Identifying factors of comfort in using hand tools

Measuring Labor Input: Construction Activity Counting Using IMU on Hand Tools

Efficient measurement of labor input is a critical aspect of on-site control and management in construction projects, as labor input serves as the primary and direct determinant of project outcomes. However, conventional manual inspection methods are off-line, tedious, and fail to capture their effectiveness. To address this issue, this research presents a novel method that leverages Inertial Measurement Unit (IMU) sensors attached to hand tools during construction activities to measure labor input in a timely and precise manner. This approach encompasses three steps: temporal-spatial feature extraction, self-similarity matrix calculation, and local specific structure identification. The underlying principle is based on the hypothesis that repetitive use data from hand tools can be systematically collected, analyzed, and converted into quantitative measures of labor input by the automatic recognition of repetition patterns. To validate this concept and assess its feasibility for general construction activities, we developed a preliminary prototype and conducted a pilot study focusing on rotation counting for a screw-connection task. A comparative analysis between the ground truth and the predicted results obtained from the experiments demonstrates the effectiveness and efficiency of measuring labor input using IMU sensors on hand tools, with a relative error of less than 5%. To minimize the measurement error, further work is currently underway for accurate activity segmentation and fast feature extraction, enabling deeper insights into on-site construction behaviors.

Exploring the importance of a usable and emotional product design from the user's perspective

Usability and emotionality are important components of user experience. However, an equal consideration of both constructs in product design is not always possible due to sometimes competitive objectives. In order to foster a user-oriented design decision in such conflicting situations, this paper examines the general importance of both constructs and their dimensions from the user's perspective while taking into account socio-demographic variables. Examination was realised by conducting a product independent anonymous online survey (n = 130). The findings confirm that both constructs are important, yet in a direct comparison, usability is perceived as more important than emotionality. Taking selected dimensions of both constructs into account, an intuitive, easy and learnable usage, suitability for the user's task and freedom from impairment are particularly important in terms of usability. An aesthetic and pleasurable product design as well as originality is essential in terms of emotionality.Practitioner summary: This paper aims for supporting user-oriented design decisions in the context of conflicting objectives occurring in the consideration of usability and emotionality in product design. The conducted survey (n = 130) revealed usability as perceived more important than emotionality. Usability may thus be prioritised within conflicting design decisions.Abbreviations: DFG: German Research Foundation; e.g.: for example; GESIS: Leibniz Institute for the Social Sciences; m: metric; M: Mean; n: number of participants; n: nominal; o: ordinal; p level: level of statistical significance; RQ: Research question; r: correlation coefficient; V: Cramer's V; χ²: Chi-square.

How to implement inclusive design into distinctive feature hand tool? a design study on fine operation-aid screwdriver

Hand tool design should integrate the concept of Inclusive Design to be accessible to most users. However, current Inclusive Design strategies of product development are mostly used in post-design evaluation. The retention of inclusive properties in product when new functions are incorporated is essential. Fine operation-aid screwdrivers are designed according to user requirements to address frequently-encountered problems when using screwdrivers namely-insufficient lighting and difficulty in properly installing screws respectively. TRIZ method is applied, comprised the improving parameters solving the problems and worsening parameters which prevents the original inclusive design factors from being damaged into the contradiction matrix, and obtains a set of innovation principles. Eight experts were consulted for their design ideas and developed two fine operation-aid screwdrivers embracing the concept of Inclusive Design. Furthermore, factors regarding the two major operating problems were added to an existing hand tools Inclusive Design Scale. After correlation analysis, the inclusive fine operation-aid screwdriver evaluation scale was established. In addition, two more screwdrivers were selected with the same functions and high reviews on the market as control samples, and 39 users were recruited using a quota sampling strategy to participate in Inclusive Design evaluations. The results revealed that the fine operation-aid screwdrivers evidently solved the two major operating problems in terms of the five dimensions including functionality, comfort, professionality, safety, and usability in the inclusive fine operation-aid screwdriver evaluation scale, thereby affirming the rationality and reliability of our hand tool development approach.

Custom-Fitted In- and Around-the-Ear Sensors for Unobtrusive and On-the-Go EEG Acquisitions: Development and Validation

OBJECTIVES

This paper aims to validate the performance and physical design of a wearable, unobtrusive ear-centered electroencephalography (EEG) device, dubbed "EARtrodes", using early and late auditory evoked responses. Results would also offer a proof-of-concept for the device to be used as a concealed brain-computer interface (BCI).

