Effect of method to support upper body on biomechanical load in bathing posture

Abstract

Our previous study proposed a biomechanical model in bathing postures. Methods to support upper body including trunk and head of bather were expected to affect physical relax and biomechanical state, such as joint torque or reaction force from bathtub, in bathing. This hypothesis was verified using the biomechanical model in bathing. Bathing postures and reaction forces from the bathtub to a human were measured for seven healthy male participants in two bathing posture conditions (posture with head supported and unsupported). A three-dimensional motion analysis system and 3D force plates were used to measure the experimental data. A biomechanical model in which a human body is represented as a link of body segments was constructed. Significant increases in joint angles of the lumbar, neck and significant decrease in the hip joint were found when bathing in posture with head supported than unsupported. In addition, in the horizontal direction, sum of reaction forces was reduced due to posture with head supported. This reduction of reaction force result in relief of biomechanical loads on ankle, knee, lumbar and neck. These results suggest that method to support upper body affects biomechanical loads on lower body as well as upper body since reduction of reaction force propagate from upper body to lower body.