Abstract
BACKGROUND:
An in-depth evaluation of user hand tool interaction aids to derive strenuous areas for redesigning.
OBJECTIVE:
In this paper, we examined user perception about the hand tool features and derived features that exert an influence on human system. This nature of study aids to reduce the risk and enhance the comfort.
METHODS:
Workers from six occupational groups participated in the study. Ergonomic checkpoints pertaining tool features and a general health questionnaire that included musculoskeletal discomforts, stress symptoms and general health complaints were administered to check user’s interaction with hand tools.
RESULTS:
Risk estimates identified varied factors such as weight of tool, improperly designed handle and sharp edges associated with workers risk to pain in upper extremities, anxiety and injury. The workers’ response indicated that handle redesign and protection against sharp-edged tools are crucial for improving comfort.
CONCLUSION:
The study aims to provide an approach to examine the characteristics of tools for redesign and increase user’s comfort and safety.
Introduction
In comparison to the developed countries, workers in developing countries get exposed to severe ergonomic stressors and thereby are at a higher risk for health hazards. Hand tools are a major part of work practice in occupations such as agriculture, metal workshops, automobile repair shops, fish processing, construction, textile, tobacco processing, manufacturing industries, assembly plants and others [1–4]. Tool characteristics such as size and weight [5], shape [6], blade properties [7] and handle type [8] exert an influence on the human system. Tools exert an influence on user’s physiological parameters such as muscle activity [4], biomechanical parameters such as force exertion, torque and contact pressures [6, 9] and subjective perceptions such as comfort [10]. After prolonged use of inappropriately designed tools, workers experience fatigue [4], cumulative trauma [6], pain and discomforts in the upper extremities [11], injuries [12], workplace accidents [4] and stress [13].
In India, use of improperly designed tools has been associated with health hazards in construction [14], automobile repair [15], fish processing[16] and weaving [17]. The literature builds a premise that varied tools employed in the Indian industrial workplace can exert an influence on the human system. There is a lack of an in-depth study, which focuses on tool characteristics and strenuous features. The current study aims [1] to make an ergonomic evaluation of tool characteristics and [2] To examine possible interaction of strennous characteristics with the users.
Methods and materials
User population
Workers from six different occupations namely powerloom weaving (N = 225), handloom weaving (N = 291), construction (N = 51), automobile repair (N = 151), tobacco processing (N = 450) and fish processing (N = 263) participated in the study (Fig. 1). In Indian unorganized sectors, work is done manually by repetitive use of tools.
Tools employed at workplaces and tasks accomplished with the tools
Powerloom weaving
Workers use varied tools such as brush to remove fibers, comb for packing the wefts, hook to drag threads through the reed, wooden shuttle wrapped with threads and scissors/cutters to trim the extra yarn and thread.
Handloom weaving
Workers run the looms manually and use tools similar to powerloom.
Construction
The job profiles of workers were pipe laying, plumbing masonry, tiles fitting, flooring and glass fitting. They employed tools such as spade, trowel, saw, shovel, hammer, drilling tool, jaws, spencer, and others.
Automobile repair
Repair workers do varied tasks such as check vehicle to find out nature, extent and place of defects, plans work, dismantling, transmission, repairing, cleaning, washing, polishing, spray painting, denting, replacing parts, relining and adjusting brakes, soldering, rebushing steering mechanism and carrying out other repairs, tuning motor by adjusting ignition, carburetor, valves and timing mechanism; testing repaired vehicles in workshop or on road. Workers use tools such as hammer, wrench, sledges, punch, snips, screwdrivers, pliers, brushes, clamps and others to do the varied tasks.
Fish processing
Fish processing workers perform tasks such as [1] packing the fishes in boxes; [2] for shrimp, lobsters, squid and other fishes, shells and skins peeled and sliced, tentacles and heads and packed in different sizes; [3] hardening the squids and cutting into rings, using sharp knives; [4] processing for ready-to-cook products, including individual quick freezing; [5] packing and transferring to cold storage, and after dispatching to consignments. Workers use varied tools such as knives, scissors, and others for fishprocessing.
