Samples of electromyography (EMG) data and gait-cycle recording for a subject. Upper panels show recording of Nordic walking (NW); lower panels show recording of level walking (LW). Left, middle and right panels indicate recordings at 60, 90 and 120 m/min, respectively. (1) and (3) show the heel strike of the left foot, and (2) shows the heel strike of the right foot. A gait cycle exists between (1) and (3), and the time between (1) and (2) includes the stance and push-off phases.