Methods and systems for tracking movement of a person, including a method comprising: arranging a plurality of sensors of a motion tracking system on a body of the person； tracking movement of the person with the plurality of sensors at least while the person performs a movement； digitally estimating, with a computing device, a position of either the first joint or the sensor on the second body member, wherein the position of the first joint is estimated using measurements of the first sensor and the position of the sensor is estimated using measurements of both the first sensor and the sensor arranged on the second body member, and wherein the position is estimated while movement of the person is tracked； digitally computing, with the computing device, an acceleration of the estimated position while movement of the person is tracked； digitally computing, with the computing device, a first comparison between the computed acceleration of the estimated position and acceleration measurements of the sensor arranged on the second body member； and digitally determining, with the computing device, the movement performed by the person based on the first comparison.
