If your back hurts, don't sit up straight in your chair
If your back hurts, don't sit up straight in your chair
Leaning back while sitting takes pressure off the spine
Chair position and posture are the first elements considered when someone who works at a desk job complains of back pain. But encouraging him or her to sit up straight might be the wrong advice, according to one expert.
Sitting in a supported semi-reclined position — 45° backward from back-straight 90° posture — places less strain on the spine, says Waseem Amir Bashir, MBChB, FRCR, a fellow of the University of Alberta (Canada) Hospital radiology department (See Figure below).
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Bashir and his colleagues used magnetic resonance imaging (MRI) to study 22 volunteers who had no history of back pain. Each subject was scanned in three different positions — sitting up straight, slouching, and reclining slightly in a 135° posture. A "positional" MRI machine was used, which allows patients freedom of motion — such as sitting or standing — during imaging. Traditional scanners have required patients to lie flat, which may mask causes of pain that stem from different movements or postures.
The researchers concluded that the strain of sitting upright for long hour creates or contributes to chronic back problems.
"A 135° body-thigh sitting posture was demonstrated to be the best biomechanical sitting position, as opposed to a 90° posture, which most people consider normal," according to Bashir. "Sitting in a sound anatomic position is essential, since the strain put on the spine and its associated ligaments over time can lead to pain, deformity, and chronic illness."
Work-related backaches a major pain
Back pain, according to the National Institute of Neurological Disorders and Stroke, is the most common cause of work-related disability in the United States and a leading contributor to job-related absenteeism. It costs Americans nearly $50 billion annually, and sitting is determined to be the root cause of the pain in many cases.
"We were not created to sit down for long hours, but somehow modern life requires the vast majority of the global population to work in a seated position," according to Bashir. "This made our search for the optimal sitting position all the more important."
When strain is placed on the spine, the spinal disks start to move and misalign. At a 90° sitting position, this movement was most prominent. The disks were least moved when subjects were sitting back at a 135° sitting position, the University of Alberta researchers found.
Sitting on a chair that provides proper support at a slight backwards tilt puts the back in this optimal position. Slouching was the most stressful position. It caused a reduction in the spinal height, creating a high level of wear and tear in the lower spine.
"This may be all that is necessary to prevent back pain, rather than trying to cure pain that has occurred over the long term due to bad postures," Bashir suggests. "Employers could reduce problems by providing their staff with more appropriate seating, thereby saving on the cost of lost work hours."
For more information:
Waseem Amir Bashir, MBChB, FRCR, fellow, musculoskeletal radiology; University of Alberta, Department of Radiology and Diagnostic Imaging, 8440-112 Street, 2A2.41 WMC, Edmonton, Alberta T6G 2B7.
Radiological Society of North America, 820 Jorie Blvd., Oak Brook, IL 60523. Online at www.rsna.org.
Chair position and posture are the first elements considered when someone who works at a desk job complains of back pain. But encouraging him or her to sit up straight might be the wrong advice, according to one expert.Subscribe Now for Access
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