Tobacco processing
Tools such as scissors to cut the leaves, blade to remove the veins, metal plate for measuring leaves and blades to cut into proper sizes were in use in tobacco processing.
Tool checklist
The subjects responded to a section about tools from a multi-method ergonomic checklist [18]. We included the strenuous tool features such as feasibility to use with alternate hands, heavy weight, inappropriate form and place of handle, sharp-edged and noise driven tool in the checklist. We asked the workers do you agree or disagree with following attributes about your tools at the workplace (1)Tool/implement has no carrying strap/back frame (2) Tool cannot be used with either hand (3) Heavy weight of the tool causes hyperextension of the wrist (4) Form and place of the handle are not designed for convenient grip (5) Power-driven tool is not designed for two-hand operation (6) Sharp edges/ridges of the tool/equipment may cause injury. Subjects responded to the checklist entries by a single digit score, on a five common severity agreement disagreement scale –strong disagreement [1] to strong agreement [5] suggesting that a low score is the positive indicator for absence of a problem. When the response was 3, 4 or 5 by users in the checklist items, the feature as strenuous. The strenuous feature was then coded as 1 and 0 for absence of stress.
Health and stress symptoms
A general health and demographic questionnaire was introduced among the workers. We asked the workers whether they had an experience of the health hazards due to hand tools they employed at work. The questionnaire covered varied health risks such as (1) injury, (2) musculoskeletal pain and discomforts in different body regions (3) stress symptoms [somatic and cognitive anxiety and chronicfatigue].
The question pertaining to injury was Did you experience an injury in the last year?
The prevalence of muscle-skeletal discomforts in the last twelve months were recorded with a questionnaire on musculoskeletal pain and discomforts [19]. The pain was recorded in eleven regions [upper back, lower back, hand, shoulder, neck, foot, palm, elbow, wrist, fingers and knee] of the body.
In addition, stress dimensions such as the somatic and cognitive anxiety Schwartz et al., [20] (physiological and psychological state of anxiety) and chronic fatigue (characterized by exhaustion, impaired sleep, lethargic and feeling of drained) were assessed [21].
Statistical analysis
Data analysis was performed using SPSS statistical software, version 16.0. The normality of data was checked by Kolmogorov-Smirnov Test with Lilliefor’s correction and the distribution of the data for most variables was found to be normal with p > 0.05 for all the variables. The reliability co-efficient for internal consistencies [Cronbach’s alpha] of the ergonomics checklists were examined and the alpha values [0.8] indicated adequate reliability. We calculated the prevalence of strenuous tool features for each occupational group. We calculated the relative risk estimates for examining the association of strenuous tool characteristics with occurrence of injury, musculoskeletal pain and discomforts and stress symptoms. The dependent variables were pain in eleven body regions, injury and stress symptoms [chronic fatigue, somatic anxiety and cognitive anxiety] and independent variables were tool characteristics.
Demographic of the worker’s population
We examined the hand tool interaction between users of six workgroups. Demographic details of the selected user population is given in Table 1. Almost all workers were relatively young. Workers employed in all the occupations except fish processing had more than or equal to ten years of experience. On an average weavers and tobacco processing workers had been in the occupation for around 20 years. Fish processing workers had spent an average of 3 years in the industry. Almost all the workers in different occupational groups worked for equal to or more than eight hours per day. Workers in tobacco processing worked for 7 hours and fish processing for 12 hoursdaily.
