An example system includes one or more sleeves, each configured for attachment to a leg and comprising a pressure sensor, an accelerometer and a magnetometer. A processor processes sensor signals from the pressure sensor, the accelerometer and the magnetometer to estimate action (A) and work (W) using event detections of peak stance and valley swing events associated with leg movement, for optimizing energy efficiency for maintaining a balance of the body leaning forward in a gravity pull-down force, with the periodic upward force of the sequential foot-thrusts with the toes.