جستجوی مقالات مرتبط با کلیدواژه « ابزار دستی » در نشریات گروه « پزشکی »

International Labor Organization (ILO) 2015 report shows that about 40% of the all total compensation for work-related diseases and accidents in the world is due to musculoskeletal disorders. According to UK Health and Safety Executive (2019) 41% of all registered Work related Musculoskeletal Disorders (WMSDs) are due to upper limbs. Barr et al. (2004) reported that most absence from work in the United States was due to musculoskeletal injuries to the hand and wrist. Hand, arm, and forearm are most important limbs of human body to work. Hand tools, especially non-powered hand tools, are responsible for a significant portion of damages. Many different types of hand tools are used in industrial, services, and domestic activities including wrenches, pliers, screwdrivers, clamps, snips, saws, etc. The use of hand tools is accompanied by repetitive movements and previous studies have shown that inappropriate design of hand tool can damage human joints, tendons and muscles. Repetitive movements are one of main causes of musculoskeletal injuries. In order to achieve high levels of comfort, safety, and efficiency of hand tools, physical abilities and limitations of users must be taken into account in design phase. Also, women and left-handed people must be considered in design of hand tools due to their different body dimensions and abilities. These factors are directly influences the trading of hand tools. Handle design is an important factor in the safe, convenient and ease of use of non-powered hand tools. Socket wrench is a single-wrench that is widely used to open and close the bolts and nuts that require high force and high speed operation. Due to wide usage of socket wrench this study aimed to investigate the relationship between physical parameters of length and diameter of handle, and weight of different models of socket wrench with electrical activity of two selected forearm muscles. We examined the correlation between three physical parameters of six trade model of socket wrenches. 

This descriptive-analytical study performed among 58 male workers of the installation and maintenance unit staff of a university. Their ages ranged from 25 to 45 years.  All participants were right-handed, healthy, and without history of upper limb injury or musculoskeletal disorders. They had at least one year of job experience in maintenance unit of university, and their body mass index was between 20-30. Six different types of socket wrench were selected and named with alphabetic codes A, B, C, D, E, F. Selected wrenches were differed in length and diameter of handle, and weight (Table 1). Table 1. Characteristics of the Socket wrenches Type of socket wrench Handle length  (mm) Handle diameter  (mm) Weight  (gr) A 225.52 25.76 439.77 B 158.30 18.14 240.21 C 235.16 37.82 570.58 D 228.78 18.36 592.08 E 186.68 29/20 348.90 F 185.70 33.56 235.21   A simulated task were designed according to usual usage of wrench users. This task was consist of opening the bolts using 6 types of wrenches. For this purpose, a wooden plate was fitted on a table with 12 fitted bolts and nuts of size 10. All bolts and nuts were fastened on the plate using a torque meter with 8 Nm. The height of task surface was in 95 percentile of elbow height of males (104 cm). However, it was possible to adjust the height of the table with the elbow height of each participant. Participants were asked to stand behind the desk and perform the activity of opening the bolts with each of six wrenches. The order of use of wrenches for each participant was random. The steps of each trial were as follows: steps 1) select the right socket; step 2) attach the socket to the handle; step 3) check turning direction; step 4) open the bolts.Surface Electromyography (SEMG) was applied to record the electrical activity of forearm muscles. The flexing muscle of the fingers and wrist extensor muscles play important role in gripping the wrench handle and using it to perform the simulated task. Therefore, the Flexor Digitorum Superficialis (FDS) and Extensor Carpi Radialis (ECR) muscles were considered for the recording the surface EMG signals. The steps of recording EMG signals were as follows: step 1) finding the flexor digitorum superficialis and extensor carpi radialis muscles on participant’s forearm; step 2) preparing the skin to conncet the electrodes; and step 3) connecting the electrodes. A surface EMG apparatus made by Biometrics Ltd. was used in this experiment. Since the independent (length and diameter of handle and weight of wrench) and dependent variables (EMG signals) were both quantitative, linear regression model was used to examine the relationship between the two quantitative variables and the data were analyzed by SPSS® 21 software. 