Results
Workers perception about tool characteristics
Workers perception about the tool’s characteristics has been shown in Fig. 2. The results indicated that construction workers perceived their tools as more strenuous compared with workers in other occupations. Amongst the weavers (handloom and powerloom), inability to use tools with alternate hands (67 and 55%), sharp edged tools (48 and 40%) and inappropriate back of tools (39 and 30) were perceived strenuous. In construction workers, sharp edges (77%), inability to use with alternate hands (75%), back of the handle (68%) and weight of the handle were reported strenuous. In automobile repair, inappropriate back of the tool (24%), heavy weight of tools (25%), inability to use tools with alternate hand (25%) and sharp edges of the tool (27%) were perceived as strenuous. In fish processing work, inability to use with alternate hands (65%), sharp edges (50%), and form and position of tools were reported to be strenuous. Amongst the tobacco processing workers, inability to use tools with alternate hands (80%), sharp edged tools (58%), inappropriate back of tools (48%) and handle of tools (24%) were strenuous.
Interaction of tools with human system
The relative risk estimates of tool characteristics and their interaction with the human system is given in Table 2.
Powerloom weaving
Inappropriate back of tools were associated with workers risk to injury (OR1.6, p < 0.05), fatigue [OR1.6, p < 0.001] and stress symptoms such as somatic anxiety (OR2.1, p < 0.01). Inability to use tools with alternate hands was associated with worker fatigue (OR1.4, p < 0.05). An inappropriate form of the handle was associated with the risk to develop chronic fatigue (OR1.7, p < 0.0001) and somatic anxiety (OR2.3, p < 0.01). Sharp edges of the tool were associated with workers risk to injury (OR1.7, p < 0.05) and chronic fatigue (OR1.9, p < 0.05).
Handloom weaving
Inability to use tools with alternate hands was associated with somatic anxiety (OR2.0, p < 0.01).
Construction
Tools with an inappropriate back were associated with risk for pain in the upper back (OR1.3, p < 0.005). Heavy weight of tools were associated with risk to pain in the lower back (OR4.5, p < 0.03). Inappropriate form and position of handle was associated with cognitive anxiety (OR10.8, p < 0.01).
Automobile repair
Inappropriate handle of the tool was associated with workers risk to pain in the fingers (OR4.5, p < 0.01). Heavy weighted tools was associated with workers risk to injury (OR3.1, p < 0.05), pain in the hands (OR3.4, p < 0.004) and pain in fingers (OR2.8, p < 0.05). Inability to use tools with alternate hands was associated with workers risk to pain in hands (OR2.3, p < 0.05) and fingers(OR4.2, p < 0.01) and injury (OR2.3, p < 0.05). Inappropriate form and position of handle was associated with workers risk of injury (OR7.2, p < 0.0001)and pain in the hand(OR3.3, p < 0.05).
Fish processing
Mismatched handle of the tool handle was associated with risk for pain in the hands (OR2.2, p < 0.05) and fingers (OR3.3, p < 0.01). Inability to use with alternate hands was associated with pain in the neck (OR2.3, p < 0.05) and hands(OR1.8, p < 0.01). Heavy weight of tools was associated with pain in the fingers (OR2.9, p < 0.05). Inappropriate grip of the tools was associated with pain in lower back (OR2.6, p < 0.05), fingers (OR3.4, p < 0.05) and injury (OR2, p < 0.05).
Tobacco processing
Inappropriate back of the tool was associated with development of pain in the neck (OR1.7, p < 0.003) and cognitive anxiety (OR1.5, p < 0.029). Inability to use tools with alternate hands was associated with workers risk for chronic fatigue (OR2.2, p < 0.05) and stress symptoms such as somatic anxiety (OR2.3, p < 0.05). Heavy weight of the tools was associated with workers risk for chronic fatigue (OR2.7, p < 0.05), cognitive anxiety (OR3.0, p < 0.05) and somatic anxiety (OR3.3, p < 0.05). Inappropriate form and position of tool handle was associated with the risk for pain (OR1.5, p < 0.05). Sharp edged tools was associated with risk for injury (OR1.7, p < 0.05).
Discussion
Several characteristics of hand tools such as handle size [22], shape [23], surface [24, 25] and texture [26] need to be considered in hand tool design. Researchers have reported that injuries to the soft tissue, wrists, and median nerve are common among workers exposed to improperly designed tools [27–30]. The study attempted to look at the workers perception of tool characteristics and find characteristics associated with their risk to varied health complaints.
