Biomechanical analysis of the upper body during overhead industrial tasks using electromyography and motion capture integrated with digital human models

In this paper, we present a biomechanical analysis of the upper body, which includes upper-limb, neck and trunk, during the execution of overhead industrial tasks. The analysis is based on multiple performance metrics obtained from a biomechanical analysis of the worker during the execution of a specific task, i.e. an overhead drilling task, performed at different working heights. The analysis enables a full description of human movement and internal load state during the execution of the task, thought the evaluation of joint angles, joint torques and muscle activations. A digital human model is used to simulate and replicate the worker’s task in a virtual environment. The experiments were conduced in laboratory setting, where four subjects, with different anthropometric characteristics, have performed 48 drilling tasks in two different working heights defined as low configuration and middle configuration. The results of analysis have impact on providing the best configuration of the worker within the industrial workplace and/or providing guidelines for developing assistance devices which can reduce the physical overloading acting on the worker’s body

Integration Of Cognitive And Physical Factors To Model Human Performance In Fluid Power Systems

Fluid power technology is constantly evolving as a result of the interaction between the human and the system. Systems such as the hydraulic excavator utilize this technology in order to deliver safe, efficient, and effective performance. However, traditional research has placed much emphasis on technical performance rather than on human components. Imbalances of this nature demonstrate inadequate understanding, lack of knowledge, and limited research on the factors affecting performance. This research aims to address these shortcomings by using an integrated approach to better model human performance in fluid power systems

Comparing the Kinematic and Kinetic Outputs from Digital Human Modeling Tools to a Lab-Based Rigid-Link Model for the Investigation of Musculoskeletal Disorder Hazards During Patient Handling

Patient repositioning tasks expose healthcare providers (HCPs) to high bone-on-bone forces, resulting in the development of musculoskeletal disorders (MSDs) (Fragala,2011). Researchers have been able to estimate biomechanical exposures during patient turning using kinematic and kinetic data collected from HCPs (e.g., Marras et al., 1999); however, many of these laboratory-based studies require considerable time and resources to execute and it also remains challenging to gather reliable data (Jäger et al., 2013). Digital human modeling (DHM) may offer unique advantages over direct measurement to estimate biomechanically relevant exposures. Investigators have used DHM to evaluate MSD hazards (Cao et al., 2013; Potvin, 2017); however, there is limited evidence on the fidelity of their outputs. The objective of this study was to compare the kinematic and kinetic outputs produced by two commercial DHM software packages against those generated using a lab-based motion-capture driven approach when analyzing HCPs performance of patient turns. Twenty-five (25) HCPs (eight males) performed a patient turn in the laboratory using a hospital bed with a live 82kg male patient. Whole body kinematics and sagittal plane video were collected. External peak hand force was measured using a force gauge. An accelerometer was placed on the sternum of the patient to identify point of initial patient motion which was assumed to represent the time-point of peak hand force application. Whole body kinematics were used to drive a rigid linked segment model for each participant using Visual3D (C-Motion Inc., Germantown, USA). Measured peak hand force was divided by two and applied to the model at the grip center of each hand at the frame of peak force application. A top down modeling approach was used to calculate trunk and shoulder joint angles and L4-L5 and shoulder joint moments about the flexion/extension axis. These outputs were extracted and compared against DHM software outputs. Siemens Jack (V 8.4) and Santos Pro DHM software packages were used to simulate the patient turn. The static patient turn posture used by the HCP was modeled using the manual joint manipulation, posture prediction and motion capture data importing approaches available in both software. Anthropometrics and peak hand force gathered from the laboratory experiment were inputted into the digital models. trunk and shoulder joint angles and L4-L5 and shoulder joint moments were computed and extracted about the flexion/extension axis from each digitally modeled posture. RMANOVAs, Pearson Product Moment correlation coefficients and Bland Altman analyses were used to compare DHM outputs to the lab-based model outputs. Results from this investigation indicate that the use of Siemens Jack’s (V 8.4) manual joint manipulation approach estimated low back and shoulder kinematics and kinetics that were in agreement with lab-based model outputs. The kinematics and kinetics computed using the posture prediction and motion capture driven approaches to modeling the patient repositioning task, using both Siemens Jack (V 8.4) and Santos Pro were not in agreement with the lab-based outputs. This may have been a result of differences in kinematic modeling assumptions related to the structure of skeletal linkage models, joint decompositions, degrees of freedom in each model and anthropometrics used in DHM software. The use of DHM tools for biomechanical analyses of patient repositioning tasks has the possibility to aide in the investigation of MSD exposures; however, it is important for investigators to understand the purpose of each DHM modeling approach as well as the underlying assumptions of digital human models that may affect kinematic and kinetic outputs used to quantify the exposure to MSDs

