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


The Fallacy of Analyzing Posture Based on the Surface Contours of the Body

by Dennis Zacharkow, PT
© 2014

According to Kendall's book Posture and Pain (1952), a standard physical therapy text for decades, ". . . an experienced observer is able, by observing the contours of the body, to estimate the position of the skeletal structures."

More recently, acupuncturist Gokhale, in her book 8 Steps to a Pain-Free Back (2008), analyzes posture with individuals fully clothed. For example, Gokhale analyzes the posture of a carpenter from Burkina Faso as follows: ". . . his belt is lower in front than in back, reflecting a pelvis that is tipped forward and a sacrum that is angled back." In this full-page photograph of the carpenter, his belt is loose fitting, and as a result is sagging down in front.

However, contrary to the above statements, studies do not verify that observing or externally measuring the surface contours of the spine, pelvis, and sacrum, accurately reflect the x-ray alignment of these structures.

X-ray studies from over seventy-five years ago by Howland (1933) and Boynton (1934) on the position of the sacrum and the lumbar spine in relation to the pelvis show a distinct difference between the external contours of the lumbar spine and sacrum, and the actual contours as revealed by x-ray.

Similarly, over fifty years later, Bundett et al. (1986) concluded that measurements of the lumbar spine and pelvic tilt taken externally with three types of goniometers and photographs, all differed significantly from measurements made internally from x-rays. Regarding the inaccuracy of some of these external measurements techniques, Boynton (1934) commented that "the fascia, muscle and fat overlying the sacrum so distorts its actual position in relation to the pelvis that the external measurement of its slope is not accurate."

Walker et al. (1987) found no apparent relationship to exist between lumbar lordosis and pelvic tilt. This study result can again be explained from research by Howland (1933) and Boynton (1934), concluding that the degree of lumbar curve and pelvic tilt depend more on the position of the sacrum with respect to the pelvis than on any other one factor.

In Howland's (1933) study, x-rays of fifty women ages 20-35 showed individual differences in the position of the sacrum in the pelvis. For some women, the sacrum appears low and horizontal in the pelvis; for other women the sacrum appears to be high and vertical in the pelvis.

Vertebral Body Curvature vs. Surface Curvature

  1. Lumbar Spine

    As explained by Burch (2002), the curve expressed by the tips of the lumbar spinous processes is not identical to the curve of the bodies of the lumbar vertebrae. The degree of curve from palpating the tips of the lumbar spinous processes is always less than the lumbar curve of the lumbar vertebral bodies as seen on x-ray. Coe (1987) recorded that the tips of the spinous processes of L2, L3, and L4 are in a straight line when the bodies of these vertebrae are curved anteriorly in a normal lordosis.

  2. Cervical Spine

    Refshauge et al. (1994) also expressed caution in inferring vertebral alignment of the cervical spine from observed surface contours. Their results showed a relatively straight vertebral body curvature in the cervical spine from x-ray analysis, in contrast to a lordotic surface curvature. The authors also found forward head position judged from surface markers tending to overestimate forward head position measured from vertebral bodies.

    According to the authors, the differences between surface curvature and vertebral body curvature "appear to be due to a combination of factors, including the length of the spinous processes and the depth of the overlying soft tissues."

Lordosis and Gluteal Prominence

In a study by Bryan et al. (1990) on the postural evaluation skills of physical therapists, 48 physical therapists ranked the amount of lordosis from most to least from photographs of three subjects. The photographs showed sagittal views of the subjects in shorts and T-shirts pulled tight to the back.

For 96 trials, only nine postural evaluations by the physical therapists in ranking the amount of lordosis were correct, for an accuracy rate of 9.3 percent.

Apparently, for most physical therapy evaluators, large measures of gluteal prominence were incorrectly rated as large measures of lordosis. For example, the subject with the least amount of lordosis measured by x-ray plus the largest measure of gluteal prominence, was rated as having the greatest amount of lordosis from the photograph in 19 out of 25 trials.

In this study, most physical therapists were obviously looking at the body contours in the photographs and misinterpreting a large gluteal prominence as a large lumbar lordosis. Physical therapists should know that the gluteal prominence is not only below the level of the lumbar spine, but also below the level of the sacrum.

Holistic Postural Correction

As postural evaluations of the position of the pelvis, lumbar spine, and sacrum are usually inaccurate when based on surface contours and external measurements, postural correction should not focus on isolated segmental changes, such as increasing or decreasing the pelvic inclination.

Instead, a holistic approach should be taken by focusing on activating the elongation reflex of the trunk, and reinforcing the proper axial relationship of the pelvis, rib cage, and head.

This is most effectively accomplished at first in the sitting position with the Posture Activators™ of sacral support and lower thoracic support. Driving and sitting with these two Posture Activators in the YogaBack Posture will pattern the neuromuscular system in the optimal elongated posture for several hours each day.

This optimal sitting posture will then easily carry over into standing, with attention then given to swaying backward from the ankles while elongating the thoracic spine. (See the standing posture exercise at the end of the article "A Holistic Approach to Correcting a Sway Back Standing Posture.")


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