proprioception from regular squatting can make a substantial contribution to keeping knees healthy. Progressive overload (beginning with a light load, then increasing gradually as the trainee is able) assists in strengthening connective tissues and muscles surrounding the joint.

Most interesting to me is the problem with what is usually recommended as "safe": squatting to parallel. At parallel (where the thigh is parallel to the floor, higher than the depth of a full squat by about 30 degrees), the compressive forces on the patella (kneecap) are actually at their highest (Huberti & Hayes, Journal of Bone Joint Surgery, 1984: 715-724). Decelerating, stopping, and reversing direction at this angle can inspire significant knee pain in even healthy people, whereas full squats present no problem. Another exercise which is supposedly "safer" is the leg extension, even though patellar tension and shear forces on the knee joint are demonstrably higher with such an exercise (see sidebar).

It is worthwhile at this point to comment on the things that do cause knee injury. The primary causes of knee injury involve:

a) twisting under a load

too much load (for example, I heard of a guy who boasted that he could squat 800 lbs. He had never done it before, and couldn't even full squat half that much, but he decided that 800 was a good round number, and he was going to attempt to quarter squat it. Long story short, knee ligaments did not agree with his assessment)

c) landing unevenly from a jump, especially with straightened rather than bent legs (this is a big problem for folks like basketball and volleyball players)

d) being in a situation where one part of the leg is held stationary while the other is moving (for example, stepping in a gopher hole while running: shin stays in place while the thigh keeps moving)

e) impact to the knee (such as a hit from the side or front in football)

f) squatting in a Smith machine which does not allow proper shifts in weight through the movement, and results in shear on knee and spine

In other words, knee injury usually results from varus or valgus force (twisting of the joint in either direction), inappropriate loading, or forcible shear across the joint. It does not occur simply from taking the knee joint through a full range of motion, using correct technique, and using a weight which is appropriate to the abilities of the trainee.
why are leg extensions hard on the knee joint?

To understand why this is, it is helpful to understand the concept of shear. Shear in this case just refers to a horizontal force on the joint. Imagine two cans stacked on top of one another, and imagine that a piece of masking tape joins them. Then, imagine what happens if you hold the top can still while you push the bottom can to one side. Eventually that tape will snap. This is a simplistic description of what happens to the knee joint in a leg extension.



Here is a simple diagram that attempts to explain the difference between the squat and the leg extension. The black lines represent the thigh bone, shin bones, and knee joint (black circle). In a squat, as shown in the figure on the left, your feet are on the ground (hopefully), and the force of the load is transmitted downwards, along the length of the bones. In a leg extension machine, there is a pad against the front of your shin or ankle, and you press against it to move the weight. The foot swings upward in an arc. Thus, as you can see in the figure on the right, the pressure is coming across the shin bones, not along their length. This creates the problem in the knee joint as the shin is pressed backwards.

Leg extensions do have their place, usually in rehab. If the leg extension machine is used, it is wise to use a smaller range of motion, perhaps the top third of the movement (from slightly bent to fully straight leg), and light weight.

This is not to say that everyone can immediately leap into full squatting. It is essential to learn to squat in a way that meets your individual needs, and I'll discuss that in Part 3. It is common to have difficulty with a full range of motion in the beginning. If knee pain is felt during the squatting motion, there are a few possible reasons. First, it is important to rule out existing pathology. Some people may indeed have knees that are so damaged that they are unable to squat, but this is rare (and these people are probably walking with a cane). In particular, full squatting is contraindicated for someone with an acute posterior cruciate ligament (PCL) injury, but these types of injuries are uncommon and usually result from something like a car accident. Someone who has rehabilitated a PCL injury can attempt full squats with light loading, and see how it goes. With correct loading and technique, anterior cruciate ligaments (ACL) and medial cruciate ligament (MCL) injuries generally don't present a problem. I know someone who is even missing an ACL on one knee, and has a reconstructed ACL on the other, and she squats quite happily.

Some people may have irritation in the joint due to things like patellofemoral syndrome or age-related degeneration, and the goal initially should be to squat in a pain-free range, while aiming to increase that range and strengthen the muscles around the joint. Some people may experience pain due to poor technique, which includes allowing the knees to cave in or twisting during the ascent. In this case, the trainer should again establish probable cause and direct attention to remedial work (such as stretching and additional strengthening) in conjunction with improving pain-free range of motion and correct technique. In Part 4 of this article, I suggest some stretches and assistance exercises to help you eliminate possible problems.

Do not do an exercise, no matter how great that exercise is, if it causes you pain. Find alternatives or modify the exercise. Full squats are great, and most folks can eventually do them....
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