Modeling Cumulative Arm Fatigue on Large Multi-touch Displays

Large multi-touch displays have long been studied in the lab, and are beginning to see widespread deployment in public spaces. Although they are technologically feasible, research has found that large multi-touch displays are not always used, and that fatigue is commonly identified as a significant barrier. Fatigue, often called the `gorilla arm' effect, prevents people from using large displays for extended periods of time. One solution to this problem is to design large-scale interfaces that can minimize actual fatigue in practice. A first step towards building such an interface is to quantify fatigue, and more importantly, to quantify it easily. While there have been methods developed to estimate arm fatigue in mid-air interaction, there remains little understanding of fatigue on touch-based interfaces. To address this gap, we propose that existing models for mid-air interaction may be effective for measuring fatigue on large multi-touch displays. We evaluated the accuracy of Jang et al.'s mid-air Cumulative Fatigue model for touch interaction tasks on a large display. We found that their model underestimates subjective fatigue for multi-touch interaction, but can provide accurate estimates of subjective fatigue after fine-tuning of model parameters. We discuss the implications of this finding, and the need to further develop tools to evaluate fatigue on large, multi-touch displays

Ergonomic Evaluation for Right Angle Power Tools: Direct Current Physical Demands Comparison – A Focus on Muscle Activity

The purpose of this study was to evaluate the differences in muscle activation and handle forces between three direct current right angle power tool fastening strategies: turbo tight, two stage without soft stop and two stage with soft stop. Thirty-six participants (20-60 yrs) were assigned to one of two experimental groups: hard-joints or soft-joints. Participants conducted fastenings at four different postures for three different target torques and muscle sEMG was collected on 16 muscles of the upper body. Data from the muscle sEMG, and forces collected at the handle were analyzed using repeated measures ANOVA with Tukey’s post hoc test to determine statistical significance (p\u3c0.05). Results found that the participants sEMG activation impulse was less for the turbo tight fastening strategy in comparison to the two-stage fastening strategy with and without soft stop. These findings were not impacted by joint type, posture or target torque

Discoverable Free Space Gesture Sets for Walk-Up-and-Use Interactions

abstract: Advances in technology are fueling a movement toward ubiquity for beyond-the-desktop systems. Novel interaction modalities, such as free space or full body gestures are becoming more common, as demonstrated by the rise of systems such as the Microsoft Kinect. However, much of the interaction design research for such systems is still focused on desktop and touch interactions. Current thinking in free-space gestures are limited in capability and imagination and most gesture studies have not attempted to identify gestures appropriate for public walk-up-and-use applications. A walk-up-and-use display must be discoverable, such that first-time users can use the system without any training, flexible, and not fatiguing, especially in the case of longer-term interactions. One mechanism for defining gesture sets for walk-up-and-use interactions is a participatory design method called gesture elicitation. This method has been used to identify several user-generated gesture sets and shown that user-generated sets are preferred by users over those defined by system designers. However, for these studies to be successfully implemented in walk-up-and-use applications, there is a need to understand which components of these gestures are semantically meaningful (i.e. do users distinguish been using their left and right hand, or are those semantically the same thing?). Thus, defining a standardized gesture vocabulary for coding, characterizing, and evaluating gestures is critical. This dissertation presents three gesture elicitation studies for walk-up-and-use displays that employ a novel gesture elicitation methodology, alongside a novel coding scheme for gesture elicitation data that focuses on features most important to users’ mental models. Generalizable design principles, based on the three studies, are then derived and presented (e.g. changes in speed are meaningful for scroll actions in walk up and use displays but not for paging or selection). The major contributions of this work are: (1) an elicitation methodology that aids users in overcoming biases from existing interaction modalities; (2) a better understanding of the gestural features that matter, e.g. that capture the intent of the gestures; and (3) generalizable design principles for walk-up-and-use public displays.Dissertation/ThesisDoctoral Dissertation Computer Science 201

Gait Changes During Exhaustive Running

Runners adopt altered gait patterns as they fatigue which may increase energy expenditure and susceptibility to certain overuse injuries. Previous investigations have described changes in muscle performance and kinematic gait variables resulting from running fatigue. The purpose of this investigation was to characterize changes in joint moment patterns that develop as runners fatigue in order to better understand the kinetic bases for kinematic fatigue effects. It was hypothesized that when fatigued, runners would demonstrate increases in stance time, peak stance phase knee flexion angle, peak knee extension moment, peak swing phase hip flexion moment, and hip extension and plantarflexion angular impulse generated during stance. Eight recreational rearfoot-striking runners (height = 170.0 ± 9.8 cm; mass = 69.6 ± 15.1 kg) ran on a force-instrumented treadmill at a velocity 5% slower than that of lactate threshold until volitional exhaustion. Force and motion data were collected each minute and analyzed at six evenly-spaced time points over the run duration. Of the six hypotheses, only stance time changed significantly (p = 0.004), increasing in a linear manner over the course of the run (r2 = 0.946). Of the remaining hypotheses, peak knee flexion (r2 = 0.899) and hip extension angular impulse (r2 = 0.608) followed increasing trends over the course of the run. Individual participants often demonstrated joint moment trends consistent with fatigue effects reported in the literature, despite inconclusive group results. High variability in individual responses underscores the complexity of gait adaptations used by distance runners as they fatigue

Topics in construction safety and health : ergonomic hazards and WMSDs : an interdisciplinary annotated bibliography

"These referenced articles provide literature on construction workers and their risk of ergonomic hazards and work-related musculoskeletal system disorders on the job." - NIOSHTIC-2NIOSHTIC no. 20068246Production of this document was supported by cooperative agreement OH 009762 from the National Institute for Occupational Safety and Health (NIOSH). The contents are solely the responsibility of the authors and do not necessarily represent the official views of NIOSH.Ergonomics-and-WMSDs-annotated-bibliography.pdfcooperative agreement OH 009762 from the National Institute for Occupational Safety and Healt