In these occupations there is use of tools such as knives, hammers, spades, etc. and repetitive tool application. When tasks require repetitive arm movements, hand-held weights are known to induce fatigue [31]. Hand muscles are sensitive to increases in handheld weight and raised arm positions [32]. Workers who perceived their tools as heavy weighted were at risk to pain in finger [fish processing], hands and fingers [automobile repair shops] and lower back [construction]. Heavy weighted tools and their use require to apply a force which increases user’s risk to pain and discomforts in different body regions [33, 34]. Thereby tools impose strain on users and increase their risk of developing pain and discomforts in different body regions.
The handles exert a significant effect on the muscular load and force applied [35]. Improperly designed handles associated with workers risk to pain in hand (automobile repair workers.), hands and fingers (fish processing), and anxiety symptoms (weavers powerloom and handloom). When the material used in tools does not give the users with appropriate grip and comfort, upper extremities bear contact stress, causing injury to the soft tissue. The handle of the tools can be coated with soft material to reduce the user’s injury. Studies done by Merlino et al. [35], Aghaadeh and Mital [12] and Armstrong [36] has reported that work-related musculoskeletal discomforts associated with inadequately designed hand tools Merlino et al., [35] and their intensive use [12, 37]. For most of the tools, the handles were straight which forced the workers to bend their wrist. In order to overcome this trouble, handles of the certain tools such as pliers could be bent to limit the wrist deviations and make sure straight wrist for horizontal application of force. The improper grip of tool handles was associated with workers risk to pain in lower back and fingers (fish processing), anxiety (automobile repair, power loom and handsome weaving) and chronic fatigue (power loom weaving). Due to the bad design and inappropriate material in tool handles, hands and fingers bear contact stress, which causes injury of hand soft tissue. Grip on tools can be improved by exploring the materials which could improve the handling ability and reduce the contact stress. The handle design can be improved by changing the diameter, material and the angle of the tool [38].
Sharp edge of tools associated with risk of injury in fish processing, tobacco processing and weaving. This nature of increased injury risk has been reported by Lander et al. [38] and Sorock et al. [39]. In our study, workers used tools with bare hands and this increased injury risk. With a sharp edge tools, donning gloves can reduce user’s injury risk considerably [40]. By designing knife with finger guards can be provided to users. However, users in this work group do not have the resources and accessibility to personal protective equipment such as gloves.
In our study, varied tool features increased workers risk to stress symptoms such as anxiety (somatic and cognitive) and chronic fatigue. When workers work with improperly designed tools, they perceive that the strenuous tool features are barriers to their task. These perceptions lead to stress development and associates with psychosomatic symptoms such as anxiety and other emotional stress symptoms [40].
The study derives an approach for considering user’s perception about the tools at workspaces and explains the influence of tools characteristic on human system. The study finds that hand tool redesigning needs a comprehensive approach with consideration of the tasks, work scenario and postures adopted when tools are in use by workers. The results of this study can give designers an insight on the specific areas and tool features which are of concern in user’s safety and well-being.
Limitations
There are few studies with similar methodological approach to derive an interaction between tools and users, thereby subjects with a similar background characteristics were not available to compare the results. Data on being injured and other health hazards were based on self-report, which could not be verified by an independent medical practitioner and physiological examination. This might be a source of information bias. This is a cross-sectional study and cautions must be taken to make inferences about observed associations. Relative risk estimates have proved useful in providing cause effect relationships. These responses may have biased, but the subjective perception of users is taken to study interactions in the recent studies done by the other researchers.
Conclusion
The study attempted to find the tool characteristics that can exert an influence on the human system. The tool features were found associated with risk to musculoskeletal discomforts, stress and injury. Redesigning tools need to consider worker’s perception about strenuous tool features. Designers must consider tool characteristics such as size, shape, weight, handle, form and grip of handle for enhancing users comfort. This will make sure the safety and comfort of workers.