Your squat depth should be as low as your body allows. This isn't necessarily a flexibility issue. It's more of a body structure/mechanical issue. I have great flexibility overall, and I can't squat ass to grass, but my legs don't reflect that. There are other contributing factors to leg size anyway, not just how low you squat.
Besides, there are other "flexibility issues" than can contribute to not being able to squat to a very low depth.....chest and shoulder tightness to name one, and lack of shoulder blade mobility to name another...it's not only about the lower body. If you can't position the bar properly on your back, your overall squat mechanics and depth, will be significantly affected.
Going a couple of inches lower isn't worth the risk in my opinion. A couple of inches isn't going to lead to any more significant addition OR loss of leg size
Keep it simple......(assuming a proper bar placement and elbow position), squat to the lowest depth you can while maintaining:
- A tight arch in your lower back
- A "big chest" (again, if the bar placement isn't correct for YOUR upper body mechanics and flexibility....you won't be able to keep your chest up and out)
- A fairly vertical shin angle at the bottom
- Proper weight distribution through your feet and hips (most of your weight on your heels and the bar loaded down through the hips)
- Focus on initiating your downward movement, by pushing your hips back, NOT just bending your knees
- While descending, your eyes AND head should be looking either straight ahead of slightly up
- When initially coming out of the bottom, your eyes should shoot up
- On heavy or max effort attempts, your entire head can shoot up as you come out of the bottom. The body is all reflexes and your body will follow where your eyes and head go. If they're going up, your body will follow
- Focus on driving our feet hard into the ground ALL THE WAY TO LOCK OUT AT THE TOP, NOT JUST AT THE BOTTOM.
**Just like bench press has a traditional sticking point, so do squats (this varies with each individual), by focusing on driving your feet into the floor and "pushing the floor away from you" the entire way up, you will maintain a tighter body position and proper bar path on the way up
- Breathe right.....before descending take in a huge belly of air AND HOLD IT, UNITL YOU EXPLODE UP. Besides increasing pressure in the abdominal cavity to stabilize the spine, it serves as a nice reminder to shoot those eyes and head up out of the bottom. As you forcefully exhale upon ascension, you shoot your eyes up at the same time. it helps establish proper timing out of the bottom of each rep.
**If you're doing higher rep sets, this wouldn't apply in the same way....unless you like passing out!
For some of the reasons mentioned above, this is why front squats are easier on the lower back....mainly because they lend themselves to a proper bar path more easily, BUT bar positioning of the upper body becomes even more important when front squatting.
I guess that wasn't a simple explanation, was it???
Of course, there's also the possibility, that back squats "aren't your friend." You may find better results implementing other lower body exercises.
It's kind of like Pull ups. Yes, they're a great back exercise, but most people suck at them, and waste time and energy doing them TOO OFTEN (I'm not saying they can't be worked into your overall program from time to time, if you can do them with fairly good form and enjoy them). Just because "they're a great exercise" doesn't mean they're right for everyone. You need to find what works for you specifically and dedicate your training time and energy to those exercises most of the time.
Lower body movements are no different