Backs are ruined by defective execution of squats, and the squats are blamed instead of the incompetent instruction. The chief mechanical cause of back injury while doing weighted squats is posterior tilting of the lifter’s pelvis, called “butt wink,” which during the squat causes reflexive flexing (bending forward) of the lifter’s lumbar spine. Those two moves together, posterior pelvic tilt and lumbar flexion, stretch the spinal erectors (muscles straightening the spine) while they are working to keep the trunk from collapsing under the weight of the barbell. Additionally, the resulting spinal alignment puts a strong squeeze on the intervertebral discs, making them susceptible to injury.
The butt wink, or posterior tilt, of the pelvis happens when one leans forward under the weight. The more one leans, the more difficult it is to prevent the butt wink, and vice versa–the less one leans forward, the easier it is to prevent it. Butt wink and the damage it may cause to the spine can be prevented by correct teaching of the squat–that is, beginning with forms in which the wink is easy to control (for an example, see instruction for the wall squat on the DVD Flexibility Express). The more one abducts and rotates the thighs externally, the deeper one’s pelvis can sink below the knees without tilting, and so the closer to vertical one can keep the trunk. To put it simply: The wider the squat, the less one leans forward. Here is a guide for teaching progression of squats:
–The lighter the weight, the less the trunk leans forward.
–The wider the stance, the less the trunk leans forward.
–When holding the weight in front of the trunk (goblet squat, front squat), the trunk leans forward less than when the weight is behind the trunk (back squat).
So here is such a progression:
goblet squat => front squat => back squat
Begin with a wide stance (like the five-step horse-riding stance) and a light weight. Practice the three forms of the squat in the above sequence, within the same workout if possible to better transfer the sense of proper position of the pelvis and spine from easier forms to more difficult forms. If you can’t do all forms well enough, then stick with the form you can do until you are ready for the next one. When comfortable, add weight. As weight increases, eventually you will have to narrow the stance while maintaining the natural lumbar lordosis–not tilting the pelvis–and keeping the trunk’s forward lean to a minimum.
Each step of the progression is to be done until the habit of keeping the natural lumbar lordosis under the weight is firmly ingrained.
If your ankle dorsiflexion is poor, you can begin the above sequence with heels on supports and then gradually lower the supports.