Too much spine flexibility will cause low back injury. Science has proven this. In symptomatic and asymptomatic workers, the differences between the two groups were things other than spine flexibility and low back strength. Although beyond the scope of this article, the differences between the two groups were faulty movement patterns, aberrant motor patterns, and core muscular endurance (not strength). Again interestingly enough, by correcting faulty movement/motor patterns, training core endurance, and training the spine in the neutral position, pain-free spine range of motion usually returns. Again, don’t train to the test!

As the spine extends (or bends backwards) the facet joints are loaded, and the interspinous ligament is compressed, both at risk for injury. Perhaps the biggest issue with spine extension is the bending of the neural arch loading the pars interarticularis. The neural arch is slightly flexible and analogous to a paper clip. It will bend back and forth several times before it breaks, but it will break. Not surprisingly, repetitive spine flexion/extension cycles causing bending of the neural arch will result in fatigue fractures, leading to spondylolisthesis- a fracture of the pars interarticularis where one vertebra actually slides forward on another due to the loss of anterior shear support