I find that when patients look in books or on the internet for answers, they tend to come up with a two dimensional answer. What I mean by this is that our bodies are not flat like a page, but are 3 dimensional. Our body moves in 3 dimensions, and this explains how injuries can occur.
Most people realize that as we reach forward towards our toes, our spine bends. What we do not think about is the SHEAR, TENSILE (tension) and COMPRESSIVE (compression) forces that are placed on the spine when we do this.
From a 3 dimensional perspective, as we bend forward, the vertebrae want to also slide forward (SHEAR), and the discs will become COMPRESSED on the front side and will become TENSE on the back side.
This is where the "core muscles" come into play. Without support from ligaments (passive) or control from muscles (active), the back can be at risk for injury
If you have any questions about back pain, or the aforementioned explanation, please see my website at www.drmchiro.com for my contact information