Development of a Grasshopper‐Leg‐Inspired Back‐Type Exoskeleton for the Reduction of Muscle Activation During Stoop Activities

ABSTRACT Farmers frequently suffer from musculoskeletal disorders, particularly lower back pain (LBP), mainly due to occupational ergonomic factors such as repetitive stooping and lifting. This study proposes using an exoskeleton to reduce LBP risk by providing external torque to the hip joints. The grasshopper‐leg‐inspired exoskeleton (GIExo) incorporates a spring actuator mimicking the lump mechanism of grasshopper legs and an actively controlled clutch to toggle assistance. Fifteen farmers ( n = 15) participated in rice field experiments under three conditions: without assistance, wearing GIExo without activation and with assistance. Electromyography (EMG) was used to monitor muscle activation while farmers performed lifting and rolling tasks. The Anybody software estimated compression and impact forces on the body before and after wearing GIExo. A body tracking experiment using YOLOv8 was conducted to evaluate the influence of GIExo on the natural movement of users. Results from Friedman test showed that GIExo reduced average activation of the upper thoracic erector spinae (TES) and lumbar erector spinae (LES) by (28.5%−35.5%) and (31.9%−35.2%), respectively, during lifting tasks, and by (52.1%−45.4%) and (64.6%−68.2%), respectively, during rolling tasks. The compression force between the 5th lumbar vertebra (L5) and sacrum (S1) decreased by 7.7% with GIExo. Furthermore, when the exoskeleton was worn in the without activation state, it did not restrict the user's range of motion. Additionally, perceived exertion and acceptance surveys evaluated user feedback on physical effort, comfort, and usability. Responses indicated reduced fatigue and overall acceptance of GIExo in real working conditions. These findings suggest that GIExo is a promising solution for reducing fatigue and musculoskeletal disorders, improving ergonomic conditions in labor‐intensive agricultural tasks such as lifting and stooping.