A Plea for Depth

"Go through a full range of motion" is the exercise equivalent of "eat your vegetables"; we've been told by our trainers/mothers that it's important, but we don't like to do it and will find every excuse we can not to. There are many different reasons to only go through a partial range of motion on any exercise -you can put more weight on the bar, you can get more reps, it seems safer- and they all have one thing in common:

With very, very rare exceptions, a full range of motion (ROM) is a requirement for optimal progress and safety. And in no exercise is the more important -or more widely ignored- than the squat. 

The squat is a scary but misunderstood beast. When broken down in to all of it's separate components, it's one of the most technically complex movements of the human body. I have textbooks with literally entire chapters  devoted to this one lift, and for good reason. However, when done correctly, the squat is perhaps the most effective, efficient, and safest exercises you can do in the gym.

Unfortunately, "correctly" means "to full depth", and this is where most people fall short (pun absolutely intended). "Full depth" means that your femur is parallel to the ground, and the crease of the hips is just slightly below the top of the knee.

Correct depth

Way too shallow. 

The head may be lower, but the hips sure aren't. 

When someone doesn't want to squat to full depth, the most common reason they give is that it hurts their knees.

This makes absolutely no sense.

You don't do partial push ups to save the elbows, and you don't do partial squats to save the knees.A review of squatting kinematics by the Journal of Strength and Conditioning Research (man, what would I do without them?) reveals that full squats are actually superior to knee extensions and partial squats during rehabilitation for a knee injury.  In fact, a partial squat is actually worse for your knees. In a partial squat, most of the stress on your knee is generated by the quadriceps pulling your tibia forward. Repetitive, one-directional pulling on any joint, knee or elsewhere, is a recipe for injury.

However, at the bottom of a full squat, the hamstrings kick in and balance the anterior stress on the knee with an opposing force. At full depth, with correct knee and foot position, the anterior and posterior forces acting on the knee are balanced. Balanced forces = safe knees.

Figure 2-11 from Mark Rippetoe's book Starting Strength, showing the forces acting on the knee at the bottom of a full squat

And no, lunges are not safer for your knees. Knee range of motion is knee range of motion.

The key here is technique. Some of the things I see people do when trying to squat (see above) are absolutely bad for the knees, and that's why proper form is so important. If you can't squat correctly, you're better off avoiding the exercise. But you'll really be missing out, and I suggest putting real effort into learning the technique and gaining the mobility necessary for a proper squat. Remember, as a personal trainer, I'm here to help you with both.

Here's a simple exercise to practice getting to full depth, which also doubles as a fantastic mobility routine for the hips.

Stand up straight with your feet shoulder-width apart and your toes pointed about 30 degrees outward. Sit down between your legs, and drop your butt as low as it will go without coming up on your toes. Put your elbows between your knees, and push them out so they track over your feet. Try to sit a bit lower. Hold the stretch for 3-5 seconds, stand up by driving your hips up and forward, and repeat for 10 reps.

A strong, full-depth squat is one of the best indicators of total-body strength and mobility we can measure. At Lift, we include it in our warm-ups, our strength and conditioning circuits, our athletic development programs, our weight-loss programs, our...well, you get the picture. We want you to get the most out of your workout, and that means doing each movement to its fullest. 

As always, go forth, get low, and lift heavy things.