topauthor: Chaffin_D* : Human-Computer Interaction Bibliography Search

[1] The Effect of Bracing Availability on Force-Exertion Capability in One-Hand Isometric Pulling Tasks INDUSTRIAL ERGONOMICS: IE6 -- Gait and Stability / Jones, Monica L. H. / Reed, Matthew P. / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 54th Annual Meeting 2010-09-27 v.54 p.1169-1173

Link to HFES Digital Content

Summary: In activities of daily living and industrial tasks people encounter obstructions in their environment that kinematically limit the postures that they can achieve. These obstructions can also provide an opportunity for additional support such as bracing with the hand, thigh or other body part. The reaction forces acting at hand or body coupling, which are in addition to those acting at the feet and task hand, may support some percentage of body weight, allow modification to postural behavior strategies, or provide the ability to generate oppositional forces relative to the task force. The effects of kinematic constraints and associated bracing opportunities on isometric hand force were quantified in a motion-capture study of 25 men and women with a range of body size. The objective of this work was to quantify the effect of bracing availability on force-exertion capability. Analyses of one-hand maximal pulling tasks demonstrated that the additional force reaction surfaces enable participants to exert more force at the task hand, by 31% on average, but these values were greatly affected by the location and utility of the constraint and the specified force direction.

[2] The Relationship between Hand Force Direction and Posture during Two-Handed Pushing Tasks INDUSTRIAL ERGONOMICS: Manual Material Handling Activities / Hoffman, Suzanne G. / Reed, Matthew P. / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 51st Annual Meeting 2007-10-01 v.51 p.928-932

Link to HFES Digital Content

Summary: Posture and external loads such as hand forces have a dominant effect on ergonomic analysis outcomes. Accurate job analyses require accurate representation of working postures and knowledge of external loads. The effects of hand force location, magnitude, and direction on whole-body posture for standing tasks were quantified in a motion-capture study of 20 men and women with widely varying body size. A subset of the data was analyzed to study the relationship between hand force direction and posture during two-handed pushing tasks performed with and without a constraint on hand force direction. Analyses demonstrated that force direction is a significant determinant of posture, and that pushing postures are consistent with several biomechanical principles.

[3] Teaching Team Behavior to Human Factors Ergonomics Students, Part II: Specifics for Forming and Developing Teams, and Using Peer Ratings EDUCATION: Teaching Team Behavior to Human Factors/Ergonomics Students, Part II: Specifics for Forming and Developing Teams, and Using Peer Ratings / Stone, Nancy J. / Moroney, William F. / Burke, C. Shawn / Caldwell, Barrett S. / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 49th Annual Meeting 2005-09-26 v.49 p.747-750

Link to HFES Digital Content

Summary: Many Human Factors/Ergonomics specialists are members of work teams. To prepare students for teamwork, the students' educational experiences need to include team building exercises and experiences. As a follow-up to the 2004 HFES panel on teaching team behavior, this panel will address more specific aspects of teaching team behavior to HF/E students. In particular, the panelists will address the issues of forming teams, developing teams, and collecting and using peer ratings. The results of this and last year's panel discussion will be used to develop guidelines for effectively teaching teamwork to HF/E students. These guidelines will be disseminated through the Education Technical Group.

[4] Critical Features in Human Motion Simulation for Ergonomic Analysis HUMAN PERFORMANCE: Lessons Learned and the Future of Human Performance Modeling / Reed, Matthew P. / Chaffin, Don B. / Faraway, Julian Proceedings of the Human Factors and Ergonomics Society 49th Annual Meeting 2005-09-26 v.49 p.1196-1199

Link to HFES Digital Content

Summary: Digital human figure models (DHM) are increasingly the tools of choice for assessments of the physical ergonomics of products and workplaces. Software representations of users and workers are used to visualize people performing tasks of interest. Analyses have usually focused on clearance and reach in static postures, not because the actual tasks are static, but rather because DHM have lacked robust, accurate motion simulation capability. Research is underway at many institutions to develop improved motion simulation methods, drawing on a wide variety of methodologies from fields such as computer graphics, kinesiology, motor control, and robotics. Experience in the Human Motion Simulation Laboratory at the University of Michigan suggests that conventional metrics of accuracy for posture and movement prediction do not adequately capture the aspects of human movement that are most important for ergonomic analysis. This paper identifies and justifies a set of these critical features.

