The average trunk posture deviations in 4-day trunk posture monitoring. The average trunk posture deviation from the neutral standing position of the subjects in 4-Day trial. Three line-segments represent the relative tilting of the 3 sensor modules to the neutral position. Dotted lines represent the posture in neutral position. The inter-segmental angles between 2 line-segments represent the trunk posture angles. (NF: without feedback, F: with feedback).