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Objective: This study aimed to investigate the effects of a head/neck supporting exoskeleton (HNSE) on the electromyographic fatigue threshold (EMGFT) of the neck and shoulder muscles during a simulated overhead work task. Background: Overhead work is a well-known risk factor for neck and shoulder musculoskeletal disorders due to the excessive strain imposed on the muscles and joints in these regions. Method: Fourteen healthy males performed a repetitive overhead nut fastening/unfastening task to exhaustion while wearing and not wearing the HNSE at two neck extension angles (40% and 80% of neck maximum range of motion). Electromyographic signals were continuously recorded from the right and left sternocleidomastoid (SCMR, SCML), splenius capitis (SCR, SCL), upper trapezius (UTR, UTL), and anterior deltoid (ADR, ADL) muscles. The normalized electromyographic amplitude (nEMG) data was time normalized, and a bisegmental linear regression was applied to determine the muscle fatigue break point. Results: The results showed a significant increase in fatigue threshold time in the SCMR (p <.001), SCML (p =.002), and UTR (p =.037) muscles when the HNSE was used. However, the EMGFT times for the right and left deltoid and left trapezius muscles showed a nonsignificant reduction due to the head/neck support exoskeleton use. In addition, the neck extension angle did not reveal a significant effect on muscles' EMGFT time. Conclusion: Overall, the findings confirmed a significant delay in fatigue onset in sternocleidomastoid muscles, as measured by the electromyographic fatigue threshold. This finding suggests that the HNSE can be an effective ergonomic intervention for reducing the risk of musculoskeletal disorders in overhead workers. However, further studies are needed to investigate the effect of the HNSE at other neck extension angles and more realistic tasks to ensure the generalizability of our results. Application: The present findings emphasize the application of the fatigue onset time to evaluate the effectiveness of ergonomic interventions, including exoskeletons, which can subsequently be utilized to alleviate postural demands and reduce the risk of musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

Objective: This study developed a fixation-related electroencephalography band power (FRBP) approach for situation awareness (SA) assessment in automated driving. Background: Maintaining good SA in Level 3 automated vehicles is crucial to drivers' takeover performance when the automated system fails. A multimodal fusion approach that enables the analysis of the visual behavioral and cognitive processes of SA can facilitate real-time assessment of SA in future driver state monitoring systems. Method: Thirty participants performed three simulated automated driving tasks. After each task, the Situation Awareness Global Assessment Technique (SAGAT) was deployed to capture their SA about key elements that could affect their takeover task performance. Participants eye movements and brain activities were recorded. Data on their brain activity after each eye fixation on the key elements were extracted and labeled according to the correctness of the SAGAT. Mixed-effects models were used to identify brain regions that were indicative of SA, and machine learning models for SA assessment were developed based on the identified brain regions. Results: Participants' alpha and theta oscillation at frontal and temporal areas are indicative of SA. In addition, the FRBP technique can be used to predict drivers' SA with an accuracy of 88% using a neural network model. Conclusion: The FRBP technique, which incorporates eye movements and brain activities, can provide more comprehensive evaluation of SA. Findings highlight the potential of utilizing FRBP to monitor drivers' SA in real-time. Application: The proposed framework can be expanded and applied to driver state monitoring systems to measure human SA in real-world driving. [ABSTRACT FROM AUTHOR]

Objective: We propose and assess galvanic vestibular stimulation (GVS) as a novel means to provide information dissociated from self-orientation. Background: In modern user interfaces, visual and auditory modalities dominate information transfer so much that these "processing channels" become overloaded with information. Fortunately, the brain is capable of processing separate sensory sources in parallel enabling alternative display modalities to inform operators more effectively and without increasing cognitive strain. To date, the vestibular system, normally responsible for sensing self-orientation and helping with balance, has not been considered as a display modality. Method: Bilateral GVS was provided at 0.6 mA for 1-second intervals with moderately high-frequency sinusoidal waveforms, designed to not elicit sensations of self-motion. We assessed subjects' ability to differentiate between two cues of different frequencies. Results: We found subjects were able to reliably distinguish between cues with an average just-noticeable difference threshold of only ±12 Hz (range across subjects: 5.4–19.6 Hz) relative to a pedestal cue of 50 Hz. Further, we found the GVS sensory modality to be robust to various environments: walking, standing, sitting, passive motion, and loud background noise. Finally, the application of the GVS cues did not have significant destabilizing effects when standing or walking. Conclusion: These results show that GVS may be an effective alternative display modality, using varying frequency to encode information. It is robust to various operational environments and non-destabilizing. Application: A fully functional display can convey information to operators of vehicles and other machinery as well as high-performance operators like astronauts and soldiers. [ABSTRACT FROM AUTHOR]