[5] A Biomechanical Basis for Low Back Injury Risk in High Exertion Tasks INDUSTRIAL ERGONOMICS: The History and Future of Ergonomics in Controlling Low Back Disorders / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 49th Annual Meeting 2005-09-26 v.49 p.1344-1348

Link to HFES Digital Content

Summary: Manual work is still very prevalent in many jobs today. This paper will explore the historic role that biomechanics has played in understanding these outcomes, as well as reviewing various prevention strategies used today.
    The focus of the presentation will be on occupational low back pain. The discussion begins with the fundamental biomechanical reality; that the lumbar spine is often subjected to extremely large compression forces when one stoops to pick up an object, even if the object is of moderate weight. The paper will discuss this outcome, as well as biomechanics research in the late 80s that lead to inclusion in 1994 of a torso twisting risk factor in the "NIOSH Lifting Guideline."
    The growing use of mechanical aids (hoists, articulated arms and conveyors) has done a great deal to alleviate high levels of low back stress while lifting, but too often these same devices require people to twist and push and pull objects. High torso muscle antagonistic actions and vertebral shear forces were being predicted in such activities, especially when fast motions were involved. Concern also over shoulder injuries was growing related to the use of these devices, leading to the need to develop and use models of whole body exertions in industry to understand the full complexity of the problems for various groups of people.
    Recently some biomechanics research began to focus on another aspect of vertebral column function that makes it vulnerable to injury, particularly during fast motions with light loads. This vulnerability is due to the column's reliance on well coordinated torso muscle contractions to control its inherent dynamic instability.

[6] Quantitative Representation of Alternative Movement Techniques and Motion Variability INDUSTRIAL ERGONOMICS: Quantification of Exposure / Park, Woojin / Chaffin, Don B. / Martin, Bernard J. / Genaidy, Ashraf M. Proceedings of the Human Factors and Ergonomics Society 48th Annual Meeting 2004-09-20 v.48 p.1423-1426

Link to HFES Digital Content

Summary: In an attempt to objectively represent and differentiate movement techniques, and further understand the variability in human motion behavior, this study presents a quantitative index termed Joint Contribution Vector (JCV) representing a motion in terms of contributions of individual joint degrees-of-freedom to the achievement of the task goal. Given a set of uncharacterized motions, the JCV index and statistical visualization and clustering methods enable identification of alternative movement techniques and graphical representation of motion variability. A motion data analysis was conducted to demonstrate the utility of the JCV index.

[7] Importance of Ergonomics for the Aging Worker INDUSTRIAL ERGONOMICS: Ergonomics and the Aging Worker / Davis, Kermit G. / Jorgensen, Michael J. / Grosch, James W. / Marras, William S. / Chaffin, Don B. / Czaja, Sara / Redfern, Mark S. Proceedings of the Human Factors and Ergonomics Society 47th Annual Meeting 2003-10-13 v.47 p.1213-1215

Link to HFES Digital Content

Summary: The purpose of the panel will be to discuss the ramifications of the numerous aging-related declines and how they impact the risk of injury in the workplace. Specific attention will be given to how the various components of the musculoskeletal system interact with each other. The discussion will provide potential intervention strategies that accommodate for the special needs of older workers. Through the diverse backgrounds of the panelists, a more comprehensive dialogue will provide better evidence of the strength and weaknesses of the literature regarding this rapidly growing at-risk population.

[8] An Analysis of Shoulder Loading Differences for Simulated Industrial Task Performance Between Injured and Non-Injured Subject Populations INDUSTRIAL ERGONOMICS: Upper Extremity Research II [Lecture] / Dickerson, Clark R. / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 46th Annual Meeting 2002-09-30 v.46 p.1133-1136

Link to HFES Digital Content

Summary: Detailed characterization of differences in motions between injured and non-injured populations has not been widely studied. These motion differences may have an impact on physical loading of injured populations performing work tasks. This study included analysis of tasks performed by three populations: control, spinal cord injured, and low back pain. Shoulder loading was examined for goal-directed simulated sagittal and lateral plane work tasks through calculation of maximum external dynamic shoulder moments. The significant main effects in determining shoulder moments included: type of task performed (one or two-handed load movement), horizontal distance to target, vertical height of target, and population membership. There was also a significant interaction effect between population and task type. This study establishes that both task requirements and injury status quantitatively effect shoulder loading, particularly for lateral motions, and suggests that ergonomists should consider factors beyond task-defined characteristics when designing job interfaces for injured populations.

