Boeing and University of Michigan Study Finds Shoulder Exoskeletons Slow Movement Speeds

Passive shoulder exoskeletons intended to assist factory employees during overhead tasks can slow physical movement and add muscular strain during multi-step work, according to two studies led by the University of Michigan and the Boeing Company. Published in the International Journal of Industrial Ergonomics and Applied Ergonomics and reported by TechXplore, the findings highlight key movement barriers that explain why factory workers often avoid wearing passive support hardware during trial runs.

In manufacturing operations such as aircraft wing assembly, workers frequently perform overhead drilling and wiring tasks that strain upper-body muscles and joints. Lightweight passive shoulder exoskeletons use spring mechanisms located in the torso of the device to provide constant upward support. Despite the intended relief, voluntary adoption among workers has remained low.

To determine why workers resist using the hardware, researchers evaluated participants across two separate trials: a laboratory hand-eye coordination test and a dynamic drill-fastening task inside a manufacturing training facility. In the lab experiment, subjects wore the Ottobock Paexo Shoulder and tapped targets arranged in a circular array at shoulder level and at 40 degrees above shoulder level. While the device did not harm targeting accuracy, error rates, or precision, it slowed movement times by 3.7% at shoulder level and by 9.7% above shoulder height.

In the training facility trial, trainees wore motion sensors on their forehead, back, upper arms, and wrists while performing an overhead drill-fastening routine requiring bit changes. Evaluated using the Rapid Upper Limb Assessment framework, the exoskeleton reduced torso flexion across all tested subtasks, lowering back injury risk. However, sensor data revealed that whenever workers lowered their arms to switch drill bits, they had to exert active muscular effort to fight against the device's constant upward push.

Because of this resistance, participant discomfort ratings did not drop consistently across target body areas. Some workers reported small reductions in discomfort, while others reported no change or increased discomfort. The researchers noted that repeatedly working against mechanical resistance over an entire shift could make passive exoskeletons more tiring than helpful.

To improve adoption, the study authors recommend that exoskeleton designers incorporate manual or automatic mechanisms allowing workers to disengage support during downward arm movements, ensuring hardware accommodates the dynamic nature of factory tasks.