A lot of back pain research is selective-evidence-based because of its focus on and around the spot where it hurts, rather than taking a global, system-wide approach to its causes and treatment.
Most people with low back pain have a pelvis that's out of alignment due to tight muscles attached to it, front, back and sides - but usually tight hamstring and buttock muscles - and maybe hip flexors.
There are a genre of people who are exceptionally aerobically fit and strong who succumb to back pain. Usually they're very inflexible. Bones in the back will usually already be out of alignment. You can test how far out of alignment but using this diagnostic procedure.
When the pelvis is out of alignment the bones above it move out of alignment. When the vertebrae move out of alignment ligaments, tendons and muscles attached to those bones are stretched beyond their pain threshold. The nucleus of one of more discs starts to get squeezed out. Then along comes an incident - often trivial - that 'tips the person over the edge' and the disc herniates.
The 'straw that breaks the camels back' usually gets the blame, whether it's bending down to pick up a leaf, swivelling round to pick up a phone book, cleaning your desk or lifting a bag of groceries into the car. It can happen to the best of us.
The bag of groceries is not the underlying cause of the problem, just one of the many straws that lob on the lower back. The groceries (the leaf, the phone book, the desk) get the blame.
This is an example of the post hoc ergo propter hoc fallacy. (If A occurs before B then A must have caused B.)
Academic bio mechanics and physiotherapists want to scare us with selective-evidence-based science. For instance, Canadian bio mechanic, Stuart McGill warns against doing situps because they place HUGE forces at the spot where discs herniate.
However, a healthy musclo-skeletal system is designed to cope with the HUGE forces he rails against.
Blaming a sit up for herniating a disc is indeed a selective piece of evidence. How far the bones of the spinal column are already out of alignment, how inflexible some of the muscles attached to it are and how weak the muscles attached to the pelvis and spine are more important factors.
The body needs persistent flexibility exercises done in sufficient dosage to keep the pelvis and spinal column in good alignment. It needs persistent strength exercises to support the bones in good alignment. (The point I suspect McGill misses is the fact that a good strength training program will also support bones in misalignment.)
But just focusing on the strength of muscles attached to the spine 'somewhere' in the vicinity of the pain misses the point. The cause of the pain is rarely at the site of the pain
The fact that the medical and therapeutic industries are fixated on the site of the pain, has perverted the course of lower back pain research. It's a system problem, that manifests itself in the lower back, not a lower back problem per se.
This means a lot of the evidence as to the cause of lower back pain is selective and if the evidence is selective then we need to be careful not to rely on it too heavily.
As for yoga, if the Chinese have been doing it for 2,000 years, I'd bet on it. I wouldn't change it. It's a musculo-skeletal health program that focuses on the musculo-skeletal system as a whole and not just on one small segment of it. I wouldn't be scared off from doing some of the poses on the say-so of latter day bio mechanics and physiotherapists.
We're dealing with a system that goes from the bottom of the feet right up to the top of the head and just about all the muscles in this chain work together to keep the bones in correct alignment - including the bones in the lower spine.
Focus on the system, not just spot where it hurts. Keep the system strong and flexible and the chances of coming down with a crook back are quite remote.
If you're searching for back pain bogy men, you've got to look further than leaves, desks, bags of groceries and situps.
In the meantime stay tuned, highly tuned and diminish your risk of joint and muscle pain by keeping yourself strong and flexible.