Prolonged sitting may alter the passive stiffness of the lumbar spine. Consequently, performing full lumbar flexion movements after extended periods of sitting may increase the risk of low back injury.
A study was performed on 12 normal subjects to quantify time-varying changes in the passive flexion stiffnes sof the lumbar spine with exposure to prolonged sitting and to link these changes to lumbar postures and trunk extensor muscle activation while sitting. The participants performed deskwork for 2 hours while sitting on the seat pan of an office chair. Moment-angle relationships for the lumbar spine were derived by pulling participants through their full voluntary range of lumbar flexion on a customized frictionless table.
It was found that lumbar spine stiffness increased in men after only 1 hour of sitting, whereas the responses of women were variable over the 2-hour trial. Men appeared to compensate for this increase in stiffness by assuming less lumbar flexion in the second hour of sitting. Changes in the passive flexion stiffness of the lumbar spine may increase the risk of low back injury after prolonged sitting and may contribute to low back pain in sitting. (Beach TA. Parkinson RJ. Stothart JP. Callaghan JP. Effects of prolonged sitting on the passive flexion stiffness of the in vivo lumbar spine. Spine 5(2):145-54, 2005
Here is a study showing how to treat low back pain by drawing in the abdominal wall as a specific exercise for the transversus abdominis muscle (in co-contraction with the multifidus). Clinical effectiveness has been demonstrated to be a reduction of 3-year recurrence from 75% to 35%.
Biomechanical effect of this specific exercise on the mechanics of the sacroiliac joint was examined on 13 healthy individuals in the prone position during the two abdominal muscle patterns by means of Doppler imaging of vibrations and simultaneous electromyographic recordings.
Contraction of the transversus abdominis significantly decreases the laxity of the sacroiliac joint. This decrease in laxity is larger than that caused by a bracing action using all the lateral abdominal muscles supporting the use of independent transversus abdominis contractions for the treatment of low back pain. (Richardson CA. Snijders CJ. Hides JA. Damen L. Pas MS. Storm J. The relation between the transversus abdominis muscles, sacroiliac joint mechanics, and low back pain. Spine. 27(4):399-405, 2002
This is a very simple exercise that can be performed while sitting, standing, walking or lying down for those who have low back pain as well as very useful as a preventive exercise for those who are not in pain.