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Biomechanics Of The Human Back And The Importance Of Correct Sitting Posture



One of the biggest complaints of people working in an office is that their backs hurt from sitting all day. Very often, office workers will sit in a chair for hours without getting up. The cause of the back pain many of us experience can partially be attributed to the length of time in which we sit, but a majority of the issue lies within our sitting posture and the design of the chairs we sit on.

How the spine works

Your spine is divided into 5 basic parts or sections:

  1. Cervical section (neck)
  2. Thoracic section (upper back)
  3. Lumbar section (lower back)
  4. Sacrum (part of the pelvis)
  5. Coccyx (tailbone)

The majority of the movements of your spine (bending forward, back, side-to-side, and rotating) occur in the cervical, thoracic, and lumbar sections of the spine. So when you experience pain in these sections of your spine, you may notice that it’s extremely difficult to perform normal movements such as bending down to pick something up or slightly turning your torso to see behind your shoulder.

The back pain that most people experience is caused by abnormalities in one or more sections of the spine (most commonly the lumbar section). A healthy spine is one where all sections are aligned correctly and all the muscles are used properly. When your body falls into an unnatural or unorthodox position for extended periods of time, it alters the positioning of the sections of your back.

Unless you have been trained to sit properly, most people will subconsciously fall into a posterior pelvic tilt position (slouching) while sitting down. The longer you continue to sit in this position, the more discomfort your back is forced to endure and over time can lead to chronic back issues.  The lumbar section of the back opens naturally when you sit upright.  When you slouch, you’re forcing the lumbar to stay open for longer than the spine can comfortably allow. Eventually, your joints will have a difficult time returning to the closed position.

When you start out by sitting in the proper position and maintain that posture, the back is able to stay aligned and all the sections of the back are working in unison.

How to sit properly

For people who have gone years sitting improperly, adjusting sitting posture might feel uncomfortable at first because it’s not something you’re used to. However, over time it will become natural and you’ll be pleased with the results.

When you sit on your chair, your back should be straight and your shoulders should be relaxed.  Your head should be upright with ears aligned directly above your shoulders.  Many people make the mistake of not properly utilizing the back of the chair. Your bottom should be up against the back of the chair and the back of your knees should extend 2-4 fingers beyond the front edge of the chair for healthy circulation.

Your bodyweight should be spread evenly on both of your hips. Your knees should be bent at a 90-degree angle and should be even with your hips or a little lower, never higher. Your feet should be flat on the floor or flat on a footrest and ideally, your legs should not be crossed.

You can consider using a lumbar pillow for your lower back to help you get comfortable or a chair with an adjustable back tilt and adjustable lumbar support.  It’s also very important to note that even with proper posture, you should not remain seated in the same position for extended periods of time. You should aim to get up at least once an hour and move around.

All chairs are not made equal

A $50 office chair from Wal-Mart might save you money today, but be prepared to experience discomfort and expect to replace the chair often.  You should also try to match the type of chair you’re using to the activity you’ll be doing when sitting. For example, if you’re doing some type of work that requires you to sit high up, you might consider ergonomic drafting stools. For most people who work in an office, look into mid-back height chairs that provide the necessary lumbar support.

Sitting postures and chair design go hand in hand. By correcting the position of your spine and finding the correct chair, you can avoid suffering from back pain in the future.