Evaluating adaptiveness of an active back exosuit for dynamic lifting and maximum range of motion

Preference-based assistance optimization for lifting and lowering with a soft back exosuit

Wearable robotic devices have become increasingly prevalent in both occupational and rehabilitative settings, yet their widespread adoption remains inhibited by usability barriers related to comfort, restriction, and noticeable functional benefits. Acknowledging the importance of user perception in this context, this study explores preference-based controller optimization for a back exosuit that assists lifting. Considering the high mental and metabolic effort discrete motor tasks impose, we used a forced-choice Bayesian Optimization approach that promotes sampling efficiency by leveraging domain knowledge about just noticeable differences between assistance settings. Optimizing over two control parameters, preferred settings were consistent within and uniquely different between participants. We discovered that overall, participants preferred asymmetric parameter configurations with more lifting than lowering assistance, and that preferences were sensitive to user anthropometrics. These findings highlight the potential of perceptually guided assistance optimization for wearable robotic devices, marking a step toward more pervasive adoption of these systems in the real world.

The perceptual and biomechanical effects of scaling back exosuit assistance to changing task demands

Back exoskeletons are gaining attention for preventing occupational back injuries, but they can disrupt movement, a burden that risks abandonment. Enhanced adaptability is proposed to mitigate burdens, but perceptual benefits are less known. This study investigates the perceptual and biomechanical impacts of a SLACK suit (non-assistive) controller versus three controllers with varying adaptability: a Weight-Direction-Angle adaptive (WDA-ADPT) that scales assistance based on the weight of the boxes using a chest-mounted camera and machine learning algorithm, movement direction, and trunk flexion angle, and standard Direction-Angle adaptive (DA-ADPT) and Angle adaptive (A-ADPT) controllers. Fifteen participants performed a variable weight (2, 8, 14 kg) box-transfer task. WDA-ADPT achieved the highest perceptual score (88%) across survey categories and reduced peak back extensor (BE) muscle amplitudes by 10.1%. DA-ADPT had slightly lower perceptual (76%) and peak BE reduction (8.5%). A-ADPT induced hip restriction, which could explain the lowest perceptual score (55%) despite providing the largest reductions in peak BE muscle activity (17.3%). Reduced perceptual scores achieved by DA and A-ADPT were explained by controllers providing too much or little assistance versus actual task demands. These findings underscore that scaling assistance to task demands improves biomechanical benefits and the perception of the device's suitability.

Elastic textile-based wearable modulation of musculoskeletal load: A comprehensive review of passive exosuits and resistance clothing

Elastic textiles play a critical role in passive wearable solutions for musculoskeletal load management in both passive exosuits and resistance clothing. These textiles, based on their ability to stretch and retract, can exhibit ambivalence in their load-modulating effects when used in occupational, rehabilitation, exercise, or everyday activity settings. While passive exosuits and resistance garments may appear similar in design, they have opposing goals: to reduce the musculoskeletal load in the case of exosuits and to increase it in the case of resistance clothing. Despite this intrinsic connection, these two approaches have not been extensively linked together. This review aims to fill this gap by examining the common and distinct principles of elastic textiles in passive exosuits and resistance clothing, shedding light on their interactions and the complex dynamics of musculoskeletal load systems. The effectiveness of different designs in passive exosuits that mimic musculoskeletal function and resistance clothing that increase the workload for strength training are critically reviewed. Current challenges in practical implementation and opportunities to improve critical issues, such as preload, thermal comfort, skin friction, and donning and doffing are also highlighted.

The effect of a soft active back support exosuit on trunk motion and thoracolumbar spine loading during squat and stoop lifts

Back support exosuits aim to reduce tissue demands and thereby risk of injury and pain. However, biomechanical analyses of soft active exosuit designs have been limited. The objective of this study was to evaluate the effect of a soft active back support exosuit on trunk motion and thoracolumbar spine loading in participants performing stoop and squat lifts of 6 and 10 kg crates, using participant-specific musculoskeletal models. The exosuit did not change overall trunk motion but affected lumbo-pelvic motion slightly, and reduced peak compressive and shear vertebral loads at some levels, although shear increased slightly at others. This study indicates that soft active exosuits have limited kinematic effects during lifting, and can reduce spinal loading depending on the vertebral level. These results support the hypothesis that a soft exosuit can assist without limiting trunk movement or negatively impacting skeletal loading and have implications for future design and ergonomic intervention efforts.

