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6 Research Recommendations The workshop members determined that an integrated er- gonomic model is needed, feasible, and useful. Whether a ~su- permodel" or a "modular approach," either constitutes a general mode! encompassing Al elements in its infrastructure. The struc- ture of such a general mode! can provide a standard protocol and common nomenclature for the collection of data and the rationale for prioritizing the following research recommendations. Recommendation 1: Establish the objectives, procedures, and out- line for the development of a general integrated ergonomic model. In this report we have identified many useful anthropomet- ric, biomechanical, and interface models. These models have been developed independently by researchers, engineers, and organiza- tions for specific purposes and use special procedures. In most cases, it is not possible to combine them. No common taxonomy exists that can classify these models in terms of an orderly sys- tem, and no common notation system exists that can describe the types, functions, and components of these models. Prepare detailed requirements and criteria for the develop ment of a common conceptual framework for an integrated er- gonomic model. These requirements should include the develop- ment of a common taxonomy and language that would permit standardization and compatibility in collection, analysis, and col- lation of data from a variety of sources. Compile an annotated list 81

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82 of assumptions and measurement techniques suitable for use by modelers (See Hertzberg, 1968; Roebuck et al., 1975~. Recommendation 2: Review and integrate existing anthropometric and biomechanical data bases. Review and assess existing anthropometric and biomechanical data bases for their suitability for inclusion in a common data base using the criteria developed in Recommendation ~ (e.g., Garrett and Kennedy, 19713. If appropriate, these data bases should be consolidates} into a basic set of anthropometric and biomechanical descriptors. Determine whether the relationships between inde- pendent body descriptors can be applied to the development of three-dimensional models. Identify data requirements for additional population groups, such as civilians, women, the elderly, children, and the physically handicapped, for whom insufficient data currently exist. The re- sult should be a list of reliable and usable modeling data, including correlation coefficients and prediction equations that would allow the calculation of data subsets that were not originally measured. Examine the assumptions and methodology employed in cur- rent data collection procedures, including the development of a standard reference system for the body ant! body segments; the development or refinement of methods for obtaining three- dimensional data, such as locating three-~nnensional subsurface landmarks from the surface of the bocly; and quantifying human body shape and contour while incorporating consideration of the effects of body motion on body size and shape. Determine whether the relationships between independent body descriptors can be established for the development of three dimensional models. Evaluate the current measurement methods, such as stereopho- tography, to provide information for the development of techniques that will make it possible to relate all landmarks and body dimen- sions to a common origin. Recommendation S: Develop methods for the analysis of muscular action and joint loads as a result of dynamic actions. Assess the use of nonintrusive systems, such as magnetic res- onance imaging (cineradiography, computerized axial tomography (CAT) scan, and ultrasound to establish the locations of subsur- face features with respect to stable, identifiable surface landmarks.

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83 Measure the muscle attachment geometry either directly on cadavers or indirectly by stimulating muscle tension under con- trolled conditions. Determine the resultant torques that are de- pendent on the geometry of the muscle attachments. Develop techniques to measure the involvement of the related muscles and the loadings on the joints. For example, consider the use of elec- tromyogramm to indicate the activity of the muscles involved under normal conditions and while fatigued (see Basmadian and DeLuca, 1985; Chaffin and Anderson, 1984; Kroemer et al., 1986~. Tech- niques are needed that allow measurements of the actual loading on the joint. Collect data on muscle and joint dynamics in a simulator under conditions of constant force fields and transitory changes in the force fields. Use the data collected by these methods to initiate the devel- opment of modem of single and cumulative trauma and bone and body segment link dynamics. Identify and evaluate existing theories on feed-fonvard and feedback signals within the body leading to the development of a suitable model of central nervous system control over muscle actions and human body motions. Recommendation 4: Develop submode~ and modular groups. Develop elemental models to provide for the development of modular groups. These ~nclucle: ~ models of specific body segments that function in coordi- nation with each other such as head and neck, lower arm and hand, lower ~d upper arm, upper arm and shoulder, foot and lower leg, lower and upper leg; ~ models of bones under stress under various anisotropic assumptions; ~ models that describe the effects of motivation on the me- chanical impedance of muscles and jowts; these should include sudden bursts and sustained action; and ~ models that describe cognitive and neural functions. Recommendation 5: Develop a mode! for the generic interface between human models and workstation models. Describe the major elements in the interactions between hu- mans and equipment in general terms. An annotated listing of

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84 these elements should cover all important interfaces that place demands on the human user physically (e.g., posture, position, reach), physiologically (e.g., strength, endurance, fatigue), and psychologically (e.g., vision, audition). Consicler grow environ- mental factors (e.g., reduced or increased gravity, acceleration, atmospheric conditions). Develop a generic taxonomy of descrip- tors of the interfaces between machines and the human operator. Generic descriptors should include: descriptions of human- machine interfaces, task requirements, specifically requirements on the human, and a definition of the interchange of information between the technical systems and the human. Recommendation 6: Develop methods and criteria for the valida- tion of ergonomic modem. Reliable and accurate models that can be validated are needed so that trust in their use can be developed and so that their trance ferability can be enhanced. Determine the feasibility and approach for the validation of integrated computer ergonomic models, in- cluding the development of external criteria.