A novel system to measure head and trunk posture during daily activities

Abstract

Although the posture and jaw function has been speculated to relate to each other, little scientific evidence is presented in humans due to lack of recording method. To clarify that, we designed and tested a standard noninvasive, accurate, and repeatable clinical method to record head and trunk posture for hours in freely behaving humans. The system was evaluated by measuring the following tasks successively conducted by five subjects: 1) reading a sheet of text (vertical and horizontal documents) while sitting on a chair, 2) sitting on a chair (in an upright position and freely), 3) walking slowly (in an upright position and freely) in a room, 4) tilting the head (anterior and posterior directions and right and left directions) and 5) turning the head (right and left) while sitting on a chair. Characteristic features were observed in the volunteers performing the reading and head movement tasks. While reading text of vertically lined letters, head movement was in the antero-posterior direction along with the direction of the letters, however, movement was limited when the volunteers read text of horizontally lined letters. During head tilting and turning, head and trunk movement was in the same direction for pitch but in the opposite direction for roll. In conclusion, this system accurately records head and trunk posture individually in human subjects; it is easily operated for clinical use and small enough to sit on the patient's trunk for hours of recording. A potential problem may be its battery consumption; however, current technology may overcome this.