In this study, we use an accelerometer sensor to measure human postural signals during a dynamic task. In previous studies, the step stability index (SSI) has been used to assess human balance via similar sensors. However, the placement of the 3 dimensional sensor differed, placed on the lower back of the subjects. To improve the detection method, we placed the accelerometer on the shoe. The purpose of this research is to compute the SSI, to evaluate whether human balance can be objectively measured with an accelerometer. The results are compared with dynamic centre of pressure (COP) measurements obtained from a force plate that serves as the ground truth. The complexity index (CI) is calculated from dynamic COP to compare with the results of SSI.