Paul Ritchey

Differences in Muscle Activity for 4 Touch Devices

The use of touch devices has become pervasive in businesses, coffee shops, homes, and schools. These devices are used for a myriad of different tasks for extended periods of time. However, there is little known about the effects on user’s muscles when these devices are used for extended periods of time. As part of a larger project, we present here results about the differing levels of muscle exertion degree of dynamic activity for muscles when people use four different touch devices—an iPod touch, iPad, touch screen desktop and a touch screen laptop. Participants completed four separate tasks with the devices and there were surprising and interesting differences found by device for the different muscles and tasks.

Standard Deviation of sEMG Measuring the dynamicity of muscle activity

Certain muscle activities (e.g. static muscle activities for prolonged periods of time) and resultant movement patterns may be associated with the development of cumulative trauma disorders. Currently, there is no simple, well-defined measure to discern if a muscle is performing a static or dynamic activity. In this paper, we present the results of a simple study designed to investigate whether the standard deviation (SD) of sEMG is an effective method of identifying muscle dynamicity. Participants completed two separate tasks with a desktop touchscreen device—one requiring static muscle movements and the other to elicit dynamic movements while we measured muscle activity. The SD was more was more varied (M = 4.8 ±.4% MVC) during the dynamic task compared to the Static task (M = 2.5 ±0.2% MVC). Participants’ muscles had a lower Mean (exertion) (M = 7.3 ± 0.8% MVC) in the dynamic task compared to the Static task (M = 11.6 ±1.1% MVC). This interaction of measure and task was significant, F(1,18) = 72.23, p < .001, η2 = 0.80. Thus standard deviation of sEMG was found to be a valid measure of muscle dynamicity.

Towards a systematic approach to real-time sonification design for surface electromyography

Abstract Surface electromyography (sEMG) is a technique for measuring the electrical activity of muscles and is often used as a biofeedback tool. However, challenges associated with the typically visual display of sEMG data have motivated researchers to find non-visual ways of displaying sEMG data, and parameter-mapping sonification has been explored in order to present sEMG data acoustically. Parameter-mapping sonification is a technique that involves mapping values in a data set to acoustic properties of sound. Sonification of EMG data has shown potential for identifying musculoskeletal disease and improving athletic and exercise performance. However, many sonification designs to date have not been systematically evaluated and there have been few quantitative approaches to objective comparisons of sonification paradigms. In this study, we performed a quantitative comparison of different sonification designs in order to test our hypothesis that different sonification designs may be better suited to different tasks. Thirty-six participants (ages 18–31, 14 male) who volunteered to listen to the sEMG sonifications created for this study were asked to identify two different features of the data: muscle activation time and muscle exertion level. Their responses were analyzed in order to determine the effect of sonification design on listener performance. Results indicated that having the sonifications spatialized resulted in the best performance for both tasks. However, different sonification designs resulted in the best performance for the muscle activation time estimation task (Pitch and Loudness mapped redundantly) and the muscle exertion level estimation task (Pitch, Loudness, and Attack mapped redundantly). Further, for the time estimation task, the use of the Attack mapping appeared to reliably inhibit performance. These findings strongly suggest that sonification designs for sEMG need to be designed differently based on the task the user is performing.

Auditory Progress Bars Estimations of Time Remaining

Auditory Progress Bars (APB) were originally intended to augment Visual Progress Bars (VPB) to create multimodal displays. More recently, APBs have been tested in absence of VPBs for use in the on-hold telephone setting. In this setting, APBs are a viable option for communicating the probable time remaining in the on-hold wait. However, past studies measure the effectiveness of APBs retrospectively, which is appropriate for understanding how accurately callers can judge how long they have been waiting on hold, but is not appropriate for determining if APBs are intuitively communicating the probable time remaining in the wait—which is more relevant to the caller’s needs. Here, we measure the effectiveness of 3 distinct APBs prospectively which is more consistent with the caller’s concern of how much longer the wait will be before their call is answered. Furthermore, we make APBs more similar to VPBs by playing the APB’s endpoint before the APB’s beginning point. We found evidence that the accuracy of prospective estimations is a product of APB design, and that the awareness of the endpoint has no affect on the accuracy of prospective estimations.

The Effects of Native Language and Gender on Procedure Performance

Objective: Evaluation of effects of native language—native (L1) versus nonnative (L2)—on procedure performance. Background: Written procedures are used by global industries to facilitate accurate and safe performance of hazardous tasks. Often companies require that all employees be sufficiently literate in English and to use only English versions. Method: Industrial tasks were tested using a virtual reality industrial environment (Second Life®) to explore effects on procedural performance and safety statement adherence. Fifty-four engineering students (27 L2) participated in the study to explore the native language variable. The participants completed the procedures under time pressure and were scored according to procedure performance and hazard comprehension. Results: Analysis of eight procedures showed significant differences between L1 and L2 for procedure performance (specifically for L2 females). There were no language fluency or hazard comprehension differences found between the two groups. Conclusion: The results suggest that (a) the lower procedure performance of L2 readers was not due to English proficiency but more likely to time pressure; (b) implications regarding single language procedures are not fully understood, particularly with regard to gender differences. Application: This research is applicable to high-risk industries providing single language, time critical procedures to multilingual workforces.

The Ergonomic Impact of Swype

Background:Shape writing is relatively new technology for on-screen keyboards that enable users of mobile touch-screen devices to input text by drawing continuous lines. With growth of touch-screen device usage, there has risen the need to investigate potential risks that may occur during prolonged usage. Objective: The biomechanical strain on upper limb muscles were assessed while study-participants used Swype technology on a tablet touch screen device and compared with traditional/regular input methods. Methods: Study-participants performed typing tasks (email and text) using Swype and regular input methods under counterbalanced conditions with sEMG data collected to measure muscle activity during tasks. Results: Email & Text had the same exertion for all muscles except the Extensor. The interaction between task and muscle was significant, F (1.6, 27.5) = 15.39, p < .001, ηp2 = 0.48. The interaction between muscle, task and method was also significant, F (2.19, 37.19) = 3.6, p = 0.03, ηp2= 0.18. Exertion was lower for Swype but with marginal significance. Overall, Email resulted in less dynamic activity than Text with Main effects F(1, 17) = 10.07, p = 0.006, ηp2 = 0.37. Extensor has more dynamic activity than other muscles with main effect F(1.8, 29.9) = 16.51, p < 0.001, ηp2 = 0.49. Conclusion: Results indicate that Swype presents no more biomechanical strain than regular input for most muscles. Swype may result in less exertion for the Extensor muscles in the lower arm. This may be particularly true for tasks requiring interactions like those found in the email task.

USER INTERFACE BIOMECHANICS: Does the Interaction Design of the User Interface Impact Ergonomic Risk Factors?

Understanding the biomechanical impact of user interfaces (UI) is a necessary first step to developing UI design heuristics capable of controlling biomechanical risks related to computer work. The goal of the study reported here is to create a self-report measure sensitive enough for use when evaluating the ergonomic risks of UI interaction. The measure will be based on measures already validated for use on other jobs. Participants completed two different computer-based tasks (clicking and typing) using a higher load input method (direct - touch screen) and a lower load input method (indirect - keyboard and mouse). After each task participants completed modified versions of existing ergonomic risk assessment measures. Overall, the self-report measures used were sensitive enough for participants to identify higher discomfort, effort and exertion with the direct input method. Interestingly, interactions between task, input method, and body region were found for discomfort with the discomfort of the direct input being higher for clicking than typing and this effect was more distinct on the shoulder and upper arms than the lower arms and wrist.