Spinal Engine Theory

Serge Gracovetsky, Ph.D.                                  

Serge Gracovetsky graduated from the nuclear physics program at the Swiss Federal Institute of Technology in 1968, and he earned his doctorate in electrical engineering from the University of British Columbia in 1970. Gracovetsky went on to become a tenured faculty member at Concordia University in Montreal where he taught for 27 years in the department of computer science and software engineering.

In the course of his career, Gracovetsky has studied subjects ranging from the injury process experienced by military jet pilots during emergency ejection to the reasoning process of physicians in making a diagnosis for low back pain.  He has founded and directed four companies devoted to developing technology to measure spinal function, based on the concept of the spine as the primary engine driving the pelvis during gait.

Gracovetsky is well known for his pioneering research on spine biomechanics and the Spinal Engine theory.  He currently serves on the scientific advisory board for the European Rolfing Association.

The human species evolved to avoid carrying unnecessary muscular masses that do not directly contribute to locomotion.  This development occurred from cleverly exploiting the Earth’s gravitational field and a few laws of physics, such as the conservation of angular momentum.

The law of conservation of angular momentum essentially describes a mechanism to transfer the action of one muscle to a distant part of the body.  The motion of one limb generates an angular momentum that must be canceled by the displacement of another limb so that the sum of the angular momentum of all the parts of the entire body remains zeroed at all times.

This law has numerous consequences for human locomotion.  Consider the motion of the pelvis during gait.  Suppose that the pelvic motion is due to application of forces produced by the legs.  Conservation of angular momentum implies that a counter-torque must be applied to the ground by the legs. This is done in some circumstances, such as skiing, when the foot forces the ski to turn in deep snow.  However, activities such as walking on tiptoes or running on ice do not transfer any torque to the ground. In other words, since little or no torque is applied by the legs to the ground, then little or no torque can be applied by the legs to the pelvis.

The consequence is unavoidable:  Since the pelvis cannot be driven from below, it must be driven from above.  Somehow, the spine generates the necessary forces to drive the pelvis.  The need to explain how the spine generates this force was the reason developing the spinal engine theory.

You may be interested to know that in 1977, two years before she passed away, Dr. Ida P. Rolf had a book published that was entitled Rolfing: Reestablishing the Natural Alignment and Structural Integration of the Human Body for Vitality and Well-Being.  In this text, in the chapter entitled Your Psoas, Rolf writes: “Sturdy balanced walking (in which the leg is flexed through activation of the psoas, not the rectus femoris) thus involves the entire body at its core level.  In such walking, each step is initiated at the twelfth dorsal vertebra, not in the legs; the legs move subsequently.  Let us be clear about this: the legs do not originate movement in the walk of a balanced body; the legs support and follow.  Movement is initiated in the trunk and transmitted to the legs through the medium of the psoas.”
Back to Gracovetsky’s research:

Locomotion is generally perceived as being the function of the legs, where the trunk is considered to be carried along in a more or less passive way. This popular hypothesis has been accepted with little substantiation. In light of the numerous observations contradicting this view, an alternative hypothesis has been proposed in which the spine and its surrounding tissues comprise the basic engine of locomotion. This theory is consistent with available experimental data which suggest that the motion of the spine precedes that of the legs. Indeed, the variations in the power delivered to the pelvis by the spine are strikingly similar to, but slightly ahead of, the variation in power at the hip.