Is there a right way to sit?

Written by:  Richard Hansen, January 14, 2009

Many professional settings require employees to be seated at their work stations for extensive periods of time.  The problem is that prolonged sitting creates an adverse environment for the back. Most workers tend to adopt a slumped or slouched position while at their desks because it takes less effort and energy than trying to sit upright.  This, however, creates an increase in anterior spinal disc stresses that can lead to herniations.

On the other hand, some employ the use of lumbar supports or ergonomic back rests to encourage them to sit with an upright posture while maintaining the normal lumbar curve.  Sitting with an upright posture, though, requires a continuous increased contraction of the spinal extensor muscles, which also impose compressive loading stress on the spine. 

There have been many research studies performed in an effort to identify the "ideal" sitting posture, without much agreement on what that is.  In a study performed by Makhsous et. al, researchers found that sitting with a reduced pelvis support, or a seat-bottom that is angled posteriorly, reduced the peak pressure on the pelvis and helped maintain the normal lumbar curve without activating additional spinal musculature than any other sitting posture evaluated.  On the other hand, a separate study by Harrison, et al, found that backrests angled between 110 and 130 degrees with additional lumbar supports have the lowest disc pressures and EMG activity in the supporting musculature. 

So which posture is best?  It turns out that neither one is.   Changing lumbar postures throughout the workday appears to be the best strategy to help minimize the risk of tissue overload (McGill).  By using a variable posture, compressive loads are constantly shifting from one tissue to another.  So the ideal sitting posture is therefore one that continuously changes. 

Prolonged sitting can lead to back troubles, but practicing the following spine-sparing tips can help reduce the risk of injury while sitting:

1. Use an ergonomic chair, but use it correctly.  Typically the chair is adjusted so the torso is positioned upright and the knees and hips are bent at 90 degrees.  This posture is good though for no more than 10 minutes.  So understand how to change the position of your ergonomic chair so that loads can be migrated from tissue to tissue to minimize micro-traumas on the spine from overload on any single muscle.
2. Take a break and leave your chair.  Stand up for 10 to 20 seconds every 10 minutes and maintain a relaxed standing posture.  Stretch your arms to the ceiling, which will gently extend your spine, perform neck rolls to relax the neck muscles, and do arm windmills or shoulder rolls to relax the shoulder muscles.  The idea is to allow time for the disc material to be redistributed.
3. Finally, find time to perform an exercise routine during the workday.  Midday is the most ideal, but stay away from exercising first thing in the morning because at this time of day the discs are the most hydrated and therefore under much higher stresses during bending activities.  Thus it is unwise to perform any form of bending activity or exercise within an hour or two of rising.