Upper leg EMG activation profiles during walking. Vastus Lateralis (VL), Rectus Femoris (RF), Biceps Femoris (BF), Gluteus Medius (GME). (A) Normalized mean EMG intensity curves for the vastus lateralis, rectus femoris, biceps femoris, and gluteous medius muscles calculated from forty consecutive strides (1.0 m/s). Control data is the grand mean of twelve control subjects. Maximum mean EMG intensity across the gait cycle is 1.0. One standard deviation above the mean is shown in gray. Vertical lines show average toe-off. Variance-to-signal ratio is shown above each plot in gray. (B) Variance-to-signal ratio of lower leg muscles calculated from 40 consecutive cycles at 1.0 m/s.