System for teaching a correct exercise or a correct trajectory of the exercise to the user, who is a moving person, the system comprising a processor unit (5) and a memory unit (6) and at least one accelerometer (4) measuring sensor communicating with each other, the sensor being connected to or in contact with at least one measuring point a region of the head or torso above the belt line of the wearers body, preferably the region of the head, chest, upper back and shoulder area, most preferably the region of the head region, for collecting measuring information describing the exercise or the trajectory from the measuring point. Provides the user in real time with a feedback signal of whether the determined motion data is within the pre-set limit values, whereby the exercise of the user takes place correctly or the trajectory is correct.
