2.7. Measurement
An IMU measures linear acceleration and rotation. The study used 2 different types of IMUs, one for intermittent measurements of postural sway and one for continuous measurements of body positions and movement. The IMU that measured postural sway was used in all 3 groups to measure postural sway in the anterior/posterior and medio/lateral directions at baseline and follow-up. During the measurements, the IMU was attached to the back, and the participant stood still for 30 s. An IMU attached to the back has shown an equally good ability to discriminate between different conditions in postural sway as other placements [