Hip, ankle, and thoracic mobility drills, core stability drills, and glute activation drills can go a long way in helping people reach proper depth. However, due to anatomical variations at the hip such as cam or pincer femoroacetabular impingement syndrome, there are plenty of lifters who will never be able to deep squat with proper form (Lamontagne 2009).

Well, as you descend into the bottom of the squat or lunge (in hip flexion and knee flexion), the rectus femoris is trying to lengthen at the knee but shorten at the hip, and ends up staying roughly the same length. Then as you ascend (performing hip extension and knee extension), the muscle is trying to shorten at the knee but lengthen at the hip, and again ends up staying about the same length. (3)