Ergonomic Simulation Revisited Using Parametric Virtual Humans in the Biomechanical Framework

The conventional CAD/CAM approach to design does not show the essential spatial relationships between user and product that are crucial for intuitive design analysis. As populations age and the home appliance market stagnates, Universal Design principles implemented with computerized virtual worlds become more important for meeting the ergonomic problems of heterogeneous populations that are increasingly difficult to adequately test with real-world subjects. Digital Human Modelling (DHM) is an emerging area that bridges computer-aided engineering design, human factors engineering and applied ergonomics. The most advanced forms of this technology are being used by many researchers for practical applications, including ergonomic analysis. However, a state of the art model of this technology has never been conceived for the conceptual design stage of a product development cycle as most conventional DHM techniques lack real time interaction, require considerable user intervention, and have inefficient control facilities and non-adequate validation techniques, all contributing to slow production pipelines. They have also not addressed the needs of the growing ageing population in many societies across the globe. The focus of this dissertation is to introduce a complete framework for ergonomic simulation at the conceptual design stage of a product development cycle based on parametric virtual humans in a prioritized inverse kinematics framework while taking biomechanical knowledge in to account. Using an intuitive control facility, design engineers can input a simple CAD model, design variables and human factors in to the system. The evaluation engine generates the required simulation in real-time by making use of an Anthropometric Database, Physical Characteristic Database and Prioritized Inverse Kinematics architecture. The key components of the total system are described and the results are demonstrated with a few applications such as kitchen, wash-basin and bath-tub. By introducing a quantitative estimation of ageing algorithm for anthropometric digital human models, products can be designed from the start to suit the ergonomic needs of the user rather than the biases and assumptions of the designer. Also, by creating a tool that can be used intuitively by non-specialists in a dynamic, real-time environment, designers can stop relying on specialists to test the safety of their ideas and start to effectively use data about populations to discover designs that can be used more easily by more people. Results have been validated with real human subjects indicating the practical implication of the total system as an ergonomic design tool for the conceptual design stage of a product development cycle

A Kinematic Analysis of Joint Angle and Center of Mass Kinematics in Automotive Manufacturing Tasks

This research aimed to determine if participants of varying anthropometrics (i.e., height) would perform automotive manufacturing tasks significantly differently based on joint angle and center of mass (COM) data. Twenty-four participants between the ages of 18 and 65 (¯x = 24.1 years, SD = 7.3) completed 14 manufacturing tasks, and their motions were recorded using two inertial motion capture (IMC) systems. Participants were chosen based on their measured height, including the 5th percentile female (Group 1-5F), 50th percentile female (Group 2-50F), or 95th percentile male (Group 3-95M) (Fryar, Gu, Ogden & Flegal, 2016). The tasks used for this study were identified as common final automotive assembly tasks by Ford, General Motors, and Stellantis. Statistical Parametric Mapping (SPM) and Statistical non-Parametric Mapping (SnPM) were used to compare joint angles between the three percentile groups and COM data within the 5F group. SPM compared the biomechanical data throughout the entire time series of data collected. SPM one-way ANOVAs (

"Production Ergonomics

"Production ergonomics – the science and practice of designing industrial workplaces to optimize human well-being and system performance – is a complex challenge for a designer. Humans are a valuable and flexible resource in any system of creation, and as long as they stay healthy, alert and motivated, they perform well and also become more competent over time, which increases their value as a resource. However, if a system designer is not mindful or aware of the many threats to health and system performance that may emerge, the end result may include inefficiency, productivity losses, low working morale, injuries and sick-leave. To help budding system designers and production engineers tackle these design challenges holistically, this book offers a multi-faceted orientation in the prerequisites for healthy and effective human work. We will cover physical, cognitive and organizational aspects of ergonomics, and provide both the individual human perspective and that of groups and populations, ending up with a look at global challenges that require workplaces to become more socially and economically sustainable. This book is written to give you a warm welcome to the subject, and to provide a solid foundation for improving industrial workplaces to attract and retain healthy and productive staff in the long run.