Objective: This study examined the interaction of gait-synchronized vibrotactile cues with an active ankle exoskeleton that provides plantarflexion assistance. Background: An exoskeleton that augments gait may support collaboration through feedback to the user about the state of the exoskeleton or characteristics of the task. Methods: Participants (N = 16) were provided combinations of torque assistance and vibrotactile cues at pre-specified time points in late swing and early stance while walking on a self-paced treadmill. Participants were either given explicit instructions (N = 8) or were allowed to freely interpret (N=8) how to coordinate with cues. Results: For the free interpretation group, the data support an 8% increase in stride length and 14% increase in speed with exoskeleton torque across cue timing, as well as a 5% increase in stride length and 7% increase in speed with only vibrotactile cues. When given explicit instructions, participants modulated speed according to cue timing—increasing speed by 17% at cues in late swing and decreasing speed 11% at cues in early stance compared to no cue when exoskeleton torque was off. When torque was on, participants with explicit instructions had reduced changes in speed. Conclusion: These findings support that the presence of torque mitigates how cues were used and highlights the importance of explicit instructions for haptic cuing. Interpreting cues while walking with an exoskeleton may increase cognitive load, influencing overall human-exoskeleton performance for novice users. Application: Interactions between haptic feedback and exoskeleton use during gait can inform future feedback designs to support coordination between users and exoskeletons. [ABSTRACT FROM AUTHOR]

Objective: In two experiments, we examined how quickly different visual alerts on a head-worn display (HWD) would capture participants' attention to a matrix of patient vital sign values, while multitasking. Background: An HWD could help clinicians monitor multiple patients, regardless of where the clinician is located. We sought effective ways for HWDs to alert multitasking wearers to important events. Methods: In two preclinical experiments, university student participants performed a visuomotor tracking task while simultaneously monitoring simulated patient vital signs on an HWD to detect abnormal values. Methods to attract attention to abnormal values included highlighting abnormal vital signs and imposing a white flash over the entire display. Results: Experiment 1 found that participants detected abnormal values faster with high contrast than low contrast greyscale highlights, even while performing difficult tracking. In Experiment 2, a white flash of the entire screen quickly and reliably captured attention to vital signs, but less so on an HWD than on a conventional screen. Conclusion: Visual alerts on HWDs can direct users' attention to patient transition events (PTEs) even under high visual-perceptual load, but not as quickly as visual alerts on fixed displays. Aspects of the results have since been tested in a healthcare context. Application: Potential applications include informing the design of HWD interfaces for monitoring multiple processes and informing future research on capturing attention to HWDs. [ABSTRACT FROM AUTHOR]

Objective: The user experience of typing on a smartwatch was evaluated with three unique input methods (tap, trace, and handwriting) while standing and while walking. Background: Despite widespread development within the technology industry, smartwatches have had a relatively slow adoption worldwide compared to smartphones. One limiting factor of smartwatches has been the lack of an efficient means of text entry. The 2017 release of Android Wear addressed this issue by providing support for native text entry (i.e., tap, trace, and handwriting). Determining how user performance and subjective ratings compare across these input methods is essential to understanding their contribution to smartwatch user experience. Method: Twenty college-age individuals typed phrases using tap, trace, and handwriting input on a smartwatch in three different mobility scenarios (standing, walking a simple course, walking a complex course). Results: Participants typed faster with trace (30 words per minute; WPM) than with tap (20 WPM) and handwriting (18 WPM), regardless of mobility. Trace also outperformed tap and handwriting across all subjective metrics, regardless of mobility. Conclusion: Trace input appears to be especially well suited for typing on a smartwatch as it was found to be objectively and subjectively superior to tap and handwriting regardless of user mobility. Objectively, typing speeds with trace are shown to be nearly two times faster than most alternative input methods described in the literature. Application: Results suggest smartwatch manufacturers should include QWERTY keyboards with trace input as a standard feature in order to provide the best overall typing experience for their users. [ABSTRACT FROM AUTHOR]

