Dr. Alf Nachemson (1931–2006) was a giant in back pain research, and unfortunately his 1981 paper about spinal forces during flexion is also one of the most misinterpreted and abused studies in the history of the field. This diagram from it specifically has been widely used to demonize flexion (stooping):
What do I mean by “demonize”? The scientifically unjustified portrayal of flexion loading on intervertebral discs as a major mechanism of back pain. And if flexion injures discs, then surely it can also be avoided to prevent and treat back pain… and so flexion avoidance became a dubious pillar of back pain rehab. Many years later, shortly before his death, Dr. Nachemson expressed his regrets (see The Back Letter):
This experiment has been misinterpreted as evidence that the disc is a significant pain generator and that increasing the biomechanical load leads to greater pain. But this study merely showed how the lumbar spine responds to normal physiologic loading in various positions of the body. It does not give any indication as to where the pain actually comes from.
Whether we get back pain is influenced by many non-obvious factors. The belief that we must not stoop to lift things is too simplistic at the least, and probably just wrong.
This quote is also from that interview, and it’s too great not to include:
One of the main goals of my career has been to determine the cause of non-specific back pain. And in this I have failed. I didn’t know the origin of back pain in those days, and I don’t know now.