Applied Ergonomics 1993, 24(6), 41)5-412 Analysis of working postures in hammering tasks on building construction sites using the computerized OWAS method Markku Mattila*, Waidemar Karwowski + and Mika Vilkki* *Tampere University of Technology, Occupational Safety Engineering, Box 527, SF-33101, Tampere, Finland ~Center for Industrial Ergonomics, Department of Industrial Engineering, University of Louisville, Louisville, KY 40292, USA The main objectives of this study were to identify the most problematic postures in hammering tasks performed at building construction sites through application of the computerized OWAS method, and to develop recommendations for improvement of working methods and workplaces. Eighteen construction workers, with mean age of 41.6, from three construction companies participated in the field study. The hammering tasks observed during the two-month period included roof boarding, concrete form preparation, clamping support braces, assembling roof frames, roof joisting, shelter form preparation, and fixing fork clamps. Three different types of hammer, including a small Fiskar's hammer, a Fiskar's construction hammer, and a Rocket hammer, were used by the workers. Of all the observations, poor working postures were observed most frequently in roof joisting (12.4% of all observations within the task), followed by concrete form preparation (8.6%), and construction of frames for the roof (7.5%). Overall, out of 593 different postures analysed, a total of 7.8% of postures adopted by the workers during various hammering tasks were classified into OWAS categories lII or IV, indicating that these postures should be corrected either soon or immediately. The computerized OWAS method for postural data analysis proved to be a very useful way to reduce postural load of dynamic hammering tasks, and allowed for efficient application of the original OWAS method. Keywords: Computerized OWAS method, postural analysis, hammering tasks Introduction Musculoskeletal disorders have proved to be a major problem for modern industrialized countries. According to the 1989 National Statistics, approximately 46% of all occupational diseases in Finland were classified as musculoskeletal diseases (Vaaranen et al, 1990). Their number has shown an increasing trend over the last few years. It was also noted that approximately 19.0% of occupational accidents resulted from sudden movements and lifting (National Board of Labour Protection, 1990). Physical workload has been recognized as a factor affecting workers' health at building construction jobs (Helander, 1981; Kumar, 1991; Mattila and Kivi, 1991). For example, about 51% of occupational diseases attributed to construction sites in Finland were linked to ergonomic factors associated with manual tasks (Vaaranen et al, 1990) and out of approximately 11 000-12 000 accidents recorded yearly at building construction sites in Sweden, 18-19% involved the use of handtools (Hammarskj61d et al, 1989). Some of the studies of handtool-related injuries revealed that hammers and hammering tasks performed in poor postures were important contributory factors to industrial accidents reported in the USA. For example, Aghazadeh and Mital (1987) performed an extensive questionnaire study to determine the frequency, sever- ity and annual cost of handtool-related injuries in industry, and to identify problem areas due to the type of tools involved in accidents, the nature of injury, and so on. Out of the total of 68 118 investigated injury cases due to non-powered tools, 6838 or about 10% were attributed to the use of hammers. For the group of accidents while using non-powered handtools, about 71.2% and 24.8% of the cases were attributed to striking by or striking against the tools and over- exertion injuries, respectively. Knives, hammers, Vol 24 No 6 December 1993 0003~3870/93/06 0405~)8 (~) 1993 Butterworth-Heinemann Ltd 405