Objective: This novel preliminary study sought to capture dynamic changes in heart rate variability (HRV) as a proxy for cognitive workload among perfusionists while operating the cardiopulmonary bypass (CPB) pump during real-life cardiac surgery. Background: Estimations of operators' cognitive workload states in naturalistic settings have been derived using noninvasive psychophysiological measures. Effective CPB pump operation by perfusionists is critical in maintaining the patient's homeostasis during open-heart surgery. Investigation into dynamic cognitive workload fluctuations, and their relationship with performance, is lacking in the literature. Method: HRV and self-reported cognitive workload were collected from three Board-certified cardiac perfusionists (N = 23 cases). Five HRV components were analyzed in consecutive nonoverlapping 1-min windows from skin incision through sternal closure. Cases were annotated according to predetermined phases: prebypass, three phases during bypass, and postbypass. Values from all 1min time windows within each phase were averaged. Results: Cognitive workload was at its highest during the time between initiating bypass and clamping the aorta (preclamp phase during bypass), and decreased over the course of the bypass period. Conclusion: We identified dynamic, temporal fluctuations in HRV among perfusionists during cardiac surgery corresponding to subjective reports of cognitive workload. Not only does cognitive workload differ for perfusionists during bypass compared with pre- and postbypass phases, but differences in HRV were also detected within the three bypass phases. Application: These preliminary findings suggest the preclamp phase of CPB pump interaction corresponds to higher cognitive workload, which may point to an area warranting further exploration using passive measurement. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to determine the effectiveness of using a leg support exoskeleton (legX) in different modes on simulated work tasks which emulate real-world job tasks.Background: Prolonged kneeling and squatting tasks increase the risk of work-related musculoskeletal disorders at the knee in industrial occupations.Methods: We evaluated legX capable of spring assistance throughout one's range of motion and/or locking support at a fixed angular position. Participants performed a dynamic panel task, alternating between hip and knee height, and a sustained floor level task with and without the exoskeleton. The exoskeleton was evaluated in spring mode, locking mode, and spring + locking mode for the panel task and only in locking mode for the floor task. The participants' (N = 15) muscle activity was recorded for the right lumbar erector spinae, thoracic erector spinae, tibialis anterior, rectus femoris, semitendinosus, and lateral gastrocnemius.Results: Significant reduction of the rectus femoris activity was observed with the exoskeleton (median reduction: 22%-56% and peak reduction: 12%-48% for the panel task and median reduction: 57% and peak reduction:34% during the floor task).Conclusion: legX significantly reduces rectus femoris activity during squatted static (floor) and dynamic (panel) work and may reduce pain and discomfort associated with squatting and potentially reduce the risk of developing knee disorders. Dynamic tasks benefit from both locking modes and spring assistance, the greatest benefit occurring with a combination of the two.Application: These results show that the legX can be beneficial to activities such as electrical panel work, grinding, sanding of larger surfaces, and concrete laying. [ABSTRACT FROM AUTHOR]

Objective: To establish the relationship between circumferential compression on the lower limb during simulated ramp and staircase profile loading, and the resultant relationship with discomfort/pain and tissue oxygenation.Background: Excessive mechanical loading by exoskeletons on the body can lead to pressure-related soft tissue injury. Potential tissue damage is associated with objective oxygen deprivation and accompanied by subjective perception of pain and discomfort.Method: Three widths of pneumatic cuffs were inflated at the dominant thigh and calf of healthy participants using two inflation patterns (ramp and staircase), using a computer-controlled pneumatic rig. Participants rated discomfort on an electronic visual analog scale and deep tissue oxygenation was monitored using near infrared spectroscopy.Results: Circumferential compression with pneumatic cuffs triggered discomfort and pain at lower pressures at the thigh, with wider cuffs, and with a ramp inflation pattern. Staircase profile compression caused an increase in deep tissue oxygenation, whereas the ramp profile compression decreased it.Conclusion: Discomfort and pain during circumferential compression at the lower limb is related to the width of pneumatic cuffs, the inflation pattern, and the volume of soft tissue at the assessment site. The occurrence of pain is also possibly related to the decrease in deep tissue oxygenation during compression.Application: Our findings can be used to inform safe and comfortable design of soft exoskeletons to avoid discomfort and possible soft tissue injury. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study is to test the unified theory of acceptance and use of technology (UTAUT) model for explaining the intention to use exoskeletons among industrial workers.Background: Exoskeletons could help reduce physical workload and risk for injuries among industrial workers. Therefore, it is crucial to understand which factors play a role in workers' intention to use such exoskeletons.Method: Industrial workers (N = 124) completed a survey on their attitudes regarding the use of exoskeletons at their workplace. Using partial least squares (PLS) path modeling, the UTAUT model and a revised version of the UTAUT model were fitted to these data.Results: The adapted UTAUT model of Dwivedi et al. (2017) was able to explain up to 75.6% of the variance in intention to use exoskeletons, suggesting a reasonable model fit.Conclusion: The model fit suggests that effort expectancy (how easy it seems to use an exoskeleton) plays an important role in predicting the intention to use exoskeletons. Social influence (whether others think workers should use exoskeletons) and performance expectancy (how useful exoskeletons seem to be for work) play a smaller role in predicting the intention to use.Applications: This research informs companies about the optimal implementation of exoskeletons by improving the determinants of acceptance among their workers. [ABSTRACT FROM AUTHOR]

