Instead, the best position for your back is somewhat reclined, sitting at a 135-degree angle rather than the 90-degree angle most office chairs are designed for.
"A 135-degree body-thigh sitting posture was demonstrated to be the best biomechanical sitting position, as opposed to a 90-degree posture, which most people consider normal," says researcher Waseem Amir Bashir in a news release. "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."
Back pain is one of the most common causes of work-related disability in the US and helping to identify bad seating postures may help protect the spine and prevent injury.
Using 'positional' magnetic resonance imaging (MRI) researchers studied the sitting positions of 22 healthy volunteers with no history of back pain. The MRI machine allowed freedom of motion, such as sitting or standing, during imaging. Conventional MRI machines require the patient to lie flat and may mask some causes of back pain.
Researchers used the MRI to examine spinal positioning while the participants assumed three different sitting positions: slouching forward (such as hunched over a desk or video game console), an upright 90-degree sitting position, and a relaxed sitting position with the back reclined backward about 135 degrees while the feet were still on the floor.
Overall, researchers concluded that the 135-degree reclining sitting position put the least stress on the spine and may reduce the risk of back pain. They recommend that people who sit for long periods of time correct their sitting posture and find a chair that allows them to recline.
"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," says Bashir. "Employers could also reduce problems by providing their staff with more appropriate seating, thereby saving on the cost of lost work hours."
Sources: Annual meeting of the Radiological Society of North America, Chicago. Nov. 26-Dec. 1, 2006. News release, Radiological Society of North America.
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