Moein Nedaei

Introduction: Scissors are essential tools in different occupations including sewing and clothes making. Improper design of fabric cutting scissors can lead to the development of musculoskeletal symptoms among users. The aim of this study was to evaluate pinch force and wrist posture while working with three designs of sewing scissors and a traditional sewing scissors.
Methods: The first model of the scissor had a bent-handle (to improve wrist posture), the second model had a thumb-ring that was located closer to the pivot (to reduce thumb’s abducted position and range of movement), and the original oval ring in the third model was changed to a hook-shaped handle (to reduce hand and finger discomfort). Pinch force was measured using a pinch gauge and wrist posture was measured in two anatomical planes including flexion/extension and ulnar/radial deviation using the observational method.
Results: The results showed significant effects of scissors' design on pinch force exertions (P < 0.01) and ulnar/radial deviation of the wrist (P < 0.001). The lowest level of pinch force decrement between pre- and post-pinch force measurements was recorded for the second model (2.4%), while the highest level was recorded for the traditional model (7%). More neutral wrist postures in ulnar/radial direction (83%) were recorded for the first model compared to the other designs.
Conclusions: The second scissors, which was designed to reduce thumb’s range of motion and abduction, showed some improvement in pinch force compared to the traditional model.

The effects of tool handle dimension (three modified designs of wrenches with 30e50 mm diameter cylindrical handles and traditional design with rectangular cross-sectional (5 mm  25 mm) handle), workpiece orientation (vertical/horizontal) and workpiece size (small/large) as well as user's hand size on wrist ulnar/radial (U/R) torque strength, usability and discomfort, and also the relationship between these variables were evaluated in a maximum torque task using wrenches. The highest and lowest levels of maximal wrist U/R torque strength were recorded for the 30 mm diameter handle and traditional wrench design, respectively. The prototype handle with 30 mm diameter, together with 40 mm diameter handle, was also better than other designs as they received higher usability ratings and caused less discomfort. The mean wrist torque strength exerted on a vertically oriented workpiece (in the sagittal plane) was 23.8% higher than that exerted on a horizontally oriented one (in the transverse plane). The user's hand size had no effect on torque exertions. The wrist torque strength and usability were negatively correlated with hand and finger discomfort ratings. The results are also discussed in terms of their implications for hand tool and workstation configuration in torque tasks involving wrenches.

The effects of three redesigned models of sewing scissors on hand performance measures, discomfort and usability were investigated, and the results were compared with those of conventional scissors. Adjustments were made to the scissors handle with emphasis on more neutral wrist postures (bent handle-model A), correction of the thumb's position and movements (model B) and reducing hand/finger discomfort (model C) while working with the tool. The results showed some improvements in hand performance, muscular effort, usability and discomfort with model B compared to the conventional model. Better hand performance and usability and lower discomfort were recorded with model C compared to the conventional model. The results suggest that the correction of the thumb's position and movement (model B) or even reduced hand/finger discomfort (model C) are perhaps more important considerations in scissors design than improved wrist posture (model A) for improving users' performance and usability of the tool.

" Katūr " , also pronounced as " kahtūr " in the local Persian varieties of Eastern Iran, is a vernacular product used by locals in eastern parts of Iran and the desert people over there in order to harvest Persian manna, also known as Taranjebīn 2 ; but the poor condition of " katur " in terms of its functional efficiency and sustainability as well as taking into account the improper situation of the user during harvest ushered into our attempt to redesign this product-which has its own particular complications and works, as a whole, in a variety of functions. Consequently morphological analysis is chosen as a solution-finding method, among many others employed by industrial designers, since it is believed, as a systematic approach, to be capable of actually simplifying complications present in the aforesaid product. But this time, contrary to the previous cases in which morphological analysis was generally applied in the rather sophisticated industrial products-undergoing mass production, it is used to redesign a non-industrial device of traditional nature. Listening, observing and collaborating with those who matter most, the actual needs and specifications of the beneficiary are extracted through months of direct contact and observing their behaviors during usage, then we attempted to redesign the current product in order to achieve a new product which meets the criteria resulted from morphological analysis while simultaneously focusing on the needs of the beneficiary and the fact that the new product should be both traditional and vernacular in origin as well as utilizing the methods at hand, so that many problems, currently observable in the product, are systematically addressed and it would be possible to produce the final redesign in either small workshops or even manually, by current " katur " users, by means of their present tools. The final solution, chosen among the appropriate redesigns, is presented in the end as a traditional product resulted from the morphological analysis method.