Most manual therapists perform gait analysis based on observation of leg movement as it relates to the pelvis (pedestrian theory of locomotion). Although the legs are obviously important factors in efficient locomotive activities…are they really the primary driving force behind body movement? It makes no sense that the torso, arms and head would not somehow contribute to gait. Since the body strives on energy conservation, the idea of dragging a heavy torso around while walking or running seems like a terrible waste of muscular mass.
Using the pedestrian theory of locomotion, try to imagine what a 100 meter Olympic sprinter’s body might look like (Figure 1). One would expect to see a tiny upper torso driven by huge powerful legs. Any added upper body weight would only serve to slow the runner down.
Those of us who’ve experienced body braces or casts will tell you that normal cross-patterned gait with reciprocal hip rotation is almost impossible. We tend to walk with an awkward ‘block-type’ stride where the QL is recruited to lift the ipsilateral leg to keep it from dragging the ground during the swing phase. This aberrant gait is also seen in our lumbar-fused and ankylosed clients…and even in infants who’ve yet to develop a stable lumbar curve. Try experimenting with this concept by placing some kind of elastic or leather support around your lower ribcage or lumbar spine. Can you feel your thorax and pelvis trying to rotate against resistance from the strap?
Spinal Engine Model
In the early 1900’s, Robert Lovett, MD, developed theories based on the assumption that a rotational component was essential to human movement. His research concluded that in the presence of normal lumbar lordosis, sidebending produced an axial torque (sidebending to one side and rotation to the other) which he labeled ‘coupled motion’.
In 1988, Serge Gracovetsky, Ph.D. expounded on this idea in his book titled ‘Spinal Engine’ by declaring that the legs were not responsible for gait but merely “instruments of expression”. He theorized that during heel strike, kinetic energy was not displaced into the earth as in the pedestrian model, but efficiently transmitted up through the myofascial system causing the spine to resonate in the gravitational field.
Therefore, during right legged weight bearing, the lumbar spine is pulled into right sidebending (left rotation) by the multifidus, longissimus, iliocostalis and thoracolumbar fascia. This action counter-rotates the pelvis as the sacrum is forced into left sidebending and right rotation (Figure 2).
This dynamic coupling at L5-S1 is essential to efficient gait and lumbar longevity. When counter-rotation of pelvis and lumbar spine is lost, the spinal engine runs out of gas allowing compressive forces to squash the L5-S1 intervertebral disc with each step. No wonder the L5 disc suffers the most herniations and is the most operated on of all spinal segments.
Are legs really necessary?
At a Rolf Institute Annual Convention in the mid 1980’s, Gracovetsky convincingly elaborated on his spinal engine theory by showing video of a man born with no legs walking with a perfect cross-patterned gait balanced only on his hips (Figure 3).
During the stance phase of walking, rotary motion is translated through the core causing storage of potential energy in deep collagen structures such as the annular disc fibers and the thoracolumbar fascia. As the spine unwinds, a pulse of kinetic (movement) energy counter-rotates the torso and pelvis and with help from four major myofascial spring systems, propels the body forward in space. (See my new “Don’t Get Married” article at Dont Get Married for a complete description of these spring systems).
For practicing somatic therapists, the spinal engine theory highlights the fundamental importance of maintaining proper function in all myoskeletal structures. It makes common sense that any restriction or ‘kink’ in the kinetic chain (fascia or skeletal), will result in dysfunction or strain elsewhere in that chain.
Bottom line: “Optimal mechanical functioning of the spine is necessary for optimal mechanical functioning of the limbs”.
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