Of Mice and Men: An Ergonomic and Market Assessment of Current Computer Mice

Gemstone Team MICE (Modifying and Improving Computer Ergonomics)Work-related Musculoskeletal Disorders (WMSDs) are conditions that develop over time due to repetitive motion and can painfully affect the fingers, wrist, arm, shoulder, back, and neck. Studies indicate a correlation between heavy computer mouse use and the prevalence of WMSDs. Our team evaluated current ergonomic mouse designs to determine which features of mice reduce excessive muscle activation and harmful arm and hand positioning while still maintaining ease of use and marketability. A motion capture system tracked arm and hand positioning, EMG analysis measured muscle activation, force sensors quantified the user‘s clicking force, and a Fitts‘ test evaluated mouse use efficiency. To determine the marketability of mice features, surveys generalized user preferences, while focus groups closely examined specific market factors. All these systems were combined to identify areas of improvement in ergonomic mouse design

Moving Away From the Traditional Desktop Computer Workstations: Identifying Opportunities to Improve Upper Extremity Biomechanics

Statement of Problem: Office computer workers have elevated risks of adverse health outcome such as musculoskeletal disorders (MSDs) associated with computer work. Although they now have many alternatives, these modern computer workstations and associated technologies require new guidelines and recommendations for proper practice. We see this as an opportunity to improve current and future computer workstation designs through an ergonomics approach by improving users’ upper extremity biomechanics while interacting with these modern technologies. Method: The dissertation first utilized a psychophysical protocol to compare users’ self-selected set ups for sitting and standing computer workstations. Users’ biomechanics and perceived comfort across different computer tasks for the two workstations are then compared. Subsequently, a hand mapping technique was developed to evaluate effects of computer pointing devices on users’ hand posture and associated forearm muscle effort using 3-D motion analysis and surface electromyography. To improve mobile device ergonomics, we investigated tablet users’ biomechanical load, comfort level and performance while performing swipe actions at different tablet locations. Results: Different selected computer workstation set ups were found for sitting and standing. Compared to sitting, users while standing kept workstation components closer to their sternum and adopted a more neutral shoulder posture while working. However, users had greater wrist extension and started reporting more low back discomfort after 45 minutes. While investigating different computer pointing devices, we found device affordance associated with significantly different hand posture and forearm muscle load. Devices that required less holding and were centrally placed associated with more neutral shoulder and hand postures, with significantly less forearm muscle load. For tablet interface, swipe locations closer to the palm had significantly smaller forearm muscle load and more neutral posture across wrist and thumb joints. Conclusion: Through empirical results described in the dissertation, we demonstrated how users’ upper extremity biomechanics can provide insights into the complex interactions between users and modern computer workstations, both as a whole and with specific components. For technology innovation, ergonomics concepts and methodologies can be used to design future generation technologies that fit users’ physical capabilities to reduce MSDs risk while promoting performance

The effect of personalised adjustments to computer workstations on the efficiency and physical comfort of computer operators

The present study sought to investigate the effects of a Standard workstation, designed for “average” users, on an anthropometrically diverse sample of computer operators, and to assess whether physical and perceptual responses, as well as performance efficiency were dependent on stature. Further investigation assessed the influence of personalised adjustments to the Standard workstation, based on the anthropometric characteristics of the subjects, as well as the introduction of a custom-designed ‘floating’ wrist support, on subject responses. All subjects (n=30) were tested in each of the three workstations: Standard, Personalised and Wrist Support. For analysis of responses in the Standard workstation, subjects were divided into three groups depending on their stature: Short (1800mm). The musculoskeletal responses indicated that Tall subjects were forced to adopt the most awkward general body postures as a result of the low computer screen. However, the low screen allowed for the Short subjects to adopt the most natural general body postures, although levels of muscular activity in the upper trapezius suggest that the muscular load imposed on both Short and Tall subjects was significantly greater than that imposed on the Medium subjects. In addition, the Medium subjects’ perceptions of the Standard workstation dimensions support the fact that this workstation was better suited to users with “average” morphologies. The responses elicited in the Personalised and Wrist Support workstations were improved significantly when compared to the Standard workstation. Joint angles were more natural, upper trapezius EMG was reduced, standard of performance improved and perceptual responses indicated a diminished incidence of body and visual discomfort, as well as greater perceived satisfaction with these workstation dimensions. The improved physical responses suggest a decrease in the risk of developing cumulative trauma disorders. Although subjects were unaccustomed to the wrist support device, this workstation demonstrated a further reduction in the range of wrist angles, as well as a general positive attitude towards the concept

Surface Electromyographic (sEMG) Transduction of Hand Joint Angles for Human Interfacing Devices (HID)

