Physical and Cognitive Load Effects Due to a Powered Lower-Body Exoskeleton

Objective: The aim of this study is to determine the effects of a powered exoskeleton on measures of physical and cognitive performance.

Background: US warfighters carry heavy equipment into battle, and exoskeletons may reduce that burden. While exoskeletons are currently evaluated for their effects on physical performance, their cognitive effects are not currently considered.

Method: Twelve military members participated in a simulated patrol task under three conditions: wearing a powered exoskeleton (PWR), an unpowered exoskeleton (UNP), and without wearing an exoskeleton (OFF). While following a confederate over obstacles at a constant pace, participants performed additional audio and visual tasks. Dependent measures included visual misses, visual reaction time, audio misses, audio reaction time, incremental lag time, and NASA-TLX scores.

Results: The variability in the follow-task lag time was lowest with OFF and highest with UNP, highlighting reduced ability to maintain pace with the exoskeleton. Visual reaction time was significantly slower with PWR compared to OFF for 5 of 12 subjects. The NASA-TLX overall workload scores were lower for OFF compared to PWR and UNP.

Conclusion: Efforts to understand individual variability are warranted such that exoskeleton designs can be used for a wider set of the population. While not all subjects had measurable differences in the selected performance tasks, the perception of increased workload was present across subjects. It remains to be determined what difference in reaction time would be operationally relevant for task-specific settings.

Application: Findings draw attention to the need to consider "cognitive fit" and subject differences in the design and implementation of exoskeletons.