Effects of a back-assist exosuit in lab-based approximations of construction tasks performed by novices and experienced construction workers

Passive back-assist exosuits may be beneficial for construction workers, but few evaluations have been conducted with actual workers and construction-relevant tasks. This paper presents a laboratory study of the HeroWear Apex exosuit with 35 participants: 15 with significant construction experience and 20 without it. Participants completed several approximations of brief construction tasks (lifting, carrying, raising boards) and three 3-min tasks (hunched standing, kneeling, hunched walking with a nail gun) with and without the exosuit. During brief tasks, erector spinae electromyograms were reduced in all tasks (Cohen's d up to -0.58), kinematics suggested load shifting from the back to the legs, and the exosuit was perceived as helpful. During 3-min tasks, the exosuit was perceived as helpful in all tasks, but only reduced erector spinae electromyograms during kneeling. Thus, the exosuit may benefit workers during several construction-related tasks, though objective benefits could not be shown in 3-min standing or walking.

Active back exosuits demonstrate positive usability perceptions that drive intention-to-use in the field among logistic warehouse workers

Back exosuits offer the potential to reduce occupational back injuries but require in-field acceptance and use to realize this potential. For this study, 146 employees trialed an active back exosuit in the field for 4 h, completing an acceptance usability survey. Comparing the 80% of employees willing to continue wearing this device (N = 117) to those who were not (N = 29) revealed that employees willing to wear this device for a longer-term study generally were more likely to perceive this back exosuit to be effective (helpful) and compatible (minimally disruptive) to their everyday work. Using an optimal tree approach, we demonstrate that intent-to-use could be predicted with 78% accuracy by interacting features of perceived exosuit effectiveness and work compatibility. This study reinforces the importance of task matching, noticeable relief, and unobtrusive design to facilitate short-term employee acceptance of industrial wearable robotic technology.

Musculoskeletal models determine the effect of a soft active exosuit on muscle activations and forces during lifting and lowering tasks

Exosuits have the potential to mitigate musculoskeletal stress and prevent back injuries during industrial tasks. This study aimed to 1) validate the implementation of a soft active exosuit into a musculoskeletal model of the spine by comparing model predicted muscle activations versus corresponding surface EMG measurements, and 2) evaluate the effect of the exosuit on peak back and hip muscle forces. Fourteen healthy participants performed squat and stoop lift and lower tasks with boxes of 6 and 10 kg, with and without wearing a 2.7 kg soft active exosuit. Participant-specific musculoskeletal models, which included the exosuit, were created in OpenSim. Model validation focused on the back and hip extensors, where temporal agreement between EMG and model estimated muscle activity was generally strong to excellent (average cross-correlation coefficients ranging from 0.84 to 0.98). Root mean square errors of muscle activity (0.05-0.10) were similar with and without the exosuit, and compared well to prior model validation studies without the exosuit (average root mean square errors ranging from 0.05 to 0.19). In terms of performance, the exosuit reduced the estimated peak erector spinae forces during lifting and lowering phases across all lifting tasks but reduced peak hip extensor muscles forces only in a squat lift task of 10 kg. These reductions in total peak muscle forces were approximately 1.7-4.2 times greater than the corresponding exosuit assistance force, which were 146 ± 19 N and 102 ± 14 N at the times of peak erector spinae forces in lifting and lowering, respectively. Overall, the results support the hypothesis that exosuits reduce soft tissue loading, and thereby potentially reduce fatigue and injury risk during manual materials handling tasks. Incorporating exosuits into musculoskeletal models is a valid approach to understand the impact of exosuit assistance on muscle activity and forces.