DESIGN

The device is composed of a custom-fitted earpiece and an ergonomic behind-the-ear piece with embedded electrodes made of a soft and flexible combination of silicone rubber and carbon fibers. The location of the conductive silicone electrodes inside the ear canal and the optimal geometry of the behind-the-ear piece were obtained through morphological and geometrical analysis of the human ear canal and the region around-the-ear. An entirely conductive generic earpiece was also developed to assess the potential of a universal, more affordable solution.

RESULTS

Early latency results illustrate the conductive silicone electrodes' capability to record quality EEG signals, comparable to those obtained with traditional gold-plated electrodes. Additionally, late latency results demonstrate EARtrodes' capacity to reliably detect decision-making processes from the ear.

CONCLUSIONS

EEG results validate the performance of EARtrodes as a circum-aural and intra-aural EEG recording system adapted for a wide range of applications in audiology, neuroscience, clinical research, and as an unobtrusive BCI.

A model-based approach for the analysis of aircraft seating comfort

BACKGROUND

Aircraft seating comfort has a significant impact on passenger on-board experience. Its assessment requires the adoption of well-designed strategies for data collection as well as appropriate data analysis methods in order to obtain accurate and reliable results.

OBJECTIVES

This paper focuses on the assessment of aircraft seating comfort based on subjective comfort responses collected during laboratory experiments and taking into account seat features and passenger characteristics.

METHODS

The subjective comfort evaluations have been analyzed using a model-based approach to investigate the relationship between overall seating comfort and specific seat/user characteristics.

RESULTS

The results show that the overall seating comfort perception is significantly influenced by the thickness of the seat pan, the backrest position (upright or reclined), the age of the passenger and the passenger perception of being comfortably supported at the lumbar region.

CONCLUSIONS

The adopted model-based approach allows the analysis of subjective seating comfort data taking into account their ordinal nature as well as the dependency between evaluations provided by the same subject.

Forearm muscular strength and performance fatigability in orthopaedic surgeons when performing bone screw fixations

This study investigated the muscle strength and performance fatigability of the forearms in eight male orthopaedic surgeons when performing bone screw fixations. Each surgeon performed an eight-bone screws operations in a porcine femur model to simulate fractural fixation using plating technique. The pre- and post-fatigue maximum isometric forces and corresponding electromyography responses were measured to assess the forearm muscle strength loss and fatigue due to screwing. Results showed that after eight bone screws were inserted, the maximal grip force, maximal driving torque and maximal push force losses were approximately 29%, 20% and 23%, respectively. While the grip force and/or driving torque acting, both the brachioradialis and extensor carpi ulnaris had a higher percentage change of EMG than the biceps brachii. The driving forces decreased with the number of screw insertions; however, the insertion time increased parabolically with the number of screws and significantly decreased the insertion rate of the screws, indicating that forearm muscle fatigue may occur in surgeons who treat fracture fixation using more than eight bone screws.

Integrating and applying models of comfort

This paper gives an overview of the relevance of the comfort concept, its definitions, boundary conditions, and stakeholders. Current comfort theories are presented and reflected on, both in their applicability and testing methodology. Questionnaires commonly used to study comfort and discomfort are also reviewed. An example of a comfort lab is introduced in its functionality and tools, which can be useful as a benchmark for others studying comfort.

Learning and Comfort in Human–Robot Interaction: A Review

Collaborative robots provide prospective and great solutions to human–robot cooperative tasks. In this paper, we present a comprehensive review for two significant topics in human–robot interaction: robots learning from demonstrations and human comfort. The collaboration quality between the human and the robot has been improved largely by taking advantage of robots learning from demonstrations. Human teaching and robot learning approaches with their corresponding applications are investigated in this review. We also discuss several important issues that need to be paid attention to and addressed in the human–robot teaching–learning process. After that, the factors that may affect human comfort in human–robot interaction are described and discussed. Moreover, the measures utilized to improve human acceptance of robots and human comfort in human–robot interaction are also presented and discussed.

A novel anatomical woodworking chisel handle

A novel anatomically shaped ("anatomical") woodworking chisel handle was developed for wood scraping operation. 18 students participated in an evaluation study to compare the new handle against seven readymade handles of ¾-inch bench chisels in the context of a standard wood scraping task. A comfort questionnaire for hand tools (CQH) and a hand-based pain map were used for evaluating and comparing the handles. 'Functionality' and 'sweating' were found to be the most and least important comfort concerns, respectively. Maximum pain was reported at distal digit 1, and least pain at proximal digit 4. The anatomical handle was rated best for most of the comfort descriptors, least painful for most hand regions and took the least time for a standardized task.

