“…A study conducted by McClymont et al showed that the mean square error, one of the variability measures, of plantar pressures significantly increased when walking faster, while the coefficient of variation, another standard variability measure, was not related to walking speed [ 43 ]. Lu et al performed a series of studies to determine the effects of different gait speeds controlled by treadmill or participants on the inclination angle of center of mass and the COP, suggesting that the minimum value of the range of the frontal inclination angle was detected at the preferred walking speed, compared to that at lower or higher speeds, either in over-ground walking or in treadmill walking [ 44 , 45 ]. These findings indicate that people might control their posture with the least effort during walking at their preferred speed.…”