Both disciplines generally agree that cross-patterned gait (opposite arm and leg moving at the same time) is a normal function of walking and running. However, supporters of the traditional “pedestrian model of gait” insist the legs are the main-event in locomotion and upright walking is a basic design where the legs propel the passive passenger – the trunk – through space. Pedestrian model proponents tend to lump the torso, arms and head together and generally dismiss the upper body as a critical player in gait mechanics.
As discussed in part 1, Canadian nuclear physicist Serge Gracovetsky, PhD, rebuked the pedestrian model by pointing out that counter-rotation of the shoulders and pelvis is an essential key to locomotion and force is not generated by the legs, but instead arises through a complex muscle/skeletal interaction propelled by what he calls a “spinal engine.” He further expounds, “Evolutionarily, locomotion was first achieved by the motion of the spine. … The legs came afterward as an improvement, not as a substitute.”
If Gracovetskys idea that the spine is the primary engine driving the pelvis has “legs to stand on” (pun intended), then manual therapy assessments and rehabilitative corrections must be modified accordingly. Since low back pain is the most common disability for people under the age of 45, the consequence of this reinterpretation of spinal function could be far-reaching. Today, researchers and clinicians worldwide are experimenting with Gracovetsky’s intriguing theory.
Since both schools of thought are supported by quality research in the gait-analysis community, I am trying hard not to marry a single model of locomotion. To prevent the struggle that accompanies divorce, I have developed assessments and corrections based on gait studies conducted by two renowned experts in the field, Serge Gracovetsky and my mentor, Philip Greenman. This osteopathic and physics collaboration paints a broader, more comprehensive picture of the walking process. Alas, in the process of marrying the two methods, some of Gracovetsky’s brilliant spinal-engine concepts have been altered. To avoid misrepresenting the views of either researcher, the proposed model in this article will simply be referenced as the “myoskeletal engine.”
The Myth of Leg Locomotion
Dr. Gracovetsky convincingly claims that, “If the legs were truly the mobilizing force propelling the body through space, a competitive sprinter with huge powerful legs and a small torso should be the fastest.” Obviously this look does not fit the picture we all see at the Beijing Olympic Games, or even in the photo of a 21-year-old South African double-amputee runner Oscar Pistorius, who finished second against top athletes from around the world in a 400-meter race at the Golden League Meet in Rome.
Initial observation of Pistorius stride shows a rhythmic cross-patterned gait and strong pelvic/shoulder counter-rotation that appears as the driving force propelling his lower extremities. In the absence of lower legs and feet, one might conclude these anterior and posterior spring systems alone provide enough thrust to propel Pistorius’ pelvis and extremities. But clearly the International Association of Athletics Federations (IAAF) disagreed - they voted to ban him from formal competition based on the conclusion this artificial “springing” mechanism somehow amplified his interaction with gravitational ground forces.
For example, if a car has a low tire and the tread begins wearing unevenly, the vehicle will begin to shake sooner or later. As the vibration makes its way through the suspension system, the tie rods start vibrating loose. If left unaddressed, damage spreads to the motor mounts. After some time, the “shaky” engine sputters to a halt. Although the low tire was the cause of the problem, it is tempting to blame the engine because the car no longer runs...

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http://erikdalton.com/media/published-articles/dont-get-married-part-2/