Finding your best seat could be a matter of degree

Positional MRI, which allows patients free range of motion during imaging, has allowed researchers to determine the optimal sitting posture to reduce chronic back problems. The technique may also be of value in future seating design.

Investigators found that sitting in an upright position places unnecessary strain on the back, leading to potentially chronic pain problems. The optimal sitting position creates a trunk-thigh angle of 135°. This position was shown to cause least strain on the lumbar spine, most significantly when compared with a typical upright 90° sitting posture.

"We were not created to sit down for long hours, but modern life requires the vast majority of the global population to work in a seated position," said lead author Dr. Waseem Amir Bashir, a clinical fellow in the department of radiology and diagnostic imaging at the University of Alberta Hospital in Canada. "This made our search for the optimal sitting position all the more important."

The study, conducted at Woodend Hospital in Aberdeen, Scotland, was presented Monday at the RSNA meeting.

Bashir and colleagues measured lumbar lordosis angles, intervertebral disc heights, and movement across the different positions on 22 normal subjects with no history of back pain or surgery using a 0.6T whole-body positional MR scanner.

The patients assumed three different sitting positions:

• a slouching position with the body hunched forward

• an upright 90° sitting position

• a relaxed position with the subject reclining backward at 135° while the feet remain on the floor

Spinal disc movement occurs when weight-bearing strain is placed on the spine, causing the internal disc material to misalign. Disc movement was most pronounced with a 90° upright sitting posture. It was least pronounced with the 135° posture, indicating that less strain is placed on the spinal discs and associated muscles and tendons in a more relaxed sitting position.

The slouch position revealed a reduction in spinal disc height, signifying a high rate of wear and tear on the lowest two spinal levels. Across all measurements, the researchers concluded that the 135° position fared the best.

"It is well known that a relationship exists between seating posture and back pain, and therefore this study has provided data that will help to reduce the incidence of chronic back problems from bad sitting positions," Bashir said.