Drivers Beware:
Lumbar Support Can Be Harmful To Your Health!


An Infant's Healthy Sitting Posture -- Why We Lose It

by Dennis Zacharkow, PT
© 2015

A nine-month-old infant can independently achieve and maintain a balanced, upright sitting posture with the proper upright relationship of the head, rib cage, and pelvis (Figure 1). As we grow up, there are three major factors in our society that result in the breakdown of our postural reflex mechanisms, the same postural reflex mechanisms that allow a nine-month-old infant to sit so well:

  1. Improper backrest design of chairs.

    Resting against the backrest of most chairs results in a distorted trunk posture, called a postural depression.1 The term postural depression refers to a "hinging forward" of the front of the rib cage towards the pelvis. This postural depression also occurs when leaning forward improperly, and collapsing the weight of the trunk onto the arms.

    Continually assuming a position of postural depression over the years will break down the normal postural reflex mechanism which involves proper activation of the abdominal muscles, back muscles, and diaphragm (the main breathing muscle).

  2. Sitting at horizontal desks.

    Using a horizontal desk for reading and writing forces one to bring the head forward to achieve the proper visual angle and visual distance to reading and writing materials. Continual use of horizontal desks alters the normal upright head-neck relationship, a key factor in proper body orientation.2-5 More recently, the same postural breakdown results from using iPads and other tablets that are lying flat on horizontal desks.

  3. Heels on shoes.

    Wearing heels on shoes results in a relaxation of important postural muscles of the foot. This causes a breakdown in the foot's postural reflex mechanism that is so critical for overall body posture.6

    The typical low heel on the standard men's dress shoe decreases the normal tension (tone) of these postural muscles by about fifty percent. As the heel height on shoes increases to two inches and higher, there is a total relaxation of these critical postural muscles of the foot.6

    Besides these three major cultural factors, the breakdown of our normal postural reflex mechanisms is intensified by several common sitting misconceptions. The two major misconceptions are the use of lumbar support and the use of reclining backrests.


  1. Anderson, T. McC.: Human Kinetics and Analysing Body Movements. London, Heinemann, 1951.
  2. Alexander, F.M.: Man's Supreme Inheritance. New York, Dutton, 1918.
  3. Cohen, L.A.: Role of eye and neck proprioceptive mechanisms in body orientation and motor coordination. Journal of Neurophysiology, 24: 1-11, 1961.
  4. Laville, A.: Postural stress in high-speed precision work. Ergonomics, 28: 229-236, 1985.
  5. Paris, S.V.: Cervical symptoms of forward head posture. Topics in Geriatric Rehabilitation, 5(4): 11-19, 1990.
  6. Stewart, S.F.: Physiology of the unshod and shod foot with an evolutionary history of footgear. American Journal of Surgery, 68: 127-138, 1945.

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