The relation between patient discomfort and uncompensated forces of a patient support device for breast and regional lymph node radiotherapy

Although many authors stated that a user-centred design approach in medical device development has added values, the most common research approach within healthcare is evidence-based medicine, which tend to focus on functional data rather than patient wellbeing and comfort. End user comfort is well addressed in literature for commercial products such as seats and hand tools but no data was found for medical devices. A commercial patient support device for breast radiotherapy was analysed and a relation was found between discomfort and uncompensated internal body forces. Derived from CT-images, simplified patient free-body diagrams were analysed and pain and comfort evaluated. Subsequently, a new patient position was established and prototypes were developed. Patient comfort- and prototype optimization was done through iterative prototyping. With this approach, we were able to compensate all internal body forces and establish a force neutral patient free-body diagram. This resulted in comfortable patient positioning and favourable medical results.

Driving comfort, enjoyment and acceptance of automated driving - effects of drivers' age and driving style familiarity

Automated driving has the potential to improve the safety and efficiency of future traffic and to extend elderly peoples' driving life, provided it is perceived as comfortable and joyful and is accepted by drivers. Driving comfort could be enhanced by familiar automated driving styles based on drivers' manual driving styles. In a two-stage driving simulator study, effects of driving automation and driving style familiarity on driving comfort, enjoyment and system acceptance were examined. Twenty younger and 20 older drivers performed a manual and four automated drives of different driving style familiarity. Acceptance, comfort and enjoyment were assessed after driving with standardised questionnaires, discomfort during driving via handset control. Automation increased both age groups' comfort, but decreased younger drivers' enjoyment. Younger drivers showed higher comfort, enjoyment and acceptance with familiar automated driving styles, whereas older drivers preferred unfamiliar, automated driving styles tending to be faster than their age-affected manual driving styles. Practitioner Summary: Automated driving needs to be comfortable and enjoyable to be accepted by drivers, which could be enhanced by driving style individualisation. This approach was evaluated in a two-stage driving simulator study for different age groups. Younger drivers preferred familiar driving styles, whereas older drivers preferred driving styles unaffected by age.

Measuring customer experience in physical retail environments

Purpose

In a world where customer empowerment is continuously increasing and changing the service landscape, retailers must provide memorable shopping experiences to retain and attract new customers. When customers decide to go shopping in physical stores, they expect to enjoy their visit, experiencing cognitive, affective, social, and physical responses evoked by in-store stimuli. The purpose of this paper is to propose and validate a scale to measure in-store customer experience (ISCX).

Design/methodology/approach

This study’s theoretical review of customer experience (CX) demonstrates that a formative model provides the best structure for measuring the construct ISCX. Furthermore, the study follows the guidelines for rigorous construction of a formative scale, which include three main stages: generation of items, scale purification, and assessment of scale validity and reliability.

Findings

The results provide evidence that a formative third-order scale with a reflective second-order dimension (social experience) and three reflective first-order dimensions (cognitive, affective, and physical experience) has satisfactory psychometric properties. The findings also provide useful information on the effect of the ISCX scale on key performance variables such as satisfaction and loyalty to the store.

Originality/value

The ISCX scale proposed constitutes a useful multi-concept diagnostic tool for use by retailers to create fully experiential shopping environments with differential value for the customer. By providing a complete, robust, precise measure of CX in a retail environment, the scale gives researchers a structured way to examine the causes and consequences of CX in retail.

Non-powered hand tool improvement research for prevention of work-related problems: a review

PURPOSE

In lower-middle-income countries, most of the work is performed manually using non-ergonomic hand tools which results in work-related health problems. Using hand tools designed in line with ergonomic principles may play an important role in reducing work-related health concerns significantly.

METHODS

Scientific databases (PubMed, EBSCOhost) and e-publishers were searched for articles from 1985 to 2015 using the following keywords: 'hand tool', 'ergonomics', 'usability' and 'design'. After applying selection criteria to 614 articles, 58 articles related to the physical design of hand tools were selected.

RESULTS

Seventeen articles were related to hand tool improvement in the manufacturing sector. Musculoskeletal disorders were found to be the most frequently occurring work-related health problems. Most of the articles focused on product and qualitative variables for improvement in hand tools, while few articles considered human and task variables.

