Measurement of prehensile grasp capabilities by a force and moment wrench: Methodological development and assessment of manual workers

Prehensile grasp capability is typically quantified by pinch and grasp forces. This work was undertaken to develop a methodology to assess complex, multi-axis hand exertions through the measurement of forces and moments exerted by the hand along and about three orthogonal axes originating at the grip centre; termed an external wrench. Instrumentation consisting of a modified pinch/grip dynamometer affixed to a 6?df force cube was developed to simultaneously measure three forces, three moments and the pinch/grip force about the centre of the grip. Twenty right hand dominant manual workers (10 male and 10 female), free of hand or wrist disorders, completed a variety of maximal strength tasks. The randomized block design involved three separate grips?–?power grip, lateral pinch and pulp pinch. Randomized within each block were three non-concurrent repetitions of isolated maximal force and moment generations along and about the three principle orthogonal axes and a maximal grip force exertion. Trials were completed while standing, with the arm abducted and elbow flexed to 90° with a wrist posture near neutral. Where comparable protocols existed in the literature, forces and moments exerted were found to be of similar magnitude to those reported previously. Female and male grip strengths on a Jamar dynamometer were 302.6?N and 450.5?N, respectively. Moment exertions in a power grip (female and male) were 4.7 Nm and 8.1 Nm for pronator, 4.9 Nm and 8.0 Nm for supinator, 6.2 Nm and 10.3 Nm for radial deviator, 7.7 Nm and 13.0 Nm for ulnar deviator, 6.2 Nm and 8.2 Nm for extensor, and 7.1 Nm and 9.3 Nm for flexor moments. Correlations with and between maximal force and moment exertions were only moderate. This paper describes instrumentation that allows comprehensive characterization of prehensile force and moment capability.     

Characterizing human hand prehensile strength by force and moment wrench

Characterizing human hand capabilities or demand created by various occupational tasks or activities of daily living has been mainly accomplished by measuring the maximum force exerted on a force dynamometer in a number of standard grips, for example power, key pinch and tip pinch grips. A framework is proposed instead to characterize human hand prehensile strength in generic form by describing external force and moment wrench capability, where a wrench is a vector describing the forces and moments applied at a point. It is further suggested that if tools and activities are characterized by the internal forces and external forces and moments required, a better understanding of the human prehension in occupational settings and during activities of daily living can be obtained. An example of using a pistol grip drill is used to show the utility of the approach.     

Characterizing human hand prehensile strength by force and moment wrench

Characterizing human hand capabilities or demand created by various occupational tasks or activities of daily living has been mainly accomplished by measuring the maximum force exerted on a force dynamometer in a number of standard grips, for example power, key pinch and tip pinch grips. A framework is proposed instead to characterize human hand prehensile strength in generic form by describing external force and moment wrench capability, where a wrench is a vector describing the forces and moments applied at a point. It is further suggested that if tools and activities are characterized by the internal forces and external forces and moments required, a better understanding of the human prehension in occupational settings and during activities of daily living can be obtained. An example of using a pistol grip drill is used to show the utility of the approach.     

IT infrastructure capabilities and IT project success: a development team perspective

In this research we investigate how IT infrastructure capabilities are related to IT project success from a development team perspective. We first conduct an extensive literature review and summarize the insights to suggest an IT infrastructure base model. Drawing upon several other bodies of literature, particularly the psychology literature, we then build upon the base model to propose an integrative research model for IT project success that considers both actual and perceived effects of IT infrastructure capabilities. This research model argues that (1) teamwork quality mediates the effect of technical and human IT infrastructure capabilities on IT project success, and (2) team perceptions of both IT infrastructure and team capabilities shape team perceived likelihood of project success, which subsequently affects team commitment that is crucial to IT project success. We also propose a direct-effect model that directly links all constructs to IT project success so that we can test the efficacy of our proposed research model by comparing all three models. We then collect empirical data (n = 91) through an online survey of CIO/CTOs and team leaders. All three models are evaluated and compared using the partial least squares method. The results show strong support for the proposed research model except for two IT infrastructure components. We discuss the practical and theoretical implications of the findings, and suggest several ways this research can be extended.     

Folding and unfolding manual wheelchairs: an ergonomic evaluation of health-care workers

The objective of this study was to test the hypotheses (i) that health-care workers vary greatly in the methods used to fold and unfold selected manual wheelchairs, and (ii) that many of the methods used include bent and twisted back postures that are known to be associated with a high risk of injury. We studied 20 health-care workers in a rehabilitation center. Subjects folded and unfolded two wheelchairs of cross-brace design, one with and one without a sling seat. As outcome measures, we used a questionnaire, time taken, visual analog scales of perceived exertion and back strain, folded width, videotape and Ovako Working Posture Analysis System (OWAS) back scores (1–4). Subjects used up to 14 different combinations of approach, hand placement and back posture to accomplish the tasks. The mean OWAS scores were in the 2.4–3.1 range and 49 (42%) of the 118 scores recorded were class 4 (back simultaneously “bent and twisted”, considered to be associated with the highest risk of injury). We also observed methods that appeared to be safe and effective. Age, gender, profession, experience and seat condition did not generally influence the outcome measures. We conclude that health-care workers use a variety of methods to fold and unfold wheelchairs, many of which include bent and twisted back postures that may carry a risk of injury. Further study is needed to confirm this risk, to identify more ergonomically sound wheelchair designs and to develop better methods of carrying out the common and important task of folding and unfolding wheelchairs.     

