Lumbar posture and muscular activity while sitting during office work

Field study, cross-sectional study to measure the posture and sEMG of the lumbar spine during office work for a better understanding of the lumbar spine within such conditions.

There is high incidence of low back pain in office workers. Currently there is little information about lumbar posture and the activity of lumbar muscles during extended office work.

Thirteen volunteers were examined for around 2h of their normal office work. Typical tasks were documented and synchronised to a portable long term measuring device for sEMG and posture examination. The correlation of lumbar spine posture and sEMG was tested statistically.

The majority of time spent in office work was sedentary (82%). Only 5% of the measured time was undertaken in erect body position (standing or walking). The sEMG of the lumbar muscles under investigation was task dependent. A strong relation to lumbar spine posture was found within each task. The more the lumbar spine was flexed, the less there was activation of lumbar muscles (P < .01). Periods of very low or no activation of lumbar muscles accounted for about 30% of relaxed sitting postures.

Because of very low activation of lumbar muscles while sitting, the load is transmitted by passive structures like ligaments and intervertebral discs. Due to the viscoelasticity of passive structures and low activation of lumbar muscles, the lumbar spine may incline into de-conditioning. This may be a reason for low back pain.