2002 IRISH SCIENTIST YEAR BOOK

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UNIVERSITY OF LIMERICK
TIM GALLWEY
RSI research at UL

Figure 1. Wrist discomfort contours (scale 0–10) for a vertical force of 20% of person’s maximum, 20 times per minute, standardised to the person’s pain threshold.

Repetitive Strain Injuries (RSI) continue to be a major source of absenteeism and worker impairment – e.g. they account for about 60% of occupational ill health in the US. It has been estimated that they cost 2.7% to 5.2% of the GNP of Nordic countries, and the European Agency in Bilbao has reported ‘ergonomic risk factors’ as being among the three highest priority areas needing research in the EU. These injuries result mainly from deficiencies in three particular areas:

 • design of products that impose poor postures and excessive loads on the soft tissues of users
• design of workplaces that induce acute muscle joint angles in the workers using them
• design of work systems that require high degrees of repetitiveness and insufficient rest time.

 The contributions of each are not known, and the behaviour of interactions between them is not understood, so additional research and development are needed.

 A consortium was set up through the EU ‘Growth’ programme to develop Musculo-skeletal Injury Reduction Tools for Health and safety (MIRTH). The partners are: University of Darmstadt (co-ordinator), DaimlerChrysler Bremen plant, University of Limerick, TECMATH (RAMSIS man-model), Institute of Biomechanics Valencia (IBV), Systema Informatics (internet software), and the Finnish Institute of Occupational Health (FIOH). University of Darmstadt is concentrating on research into the applicability of existing tools in automobile assembly work and developing improvements to use in MIRTH. FIOH will concentrate on injuries in E-commerce, and IBV will provide tools to model the biomechanics of the injuries. The final tool will be programmed for use in conjunction with RAMSIS. The total value of the project is €1.6M approximately.

 UL is building on work done already under the Brite-Euram IDEA Project where discomfort profiles and formulae were derived for the wrist alone and the forearm alone. Wrist discomfort contours for one combination of force and rate of movement are shown in Figure 1 for combinations of vertical bending (Flexion/Extension) and sideways deviation (Ulnar/Radial). For the forearm, the effect depends on elbow angle, axial force, and grip exerted. One result for a combination of these is shown in Figure 2 where it should be noted that supination means clock-wise rotation of the right arm, and pronation means the opposite. Note also that all these results are standardised to the anatomy and strength of the individual instead of some ‘average person’, so that they can be applied to risk analysis of individuals.

Click here for enlargment of diagram
Figure 2. Standardised forearm discomfort curves and equations for a torque of 20% of maximum 20 times per minute, with zero axial force and zero grip force.

In MIRTH, UL will derive visual aids (e.g. Figure 1) and equations for combined forearm, wrist and upper arm articulations for a variety of loads that give rise to discomfort, and hence lead subsequently to injury. Effort will be concentrated on assembly operations in the electronics industry. Data will be collected with portable equipment at the work site and will then be simulated with larger samples of people in controlled conditions in the laboratory. Figure 3 shows the rig for examining combined wrist bending and gripping. The work will extend over three years and employ two doctoral students and a senior postdoctoral fellow. Funding to UL amounts to just over € 182,000.

 The final result of the project will be a software tool usable by a wide cross-section of people employed in the design of products and workplaces. It will be offered on the Internet with a Computer Based Training program (developed by Systema) and a CD-ROM with a suite of case study applications to assist users. The whole project is scheduled to last three years, and the products will be available about a year after that. Due to their ease of use and speed, these tools will enable more situations to be analysed, in more detail, more thoroughly, and in less time. Significant gains are expected in worker health, productivity, and quality of work, and analyses across a wide range of Ergonomics interventions show a likely benefit:cost ratio of about 10:1.


Figure 3. Test rig to simulate tasks requiring simultaneous bending of the wrist and various levels of grip force.

Contact: Dr Tim Gallwey,
Manufacturing and Operations Engineering, UL;
Tel.: 061-202851; Fax: 061-202913;
E-mail: timothy.gallwey@ul.ie