The aim of this thesis is to estimate the base of support (BoS) during gait, defined as the area over which the body is supported during the double-support phase. To reach this goal, both absolute and relative orientation and position of the feet are required. The relative orientation is achieved by sensor fusion algorithms that combine information from accelerometers, gyroscopes and magnetometers. In fact, in this study the orientation is obtained by using Magneto-Inertial Measurement Units (MIMUs) that are suitable for measurements outside of motion analysis laboratory and over extended period of time. However, the use of inertial technology itself does not allow to obtain the absolute position estimation due to the lack of a global reference with fixed origin.