CONCLUSIONS

Literature shows that hand tool improvement studies have been given less importance in low-income and lower-middle-income countries. However, some work of significance is reported in the agriculture sectors of these countries. Hence, it is concluded that ergonomic intervention in hand tools is much needed for those industries which employ traditional methods of working.

Using archetypes to create user panels for usability studies: Streamlining focus groups and user studies

Designers at the conceptual phase of products such as headphones, stress the importance of comfort, e.g. executing comfort studies and the need for a reliable user panel. This paper proposes a methodology to issue a reliable user panel to represent large populations and validates the proposed framework to predict comfort factors, such as physical fit. Data of 200 heads was analyzed by forming clusters, 9 archetypal people were identified out of a 200 people's ear database. The archetypes were validated by comparing the archetypes' responses on physical fit against those of 20 participants interacting with 6 headsets. This paper suggests a new method of selecting representative user samples for prototype testing compared to costly and time consuming methods which relied on the analysis of human geometry of large populations.

Aircraft passenger comfort experience: underlying factors and differentiation from discomfort

Previous studies defined passengers' comfort based on their concerns during the flight and a set of eight experiential factors such as 'peace of mind', 'physical wellbeing', 'pleasure', etc. One Objective of this paper was to determine whether the factors underlying the passengers' experience of comfort differ from those of discomfort. Another objective was to cross-validate those factors. In the first study, respondents provided written reports of flight comfort and discomfort experiences separately and gave ratings on the impact of the eight factors on each experience. Follow up interviews were also conducted. Significant difference was found between comfort and discomfort ratings for two factors of 'pleasure', denoted by one's concern for stimulation, ambience and exceeded expectations, and 'physical wellbeing' characterized in terms of bodily support and energy. However, there were no significant differences between the comfort and discomfort ratings on the other six factors. The evidence does not support the proposition that passenger comfort and discomfort are underline by different sets of factors. It is therefore suggested that the evaluation of overall passenger comfort experience, as a whole, employ one spectrum ranging from extreme comfort to discomfort. In study two, a pool of comfort descriptors was collected. Those that were less relevant to passenger comfort were eliminated in a number of steps. Factor analysis was used to classify the remaining descriptors, using respondents' ratings on their potential impact on passenger comfort. Seven factors corresponded to the pre-determined passenger comfort factors from previous research, validating those with an exception of 'proxemics' (concerning one's privacy and control over their situation) but it was argued that this is due to the nature of the factor itself, which is context dependent and generally perceived unconsciously.

Ergonomics and comfort in lawn mower handle positioning: An evaluation of handle geometry

Hand operation accompanied with any combination of large forces, awkward positions and repetition may lead to upper limb injury or illness and may be exacerbated by vibration. Commercial lawn mowers expose operators to these factors during actuation of hand controls and therefore may be a health concern. A nontraditional lawn mower control system may decrease upper limb illnesses and injuries through more neutral hand and body positioning. This study compared maximum grip strength in twelve different orientations (3 grip spans and 4 positions) and evaluated self-described comfortable handle positions. The results displayed force differences between nontraditional (X) and both vertical (V) and pistol (P) positions (p < 0.0001) and among the different grip spans (p < 0.0001). Based on these results, recommended designs should incorporate a tilt between 45 and 70°, handle rotations between 48 and 78°, and reduced force requirements or decreased grip spans to improve user health and comfort.

Ergonomic evaluation of the operating characteristics of the 6MF-30 portable pneumatic extinguisher

The 6MF-30 portable pneumatic extinguisher, which is one of the most widely used pieces of equipment for fighting forest fires in China, can produce great physical discomfort for the wearer. To mitigate the physical discomfort associated with the use of the 6MF-30, the operating characteristics of this machine were ergonomically evaluated. Fourteen subjects were instructed to operate the 6MF-30 portable pneumatic extinguisher using three different carrying postures (oblique strap, vertical strap and no strap) two different motions (stationary and swinging) during a simulated firefighting task. Dependent measures included heart rate (HR), electromyography (EMG) data and a subjective assessment (measured as the degree of fatigue in the left arm, right arm and waist). The EMG data were acquired from the palmaris longus and the biceps brachii of the left arm of each subject. Variance analysis indicated that the effects of the carrying posture on the HR (p < 0.001), the EMG data of the left arm (the p value of the palmaris longus is 0.001 and the p value of the biceps brachii is 0.015), and the degree of fatigue of the left and right arms (p < 0.001) were significant, while the effects of motion on all of the dependent measures, and the effects of carrying posture on the degree of fatigue of the waist were not significant. The effect of an oblique strap on the whole-body load is minimal, and the use of the equipment without a strap produced significantly greater physical discomfort for the wearer than did the oblique strap and the vertical strap. The results suggest that the strap of the 6MF-30 can help Chinese forest firefighters to lessen physical stress when operating the 6MF-30, and the use of the oblique strap should be adopted as the standard position.

