Alignment is a bit of a buzz word in yoga these days. More and more styles and studios teach "alignment-focused" asana classes, and yet the physical practice of yoga still varies widely.
So what is alignment? Is it whatever a particular teacher or lineage says it is? Well, to put it simply, yeah, it kind of is.
"Alignment" as a category is merely an organizing principle within a system that keeps that system operating smoothly. Different approaches therefore end up with different principles of alignment. As best I understand, Iyengar yoga uses props and specific asana shapes to help students move continuously deeper into the capacity of their bodies. Ashtanga yoga lets the ease of breath determine whether or not a student's posture needs to change. Those are just two examples among dozens, the effects of any of these on you and your practice will be just as varied as the practices themselves.
ISHTA Yoga combines appreciation of anatomical alignment with a deep understanding of energetic alignment so that the physical body is kept steady and spacious, which allows an easy flow of not only movement through joints, tissues, nerves, etc, but also of prana (life force) through the subtle body. Anatomical alignment is any alignment that allows the normal functioning of the body to continue unimpeded without damage to any system (musculoskeletal, circulation, digestion, etc). Energetic alignment is similarly any alignment that allows free flow of the electricity that animates us!
Those are pretty broad definitions, so ISHTA teachers "break down" the skeleton into seven segments as a means to organize how they direct postural alignment. Each of these segments also corresponds with a chakra (energy center along the spine): segment 1, the legs and feet, corresponds with the first chakra; segment 2, the pelvis, corresponds with the second chakra; and so on. We typically address postural alignment from the foundation up (e.g., the feet up in tadasana/standing, the forearms up in headstand), paying careful attention to "ripple effects", because the alignment in one segment will by definition effect the alignment of at least the segments above and/or below.
In my experience, any misalignment, any imbalance of space or strength, effects your entire system in some way. Luckily, by the same token, one small shift to improve alignment will also begin to effect the whole system. (Our bodies are SUPER SMART.) Very often, I will guide a student to change her foot placement in order to create a shift in her hips and spine --a shift I don't necessarily need to ask for explicitly because she goes ahead and reorganizes her body to a comfortable position above the new foundation.
I love this approach because it is fairly intuitive once you have some appreciation for the skeleton and its structure. It also reminds me that before you change anything else in yourself, it can be useful to set a good foundation for the shift that's about to occur. You end up taking smooth steps of change rather than tumbling into an earthquake of change (which can be just as educational!).
I am also a student of the Alexander Technique (AT). AT helps students discover unconscious postural habits and then gradually “undo” those habits by, quite "simply", not doing them. AT teachers use hands-on guidance to help students identify the habits that need undoing, and while there is certainly space for foundation up adjustments, AT teachers typically address imbalances by starting with the head and neck. When the head doesn't balance evenly on top of the spine, it's a foregone conclusion that compression (lack of space) elsewhere in the body will be evident. Just as you need a strong foundation for shifting into your tallest, broadest, strongest self, you also need all the space that you can occupy available to you to fill! If a student's head sits forward of her neck or schlumps down, her skeleton does not have its full vertical height to organize into.
Having the benefit of an ISHTA and AT education, I teach "alignment" using both poles of "space making". Set your foundation so you can grow. Free your head so you can reach your greatest potential. And in the middle --well, your body will know exactly what to do. I've learned over the years from my AT study and my meditation practice that they key aligning myself is to undo unconscious patterns. That's not easy; it takes a deep consciousness of self and a willingness to let go of habits with which I have long identified. But if we can all commit to getting to know ourselves, the rest --the alignment of our bones and the energy that flows through them-- will take care of itself. That's the intelligence of evolution and the universe at work for you!
hari om tat sat!