[9] A Motion Modification Algorithm for Memory-Based Human Motion Simulation INDUSTRIAL ERGONOMICS: Ergonomic Movement Research [Lecture] / Park, Woojin / Chaffin, Don B. / Martin, Bernard J. Proceedings of the Human Factors and Ergonomics Society 46th Annual Meeting 2002-09-30 v.46 p.1172-1175

Link to HFES Digital Content

Summary: Simulating human motions in the virtual CAD world is important in the computerized ergonomic design of products and workplaces. The present study introduces a novel, memory-based approach for simulating realistic human motions and presents a motion modification algorithm. In this novel approach, realistic human motions are simulated by modifying existing motion samples stored in a motion database. The proposed motion modification algorithm was found to be able to simulate human motions accurately. The memory-based motion simulation approach has advantages over existing simulation models as it can simulate qualitatively different types of motions on a single platform, predict motions of different styles, and continually learn new motions.

[10] Simulation of Simultaneous Muscle Strength and Balance Constraints during One and Two Handed Lifting INDUSTRIAL ERGONOMICS: Trunk/Torso Modeling [Lecture] / Chaffin, Don B. / Woolley, Charles B. Proceedings of the Human Factors and Ergonomics Society 45th Annual Meeting 2001-10-08 v.45 p.1007-1010

Link to HFES Digital Content

Summary: This paper addresses the complex issues affecting the postures people choose to use when attempting moderate load lifting exertions. In essence, lifting exertions are known to require a person to utilize muscle strength capabilities at each joint while also maintaining balance. As loads in the hand are located further away from the person both muscle and balance requirements increase. By setting population limits to accommodate both a 90%tile muscle strength capability and a functional balance capability within the University of Michigan's 3D Static Strength Prediction Program, it was possible to run a set of trials which demonstrate the importance of both constraints when lifting loads in one and both hands placed at different horizontal distances away from the body. A small study showing the effects of one handed bracing was also performed. Results indicate that subtle changes in body postures and or hand bracing can affect the maximum distance a moderate load can be lifted. This demonstrates the general nature of the biomechanical strength and balance problems associated with the horizontal location of a moderate load, even when one handed bracing is possible.

[11] Modifying Motions to Meet New Constraints 5: INDUSTRIAL ERGONOMICS: Biomechanical Modeling [Research] / Park, Woojin / Chaffin, Don B. Proceedings of the Joint IEA 14th Triennial Congress and Human Factors and Ergonomics Society 44th Annual Meeting 2000-07-30 v.44 n.5 p.280-283

Link to HFES Digital Content

[12] EDITED BOOK Handbook of Human Factors / Salvendy, Gavriel 1997 p.1600 New York John Wiley & Sons Wiley-Interscience