Objective: This pilot study proposed and performs initial testing with Exoscore, a design evaluation tool to assess factors related to acceptance of exoskeleton by older adults, during the technology development and testing phases.Background: As longevity increases and our aging population continues to grow, assistive technologies such as exosuits and exoskeletons can provide enhanced quality of life and independence. Exoscore is a design and prototype stage evaluation method to assess factors related to perceptions of the technology, the aim being to optimize technology acceptance.Method: In this pilot study, we applied the three-phase Exoscore tool during testing with 11 older adults. The aims were to explore the feasibility and face validity of applying the design evaluation tool during user testing of a prototype soft lower limb exoskeleton.Results: The Exoscore method is presented as part of an iterative design evaluation process. The method was applied during an exoskeleton research and development project. The data revealed the aspects of the concept design that rated favorably with the users and the aspects of the design that required more attention to improve their potential acceptance when deployed as finished products.Conclusion: Exoscore was effectively applied to three phases of evaluation during a testing session of a soft exoskeleton. Future exoskeleton development can benefit from the application of this design evaluation tool.Application: This study reveals how the introduction of Exoscore to exoskeleton development will be advantageous when assessing technology acceptance of exoskeletons by older adults. [ABSTRACT FROM AUTHOR]

Objective: In this study, the reliability of measures of upper body postural behavior (head, thorax, neck, and arm) during sustained office work was evaluated.Background: Although there has been a substantial body of research examining the technical aspects of posture measurement in office workers using motion sensors, there is a paucity of literature examining whether posture-related behaviors are actually consistent among office workers in the field on different days and times.Method: Thirty one office workers performed their usual work for three, 1-hr sessions (two morning sessions and one afternoon session) while wearing wireless motion sensors. Reliability coefficients of the derived measures of postural behavior were calculated.Results: Most (30/31) of the postural behavior measures demonstrated modest to excellent reliability (ICC 2.1: 0.48-0.84). Reliability appeared to be mildly affected by factors such as the time of day recordings were taken and variations in desk setups.Conclusion: The findings suggest these measures may be a reliable method for evaluating postural behavior in the office work environment in future studies.Application: Postural measurement using a technical motion sensor described an acceptable reliability to be used for risk assessment in the workplace. Consideration of assessment time and desk setting would increase the accuracy of postural measurement. [ABSTRACT FROM AUTHOR]

Objective: This study evaluated the individual and combined effects of voice (vs. manual) input and head-up (vs. head-down) display in a driving and device interaction task.Background: Advances in wearable technology offer new possibilities for in-vehicle interaction but also present new challenges for managing driver attention and regulating device usage in vehicles. This research investigated how driving performance is affected by interface characteristics of devices used for concurrent secondary tasks. A positive impact on driving performance was expected when devices included voice-to-text functionality (reducing demand for visual and manual resources) and a head-up display (HUD) (supporting greater visibility of the driving environment).Method: Driver behavior and performance was compared in a texting-while-driving task set during a driving simulation. The texting task was completed with and without voice-to-text using a smartphone and with voice-to-text using Google Glass's HUD.Results: Driving task performance degraded with the addition of the secondary texting task. However, voice-to-text input supported relatively better performance in both driving and texting tasks compared to using manual entry. HUD functionality further improved driving performance compared to conditions using a smartphone and often was not significantly worse than performance without the texting task.Conclusion: This study suggests that despite the performance costs of texting-while-driving, voice input methods improve performance over manual entry, and head-up displays may further extend those performance benefits.Application: This study can inform designers and potential users of wearable technologies as well as policymakers tasked with regulating the use of these technologies while driving. [ABSTRACT FROM AUTHOR]