The effect of load and technique on biomechanical and psychophysical responses to level dynamic pushing and pulling

Pushing and pulling research has yet to fully elucidate the demands placed on manual workers despite established epidemiological links to musculoskeletal disorders. The current study therefore aimed to quantify biomechanical and perceptual responses of male operators to dynamic pushing and pulling tasks. Three common push/pull techniques (pushing, one handed and two handed pulling) were performed at loads of 250kg and 500kg using an industrial pallet jack in a laboratory environment. Thirty six healthy male subjects (age: 21 ±2 years, stature: 1791 ±43 mm and body mass: 77 ±10 kg) were required to perform six loaded experimental and two unloaded control conditions. Hand force exertion, muscle activity and gait pattern responses were collected during 10m push/pull trials on a coefficient controlled walkway; body discomfort was assessed on completion of the condition. Horizontal hand force responses were significantly (p<0.05) affected by load, with a linear relationship existing between the two. This relationship is determined by specific environmental and trolley factors and is context specific, depending on factors such as trolley maintenance and type of flooring. Hand force exertion responses were tenuously affected by technique at higher loads in the initial and sustained phases, with pushing inducing the greatest hand forces. Comparison of the motion phases revealed significant differences between all three phases, with the initial phase evidencing the greatest hand forces. Muscle activity responses demonstrated that unloaded backward walking evoked significantly higher muscle activation than did unloaded forward walking whilst increased muscular activity during load movement compared to unloaded walking was observed. However increasing load from 250kg to 500kg did not significantly impact the majority of muscle activity responses. When considering technique effects on muscle activity, of the significant differences found, all indicated that pushing imposed the least demand on the musculoskeletal system. Gait pattern responses were not significantly affected by load/technique combinations and were similar to those elicited during normal, unloaded walking. Perceptually, increased load led to increased perception of discomfort while pushing resulted in the least discomfort at both loads. From these psychophysical responses, the calves, shoulders and biceps were identified as areas of potential musculoskeletal injury, particularly during one and two handed pulling. Pushing elicited the highest hand forces and the lowest muscle activity responses in the majority of the conditions whilst psychophysical responses identified this technique as most satisfactory. Current results advocate the use of pushing when moving a load using a wheeled device. Suitability of one and two handed pulling remains contradictory, however results suggest that one handed pulling be employed at lower loads and two handed pulling at higher loads

A comparative analysis of instructional techniques toward long-term positive ergonomics transformation for the early career sonographer

The past two decades have demonstrated sonographer work-related musculoskeletal disorder (WRMSD) rates between 80.0 to 90.4%. A surprising revelation made by sonographers was that educators were not perceived as the primary providers of ergonomics instruction. For these reasons, a mixed methods study was performed, involving a causal-comparative component with a longitudinal perspective, a quasi-experimental element, and limited observations and interviews. The study followed four years of sonography graduates through the early career scan period, comparing transmissional, transactional, and transformational learning results. The study’s goal was to determine whether transformative ergonomics learning in a collaborative and reflective environment could demonstrate a significant difference in the reduction of negative scan habits associated with reported musculoskeletal disorders (MSDs), compared to transmissional and transactional learning. Testing revealed that a typical early career sonographer was unaware of the high percentage of musculoskeletal injuries (MSIs) in the field, nor readily perceived personal risks despite possessing knowledge of other injured sonographers. Nevertheless, nearly three-fourths of the study’s subjects described work-related MSD complaints before the five year career period, with shoulders, neck, wrist, and back areas being most common among both general and cardiac sonographers. Determining early scan risk behaviors that coincide with early pain reports and working toward preventative corrective actions may, in fact, reduce the likelihood of such future WRMSD complaints. Photoplethysmography (PPG) recordings during challenging maneuvers demonstrated additional benefit toward the reduction of negative scan behaviors; while transformational learning demonstrated significant benefit in both reducing negative scan behaviors and increasing positive behaviors. Transformational learners expressed more empowerment toward reducing personal risk susceptibility through collaborative recognition and corrective action planning measures. Transformational learners also cited positive attitudinal impact in peer collaboration, while demonstrating a noticeable change in MSI personal risk ratings at the conclusion of learning. The study also revealed that, despite ergonomics learning, early career sonographers did not respond as readily to corrective feedback until personally experiencing an MSI. However, transformational learners demonstrated much greater responsiveness to corrective feedback than did the other learning classifications. This higher transformational level of learning provided evidence toward reduction of WRMSDs among sonographers through responsiveness of corrective action planning

