With any posture in yoga there are two questions: How to do it safely and effectively, but also Why to do it at all. When I was very young and trying out yoga poses I saw on Lilias, or in books and so on, I would see a cool looking pose and try to mimic it. It was all about the pose. But when you do that you start to realize that some poses feel good, and that they might feel good at particular times of the day, or after other activities. That is why I tell my students “Think of the posture as a tool, rather than as a goal”. You would not use a hammer when you need to saw wood. Of course once you identify what you want to do and what tool you need to do it, you need to know how to use the tool effectively and safely. Effectively means that you will be able to hammer in the nail you want in the place you want it, and safely means not banging your thumb.
However, just having a list of problems and projects and tools is not going to be enough. Because (I believe) in its essence yoga is about balancing opposite pulls. So the tool analogy is not enough. Sometimes I talk about the squishy toys (my kids used to love those): push hard enough on one part and the fluid bulges into another part. Push really hard and the toy will break. This is why in all physical disciplines you hear about the kinetic chain. That is the old “the shin bone is connected to the knee bone” thing. What you do in one area will flow outward into other parts of the system, and without working with synergistic pulls you can create imbalance. For instance if you do half an hour of bench pressing 3 days a week for a year, and never do any sort of back work you will have a muscular chest, but a very rounded back.
To see what you need to create balance you need connection. And I prefer the word connection to control (apologies to Joseph Pilates), as to me the word control suggests that the thing controlling is somehow outside of the system. We connect the understanding with the tools and implement their use in a balanced way.
To see what benefits might accrue from backbends (and particularly cobra), as well as to see how it must be balanced, and how to do it safely and effectively it is important first to think about some anatomy. (Is she finally going to talk about cobra? My goodness, how much context do you need?)
I did a whole blog a while back on the spine and spinal twists, so I will suggest reading that if you want more depth.
The spine sits between the shoulders and the hips. There are 33 vertebrae, with 5 sections. The sections are defined by, among other things, a set of balanced curves. The first curve is inward at the neck (cervical). The second is outward at the upper back (thoracic), the third is inward at the low back (lunbar), and the last two follow the lumbar curve, but have little movement (sacral and coccygeal). Each vertebrae is shaped and sized differently, with each of the 5 areas being similar (and yes, the top two are quite different... they are shaped to help rotate the head, so put them aside for the moment). Generally (except at the top and bottom) the vertebrae look like misshapen doughnuts. On the back half of the doughnut are various bony projections that allow complex attachments to each other, and to supporting muscles. The front half is more smooth, and above and below attaches to the next vertebrae in line with a soft disc between. In the center of the doughnut is a hole, each of the holes stack over the next, and the spinal column runs down through this hole. In front and behind the spine there are ligaments, holding the system together, and lots and lots of muscles that contract to provide multiplicity of movement: from belly dancing to building sand castles to rock climbing.
Here are a few things to keep in mind when tackling back bends:
It is important to lengthen and create space before actually bending.
Gravity and body weight push down on the spine. This pressure is greater in the lower vertebrae than the higher. That is one reason the lower vertebrae are bigger and heavier. (And certain positions will put more pressure on the lumbar area. Sitting puts more pressure than does standing, and sitting and bending forward puts the most. Back bends actually help balance the strain of such forward bends)
Interestingly, with age the blood vessels no longer directly provide nourishment to the discs. So backbending and twisting become extremely important in pushing fluid around and hydrating the discs. When the discs are hydrated they keep the bones from sitting too close together and so promote movement. And help avoid the loss of height you see so much with age. Something like 25% of the length of the spine is in the discs.
It is important to balance strength with flexibility; in particular it is important to engage the core.
While the rib cage helps keep the thoracic spine stable, the lumbar spine has no such help. It is the strength of the core muscles that helps stabilize this part of the spine. That ligament on the front of the spine will help keep the vertebrae from sliding on each other, but intra abdominal contraction helps to avoid over stretching at that area.
Do not forget to think about the shoulders and hips in any back bend.
The spine may be flexible or not, but it is attached at top to shoulders and at bottom to pelvis and if those areas are tight or unbalanced the spine will tend to go out of balance to try to compensate (like a functional scoliosis developing in response to one hip being pushed up.
It is also helpful to do range of motion exercises to prepare for deeper holds. Vinyasa can be very helpful here, as is the viniyoga technique of coming into a held position and moving in and out of a range of motion to create fluidity in tight spaces
More is not always better.
I always ask my students: Do you want to be on the cover of a yoga magazine, or an olympic gymnist, or do you want to enhance your OWN health and well being?
While the sternum and ribs stabalize the vertebrae if you push too far here the vertebrae can rotate slightly, and as they are attached to the ribs the ribs will also and that will be rather uncomfortable, and possibly not healthy, given that in front the ribs are protecting the heart and other internal organs.
Certain areas of the spine have more movement (such as T11 and 12, or L5 S1 where most of the lumber bend is generated). Too much lift will tend to go to those areas where the movement is greatest, and too much movement can overstretch the ligament, or push the disc place. Getting the soft center of the disc herniated or pushed into the nerves running down the back is not something you want to do.
Use the whole system.
The natural range of motion may be different in different parts of the spine, but if you engage a small amount at each place you will open the whole system more, and avoid over stressing the more fluid places.
Be aware of the neck.
Doing jalandhara bandha is helpful to take pressure from C7 T1 where the spinal curve shifts. Flex the neck slightly first, and then draw the chin slightly up.
Beware of tingling and numbness.
These are signs of nerve compression. If you feel these remember that pain is your friend, and it is warning you not to take this road farther. Please do contact a health care provider if you experience either of these things.
So why do we practice back bends?
To balance our forward bends
To stretch the spinal flexors
To hydrate the spinal discs and promote fluidity of movement through life
To strengthen the muscles of the back, shoulders and seat
And one last thing of note: while forward bends are associated more with parasympathetic nervous excitation (i.e. they promote relaxation), back bends are associated with sympathetic excitation. When feeling sluggish and tired and unfocused, backbends can be very helpful. BKS Iyanger actually recommended them to fight depression. While I think we need a lot more research to delineate and quantify such an association, there is a good bit of research out there to suggest the strong benefits for mood and quality of life from yoga practice. And, if done safely the side effects are pretty much all positive.