I really get tired of this whole posture issue and back pain. For those of us who have literally spent years treating back patients, as well as reading the literature, it gets old.
If you have back pain and are trying to figure things out, know that the whole theory of correcting your posture to relieve pain has some very serious flaws. The first issue is whether "bad" posture causes pain, and the second is whether we can change a person's posture at all. The research clearly says "NO" to both questions. For instance, on the issue of the association between posture and back pain, one study X-rayed 600 backs and measured subjects curves in the lower back (Hansson 1984). Some of the 600 subjects had acute (short term) back pain, some chronic (long term) back pain, and some no pain at all. The study reported NO association to be found between pain and spinal posture, which means that looking at the postural curve of one's back tells you nothing about how much pain someone has/will have.
Yet other studies have looked at things such as how far a person's head sticks out in front of them- known as the forward head posture- and all have reached similar conclusions that this has nothing to do with how much pain one has (Braun 1991). For gosh sakes, one study even took college freshman, measured their postural asymmetries (such as one hip or shoulder higher than the other), and then followed them for some 25 YEARS. The results? Postural asymmetries were NOT predictive of OR associated with future episodes of low-back pain, mid-back pain, or neck pain (Dieck 1985).
But can stretching and strengthening even change posture? Studies and review articles on the subject clearly say "NO" (Hrysomallis 2001). These are the kind of studies where objective measurements are taken of a subject's posture, and then participants go through a stretching or strengthening program for a period of time- and then are re-measured to see if any posture changes have taken place. For example, popular treatments, such as stretching out "tight" hamstrings, does not change the position of the pelvis- and in turn the curve of your low back (Li 1996). There's tons more good research I could cite, but you get the point- its all out there, been published for years. However despite the fact there's just no solid evidence to support this popular "posture therapy", it doesn't stop people from practicing it and perpetuating these myths. Either medical practitioners/writers aren't reading the literature, or they're choosing to ignore it. Whatever the case, it's just not a good thing for people with back pain.
But hey, don't get me wrong- that's not to say that a person won't read a book like this and get great results. Just keep in mind that when someone does a particular treatment and feels better, that does NOT prove that it was the treatment that did the trick. Without going into detail, there are a lot more factors to consider such as the natural history of a disease, regression to the mean, the placebo effect, or the outright belief that the therapy will work. That's why we have control groups to sort it out for us.
My advice? Stick to forms of therapy that have been supported in published, well-done clinical trials. Hope this helps.