An aim of ergonomics is to design workplaces, systems, products, and tools, to accommodate human variability. Paradoxically however, conventional analytic techniques focus on average behaviour. This paper illustrates the importance of considering individual differences in movement kinematics through an examination of the wrist postures adopted during the use of two different pointing devices. An implication of these data is that the introduction of an alternate pointing device such as a

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... l should be considered as an intervention, but that the intervention should be undertaken with care to ensure that the exposure to extreme wrist postures is reduced. The paper concludes by describing issues related to the use of such multiple case studies in ergonomics research. Relevance to industry As well as being different sizes, people also differ in the way they use tools. The consequence is that the effect of an intervention may differ between individuals.