ISBN: 0-471-11690-4; OCLC 35986430

2nd edition

1. THE HUMAN FACTORS FUNCTION
1. The Human Factors Profession
	+ Helander, Martin
2. Systems Design and Evaluation
	+ Czaja, Sara J.
2. THE HUMAN FACTORS FUNDAMENTALS
3. Sensation and Perception
	+ Proctor, Robert W.
	+ Proctor, Janet D.
4. Information Processing
	+ Wickens, Christopher D.
	+ Carswell, C. Melody
5. Learning
	+ Koubek, Richard J.
	+ Benysh, Susan A. H.
	+ Tang, Eric
6. Human Error
	+ Park, Kyung S.
7. Perceptual Motor Skills and Human Motion Analysis
	+ Regan, David
8. Engineering Anthropometry
	+ Kroemer, Karl H. E.
9. Biomechanics of the Human Body
	+ Marras, William S.
10. Work Physiology -- Fatigue and Recovery
	+ Rodgers, Suzanne H.
3. JOB DESIGN
11. Allocation of Functions
	+ Sharit, Joseph
12. Task Analysis
	+ Luczak, Holger
13. Mental Workload
	+ Tsang, Pamela S.
	+ Wilson, Glenn F.
14. Job and Team Design
	+ Medsker, Gina J.
	+ Campion, Michael A.
15. Participatory Ergonomics
	+ Wilson, John R.
	+ Haines, Helen M.
16. Models in Training and Instruction
	+ Swezey, Robert W.
	+ Llaneras, Robert E.
17. Computer-Based Instruction
	+ Brock, John F.
18. Organizational Design and Macroergonomics
	+ Hendrick, Hal
19. Socially Centered Design
	+ Stanney, Kay M.
	+ Maxey, Jeffrey L.
	+ Salvendy, Gavriel
4. EQUIPMENT, WORKPLACE, AND ENVIRONMENTAL DESIGN
20. Visual Displays
	+ Bennett, Kevin B.
	+ Nagy, Allen L.
	+ Flach, John M.
21. Controls
	+ Bullinger, Hans-Jorg
	+ Kern, Peter
	+ Braun, Martin
22. Nonconventional Controls
	+ McMillan, Grant R.
	+ Eggleston, Robert G.
	+ Anderson, Timothy R.
23. Biomechanical Aspects of Workplace Design
	+ Chaffin, Don B.
24. Noise
	+ Crocker, Malcolm J.
25. Vibration and Motion
	+ Griffin, Michael J.
26. Illumination
	+ Boyce, Peter R.
27. Toxicology and Thermal Comfort
	+ Konz, Stephan A.
28. Climate and Clothing
	+ Bensel, Carolyn K.
	+ Santee, William R.
29. Design for Macrogravity and Microgravity Environments
	+ Albery, William B.
	+ Woolford, Barbara
30. Architecture and Interior Design
	+ Harrigan, John E.
5. DESIGN FOR HEALTH AND SAFETY
31. Occupation Risk Management
	+ Zimolong, Bernhard
32. Work Schedules and Sustained Performance
	+ Tepas, Donald I.
	+ Paley, Michael J.
	+ Popkin, Stephen M.
33. Psychosocial Approach in Occupational Health
	+ Kalimo, Raija
	+ Lindstrom, Keri
	+ Smith, Michael J.
34. Manual Materials Handling
	+ Ayoub, M. M.
	+ Dempsey, Patrick
	+ Karwowski, Waldemar
35. Work-Related Musculoskeletal Disorders of the Upper Extremities
	+ Karwowski, Waldemar
	+ Marras, William S.
36. Warnings and Risk Perception
	+ Laughery, Kenneth R., Sr.
	+ Wogalter, Michael S.
6. PERFORMANCE MODELING
37. Decision Making
	+ Lehto, Mark R.
38. Feedback Control Models -- Manual Control and Tracking
	+ Hess, Ronald
39. Supervisory Control
	+ Sheridan, Thomas B.
40. Cognitive Modeling
	+ Eberts, Ray
41. Computer Modeling and Simulation
	+ Laughery, K. Ronald, Jr.
	+ Corker, Kevin
42. Decision Support Systems
	+ Sage, Andrew P.
7. EVALUATION
43. Data Collection and Evaluation of Outcome Measures
	+ Salvendy, Gavriel
	+ Carayon, Pascale
44. Exploratory Sequential Data Analysis: Qualitative and Quantitative Handling of Continuous Observational Data
	+ Sanderson, Penelope M.
	+ Fisher, Carolanne
45. Effectiveness Testing of Complex Systems
	+ Pejtersen, Annelise Mark
	+ Rasmussen, Jens
46. Usability Testing
	+ Nielsen, Jakob
47. Maintainability
	+ Majoros, Anthony E.
	+ Boyle, Edward
48. Human Factors Audits
	+ Drury, Colin G.
49. Assessing Cost/Benefits of Human Factors
	+ Rouse, William B.
	+ Boff, Kenneth R.
8. HUMAN-COMPUTER INTERACTION
50. Design of Computer Terminal Workstations
	+ Smith, Michael J.
	+ Cohen, William J.
51. Software-User Interface Design
	+ Liu, Yili
52. Virtual Environments
	+ Bullinger, Hans-Jorg
	+ Bauer, Wilhelm
	+ Braun, Martin
53. Social Computing: Computer Supported Cooperative Work and Groupware
	+ Barua, Anita
	+ Chellappa, Ramnath
	+ Whinston, Andrew B.
54. Human Factors in Information Access of Distributed Systems
	+ Reaux, Ray
	+ Carroll, John M.
55. Multimedia
	+ Chignell, Mark H.
	+ Waterworth, John A.
9. SELECTED APPLICATIONS OF HUMAN FACTORS
56. Human Factors in Manufacturing
	+ Karwowski, Waldemar
	+ Warnecke, Hans-Jurgen
	+ Hueser, Manfred
57. Automation Surprises
	+ Woods, David D.
	+ Sarter, Nadine
	+ Billings, Charlie
58. Human Factors in Process Control
	+ Moray, Neville
59. Human Factors in Transportation
	+ Waller, Patricia F.
	+ Green, Paul A.
60. Design for People with Functional Limitations Resulting from Disability, Aging, or Circumstance
	+ Vanderheiden, Gregg C.