Objective classification of performance in the use of a piercing saw in jewellery making

Data from 15 jewellery students, in their 1st and 3rd years of training, were analysed to show how data collected from work settings can be used to objectively evaluate performance in the use of tools. Participants were asked to use a piercing saw to cut 5 lines in a piece of metal. Performance was categorised in terms of functional dynamics. Data from strain gauges and a tri-axial accelerometer (built into the handle of the saw) were recorded and thirteen metrics derived from these data. The key question for this paper is which metrics could be used to distinguish levels of ability. Principal Components Analysis identified five components: sawing action; grasp of handle; task completion time; lateral deviation of strokes; and quality of lines cut. Using representative metrics for these components, participants could be ranked in terms of performance (low, medium, high) and statistical analysis showed significant differences between participants on key metrics.

Practicing universal design to actual hand tool design process

UD evaluation principles are difficult to implement in product design. This study proposes a methodology for implementing UD in the design process through user participation. The original UD principles and user experience are used to develop the evaluation items. Difference of product types was considered. Factor analysis and Quantification theory type I were used to eliminate considered inappropriate evaluation items and to examine the relationship between evaluation items and product design factors. Product design specifications were established for verification. The results showed that converting user evaluation into crucial design verification factors by the generalized evaluation scale based on product attributes as well as the design factors applications in product design can improve users' UD evaluation. The design process of this study is expected to contribute to user-centered UD application.

Finite element evaluation of the effect of fingertip geometry on contact pressure during flat contact

Several studies investigated the mechanical loads developing in the hands during the use of various products in order to enhance user's performance, increase satisfaction and lower the risk of acute and cumulative trauma disorders. Values of pressure discomfort (PDT) and pressure-pain threshold (PPT) were, hence, provided. PDT and PPT may differ significantly for each subject and area of the hand because of psychological and physiological factors. A finite element study of the effect of fingertip anthropometry and anatomy geometry on mechanical loads developed during grasping is carried out in this research in order to assess physiological aspects behind variations of PDT and PPT existing between different subjects. It is found that the underlying anatomical structure and geometry (especially of the bone) significantly affect contact pressure distributions and pressure peak values. The largest difference in peak contact pressure between two different fingertips was in fact 27% for the same applied force. Furthermore, contact pressure distributions varied significantly between different subjects. The findings of this research provide novel insight into the phenomena of human grasping and the variation of contact pressure from subject to subject.

Hand cumulative trauma disorders in Nigerian custom tailors: the need for redesign of manual scissors

Cutting scissors are important working tools for Nigerian custom tailors (CTs) but its usage apparently does not meet the ergonomics need of these artisans. A survey was carried out amongst CTs using questionnaires to obtain their background social-occupational demographics and observation methods to study their work performance, use of scissors and any cumulative trauma disorder (CTD) in their hands. Thicknesses of various fabrics were measured and comparison between Western world's custom tailoring job and the Nigerian type was done. The results showed some CTD risk factors with finger contusions on the 71 CTs evaluated. The right-hand contusions were traced to the constant usage of unpadded manual scissors with ungloved hands. Disparity between Western and Nigerian tailoring practice may account for the high occurrence of disorders in Nigerian CTs. Since hand dimensions are crucial in the design of hand tools, it is therefore concluded that hand anthropometry of Nigerian CTs and soft padding of manual scissors may mitigate CTD burdens on CTs' hands.

PRACTITIONER SUMMARY

Cumulative trauma disorders on the hands of low-income Nigerian CTs needed investigation. This was done via self-assessment and observational methods of the artisans’ work system. Frequent usage of unpadded manual scissors with un-gloved hands cause and exacerbate the problem. Hand anthropometry of users is crucial in scissors manufacturing.

