  We apply the laws of human gait vertical ground reaction force and discover
the existence of the phenomenon of least action principle in gait. Using a
capacitive mat transducer system, we obtain the variations of human gait
vertical ground reaction force and establish a structure equation for the
resultant of such a force. Defining the deviation of vertical force as an
action function, we observe from our gait optimization analysis the least
action principle at half of the stride time. We develop an evaluation index of
mechanical energy consumption based upon the least action principle in gait. We
conclude that these observations can be employed to enhance the accountability
of gait evaluation.
