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child with slumped sitting

Mom gives the okay to sit slumped? One study’s take on sitting posture and thoughts from the Posture Expert

I continue to receive articles quoting a poorly thought-out, “new” 2006 study showing that there is less mechanical stress on the low back when sitting reclined at 135° as opposed to sitting up straight.

Researchers assessed low back stress by measuring the motion of the intervertebral disc material in three positions: slouching forward, upright and reclining backwards. They found that there was less disk motion when reclining backwards than there is when sitting upright. They concluded that since when there is undue stress on a disc, it moves, so therefore if the disc moves, there is “undue stress”.

The study was presented at a MRI meeting, but as far as I could find the study was not published in a peer-reviewed journal. From what I can see, there are at least two very significant problems with their reasoning and conclusions:

Logic error: Assumed causality. In other words, because undue stress makes a disk move, they are assuming a disk moving is necessarily indicative of undue stress. It might, or might not. For example, is this true? Whenever it rains, everyone opens their umbrellas. Therefore, if everyone opens their umbrellas, it will rain.

Relevance: Sitting affects the whole body in posture, not just the low back. If a computer monitor is perpendicular to your eye level, working in their recommended reclined position would require you to flex your neck forward an additional 45° (135-90). It is pointless at best to recommend a work posture to relieve mechanical stress on one area by transferring it to another.

DrW’s Personal comment: The press received by this piece is another example of short-sighted cultural relativism — “Mom was wrong–it’s really ok to slump!”


“The Way You Sit Will Never Be the Same! Alterations of Lumbosacral Curvature and Intervertebral Disc Morphology in Normal Subjects in Variable Sitting Positions Using Whole-body Positional MRI.”  Waseem Bashir MBChB, Tetsuya Torio MD, Francis Smith MD, Keisuke Takahashi, Malcolm Pope PhD. Annual Meeting of the Radiological Society of North America (RSNA).


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