A comparison of clutching movements of freely adjusted and imposed pedal configurations for identifying discomfort assessment criteria

This paper focuses on the effects of the free pedal position adjustment on clutching movements of the left lower limb as well as on the perceived discomfort. Six automotive clutch pedal configurations were tested by 20 subjects (5 young females, 5 young males, 5 older females, 5 older males) using a multi-adjustable experimental mock-up. Results showed that the pedal position was adjusted to ensure a good starting pedal position allowing a less flexed ankle and avoiding unnecessary leg displacement from the foot rest to the position at start depression. Pedal position adjustment seemed not motivated by reducing joint torque though discomfort ratings were found significantly correlated with knee and ankle torques at the end of depression. The present work also illustrates that the less-constrained motion concept is helpful for a better understanding of people preference and useful for identifying motion-related biomechanical parameters to be considered for defining assessment criteria.

Comparison of subjective comfort ratings between anatomically shaped and cylindrical handles

Most authors have provided diameter recommendations for cylindrical handle design in order to increase performance, avoid discomfort, and reduce the risk of cumulative trauma disorders. None of the studies has investigated the importance of determining the correct handle shape on the subjective comfort ratings, which could further improve the handles' ergonomics. Therefore, new methods based on a virtual hand model in its optimal power grasp posture have been developed in order to obtain customised handles with best fits for targeted subjects. Cylindrical and anatomically shaped handles were evaluated covering ten subjects by means of an extensive subjective comfort questionnaire. The results suggest large impact of the handle shape on the perceived subjective comfort ratings. Anatomically shaped handles were rated as being considerably more comfortable than cylindrical handles for almost all the subjective comfort predictors. They showed that handle shapes based on optimal power grasp postures can improve subjective comfort ratings, thus maximising performance. Future research should consider real conditions, since the comfort ratings can vary based on the specific task and by the tool selected for the task.

Recommendations for tool-handle material choice based on finite element analysis

Huge areas of work are still done manually and require the usages of different powered and non-powered hand tools. In order to increase the user performance, satisfaction, and lower the risk of acute and cumulative trauma disorders, several researchers have investigated the sizes and shapes of tool-handles. However, only a few authors have investigated tool-handles' materials for further optimising them. Therefore, as presented in this paper, we have utilised a finite-element method for simulating human fingertip whilst grasping tool-handles. We modelled and simulated steel and ethylene propylene diene monomer (EPDM) rubber as homogeneous tool-handle materials and two composites consisting of EPDM rubber and EPDM foam, and also EPDM rubber and PU foam. The simulated finger force was set to obtain characteristic contact pressures of 20 kPa, 40 kPa, 80 kPa, and 100 kPa. Numerical tests have shown that EPDM rubber lowers the contact pressure just slightly. On the other hand, both composites showed significant reduction in contact pressure that could lower the risks of acute and cumulative trauma disorders which are pressure-dependent. Based on the results, it is also evident that a composite containing PU foam with a more evident and flat plateau deformed less at lower strain rates and deformed more when the plateau was reached, in comparison to the composite with EPDM foam. It was shown that hyper-elastic foam materials, which take into account the non-linear behaviour of fingertip soft tissue, can lower the contact pressure whilst maintaining low deformation rate of the tool-handle material for maintaining sufficient rate of stability of the hand tool in the hands. Lower contact pressure also lowers the risk of acute and cumulative trauma disorders, and increases comfort whilst maintaining performance.

Interdisciplinary approach to tool-handle design based on medical imaging

Products are becoming increasingly complex; therefore, designers are faced with a challenging task to incorporate new functionality, higher performance, and optimal shape design. Traditional user-centered design techniques such as designing with anthropometric data do not incorporate enough subject data to design products with optimal shape for best fit to the target population. To overcome these limitations, we present an interdisciplinary approach with medical imaging. The use of this approach is being presented on the development of an optimal sized and shaped tool handle where the hand is imaged using magnetic resonance imaging machine. The obtained images of the hand are reconstructed and imported into computer-aided design software, where optimal shape of the handle is obtained with Boolean operations. Methods can be used to develop fully customized products with optimal shape to provide best fit to the target population. This increases subjective comfort rating, performance and can prevent acute and cumulative trauma disorders. Provided methods are especially suited for products where high stresses and exceptional performance is expected (high performance tools, professional sports, and military equipment, etc.). With the use of these interdisciplinary methods, the value of the product is increased, which also increases the competitiveness of the product on the market.

