Recently, I've read some articles that suggest that you should go below 90 degrees.
On the other hand, I've talked with a trainer in my gym, and he usually places a bench behind him so that he couldn't go below 90.
What is your take? Below 90 or 90?
Note: When I'm talking about degrees, I mean the angle your shin bone and femur makes.
A proper squat involves the hip joint ending up below the knee joint as seen from the side (see the image above). This is called squatting "below parallel". Many studies indicate that "squats, when performed correctly and with appropriate supervision, are not only safe, but may be a significant deterrent to knee injuries". A look at weight training injury rates and using common sense when thinking about the third world squat, how you sit on any low surface (e.g. toilet), and the fact that olympic weightlifters - who routinely squat crazy loads WAY below parallel - can still walk should also be fairly convincing.
It's not about anyone's personal "take" on the subject. It's about what your knees can handle. People who hurt themselves doing deep knee bend squats are either not flexible enough to do them, or are using bad technique. As a blanket rule, we just say not to go past 90 degrees because just about anyone's knee will bend to 90 degrees with weight without risk of injury.
If you want to go further, go further but do so with caution, a small amount at a time (low or no weight is suggested while training for deep knee bend squats). This will ensure that your ligaments and muscles are prepared for the extra strain. Going below a 90 degree bend will cause quite a bit of extra stress on an exponential curve (the deeper you go, the higher stress coming back up). If you feel any pain or "stretching" in the knees, you're going too far.
Technique:
To avoid injury:
Your knee is designed to squat low. Babies learning to stand squat well below parallel.
Usually the problem from squat depth is not the knees but the lower back. As you get lower, your hamstrings stretch to the point that your hips are pulled. The first thing noticed is that your lower back is losing concavity.
So I would say that you can go deep until your lower back rounds. Work on getting this as low as possible, to increase your strength and flexibility.
Agree with everything md5sum says. Also would like to add one more technique to the list: when you go down into your squat, don't think of letting gravity pull you down or the weight of the bar pushing you down. Visualize using your muscles and core tension to pull yourself down into the squat. This will maintain a muscular tension throughout your body that will not only help you lift more, but also help avoid injury.
Squats that aren't low enough usually involves more weights, which for a lot of people give a lot more pressure on the back.
If done properly, ATG (all the way to the ground) squats are excellent. The problem is that the majority of people don't know proper squat form, so I wouldn't recommend this until a person has learned good form. Here are some resources that have really helped me a lot:
Part 1 of a 4 part series on squatting - "So You Think You Can Squat".
Also, one great way to increase strength safely is to do a box-squat, which is essentially what your trainer is doing. If you are using a bench for box squats, this is generally slightly above parallel.
Just adding to the mix here.
Personally, I go as deep as possible with my lighter weights as I am warming up. I start with the bar only, then add a 45 on each side. I squat until my butt hits my ankles.
Once I get to 225 or greater (2 45s on each side), then I only go down roughly parallel to the floor.
Use your better judgement on this. If you feel like you are about to blow out a knee or break something by going down further - DON'T!
This is a short, useful video that gives some tips on squats. Would still be good to hear all your comments on whether the full range of squat motion is advised or not.
Here are some of the most important tips from the video:
Bring your elbows BELOW the bar (or even slightly ahead)
Become more flexible at your shoulders so you can stretch it to the maximum to achieve tip #1
Initiate the movement by bending the knees, go all the way down and all the way back up
Go for full range of motion which helps train the full leg and the glutes
Drive up with your legs. Do not lean forward as the hip goes up.