The mean of participants’ age, height and weight were 39.95 year, 175.7 cm, and 72.9 kg, respectively. Mean and standard deviation of normalized electrical activity of FDS and ECR muscles are shown in Table 2. Table 2. Mean (SD) of normalized electrical activity of flexor digitorum superficialis and extensor carpi radialismuscles Type of socket wrench Mean (SD) of electrical activity of muscles (mv/s) FDS muscle ECR muscle A 0.45(0.21) 0.47(0.22) B 0.61(0.25) 0.48(0.23) C 0.43(0.23) 0.46(0.24) D 0.55(0.24) 0.45(0.21) E 0.48(0.23) 0.44(0.21) F 0.50(0.22) 0.43(0.22)  The results showed that the lowest level of electrical activity of FDS muscle was belonged to type C wrench, which had the longest handle length and largest handle diameter. On the opposite side, the highest level of electrical activity of FDS muscle was belonged to type B wrench with shortest handle length and smallest handle diameter. Lowest and highest levels of electrical activity of ECR muscle were belonged to type F and B wrenches, respectively.A linear regression test was used to examine the relationship between the electrical activity of Flexor Digitorum Superficialis muscle and the physical parameters of the socket wrenches. The results showed that there is a significant relationship between the electrical activity of FDS muscle and the wrenches’ handle length and diameter (p-value<0.001). Based on regression models, for one millimeter increase in handle length and diameter, the level of electrical activity of the flexor muscles decreased by 0.001 and 0.007 mV, respectively. Simple and multiple regression models showed no significant relationship between the electrical activity of ECR muscle and physical parameters of wrenches (p-value>0.001). Discussion and

In the present study, relationship between three physical parameters (handle length, handle diameter and weight of wrench) of six type of socket wrenches with electrical activity of two important muscles involved in using this hand tool was investigated. The results showed that increasing or decreasing socket wrench length, handle diameter, and weight were associated with changes in the electrical activity level of FDS muscle. However, no relationship found for ECR muscle. The findings showed that lowest and highest muscle force for opening the bolts were applied in using wrench type C (maximum length) and wrench type B (lowest length), respectively.Li (2002) showed that new designs of handle for powered and non-powered hand tools can decrease the unnatural postures, including flexion, extension, radial deviation, and ulnar deviation. He showed that flexor digitorum superficialis and the flexor carpi ulnaris of the right forearm may be significantly reduced when using the new designs of pliers. Dong et al (2006) and Ozawa (2001) reported similar finding. They showed that physical characteristics of hand tools can strongly effect the muscular effort required to work with hand tools used by dentists.The present study showed that there is no significant relationship between the weight of the wrench and the electrical activity level of the Flexor Digitorum Superficialis muscle. This indicates that muscles other than FDS are involved in controlling the weight of hand tool.In power grip tasks (such as working with a wrenches), the handle diameter and length of the tool are important parameters. Therefore, wrenches with a longer handle length and a larger handle diameter provide the lowest level of electrical activity of the FDS muscle to open the bolts. This results to lower levels of muscle fatigue. Therefore, the force required to open the bolts can be reduced by choosing a longer handle and a larger handle diameter (near to optimum diameter). The findings of this study can be used by hand tools manufacturers to improve tool design. Also, differences in the ergonomic characteristics of different types of a hand tool can be well documented using electromyography. The generalization of the findings of this study should be considered to its limitations. In this study, the performance of Flexor Digitorum Superficialis muscle and Extensor Carpi Radialis muscle were recorded for a short time task. Therefore, the level of muscle fatigue that occurs in participants may vary in actual and long-term conditions. Also, the effect of roughness and softness of the handle on the grip power and electrical activity of the muscles were not examined in this study. Thus, it is suggested that the effect of this variables along with other physical factors be investigated in future studies.