User-oriented evaluation of mechanical single-channel axial pipettes

Hand tools should be designed so that they are comfortable to use, fit the hand and are user-oriented. Six different manual, single-channel axial pipettes were evaluated for such objective outcomes as muscular activity, wrist postures and efficiency, as well as for subjective outcomes concerning self-assessed features of pipette usability and musculoskeletal strain. Ten experienced laboratory employees volunteered for the study. The results showed that light and short pipettes with better tool comfort resulted in reduced muscular activity and perceived musculoskeletal strain when they were compared with a long and heavy pipette. There were no differences in the efficiency between the different pipettes. Combining both the objective and subjective measures enabled a broader evaluation of product usability. The results of this study can be used both in product development and as information on which to base the purchase of new pipettes for laboratory work.

Ergonomics in developing hand operated maize dehusker-sheller for farm women

A hand operated maize dehusker-sheller to be operated by farm women was designed and developed to dehusk and shell the maize cobs using ergonomics (anthropometric, strength and physiological workload). Axial-flow maize dehusker-sheller with 540 mm cylinder length and 380 mm diameter required 3.03 N-m torque on cylinder shaft while operating at 5.6 m s(-1) peripheral speed and 100 kg h(-1) feed rate by feeding cob one by one. This torque was 30% of isometric torque obtained at front position of handle (greatest distance) with lowest crank length. The heart rate of subject while operating the maize dehusker-sheller at 54 rpm (5.6 m s(-1)) was 142 beats min(-1). The output of 60 kg h(-1) was obtained at the feed rate of 80 kg h(-1). Two subjects can operate the machine for an hour with a rest pause of 15 min by swapping the operation.

Editorial: comfort and discomfort studies demonstrate the need for a new model

The term comfort is often seen relating to the marketing of products like chairs, cars, clothing, hand tools and even airplane tickets, while in the scientific literature, the term discomfort shows up often, since it is used in research. Few papers explain the concept of a localized comfort experience in relation to product use, although people use these products daily. Therefore, in this special issue, the concept of product comfort is studied further. In this editorial an overview of comfort models has been made, evaluated with the papers from the special issue and a new comfort/discomfort model is proposed to increase our understanding of the factors influencing comfort and discomfort experiences.

Relationships between subjective and objective measures in assessing postural stresses

The purpose of this study is to investigate the relationships between subjective measures of discomfort and objective measures related to the assessment of postural stresses based on literature survey. Objective measures included posture holding time, maximum holding time (MHT), torque at joints, lifting index (LI) and compressive force (CF) at L5/S1. The major relationships identified in this literature survey were the following: 1) postural discomfort linearly increased with increasing holding time, and holding force, 2) whole body discomfort was inversely linearly proportional to the MHT, 3) body-part discomfort was related to objective measures such as torque at the relevant joint, 4) discomfort was strongly linearly related to LIs and CFs, and 5) the discomfort measured with the magnitude estimation was linearly related to that measured with Borg CR10. Thus, it is thought that discomfort might be used as a measure for quantifying postural stresses.

Comparison of comfort, discomfort, and continuum ratings of force levels and hand regions during gripping exertions

The goal of this study was to compare three different evaluation systems of comfort, discomfort, and a continuum for the force levels and hand regions when gripping hand tools. Seventy-two participants were assigned to three groups, each group testing a different evaluation system. Each participant exerted ten levels of submaximal voluntary contractions on hand tools and used their assigned evaluation system to evaluate comfortable or uncomfortable feelings for the force levels and five different regions of the hand. The participants generally rated higher discomfort as required forces increased, but the discomfort and continuum evaluation systems were better than the comfort evaluation system because gripping exertion was related to the physical aspects of the hand tools and their users. Based on the results of the continuum evaluation system, the feeling changed from comfort to discomfort at 65% maximum voluntary contraction. The palm was the region of the hand with the most discomfort. Other design factors affecting comfort need to also be considered in order to better understand hand tool use.

Perception of products by progressive multisensory integration. A study on hammers

The aim of this work is to determine the influence of multisensory (visual-haptic) integration and the level of interaction (seeing photographs, seeing the actual product, touching it and using it) on the perception of products, including perceived ergonomics. The product selected for the experiment was the hammer, as this will help to establish whether emotional design studies can also apply to 'commercial' products. Subjective opinions of users were evaluated through semantic differential tests. A factor analysis identified six semantic factors or axes (Quality/Robustness, Ergonomics/Appearance, Innovation, Lightness, Dynamic Effects, and Efficacy). Results show that Lightness and Dynamic Effects are quite sensitive to the level of interaction, while Ergonomics/Appearance is partially affected. However, the perceptions of Innovation, Quality/Robustness and Efficacy are not so affected and they could be detected through a lower level of interaction (i.e. seeing photographs). This suggests that commercial products seem sensitive to emotional design studies and that multisensory integration enhances the perception of the factors that are clearly linked with physical interaction between users and tools, i.e. Ergonomics/Appearance, Lightness and Dynamic Effects. Additionally, it should be highlighted that some aspects related with the ergonomics and ease of use of products are also perceived at different stages of interaction.