This is an investigation of the use of surface electromyography (sEMG) as a tool to improve human interfacing devices (HID) information bandwidth through the transduction of the fingertip workspace. It combines the work of Merletti et al and Jarque-Bou et al to design an open-source framework for Fingertip Workspace based Human Interfacing Devices (HID). In this framework, the fingertip workspace is defined as the system of forearm and hand muscle force through a tensor which describes hand anthropometry. The thesis discusses the electrophysiology of muscle tissue along with the anatomy and physiology of the arm in pursuit of optimizing sensor location, muscle force measurements, and viable command gestures. Algorithms for correlating sEMG to hand joint angle are investigated using MATLAB for both static and moving gestures. Seven sEMG spots and Fingertip Joint Angles recorded by Jarque Bou et al are investigated for the application of sEMG to Human Interfacing Devices (HID). Such technology is termed Gesture Computer Interfacing (GCI) and has been shown feasible through devices such as CTRL Labs interface, and models such as those of Sartori, Merletti, and Zhao. Muscles under sEMG spots in this dataset and the actions related to them are discussed, along with what muscles and hand actions are not visible within this dataset. Viable gestures for detection algorithms are discussed based on the muscles discerned to be visible in the dataset through intensity, spectral moment, power spectra, and coherence. Detection and isolation of such viable actions is fundamental to designing an EMG driven musculoskeletal model of the hand needed to facilitate GCI. Enveloping, spectral moment, power spectrum, and coherence analysis are applied to a Sollerman Hand Function Test sEMG dataset of twenty-two subjects performing 26 activities of living to differentiate pinching and grasping tasks. Pinches and grasps were found to cause very different activation patterns in sEMG spot 3 relating to flexion of digits I - V. Spectral moment was found to be less correlated with differentiation and provided information about the degree of object manipulation performed and extent of fatigue during each task. Coherence was shown to increase between flexors and extensors with intensity of task but was found corrupted by crosstalk with increasing intensity of muscular activation. Some spectral results correlated between finger flexor and extensor power spectra showed anticipatory coherence between the muscle groups at the end of object manipulation. An sEMG amplification system capable of capturing HD-sEMG with a bandwidth of 300 and 500 Hz at a sampling frequency of 2 kHz was designed for future work. The system was designed in ordinance with current IEEE research on sensor-electrode characteristics. Furthermore, discussion of solutions to open issues in HD-sEMG is provided. This work did not implement the designed wristband but serves as a literature review and open-source design using commercially available technologies

Evaluating muscle activity during work with trackball, trackpad, slanted, and standard mice

Objectives: Mouse is one of the most important data entry devices for computers. Undesirable and prolonged postures during work with the computer mouse increase workload, muscle aches and upper extremity musculoskeletal disorders. The present study aimed to evaluate and compare muscle activity during the use of 4 types of mouse, including trackball, trackpad, slanted and standard by Electromyography (EMG). Methods: This experimental study included 15 subjects (7 men and 8 women). The electrical activity of EDC, ECU, ECR, FDS, PQ, and FDL muscles was recorded by EMG while performing a standard task with each mouse. The order of using each mouse was randomized. The obtained results were analyzed by SPSS using the measures of central tendency, Friedman's test, and Independent Samples t-test. Results: The results of assessing the electrical activity level of muscles suggested no statistically significant difference in the recorded EMG between FPL, FDS, and PQ muscles while working with the 4 mice. The electrical activity reduced in EDC, ECR, and FPL muscles with the use of slanted mouse, compared to that of other mice (P < 0.05). Discussion: There was no significant differences between the electrical activity of FDS, FPL, and PQ muscles during work with the studied mice. Furthermore, the activity of EDC, ECR, and FPL muscles reduced during work with a slanted mouse, compared to the other types. The habit of using a new mouse can affect the level of muscle activity; thus, the use of a slanted mouse may reduce the incidence of musculoskeletal disorders in the wrist and hand of users in the long run. © 2019 University of Social Welfare and Rehabilitation Sciences

A musculoskeletal model of the human hand to improve human-device interaction

abstract: Multi-touch tablets and smart phones are now widely used in both workplace and consumer settings. Interacting with these devices requires hand and arm movements that are potentially complex and poorly understood. Experimental studies have revealed differences in performance that could potentially be associated with injury risk. However, underlying causes for performance differences are often difficult to identify. For example, many patterns of muscle activity can potentially result in similar behavioral output. Muscle activity is one factor contributing to forces in tissues that could contribute to injury. However, experimental measurements of muscle activity and force for humans are extremely challenging. Models of the musculoskeletal system can be used to make specific estimates of neuromuscular coordination and musculoskeletal forces. However, existing models cannot easily be used to describe complex, multi-finger gestures such as those used for multi-touch human computer interaction (HCI) tasks. We therefore seek to develop a dynamic musculoskeletal simulation capable of estimating internal musculoskeletal loading during multi-touch tasks involving multi digits of the hand, and use the simulation to better understand complex multi-touch and gestural movements, and potentially guide the design of technologies the reduce injury risk. To accomplish these, we focused on three specific tasks. First, we aimed at determining the optimal index finger muscle attachment points within the context of the established, validated OpenSim arm model using measured moment arm data taken from the literature. Second, we aimed at deriving moment arm values from experimentally-measured muscle attachments and using these values to determine muscle-tendon paths for both extrinsic and intrinsic muscles of middle, ring and little fingers. Finally, we aimed at exploring differences in hand muscle activation patterns during zooming and rotating tasks on the tablet computer in twelve subjects. Towards this end, our musculoskeletal hand model will help better address the neuromuscular coordination, safe gesture performance and internal loadings for multi-touch applications.Dissertation/ThesisDoctoral Dissertation Mechanical Engineering 201

