looks like a good example of how people have complicated back problems in later years. can anyone say bulging discs? =3
A disc injury is a complicated mixture of injury, physiological, and genetic events and overlap in such a complicated way most physicians just say "pulled low back muscle." I find it hard to believe that 4 sets of good morning exercises performed once per week with good form would cause back problems in later life.
The #1 cause of low back pain I see is due to genetic factors. You get mom's eyes, dad's nose, why wouldn't you get their facet tropism and narrowed spinal canal? Take into account the amount of repeated injury to the anular fibers and a history of smoking and commercial driving and you have a classic example of someone with chronic back problems.
Anular fibers tear from the center and progressively work their way outwards. As they tear outwards towards the outer 1/3 of the disc the nerves that supply the disc start to grow inward along the injury. This causes progressively worse pain with each repeated injury. The repeated injury also causes the discs to degenerate faster and sets up potential protrusions, herniations, bone spurs, and stenosis. The size of the spinal canal is a major factor involved in this because a large canal can accommodate a larger bulge/protrusion than a smaller one. This is why almost everyone that has an MRI shows at least one bulge in their spine but show no symptoms. This is why an MRI is useless without a good clinical diagnoses.
I cannot see how a properly performed deadlift or good morning exercise is going to injure a healthy disc unless the disc is not healthy and already injured and the person is stupid and works through their pain causing further injury. A healthy disc is so strong that straight compressive forces will collapse the vertebra before rupturing the disc. Although once you introduce a sheer effect with a rotational component causing taughtness in the anular fibers the disc is now in it's weakest state and at it's highest risk of injury.
The short answer is to never work the low back when it hurts. Always start with light weight and work your way up. If an exercise causes low back discomfort lower the weight and sets. If the pain still persists discontinue the exercise.
When a disc is injured especially when nerve compression is involved a monosynaptic reflex is created which causes a spasm of the muscles surrounding the injured area. Almost everyone (including most doctors) perceives this as a pulled muscle and muscle spasm and not a disc injury especially if there is no radiculopathy. A typical (bad) course of treatment is aimed at directly relieving the muscle spasm and not the disc injury and inflammation around the disc. If the disc injury is treated the muscle spasm will reduce. As a rule of thumb, treat all low back pain as a disc injury as that is the most likely cause. (use ice NOT HEAT, lay with your legs elevated, and try a series of low back manipulations from an MD,DO,DC.)