A sensor cluster to monitor body kinematics

Several different factors have been proposed to contribute to the development of chronic low back pain (LBP). Specifically, researchers and clinicians have proposed that impairments of low back posture and movement, particularly during functional activities, are important to address during intervention. However, objective measures of posture and movement are typically only measured in the laboratory setting. Observation of posture and movement in laboratory is limited because people with LBP may not perform naturally when they are being observed, and observation in a single session does not provide information about the duration of postures or frequency of movements across the day. In this paper, we present a wireless body sensor cluster formed by up to seven sensors in order to monitor spine posture and movement both in absolute and relative coordinate systems. The Body Kinematics Monitoring (BKM) system measures the magnitude and frequency of spine movements, and duration of spine postures in 3D, without impeding natural movement. The BKM node developed in this study is 3.0cm in diameter, and contains a 9-axis motion processor that records the raw inertial information of different spine regions. The system offers a standard Bluetooth Low Energy (BLE) protocol to communicate with mobile or fixed hosts. The BKM system has been validated in the laboratory by measuring lumbar spine postures on a mechanical spine testing platform across a known range of angles.