Influence of an on-body lifting aid (HAL® for Care Support) on kinematics during repetitive lifting in healthy men

Abstract

Work-related lower back pain (LBP) leads to socio-economic burden and demands solutions. The hybrid assistive limb (HAL) for Care Support (Cyberdyne Inc., Ibaraki, Japan) is an active on-body lifting aid to assist joint motion according to the wearer’s voluntary motor drive to reduce the lumbar load. A few studies investigated HAL and stated efficacy in terms of enhanced performance and reduced fatigue, yet the question remained if the use of HAL may result in a different execution of movement, for example by influencing the kinematics of the lower extremities. The aim of this study was to determine the influence of HAL on kinematics of the lower limbs and the spinal column during repetitive freestyle symmetrical lifting. Kinematic data was recorded by an inertial measurement unit sensor system in 11 healthy men lifting and lowering a 19.5 kg barbell under three conditions (no HAL, HAL Level 3/5, HAL Level 5/5). Outcome parameters were maximum and minimum angles as well as range of motion (ROM) of thoracic spine, lumbar spine, hip- and knee joint in sagittal plane. We found a significantly decreased ROM of the lumbar spine as well as a significantly reduced maximum and minimum thorax extension when starting lifting and in upright position after lifting, respectively, while using HAL. Influence of HAL on the kinematics of the lower limbs was not significant. Differences between both evaluated HAL conditions were not significant. This study proved limited lumbar spine ROM and reduced thorax extension without alterations of lower limbs kinematics when using HAL. This might potentially decrease the risk of work-related LBP.