Regardless of stance width, degree of toe out, trunk angle, or squat variation, three factors should ALWAYS be present for optimal squat form. There are my requirements to load on day one!
Law 1: Heels Stay on the Ground
Regardless of squat variation or body anthropometrics, it is imperative that the heels stay on the ground to optimize squat form. Failure to do so can put excessive stress on the anterior knee, improperly distributing the forces of the squat.
While this issue could be due to either a true lack of ankle dorsiflexion or a simple inability to perform the squat, we don’t want to allow the clients’ heels to come off of the ground.
Law 2: No Excessive Knee Valgus
During the squat, we want to limit excessive caving in of the knees, better known as dynamic knee valgus. While some knee valgus is certainly not a problem, excessive valgus is usually a result of improper neuromuscular control of the hip.
If the hip musculature allows excessive femoral internal rotation to occur, the knees will be sure to go into excessive valgus. This is why, more likely than not, the "knees out" and "feet turned out" cues will be needed for most people who are new to the squat.
Law 3: No Excessive Lumbar Flexion
The third law for squatting is to avoid excessive lumbar flexion and pelvic posterior tilt. As a caveat, there is nothing inherently evil about lumbar flexion. In fact, I wrote about this right HERE. It is a normal movement that we utilize on a daily basis.
With the squat, however, especially a loaded squat, we want to minimize this as it could place excessive stress on low back. While a small amount of “butt wink” – or lumbar flexion, is acceptable, and probably not much of an issue, it is the excessive amounts we should not allow.
These are my three laws to squatting. I've found that failure to follow these, in most cases, is due to improper coaching vs. true mobility issues. If the trainee can keep the heels on the ground and has no excessive knee valgus or lumbar flexion, I have no problem loading them on day one.
Will it look perfect? Probably not? Is it a "recipe for injury or dysfunction" if their body weight squat isn't perfect prior to loading? Probably not either. Often times things just sort their way out as you begin to safely and progressively load them. Abide by these three laws and start squatting!