Wearable Sensor System for Lumbosacral Load Estimation by Considering the Effect of External Load

Anteflexion of the spine is a crucial motion in performing many tasks during work and daily life. It is particularly important in tasks such as providing care to others and carrying objects. To devise measures for preventing back pain, it is necessary to determine the postures associated with high risk of low back pain. Postures that increase lumbosacral load should be identified to reduce the risk of low back pain. In previous work, the relationship between posture and intervertebral loading was clarified, and the centers of gravity in the upper body and the waist shape were estimated. Moreover, individual differences were considered to improve the accuracy of the estimation. This method can estimate the lumbosacral load with sufficient accuracy. However, lumbosacral loading was examined in relation to posture and increases with external load. Therefore, the external load should be included in lumbosacral load estimation. In this study, we developed a back muscle exertion estimation method by using stiffness sensors to measure back muscle exertion, because the back muscle exertion changes with the external load. We conducted experiments in which participants wore the sensor system and the lumbosacral load was estimated from the external load. Estimation using the muscle stiffness sensors was better than previous estimation methods.