An apparatus and method determine movement information for a user that carries an accelerometer whilst moving. The apparatus receives acceleration data from the accelerometer defined relative to a frame of reference of the accelerometer. A transformation is determined and applied to the acceleration data or to data derived from the acceleration data to determine acceleration data is a user frame of reference that includes a user direction of travel and a side to side direction transverse to the user direction of travel. The acceleration data or data derived from the acceleration data is analyzed to determine a time period corresponding either to a user stride period or to a step period as the user is walking or running; and information about accelerations in the side to side direction are used to disambiguate whether the determined time period corresponds to the user stride period or to the user step period.