Drawing on more than 30 years in the fitness industry, Mark Rippetoe writes that an “active hip” can help clean up problems associated with the squat. Dr. Stef Bradford and Dr. Lon Kilgore, Rippetoe’s long-time collaborators, also contributed to this article.
When we squat, the standard range of motion criterion for the exercise is “below parallel.” This is defined as the hip joint identified at the apex of the hip angle (the “corner” in your shorts over the hip) as it drops below the knee (the top of the patella).
Most people who have trouble with the squat are having trouble getting good depth while keeping their low back from rounding. Pretty much anybody can get deep if they allow the lumbar spine to relax into flexion, a phenomenon known in some circles as the “butt wink.” Shoving the knees out of the way on descent and keeping them there so that the adductors can do their job is accomplished by an external rotation of the hip.
The concept of the active hip is best understood as the use of an actively locked lumbar extension and actively shoved-out knees, which results in a below-parallel squat that incorporates a stretch reflex using all the muscles of the posterior chain in the most optimal way possible. The active hip gets the thighs out of the way of the pelvis so that good depth can be more easily obtained. At the same time, it makes the squat stronger and more powerful because of the more effective use of more muscles over a wider range of motion.