Before studying these procedures, it is useful to consider some of the benefits to be gained by this process. First, utilizing primitive postures creates the conditions within which it is safe to let go. The upright support system, as we've seen, is highly unstable; once it begins to work inefficiently, muscles begin to compensate and it becomes nearly impossible to release the resulting tensions because to do so would compromise balance. When we assume developmentally primitive positions, it becomes much easier to release tensions because we are free of the fear of falling and more supported. Beginning with the more secure prone or supine postures, we can progress to the less secure ones.
Second, primitive postures provide more fulcrums of support and tactile feedback from the ground. When we are standing, the only physical contact we have with the ground consists of three points of support on each foot. When we are prone, semi-supine, or four-footed, we have more fulcrums of support, and they are more strategically placed. This tends to elicit supporting responses -- having our elbows on the ground allows us to let go in the shoulders and widen the back; the forehead against the ground allows us to untwist and release the neck muscles; knees contacting the ground makes it easier to lengthen and release the thigh and hip muscles. The pressure of these weight-bearing points also helps to educate the antagonistic muscle groups around the joints, as when we're on our knees and this helps us to let go in the hips and to stimulate and educate the surrounding muscle groups.
Third, and perhaps most importantly, the bony fulcrums provide points of support so that muscles can release between their bony contacts. The semi-supine position, for instance, provides five main areas of support: the sacrum/posterior iliac crests, the shoulder blades, and the occiput. With these points of support, the extensor muscles of the back can release and let go, establishing elasticity in the back. The support of the trunk also allow muscles in the ribs to release so that, if the trunk is twisted, it can de-rotate. In short, supporting parts of the skeleton with the aid of gravity allows muscles to let go into length, establishing antagonistic or lengthened action of muscles.