In this paper, a biotechnical device for recording and assessing a person's physical activity is presented, which is a dumbbell equipped with a microprocessor board and inertial sensors. To restore the trajectory of the projectile, a gyroscope and an accelerometer are used. The trajectory of the motion is based on the coordinates: the angles of rotation and displacement. The movement is calculated by double integration of the accelerometer readings, the angles of rotation of the dumbbell are determined by integrating the angular velocity of rotation of the gyroscope. The data read from the sensors is fed to the microprocessor board, where they are filtered andprocessed. Based on the processed data, the trajectory of the projectile's motion is constructed. The weight of the dumbbell is 0.50 kg, the total mass of the device is 0.54 kg. The developed biotechnical device is able to detect the elbow joint pathology of the upper human shoulder girdle and to assess the physical parameters of the patient with injuries of the elbow joint.