[13] State of the Art and Current Activities in Human Modelling Technology GENERAL SESSIONS: Panel / Nayar, Narinder / Badler, Norm / Carrier, Robert / Chaffin, Don / Liu, Yili / Duncan, Jerry / Nelson, Cynthia / Obergefell, Louise / Smith, Barry / Roebuck, John Proceedings of the Human Factors and Ergonomics Society 39th Annual Meeting 1995-10-09 v.1 p.516-518

WARNING: THE ABSTRACT OF THIS ENTRY HAS NOT BEEN VALIDATED

Summary: Computer-based human modelling technology has been in existence since the early 1980s. However, most earlier human models were either hard to use or lacked appealing graphics. With rapid developments in 3D computer graphics, it is now possible to interactively manipulate and analyze human models in a virtual environment. This coupled with growing user interest has spurred rapid development and use of human modelling and simulation.

[14] Stability Limits in Extreme Postures: Effects of Load Positioning and Foot Placement INDUSTRIAL ERGONOMICS: Lifting and Carrying [Lecture] / Holbein, M. A. / Chaffin, D. B. Proceedings of the Human Factors and Ergonomics Society 39th Annual Meeting 1995-10-09 v.1 p.655-659

WARNING: THE ABSTRACT OF THIS ENTRY HAS NOT BEEN VALIDATED

Summary: Although injuries related to postural stability are prevalent, ergonomic job analyses have traditionally not addressed stability issues. In this research, functional stability limits are quantified for persons standing in extreme postures under various external load and foot positioning conditions. Six subjects were tested while standing unladen and while holding a 5.2 kg load. The foot positions, or bases of support (BOS), were varied in width of the stance and sagittal separation of the feet. They were asked to lean and displace their center of gravity (COG) as far as possible in eight directions to the sides and front of the body. Stability measures based on these COG displacements were calculated. All controlled variables significantly affected the stability measures. When standing unladen, subjects extended their COG to within 99% of their BOS limit. Movement was much more restricted when leaning while handling a load (89%), especially holding it with one hand on the shoulder (84%). On average, increased separation of the feet in a particular direction resulted in larger COG displacements in that direction. The results are discussed relative to their effects on balance and stability modeling.

[15] The Philosophy of Ergonomics Standards INDUSTRIAL ERGONOMICS: Panel / Peacock, Brian / Orr, Gary / Chaffin, Don / Leamon, Tom / Radwin, Rob Proceedings of the Human Factors and Ergonomics Society 39th Annual Meeting 1995-10-09 v.1 p.678

WARNING: THE ABSTRACT OF THIS ENTRY HAS NOT BEEN VALIDATED

Summary: The panel will include speakers from Government (Gary Orr), Academia (Don Chaffin), Insurance (Tom Leamon), the HF&ES (Rob Radwin), Industry (Brian Peacock, Panel Chair), the Legal Profession (TBD) and Labor (TBD)
After a hectic few years the promised OSHA ergonomics standard has been relegated to the back burner. Various sets of material were distributed, including a draft proposed standard along with extensive appendices. Much has been said and written regarding the scientific basis, the economic implications and the legal ramifications of the standard. Many other attempts have also been made to produce material that represents the general opinion of the profession, including ANSI Z365, the State of California and British Columbia. The issue of standards will not go away and it is probably appropriate at this time to step back and discuss some philosophical issues associated with standards.
Operational concepts:

Ergonomics is broader in content and application than the prevention of acute and cumulative trauma disorders and so a standard should adopt a more specific title such as a Musculo Skeletal Disorder Prevention Standard.
Programmatic Guidelines should describe the general content of ergonomics activity such as Job Analysis, Hazard (or Error) Reduction, Training, Medical (or Risk) Management, Record Keeping and Reporting.
Performance Requirements should refer to specific outcome measures such as injury / illness incidence and severity, productivity, product quality and indications of motivation such as attendance.
Design Specifications should take the form of quantitative statements regarding systems, products, processes and environments.
Standards should include probabilistic statements such as target population selection and training characteristics and levels (percentiles) of accommodation, risk or protection.
Physical (mental) work should be optimized, not minimized.
Classical "reductionist" science in this area will always require interpolation or extrapolation before being of value in standards
1. Is there sufficient need for a standard because of the level of outcomes (such as occupationally induced cumulative trauma)?
2. Is there sufficient scientific evidence relating "doses" and responses to form the basis of a standard?
3. Is our profession being fairly criticized because of our failure to reach agreement on standards?
4. Should a standard take the form of programmatic guidelines, performance requirements or design specifications?
5. What levels of accommodation / protection are appropriate for work standards and to what extent should standards assume certain levels of population selection and training?
6. Following the analogy of the recent changes in vehicular speed limits, should the issue of standards be left to the individual states?
7. How can consensus be achieved?

[16] A Biomechanical Investigation of the Asymmetric Multiplier in the Revised NIOSH Lifting Equation INDUSTRIAL ERGONOMICS: Lifting and the NIOSH Guideline [Lecture] / Nussbaum, Maury A. / Chaffin, Don B. / Page, George B. Proceedings of the Human Factors and Ergonomics Society 39th Annual Meeting 1995-10-09 v.1 p.709-713

WARNING: THE ABSTRACT OF THIS ENTRY HAS NOT BEEN VALIDATED

Summary: There is growing evidence, from epidemiological and biomechanical sources, that lifting performed in asymmetric postures is a risk factor for the development of a musculoskeletal injury. In the recent update of the NIOSH Lifting Guide, a linear Asymmetric Multiplier was added to account for this type of risk. The present study addresses the form of this Multiplier through analysis of several asymmetric lifting tasks. Both spinal loading and a derived metric of muscle injury risk were calculated as a function of asymmetry angle. The results suggest that there is a non-linear increase in injury risk with respect to asymmetry. Only moderate increases in risk were predicted for asymmetry of 0°-30°, and sharply increasing risk as asymmetry reaches 90°, implying that ergonomic intervention should be concentrated on tasks with the highest asymmetries.

[17] Frame of Reference in Posture Specification for Computer-Aided Ergonomic Analysis COMPUTER SYSTEMS: Virtual Reality and Virtual Environments [Lecture] / Zhang, Xudong / Liu, Yili / Chaffin, Don Proceedings of the Human Factors and Ergonomics Society 38th Annual Meeting 1994-10-24 v.1 p.290-294

Summary: An experiment was conducted to examine the effect of the congruency between the reference frame adopted to perceive and record postures and the one employed in a computer-aided ergonomics software on human posture specification performance. The role that the interface can play in enhancing the congruency was also investigated. The subjects were presented with the photographs of a working posture, and were required to manipulate the human stick figures generated by the ergonomics software to match the posture in the photographs. The experiment showed that the congruency played a significant role in facilitating the performance of posture specification for ergonomic analysis. It also demonstrated a clear advantage of using a 3-D humanoid display to improve the congruency when it is not achievable in the pre-analysis posture data-collection. Implications for ergonomic job analysis and ergonomics software design are discussed.

[18] Age Effects in Biomechanical Modeling of Static Lifting Strengths INDUSTRIAL ERGONOMICS: Lifting [Lecture] / Chaffin, Don B. / Woolley, Charles B. / Buhr, Trina / Verbrugge, Lois Proceedings of the Human Factors and Ergonomics Society 38th Annual Meeting 1994-10-24 v.1 p.658-661

Summary: There is growing awareness that age results in reduced strengths in the population, and that significant decreases start in the 5th decade. The magnitude of the decrease in strength depends on the specific muscle function being tested. Because of differential effects it is not clear how various decreases could alter whole-body strength performance. This paper describes how specific strength decreases measured in an older population of men and women could affect their whole-body exertion capabilities in selected scenarios. A computerized strength prediction program is used to both predict the whole-body strength changes with age, and to study how older populations can alter their postures to achieve maximum exertion capability. The results indicate that different muscle group strengths decline by 5% to 70% with age, depending on which muscle group is tested. These changes have profound effects on whole-body exertion capabilities, which also are shown to depend on specific postures used to perform the exertions.

