Exoskeleton Usability Questionnaire: a preliminary evaluation questionnaire for the lower limb industrial exoskeletons.

Exoskeleton robots are a promising solution to reduce musculoskeletal disorders (MSDs) in different work environments, but a specific usability scale for evaluating them is lacking. This study aimed to develop and verify a preliminary Exoskeleton Usability Questionnaire (EUQ) for the lower limb exoskeletons by creating a draft survey questionnaire from existing questions in prior studies. An experiment was conducted with 20 participants who performed a specific task while wearing three lower limb robots and provided subjective feedback using the developed questionnaire. Data were analysed using exploratory and confirmatory factor analysis (CFA), resulting in a usability evaluation questionnaire for exoskeleton robots clustered into four main factors: mobility, adjustability, handling and safety. This study's findings are expected to be useful in evaluating the usability of the lower limb exoskeletons in both general production sites and agricultural work, which can aid in reducing the prevalence of lower limb MSDs.Practitioner Summary: This study developed a preliminary subjective usability evaluation questionnaire for exoskeleton robots. The questionnaire is clustered into four main factors: mobility, adjustability, handling and safety. These findings provide a valuable tool for assessing exoskeleton usability, potentially reducing musculoskeletal disorders (MSDs) in various work environments.

A passive upper-limb exoskeleton reduced muscular loading during augmented reality interactions.

The aim of this study was to evaluate a passive upper-limb exoskeleton as an ergonomic control to reduce the musculoskeletal load in the shoulders associated with augmented reality (AR) interactions. In a repeated-measures laboratory study, each of the 20 participants performed a series of AR tasks with and without a commercially-available upper-limb exoskeleton. During the AR tasks, muscle activity (anterior, middle, posterior deltoid, and upper trapezius), shoulder joint postures/moment, and self-reported discomfort were collected. The results showed that the exoskeleton significantly reduced muscle activity in the upper trapezius and deltoid muscle groups and self-reported discomfort. However, the shoulder postures and task performance measures were not affected by the exoskeleton during the AR interactions. Given the significant decrease in muscle activity and discomfort without compromising task performance, a passive exoskeleton can be an effective ergonomic control measure to reduce the risks of developing musculoskeletal discomfort or injuries in the shoulder regions.

Evaluation of the Efficacy of a Lift-Assist Device Regarding Caregiver Posture and Muscle Load for Transferring Tasks.

The aim of this study was to confirm the effect of a lift-assist device when performing a patient-lifting task. Ten working caregivers participated in this experiment, and lifting patients from bed to wheelchair (B2C) and wheelchair to bed (C2B) was performed for manual care (MC) and lift-assist device (robot) care (RC). EMG sensors and IMU motion sensors were attached as indicators of the assistive device's effectiveness. EMG was attached to the right side of eight muscles (UT, MD, TB, BB, ES, RF, VA, and TA), and flexion/extension angles of the neck, shoulder, back, and knee were collected using motion sensors. As a result of the analysis, both B2C and C2B showed higher muscle activities in MC than RC. When using a lift-assist device to lift patients, the RC method showed reductions in muscle activities compared to MC. As a result of the work-posture analysis, both the task type and the task phase exhibited pronounced reductions in shoulder, back, and knee ROM (range of motion) compared to those of MC. Therefore, based on the findings of this study, a lift-assist device is recommended for reducing the physical workloads of caregivers while performing patient-lifting tasks.

Efficacy of passive upper-limb exoskeletons in reducing musculoskeletal load associated with overhead tasks.

Overhead work can pose substantial musculoskeletal stress in many industrial settings. This study aimed to evaluate the efficacy of passive upper-limb exoskeletons in reducing muscular activity and subjective discomfort ratings. In a repeated-measures laboratory experiment, 20 healthy male participants performed 10-min drilling tasks with and without two passive upper-limb exoskeletons (VEX and Airframe). During the tasks, muscle activity in eight muscles (upper limb - upper trapezius, middle deltoid, biceps brachii, triceps brachii; low back - erector spinae; lower limb - rectus femoris, biceps femoris, tibialis anterior) was collected using electromyography as a physical exertion measure. Subjective discomfort rating in six body parts was measured using the Borg's CR-10 scale. The results showed that muscle activity (especially in the upper-limb muscles) was significantly decreased by 29.3-58.1% with both exoskeletons compared to no exoskeleton condition. The subjective discomfort ratings showed limited differences between the conditions. These findings indicate that passive upper-limb exoskeletons may have potential as an effective intervention to reduce muscular loading and physical exertion during overhead work.

Ergonomic Assessment of a Lower-Limb Exoskeleton through Electromyography and Anybody Modeling System.

The aim of this study was to determine the muscle load reduction of the upper extremities and lower extremities associated with wearing an exoskeleton, based on analyses of muscle activity (electromyography: EMG) and the AnyBody Modeling System (AMS). Twenty healthy males in their twenties participated in this study, performing bolting tasks at two working heights (60 and 85 cm). The muscle activities of the upper trapezius (UT), middle deltoid (MD), triceps brachii (TB), biceps brachii (BB), erector spinae (ES), biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA) were measured by EMG and estimated by AMS, respectively. When working at the 60 cm height with the exoskeleton, the lower extremity muscle (BF, RF, TA) activities of EMG and AMS decreased. When working at the 85 cm height, the lower extremity muscle activity of EMG decreased except for TA, and those of AMS decreased except for RF. The muscle activities analyzed by the two methods showed similar patterns, in that wearing the exoskeleton reduced loads of the lower extremity muscles. Therefore, wearing an exoskeleton can be recommended to prevent an injury. As the results of the two methods show a similar tendency, the AMS can be used.

Evaluation of subjective perceived rating for grip strength depending on handedness for various target force levels.

BACKGROUND: Measurement of hand exertion is very important to quantify the risk of Work-related Musculoskeletal Disorders (WMSDs) in manufacturing fields. Although a direct measurement is the most accurate way to quantify physical load, it is expensive and time consuming. To solve this limitation, a subjective self-report method has been proposed as a possible alternative. OBJECTIVE: The purpose of this study was to analyze the accuracy of subjective perception for grip force exertions associated with handedness (dominant and non-dominant hands). METHODS: A total of nine healthy adults participated in this study. All participants were asked to exert hand grip forces for randomly selected target force levels without any information about the actual target force levels. Then, participants were also asked to rate the subjective perception of their exertion level using % Maximum Voluntary Contraction (MVC) after each hand grip force exertion. RESULTS: The trend of subjective perception for various target force levels was different according to the handedness. In the case of the dominant hand, participants tend to rate less MVC levels (under-estimation) than the actual target force levels at lower than 50% MVC, whereas they tend to rate more MVC levels (over-estimation) than the actual target force levels at higher than 50% MVC, respectively. In case of non-dominant hand, generally participants showed over-estimate for all levels of MVCs in this study. CONCLUSIONS: According to the results of this study, subjective perception of exertion showed different patterns on the handedness (S-shape for dominant hand vs. over-estimation for non-dominant hand) for various target force levels. Therefore, it would be necessary to apply different criteria for each hand to evaluate subjective perception of hand grip exertion tasks.