Volume 16, Issue 3 (9-2019)                   ioh 2019, 16(3): 84-95 | Back to browse issues page

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khakkar S, Choobineh A, Salmani Nodooshan H. Designing, making and Evaluating an Ergonomic Pen to Increase User Comfort and Improve Posture of Hands, Wrists, and Fingers. ioh. 2019; 16 (3) :84-95
URL: http://ioh.iums.ac.ir/article-1-2484-en.html
, salmanyhamid@gmail.com
Abstract:   (2077 Views)
Background and aim:
Musculoskeletal Disorders (MSDs) are widespread around the world and are the second most common cause of disability in work settings. A number of occupational factors such as forceful exertions, awkward postures, repetitive movements, and local contact stress can lead to the development of musculoskeletal problems. There is an association between the use of hand tools and onset of work-related musculoskeletal symptoms. Working with hand tools exposes users to one or more of these factors. Using hand tools, particularly if the job requires using the tools for a prolonged period of time, may also cause increased discomfort and fatigue which may be due to the existence of high stresses on the anatomical structures of the hand. Carpal Tunnel Syndrome (CTS) and writer’s cramp are common injuries among writers, which may occur through excessive precise activity with the exertion of hands and fingers during writing, particularly with inappropriate techniques. There is strong evidence of a positive association between exposure to a combination of ergonomic risk factors (e.g., force and repetition, force and posture) and CTS. Writer’s cramp appears to be triggered by writing for long period of time.
Ergonomic hand tool design involves optimizing the handle to effectively carry out the intended function of the tool with the least load to muscles, tendons, skin, and joints. One aspect of this process is to optimize hand–tool contact area in order to maximize grip strength, minimize contact stress with special interest to sensitive areas of the palm and wrist, and provide appropriate tactile feedback. The grip strength is determined by the biomechanical advantage created by finger joint angles as well as the physiological advantage associated with the differences in muscle length. The hand posture and the related grip strength are influenced by the shape of the handle and the hand size.
Anthropometric data provides information on static dimensions of the human body in standard postures. Anthropometric measurement of human limbs plays an important role in design of workplace, clothes, hand tools, and many products for human use. To design any product for human use, human factors engineers/ergonomists have to rely on anthropometric data, otherwise, the output product may turn out to be a non-ergonomically designed product or the product may turn out to be ergonomically incompatible. The interaction of handle size and shape with the kinematics and anthropometry of the hand have a great effect on hand posture and grip strength. The process of designing and selecting the hand tools to provide a better fit for the user lies on the shoulders of human factor engineers /ergonomists. Poor ergonomic hand tool design is a well-known factor contributing to biomechanical stresses and increasing the risk of cumulative trauma and carpal tunnel syndrome disorders of workers. Hand anthropometry is useful for determining various aspects of industrial machineries, so as to design the equipment and machines for higher efficiency and more human comfort.
Handwriting is an important skill for school-aged children and there is clear relationship between pencil grip posture and handwriting skills. Ergonomic factors like pencil grip, paper position, sitting posture for writing, upper extremity stability and mobility, should be considered with the purpose of effectively promoting efficient handwriting skills. Ergonomically designed hand tools can reduce user discomfort, biomechanical stresses, and risk factors for musculoskeletal symptoms and injuries in hands. Furthermore, by improving the quality and usability of hand tools, it is possible to improve efficiency and work productivity. Using an ergonomic pen is an effective solution to reduce upper limbs musculoskeletal disorders. Using a pen with ergonomic design, especially from childhood, can cause to create a right grip posture for writing and improves the pen grip posture among older people. By getting upper limbs at neutral posture, writing is more comfortable lower chance of hand injuries.
Given the above, the aims of this study were to design, fabricate and evaluate a new type of pen to improve the posture of the wrists, hands, and fingers, and enhance writers’ comfort.
Materials and Methods:
This interventional study was carried out in the Department of Ergonomics, Shiraz University of Medical Sciences from October 2013 to May 2014. The study consisted of 3 phases, including:
a) Designing an ergonomic pen: by reviewing the literature and evaluating the features of the available pens, the idea of the design of a new pen was formed. The features, such as optimal grip, attractive and desirable form, reducing contact stress and muscles fatigue, as well as adapting to hand size for everybody, were focused in the design process.
b) Fabricating the model and the prototype of the pen based on anthropometric data:
the anthropometric parameters of hand that were considered in the design of the pen included: the length of the thumb, the index finger, the middle finger, and hand thickness. The models of the pen were made by plaster. After modifying the details and layout of the pens, one size of the models was made from the final material. It should be mentioned that the prototype was designed and made just for right-handed people.
c) Assessment of some parameters of the new ergonomic pen: In the next step, the ultimate prototype with its final materials was assessed. A new pen made by a 3-dimensional printer and three common pens were compared by 28 subjects. The participants had no musculoskeletal symptoms in the upper limp. The data collection tools consisted of visual analog scales (VAS) and Borg’s rating physical effort scale. After the users performed the writing tasks by four pens, they were asked to rate comfort using the VAS. VAS is a 10-cm instrument, with values from zero representing extremely uncomfortable and to 10 indicating extremely comfortable. The physical exertion/stress felt by each user during the writing task was evaluated using Borg scale of 6-20. In this scale, the values near 20 and 6 represented more difficulty and more comfort, respectively. This scale has been used in a number of studies.
Data were statistically analyzed by one-way ANOVA and independent t-test using SPSS software version 21.
The means (SD) of age and duration of working with pen per day (Hrs) in the subjects studied were 22.17 (3.41) and 5.83 (1.22), respectively. In accordance with the basic idea, the pen was designed in five sizes for percentiles of 5th, 25th, 50th, 75th, and 99th to cover at least 90% of the target group. The prototype was one size of the pen models that was printed by 3D printer. The highest mean (SD) of the users’ comfort was 8.35 (0.95) related to the newly designed pen. The results revealed a reduction in the users’ rating of perceived exertion while writing with the new pen.
In this study, a new type of pen was designed and fabricated to improve upper limb and hand postures while writing. According to findings of this study, the new pen helped correct the grip of hand while writing. The results of this study showed that the ergonomically designed pen was more comfortable to use. Also, it exerted less physical stress on tissues of hand compared to the other evaluated pens during writing. The new ergonomic pen with specific features (i.e., different form, and design in various sizes to provide more adaptation with hand) increased the users’ comfort and reduced the users’ physical exertion while writing. It is believed that using the new ergonomic pen can prevent and reduce wrist and hand musculoskeletal injuries such as carpal tunnel syndrome and cramp in the long periods of time.
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Type of Study: Applicable | Subject: Micro Ergonomics
Received: 2018/08/2 | Accepted: 2019/05/30 | Published: 2019/08/31

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