A versatile knee exoskeleton mitigates quadriceps fatigue in lifting, lowering, and carrying tasks.

The quadriceps are particularly susceptible to fatigue during repetitive lifting, lowering, and carrying (LLC), affecting worker performance, posture, and ultimately lower-back injury risk. Although robotic exoskeletons have been developed and optimized for specific use cases like lifting-lowering, their controllers lack the versatility or customizability to target critical muscles across many fatiguing tasks. Here, we present a task-adaptive knee exoskeleton controller that automatically modulates virtual springs, dampers, and gravity and inertia compensation to assist squatting, level walking, and ramp and stairs ascent/descent. Unlike end-to-end neural networks, the controller is composed of predictable, bounded components with interpretable parameters that are amenable to data-driven optimization for biomimetic assistance and subsequent application-specific tuning, for example, maximizing quadriceps assistance over multiterrain LLC. When deployed on a backdrivable knee exoskeleton, the assistance torques holistically reduced quadriceps effort across multiterrain LLC tasks (significantly except for level walking) in 10 human users without user-specific calibration. The exoskeleton also significantly improved fatigue-induced deficits in time-based performance and posture during repetitive lifting-lowering. Last, the system facilitated seamless task transitions and garnered a high effectiveness rating postfatigue over a multiterrain circuit. These findings indicate that this versatile control framework can target critical muscles across multiple tasks, specifically mitigating quadriceps fatigue and its deleterious effects.

The influence of lateral stabilization on walking performance and balance control in neurologically-intact and post-stroke individuals.

BACKGROUND: Individuals post-stroke have an increased risk of falling, which can lead to injuries and reduced quality of life. This increased fall risk can be partially attributed to poorer balance control, which has been linked to altered post-stroke gait kinematics (e.g. an increased step width). The application of lateral stabilization to the pelvis reduces step width among neurologically-intact young and older adults, suggesting that lateral stabilization reduces the need for active frontal plane balance control. This study sought to determine if lateral stabilization is effective at improving common measures of gait performance and dynamic balance in neurologically-intact and post-stoke individuals who responded to the stabilization by reducing their step width. METHODS: Gait performance was assessed by foot placement and propulsion symmetry while dynamic balance was assessed by peak-to-peak range of frontal plane whole body angular momentum (HR) and pelvis and trunk sway. FINDINGS: Controls and post-stroke Responders who reduced their step width in response to stabilization also reduced their mediolateral pelvis sway, but did not exhibit changes in gait performance. Contrary to expectations, both groups exhibited an increased HR, possibly indicative of decreased balance control. This increase was the result of increased relative velocity between the pelvis and head, arms and trunk segment. INTERPRETATION: These results suggest that a reduction in pelvis motion alone, as opposed to relative motion between the pelvis and upper body, may increase HR, decrease balance control and diminish gait performance. This finding has important implications for locomotor therapies that may seek to reduce pelvis motion.