Supporting upper limb movements with a soft robot after a brachial plexus injury.

Brachial plexus injury causes severe arm weakness, forcing patients to rely on compensatory movements for daily activities. Most robotic solutions target isolated elbow or hand function, whereas multi-joint assistance remains limited. Here we show that a soft wearable exosuit providing shoulder and elbow assistance through pneumatic actuation and inertial sensing improves arm function in 14 adults with chronic traumatic brachial plexus injury, including six with complete lesions and ten after nerve transfer surgery. In single-session testing, the device increases active range of motion ( + 80-180%) and static endurance ( + 160%), reduces perceived effort near to zero, lowers muscle activity (-30-60%) and fatigue, and preserves moderate-to-high sense of agency and good satisfaction. In a subset of four participants, functional task performance improves (Action Research Arm Test +4.5 points on average) and movements become smoother and less compensatory. These results show that soft multi-joint assistance can provide immediate benefits during use and support further development of wearable assistance for people with brachial plexus injury.