Iran Occupational Health

Background and aims: Despite automation, still many occupations require the use of hand tools in their routine activities. Scissors are essential tools for many workers in different occupations such as sewing and clothes making.The aim of this study was to investigate the effects of three re-designed models of sewing scissors (models A, B and C) on user performance, tool usability and hand and finger discomfort, and to compare their performances against those with traditional sewing scissors (model D).

Methods: The prototype sewing scissors were designed based on the results of a pilot study and general ergonomic design principles. Modifications were made to the tool handle so that the model A had a bent-handle, thumb-ring was located closer to the pivot in model B, and the original oval ring was changed to a hook shaped handle in model C. User performance was measured using simultaneous recording of the task completion time and error rate, usability was evaluated using system usability scale (SUS) and hand and finger discomfort was evaluated using a hand map and severity scale.

Results: The results showed significant effect of handle shape on user performance (p < 0.001), tool usability (p < 0.001) and hand and finger discomfort (p < 0.01). User performance was better while working with sewing scissors models B and C than with other models (p < 0.01). SUS scores recorded for scissors model B (p < 0.01) and model C (p < 0.05) were significantly higher that recorded for the traditional model. Working with the traditional scissors and scissors model A caused more hand and finger discomfort in the hypothenar and lower part of the thumb than other models.       

Conclusion: Generally, scissors models B and C were comparable and caused some improvements in user performance, tool usability and reduced hand and finger discomfort compared to the traditional model, while no improvement was observed with scissors model A in this regard.