One of the biggest mistakes that most lifters make when they squat is the belief that they should lower their body straight down. This is not only inefficient, but will likely stress thier ankles, knees and lower back. Instead of squatting straight down or moving first at the knees (flexion), you should first hinge at the hips backward.
Most times the lifter is thinking too much north/south (straight up and down) and not enough east/west (hip hinging to load the posterior chain).
Why Is Hip Hinging Important?
It gets the weight distributed across your hips, glutes, and hamstrings. The most common cues to move the lifter into the hip hinge correctly are sit back, back, back, knees out, and spread the floor. These are all great, but if you don’t know how to hip hinge, the cues will seems like nonsense.
How To Hip Hinge Correctly?
Step 1: Before any movement occurs, stay tight and create lots of full body tension. This will ensure you to load the spring as you descend. Getting tight is referred as irradiation (in the RKC) and is a combination of breathing and flexing all of your muscles tight as hell.
Step 2: Slide the hips back and turn your "side ass" on by spreading the floor and pushing your knees out.
Step 3: Keep your torso upright and stay tall. Your goal is to remain tight in the core and move the weight with your hips and hamstrings; not your lower back,which happens when you lose position and fall forward in the hole.