Occupational Lower Extremity Risk Assessment Modeling

Introduction: Lower extremity (LE) work-related musculoskeletal disorders (WMSDs) are known to occur with cumulative exposure to occupational and personal risks. The objective of this dissertation study was to find if creating a quantifiable risk detection model for the LE was feasible. The primary product of the literature review conducted for this study resulted in focusing the attention of the model development process onto creating the initial model of the LE for assessing knee disorder risk factors. Literature Review: LE occupational disorders affect numerous industries and thousands of people each year by affecting any one of the musculoskeletal systems deemed susceptible by the occupational and personal risk factors involved. Industries known to be affected tend to have labor intensive job descriptions. Some of the numerous industry examples include mining, manufacturing, firefighting, and carpet laying. Types of WMSDs noticed by the literature include bursitis, osteoarthritis, stress fractures, tissue inflammation, and nerve entrapment. In addition to the occupationally related disorders that may develop, occupationally related discomforts were also taken into consideration by this study. Generally, both the disorders and the discomforts can be traced to either a personal or occupational risk factor or both. Personal risk factors noted by the literature include a person\u27s physical fitness and health history (such as past injuries). Meanwhile, occupational risks can be generalized to physical postures, activities, and even joint angles. Prevalence data over a three year interval (2003-2005) has found that LE WMSDs make up on average approximately 7.5% of all the WMSD cases reported to the US Occupational Safety and Health Administration (OSHA). When the literature is refined to the information pertaining to occupational knee disorders, the mean prevalence percentage of the same three year range is about 5%. Mean cost for knee injuries were found to be $18,495 (for the year between 2003 and 2004). Methodology: Developing a risk model for the knee meant using groups of subject matter experts for model development and task hazard analysis. Sample occupational risk data also needed to be gathered for each of a series of tasks so that the model could be validated. These sample data were collected from a sample aircraft assembly plant of a US aerospace manufacturer. Results: Based on the disorder and risk data found in the literature, a knee risk assessment model was developed to utilize observational, questionnaire, and direct measure data collection methods. The final version of this study\u27s knee model has an inventory of 11 risk factors (8 occupational and 3 personal) each with varying degrees of risk exposure thresholds (e.g., high risk, moderate risk, or minimal risk). For the occupational risk assessment portion of the model, the results of task evaluations include both an occupational risk resultant score (risk score) and a task risk level (safe or hazardous). This set of results is also available for a cumulative (whole day) assessment. The personal risk assessment portion only produces a risk resultant score. Validation of the knee risk model reveals statistically (t (34) = 1.512, p = 0.156), that it is functioning as it should and can decide between hazardous and safe tasks. Additionally, the model is also capable of analyzing tasks as a series of cumulative daily events and providing an occupational and personal risk overview for individuals. Conclusion: While the model proved to be functional to the given sample site and hypothetical situations, further studies are needed outside of the aerospace manufacturing environment to continue testing both the model\u27s validity and applicability to other industrial environments. The iterative adjustments generated for the occupational risk portion of the model (to reduce false positives and negatives) will need additional studies that will further evaluate professional human judgment of knee risk against this model\u27s results. Future investigations must also make subject matter experts aware of the minimal risk levels of this knee risk assessment model so that task observational results are equally comparable. Additional studies are moreover needed to assess the intimate nature between variable interactions; especially multiple model defined minimal risks within a single task