The usability and ergonomics of axes

This study evaluated the ergonomics and usability of axes. Several methods were used, namely measurement of impact velocity, the determination of kinetic energy, splitting performance tests, durability tests of blades and handles, and user trials. The mean velocity used in the striking was 9.6m/s (8.9-10.3m/s, SD 1.5). In the durability tests, the blades withstood the test reasonably well. In the bending tests, there were differences in the durability of the handles, which related to their material. A wide variation in the durability of the axe handles was also observed. User trials were conducted to evaluate the various features of the axes.

Application of the QFD as a design approach to ensure comfort in using hand tools: can the design team complete the House of Quality appropriately?

Quality Function Deployment is proposed as an effective design method to integrate ergonomics needs and comfort into hand tool design because it explicitly addresses the translation of customer needs into engineering characteristics. A crucial step during QFD concerns the linking of engineering characteristics to customer needs in the House of Quality by the design team. It is generally assumed (looking at all the QFD success stories) that design teams can accurately predict the correlations between customer needs and engineering characteristics (also referred to as "Whats"/"Hows" correlations). This paper explicitly tests this assumption by comparing the "Whats"/"Hows" correlations estimated by a design team with those observed in a systematic user evaluation study, which has not been done before. Testing the assumption is important, because inaccurate estimates may lead to ergonomically ineffective (re)design of hand tools and a waste of company resources. Results revealed that the design team's correlation estimates were not as accurate as is generally assumed. Twenty-five percent of the estimates differed significantly with those observed in the user evaluation study. Thus, QFD is a useful method to assist design teams in designing ergonomically more comfortable hand tools, but only on the condition that the correlations between customer needs and engineering characteristics are validated, preferably by means of a systematic user evaluation study.

Perception and biomechanics data in a manual handling task: a comparative study

This paper explores the use of subjective perception tasks and its correlations with biomechanical data in the evaluation of manual material handling. Three main dimensions were considered for perception: physical regroups sensations issued from a specific body area; operative regroups feelings related to the execution of the task; and performance regroups feelings that involve a judgement on the execution or reflect overall sensations. The following questions were then explored. To what extent are perception data related to biomechanics data? Do both approaches lead to similar conclusions or interpretations when effect of practice, format and off-centre were tested? How can they complement one another? The task consisted of transferring 50 series of three 15 kg loads in order to verify the impact of free practice, format (box/cylinder) and load centre of gravity position. Eleven subjects rated perception on a CR-10 scale (Borg 1982) after each series. The session was completed with an interview on perception. The net resulting moment was systematically found to be the best correlated with data perception. While all physical and performance items corresponded in various ways to biomechanics data, perceptions associated with operative dimension appeared to be less related with biomechanical data. As regards the impact of practice, format and off-centre, both approaches would lead to the same conclusions, except for the effect of the off-centre. Verbal data add rational information about how or why perception can or cannot be reflected in biomechanics data. How both approaches can be matched more closely in manual handling is discussed.

Cognitive aspects of tool use

Tool use has traditionally been viewed as primarily a physical activity, with little consideration given to the cognitive aspects that might be involved. In this paper, a new approach to considering tool use in terms of Forms of Engagement is presented and discussed. This approach combines notions of schema from cognitive psychology with the idea of task-specific devices to explain psychomotor aspects of using tools. From the perspective of Forms of Engagement, various aspects of craftwork and skilled tool use are considered.

Identifying predictors of comfort and discomfort in using hand tools

The aim of the study was to identify predictors of comfort and discomfort in using hand tools. For this purpose, the comfort questionnaire for hand tools (CQH) was developed based on the results of a previous study. In the current study, four screwdrivers were evaluated on comfort (expected comfort at first sight and comfort after short time use) using the CQH and discomfort (local perceived discomfort). The results showed that expected comfort at first sight was predicted by aesthetics. Additionally, functionality and physical interaction, and adverse body effects were the major predictors of overall comfort after short time use. Discomfort was predicted by adverse body effects only. It is concluded that comfort and discomfort in using hand tools have partly the same underlying factors: discomfort feelings also affect the comfort experience.