 Hand anthropometric data can help us properly design hand tools for better efficiency and less fatigue in the individuals. The aim of this study is to measure and analyze hand anthropometric data of Iranian farmers in order to determine the characteristics of farmers' hands separately for each ethnicity so that they can be used to design hand tools and working stations. In order to design the appropriate hand tools, 8 dimensions were measured in Iranian farmers. This study was conducted by measuring the hand dimensions of 600 farmers in four ethnicities of Lor, Kurd, Arab, and Fars in Iran and comparing them with each other, as well as other countries which have measured their employees' hand dimensions to design hand tools appropriate for their countries.Results showed that the mean length of hand (19.82±1.53), hand metacarpal width (9.47±1.59), hand width to thumb tip (11.81±1.33), and hand metacarpal thickness (2.78±0.29) in Kurds ethnicity; palm length  (10.82±0.84) in Arab ethnicity; and index finger diameter (2.40±0.39) and hand circumference (28.71±1.51) in Fars ethnicity were the greatest values. The results of comparison made between hand dimensions and those of other countries showed that the Iranian metacarpal hand width is larger than countries such as India, northern Nigeria, and Jordan. In addition, the hand thickness of Nigerian people is greater compared to Iranians'. These findings can help interior designers be able to design appropriate hand tools that cause a reduction in ergonomic problems in domestic farmers.

There are various models of socket wrench in the market varying in the length and diameter of handle and weight. Each of these features alone can modify the force applied by the hand and affect how comfortable the user is. The purpose of this study was to investigate the relationship between dimensional properties and weight of several models of socket wrench with their usability index score.  

58 male technicians from maintenance units of Shahid Beheshti University of Medical Sciences performed the task of opening 12 bolts with 8 N/m of torque using 6 models of socket wrench with different physical properties. The sample size was selected based on proposed figures for usability studies.  The System Usability Index (SUS) validated questionnaire was used to determine the usability score of each model after the experiment. The study was conducted in 2017. SPSS 21 was used for data analysis.

The results showed that there was a significant relationship between usability index score and dimensional properties and weight of wrenches (P<0.001). Wrench models with longer handle and diameter size close to optimum range of diameter of hand tools for male users had a higher usability score, and participants reported a better test experience with these models.

Using the System Usability Index (SUS Questionnaire) to measure the quality of human-centered design of hand tools is a good way to evaluate and select the hand tools that are widely used by technical staff. The results of this study are valid for short-term applications of wrenches. However, for long time activities, epidemiological and physiological evidences such as EMG should also be used.
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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).
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.
The results showed significant effect of handle shape on user performance (p 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.

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.
The first model 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 observational method.
The results showed significant effects of scissors design on pinch force exertions (p 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.

In our daily lives hand tools are often used in many work situations. With respect to design characteristics, hand tools can be considered a risk factor when a high level of repetition are required or when awkward postures are adopted. Therefore attention to ergonomics design rules for hand tools is the most important factor in design process. With this in mind, the aim of the present study is to evaluate a new model of home stripper which designed based on ergonomics rules. Ten healthy female subjects participate in this study. Seven tests were considered for each subject. The subject was instructed to strip a cucumber using six commercial models as well as with a new model, separately. The surface electromyography (EMG) signals were recorded from three muscles: biceps brachii, triceps brachii, and flexor digitorum. To make possible the comparison between models in all experiments varied between the subjects, the raw EMG signals was normalized. For biceps brachii muscle, the analysis of variance revealed that there was no significant difference on the mean EMG data among all models, however muscular activity for the new model of stripper was found lower than the other models. The results indicated that the changes among the mean EMG data of models for triceps brachii, and flexor digitorum muscle were found significant. Tukey tests shows that differences between the EMG data for the new model with one commercial model were significant. A new model with commercial models of stripper was tested to evaluate the effects of design characteristics on EMG signals. The results of this study show that muscular activity is mostly related to specific design of hand tools considering form, shape and product design aspects.