Proposal of Non-rotating Joint Drive Type Mechanical Assist Device for Squat Lifting by Using Leaf and Compression Spring

Lower back pain is a major health concern worldwide. A cause of lower back pain is the burden on the lumbar region caused by the handling of heavy objects. The Ministry of Health, Labour and Welfare in Japan recommended “squat lifting” to reduce the burden. However, the technique is not very popular although it supports a large force on the lower limbs. Therefore, the aim of this study is to develop a power assist suit for squat lifting. In the study, we propose a knee joint extension mechanism by using a leaf spring. Subsequently, we discuss the estimation of joint torque from the motion analysis of squat lifting to construct a prototype. Finally, we describe the performance of a prototype mounted on a human body. The results indicate that the %MVC of the rectus femoris while performing squat lifting using the prototype is 53% lower than the value obtained without using the prototype.