Energy transfers in the spinal engine.

Locomotion is generally perceived as being the function of the legs. The trunk is considered to be carried along in a more or less passive way. This popular hypothesis appears to have been accepted with little substantiation. In light of the numerous observations contradicting this view, we have proposed an alternative hypothesis 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.