Much like last week when we stretched our wrists, stretches for the back can be done in many variations and it is my belief that you should always balance a Flexion Stretch (bending forward) with an Extension Stretch (bending backwards). I have chosen simple and safe stretches to write about here, but always remember as you become more familiar with stretching you can explore other variations of this (and any other) stretch.
With regard to which muscles you are stretching - as most people would probably be aware there are many, many muscles that will be stretched by these techniques so it might just be easier to visualise keeping your spine supple and flexible by doing these stretches.
To stretch your Back Extensors (or a Flexion Stretch) - Start by sitting in a chair. It is best to use a static chair (one without castors or wheels) because it wont be able to move under you while you are stretching, and this reduces the risk of injury or mishap. It should be high enough so that your hips and knees both make right angles (90 degrees), and your feet should be a little wider than shoulder width apart. Your arms are simply passengers on this stretch so they can be put wherever they are most comfortable for you. When you are ready to stretch, simply roll your spine forward from the top - reaching out and towards the floor through your knees- continuing as far as you can. This stretch is gentle enough that you can hold the stretch position for as long as you want, but you should hold it for a minimum of 15-20 seconds to gain any benefit.
To stretch your Back Flexors (or an Extension Stretch) - This stretch is done most easily and safely using a Fit Ball (aka Swiss Ball, Gym Ball ... the big inflated one, not the smaller heavier Medicine Ball). If you don't have one you can modify the stretch to get the same/similar result, but it is always safest using the Fit Ball. Start by sitting on the Fit Ball and balancing your weight. Then gently walk forward rolling your bottom forward on the ball until you can lie backwards to put your back on the top of the ball. Then simply position your self so that you are comfortable and relax onto the convex curve of the ball. I believe this is the safest way to do an Extension Stretch for your back because your entire back is supported by the ball while allowing it to extend fully. Again, your arms can rest anywhere they are comfortable, but if you let them fall over your head you will probably be able to feel a stretch through your anterior shoulder and chest as well. Also, this stretch is gentle enough to hold as long as you like as well - much the same as the Flexion Stretch above, so the same time principles will apply.
As far as breathing is concerned, it is not necessarily as important with these stretches as it is with other stretches - much like last weeks wrist stretches. You can feel comfortable just breathing normally while you stretch, and in fact you will probably get the most benefit from both of these stretches by relaxing completely into them and just 'being' there for upto a couple of minutes.
Where you feel either of these stretches the most will depend on where you are the tightest. Some people will feel the Flexion Stretch more in their upper back and shoulders, while others will feel it more in their lower back. A good thing about these stretches is that they will let you know where along your spine you need to improve your flexibility to increase your personal comfort levels.
It can be easy to over stretch any muscle, and the spine is a sturdy but delicate structure and hyperflexion can injure your spinal cord. Always stretch gently and firmly, and not quickly or with rapid, bouncing movements. Regularity and Frequency are your best friends in stretching, and are the key to increasing your flexibility and benefit for effort.
Always remember to relax into your stretches - don't fight against the stretch (it may cause more harm than good), and always do each stretch 3 times, at least twice each day.
These stretches were not taken directly from any source, but reference is made to "The Anatomy of Stretching" by B. Walker pp77, and "Stretching Anatomy" by A.G. Nelson & J. Kokkonen pp56.