[19] Evaluation of Limiting Strength Constraints in a Comprehensive Biomechanical Model INDUSTRIAL ERGONOMICS: Strength / Kerk, Carter J. / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 37th Annual Meeting 1993-10-11 v.2 p.739-743

Summary: The strength constraints in a two-dimensional static human force exertion capability model (HFEC) have been evaluated using eight male and female subjects of varying anthropometry and strength capability. The model comprehensively estimates feasible exertion capability under symmetric conditions using a set of fifteen linear constraint equations from three constraint classes: strength, stability, and coefficient of friction (COF). This evaluation examines the nature of the limiting strength constraints. The computer model aided in designing tasks (combining posture with force exertion direction) that isolated upper extremity strength constraints and hip/torso strength constraints from stability and COF constraints. Subject performances of maximum exertions were recorded using force platforms and a multi-axis load cell to record external reaction forces at the hands and feet. Body posture was recorded with a 2D motion analysis system. The observed hand force exertions were compared to the exertions predicted by the model. The identity of the limiting constraints was well predicted by the model. The location of the constraints was logical and predictable. The results are discussed in the context of other modeling approaches as well as implications for future research. The HFEC approach shows excellent potential as an ergonomic engineering tool for teaching, evaluation, and design.

[20] Can Biomechanically Determined Stress be Perceived? INDUSTRIAL ERGONOMICS: Cognitive Biomechanics / Thompson, Deborah D. / Chaffin, Don B. Proceedings of the Human Factors and Ergonomics Society 37th Annual Meeting 1993-10-11 v.2 p.789-792

Summary: Back and overexertion injuries are a costly and debilitating problem in industry. It has been suggested that the best protective action in the prevention of back injuries is to rely on a person's perception of the risks, and allow them to operate within them. However, this assumes that a person is aware of the sensory information from the body concerning unsafe levels of stress, particularly in the back. Unfortunately, there is some question as to whether this assumption is valid. The purpose of this study was to determine how well physical stress resulting from performing occasional lifting exertions could be perceived. This required an evaluation to determine how perception (psychophysical approach) relates to physical tolerances (biomechanical approach). The results showed that back stress resulting from occasional lifting exertions is not well perceived in general. The fact that the stress was not well perceived by some may indicate why low back injuries are so pervasive in the population, and why engineering and ergonomic changes are needed to reduce the exposure to conditions that would overstress the back.

[21] Some Ergonomic Considerations in the Design of Material Handling Devices INDUSTRIAL ERGONOMICS: Lifting/Manual Material Handling / Resnick, Marc L. / Chaffin, Don B. Proceedings of the Human Factors Society 36th Annual Meeting 1992-10-12 v.1 p.644-648

Summary: Material handling devices (MHD's) are being proliferated in factory workplaces to prevent workers from being injured due to the lifting of heavy loads. These devices require exertions which have not been adequately studied from an ergonomic perspective. Jobs with MHDs often require complex 3-dimensional movements and loaded axial rotation. One type of MHD, an articulated arm, was used to investigate the effects of inertial load, arm joint friction, and positioning accuracy requirements. The kinematic variables of peak push and pull hand forces, velocities, and accelerations were measured or computed in both a task that allowed sagittally symmetric postures as well as one in which loaded axial torso rotation was required. Greater inertial loads increased the peak push and pull hand forces in all cases by an average of 20%. The activation of a 40 psi brake at both joints of the articulated arm increased the peak hand forces by about 40% on average and decreased the peak velocities and accelerations in both tasks by about 20% and 15% respectively. The effects of positioning accuracy required were not as universal. There was a 10% decrease in peak velocity and acceleration for smaller target size in the sagittally symmetric task but no significant effect in the torso twisting task. The study generated some guidelines for the implementation of MHD's, and suggests some areas where further research is required.

[22] Biomechanical Analysis of Horizontal Movement Strategies in the Sagittal Plane Industrial Ergonomics: Biomechanical Analysis and Modeling / Resnick, Marc L. / Chaffin, Don B. / Erig, Muzaffer Proceedings of the Human Factors Society 35th Annual Meeting 1991-09-02 v.1 p.785-789

Summary: N/R

[23] Biomechanical Aspects of Workplace Design 5. Equipment and Workplace Design / Chaffin, Don B. Handbook of Human Factors / Salvendy, Gavriel 1987 n.5.4 p.601-619 New York John Wiley & Sons

Objectives of Work-Space Design
Traditional Work-Space Design Criteria -- Motion Economy
Contemporary Work-Space Design to Reduce Biomechanical Stress
Guidelines for Workplace and Machine Control Layout
Summary
References