After placement of markers and recording electrodes, the subjects will be instructed to walk down the gait lab runway over the force platform. Simultaneous kinematic, EMG and force plate data is collected. Between 3 and 10 strides of data are collected depending on the degree of variability in the gait pattern. When assistive devices ( canes etc.) or orthotic devices are used, the subject may be asked to ambulate with and without the gait aid.