It seems that "Sit up straight" is a parental command that just lost its thunder.
It turns out sitting up stick-straight is bad for the back, researchers say.
Your back is best off in a reclining position, which takes pressure off the spinal disks in the lower back, compared to the upright posture that most people consider normal, according to new research presented today at the annual meeting of the Radiological Society of North America.
"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," said Waseem Bashir, the study's author, in a news release.
Though reclining might relieve strain, it won't necessarily alleviate back pain.
Researchers used a positional MRI scanner to collect images from 22 volunteers with no history of back pain.
A positional MRI, as opposed to the better-known tunnel MRI, allows patients to move around during imaging and allows scientists to see how different body positions affect the back and spine.
Using the MRI images, scientists determined which sitting position -- with feet still on the floor -- put the least stress on the back by measuring changes in the height between vertebral discs and other changes in the way the spinal column was curved.
Images of volunteers sitting upright at 90 degrees showed more signs of strain on the spine than images of those who were reclining at 135 degrees.
This reclining position also put less strain on the spinal disks and associated muscles and tendons compared to slouching forward, the study authors say.
Researchers conclude the reclining posture is the best and recommend that patients invest in some home or office furniture that is ergonomically designed to let someone sit in this "optimal position."
It's well known that normal day-to-day living puts a lot of strain on the back and spine.
Most Americans sit all day at home or at the office, and over time that strain can lead to more serious back problems.
Back pain is one of the most common reasons people miss work.
"Sitting and standing for prolonged periods is fairly unique to humans and puts an enormous energy and mechanical strain on the body," said Dr. Stephen Ondra, a professor of neurological surgery at Northwestern University in Chicago.
The real question, Ondra added, is what can we do to take some stress off the lower back and slow "the inevitable rate of degeneration that life creates in the low back."
The study's authors are optimistic that they've found the answer -- kick back and relax at a 135-degree angle.
"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 said.
That conclusion is a "leap of faith," doctors say. The study did not look at back-pain sufferers -- all study volunteers were entirely back-pain free -- and doctors can't say for sure whether or not the strain that Bashir and his colleagues observed relates to pain per se.
Critics say it did not make a lot of sense to find a solution to back-pain problems based on a small study of patients who do not experience persistent pain.