Development and Validation of the Self-report Ergonomic Assessment Tool (SEAT)

Despite considerable advances in the practice of office ergonomics, office workers are still suffering from musculoskeletal disorders (MSDs). These disorders, like carpal tunnel syndrome, can lead to high medical costs for employers and intense pain and discomfort for employees. The design of software office workers use could be a contributing factor to their risk of developing MSDs and a tool sensitive enough for evaluating ergonomic risks associated with the design of software is needed. Presented here are the results of a series of three studies focused on the development, improvement, and validation of a Self-report Ergonomic Assessment Tool (SEAT). The SEAT was found to comprise two important factors, stress and strain, and was found to be sufficiently consistent and sensitive to the exertions and postures related to office work. Data from two studies were used to validate stress components of the SEAT, e.g., postures, by using recorded videos and comparing participants’ responses on the SEAT to those of trained raters. Results showed that participants were unable to reliably self-report stressors. Data from one study was used to validate the strain components of the SEAT by comparing participants’ self-reported discomforts to muscle activity measured via surface electromyography and muscle oxygenation measured via near infrared spectroscopy. Participants’ self-reported discomfort did correlate with these physiological measures, however, important exceptions revealed opportunities for future development and testing of the SEAT

Flexor Dysfunction Following Unilateral Transient Ischemic Brain Injury Is Associated with Impaired Locomotor Rhythmicity

Functional motor deficits in hemiplegia after stroke are predominately associated with flexor muscle impairments in animal models of ischemic brain injury, as well as in clinical findings. Rehabilitative interventions often employ various means of retraining a maladapted central pattern generator for locomotion. Yet, holistic modeling of the central pattern generator, as well as applications of such studies, are currently scarce. Most modeling studies rely on cellular neural models of the intrinsic spinal connectivity governing ipsilateral flexor-extensor, as well as contralateral coupling inherent in the spinal cord. Models that attempt to capture the general behavior of motor neuronal populations, as well as the different modes of driving their oscillatory function in vivo is lacking in contemporary literature. This study aims at generating a holistic model of flexor and extensor function as a whole, and seeks to evaluate the parametric coupling of ipsilateral and contralateral half-center coupling through the means of generating an ordinary differential equation representative of asymmetric central pattern generator models of varying coupling architectures. The results of this study suggest that the mathematical predictions of the locomotor centers which drive the dorsiflexion phase of locomotion are correlated with the denervation-type atrophy response of hemiparetic dorsiflexor muscles, as well as their spatiotemporal activity dysfunction during in vivo locomotion on a novel precise foot placement task. Moreover, the hemiplegic solutions were found to lie in proximity to an alternative task-space solution, by which a hemiplegic strategy could be readapted in order to produce healthy output. The results revealed that there are multiple strategies of retraining hemiplegic solutions of the CPG. This solution may modify the hemiparetic locomotor pattern into a healthy output by manipulating inter-integrator couplings which are not damaged by damage to the descending drives. Ultimately, some modeling experiments will demonstrate that the increased reliance on intrinsic connectivity increases the stability of the output, rendering it resistant to perturbations originating from extrinsic inputs to the pattern generating center

The effects of sr2w-1 supplementation on high-intensity cycling performance and lactate metabolism

Purpose: The purpose of this investigation was to examine the effects of SR2W-1 herbal supplementation on cycling performance, muscle and blood lactate, and various physiological parameters including blood glucose, heart rate (HR), rating of perceived exertion (RPE), oxygen consumption (VO2), expired ventilation (VE), respiratory exchange ratio (RER), and femoral artery blood flow. Methods: Seven recreational cyclists (Age: 26.7 ± 9.8 yrs, Height: 172.5 ± 13.3 cm, Weight:67.1 ± 10.7 kg, and VO2max: 59.5 ± 11 mL/kg/min) performed 20-min of steady-state cycling (~85% VO2max, 212.1 ± 25.0 W) followed by three 1-min high intensity intervals at VO2max workload (272.9 ± 26.9) with 30-sec active recovery periods at 100 watts. Following intervals, a 15-min passive recovery period preceded a ride to fatigue at VO2max workload. Subjects completed trials on four occasions; preceding and following 21 days of 1000mg/d SR2W-1 (EXP) or 1000mg/d placebo (PLA) assigned in random order. The Wilcoxon Signed-Rank Test was used to compare change-scores from pre- to post- PLA and EXP conditions. Results: No differences reported for any dependent variable and performance times were not different between PLA (pre-PLA: 180 ± 48 s; post-PLA: 198 ± 56 s) and EXP (pre-EXP: 170 ± 57 s; post-EXP: 191 ± 50 s). Conclusion: Notwithstanding the small sample size, 3 weeks of SR2W-1 supplementation does not appear to aid cycling performance, attenuate skeletal muscle fatigue, or modify general physiological responses to exercise