The answer is motor control. When the interaction between the nervous system, muscles and joints are good we have good motor control. A motor control error can result in a temporary reduction in activation to one of the intersegmental muscles. This may allow rotation at just a single joint to the point at which passive or other tissues could become irritated or injured. This explains how injury might occur just by bending over to pick up a pencil or other light loads.
Any motor control error can cause a short and temporary reduction in activation to one, or more, of the intersegmental muscles. Other common causes that lead to low back disc pain include:
* Flexing the spine over & over.
* Full flexion (bending over) with the following situations makes the spine more vulnerable:
1) excessive loads
2) insufficiently warming up the spine
3) bending over early in the morning
4) after prolonged sitting