Maximal manual stretcher carriage: performance and recovery of male and female ambulance workers

The effects of a maximal duration stretcher carriage on heart rate (HR), lactate concentration, hand steadiness and hand-grip strength were studied up to 72 h post-exercise in 17 male and 15 female military ambulance personnel. Using both hands for transport, the participants walked on a treadmill ergometer at a speed of 4.5 km/h. Force measurements at the handlebars yielded mean loads of 245 N (25 kg) on each side. Each step on the treadmill induced additional force oscillations with peak forces up to 470 N corresponding to 130% (women) and 98% (men) of maximal voluntary contraction (MVC). In the males the maximal transport time was about twice the time in women (mean +/- SD: 184 +/- 51 s vs. 98 +/- 34 s). These differences had no significant effect on HR and lactate values. The same applies to hand steadiness, which showed only a transient deterioration immediately after exercise. In contrast to these parameters, substantial differences were seen in hand-grip strength recovery. Immediately after exercise, maximal hand-grip strength decreased by 150 N (25% MVC) in the males vs. 50 N (14%) in the females. Irrespective of gender, individuals with larger hand-grip strength and longer carriage durations (range 120 s-280 s) showed the slowest strength recoveries (up to 72 h) as compared to 1 h of recovery in participants with short transport durations (range 27 s-120 s). These findings suggest that the increasing number of eccentric strains during uninterrupted stretcher carriage induces cumulative muscle damages that may require some days for complete recovery.     

Maximal manual stretcher carriage: performance and recovery of male and female ambulance workers

The effects of a maximal duration stretcher carriage on heart rate (HR), lactate concentration, hand steadiness and hand-grip strength were studied up to 72 h post-exercise in 17 male and 15 female military ambulance personnel. Using both hands for transport, the participants walked on a treadmill ergometer at a speed of 4.5 km/h. Force measurements at the handlebars yielded mean loads of 245 N (25 kg) on each side. Each step on the treadmill induced additional force oscillations with peak forces up to 470 N corresponding to 130% (women) and 98% (men) of maximal voluntary contraction (MVC). In the males the maximal transport time was about twice the time in women (mean ± SD: 184 ± 51 s vs. 98 ± 34 s). These differences had no significant effect on HR and lactate values. The same applies to hand steadiness, which showed only a transient deterioration immediately after exercise. In contrast to these parameters, substantial differences were seen in hand-grip strength recovery. Immediately after exercise, maximal hand-grip strength decreased by 150 N (25% MVC) in the males vs. 50 N (14%) in the females. Irrespective of gender, individuals with larger hand-grip strength and longer carriage durations (range 120 s–280 s) showed the slowest strength recoveries (up to 72 h) as compared to 1 h of recovery in participants with short transport durations (range 27 s–120 s). These findings suggest that the increasing number of eccentric strains during uninterrupted stretcher carriage induces cumulative muscle damages that may require some days for complete recovery.     

The evaluation of force exertions and muscle activities when operating a manual guided vehicle

A manual guided vehicle (MGV) is used to handle heavy materials in thin film transistor-liquid crystal display (TFT-LCD) manufacturing clean rooms. This study focuses on evaluating the force exertions and muscle activities in MGV operations. The independent variables include gender, force direction, handle height, load handled and wheel diameter of the MGV. The results show the force direction, handle height and load handling effects are significant in most measures except for F_ending (the peak force required to stop the MGV) and the EMG of the anterior deltoid. The wheel diameter had a significant effect on F_initial (the peak force required to move the MGV) and F_ending responses. Gender did not significantly effect any measures. Moreover, the pushing and pulling force is less at 115 cm handle height than at 101.5 cm and 88 cm handle heights. Using 15.3 cm (6 inch) diameter wheels requires less force than 20.3 cm (8 inch) diameter wheels because the two front wheels are fixed and the two rear wheels are rotatable. The design implications are discussed.     

MAPO index for risk assessment of patient manual handling in hospital wards: a validation study

Manual handling of disabled patients – as regards movement – is one of the major factors affecting acute low back pain of exposed nursing staff. In the absence of quantitative methods assessing this kind of risk, the Research Unit Ergonomics of Posture and Movement of Milan developed in 1997 a risk assessment method called Movement and Assistance of Hospital Patients (MAPO), which is applicable in hospital wards.

A first study conducted in 1999 allowed the identification of three levels of MAPO index corresponding with increasing probabilities of being affected by acute low back pain. In accordance with the well-known traffic light model, for MAPO index values between 0 and 1.5 the risk is considered to be absent or negligible. For values between 1.51 and 5.00 the risk is considered to be moderate. For values exceeding 5.00 the risk is considered to be high. In view of the limitations of the previous study, the results needed confirmation and so, in 2000–2001, another cross-sectional study was carried out, which included 191 hospital wards for acute and chronic patients and 2603 exposed subjects. This paper presents the analytical results of the association between the MAPO index and acute low back pain in this new data sample.

The agreement between results of the two studies indicates that the MAPO index can be used as a risk index, although with some caution, as detailed in the paper. It can assess the risk exposure level of patient manual handling in wards and can be a useful tool for planning effective preventive actions to reduce the risk of work-related musculoskeletal disorders in health-care workers looking after disabled patients.     

MAPO index for risk assessment of patient manual handling in hospital wards: a validation study

Manual handling of disabled patients - as regards movement - is one of the major factors affecting acute low back pain of exposed nursing staff. In the absence of quantitative methods assessing this kind of risk, the Research Unit Ergonomics of Posture and Movement of Milan developed in 1997 a risk assessment method called Movement and Assistance of Hospital Patients (MAPO), which is applicable in hospital wards.A first study conducted in 1999 allowed the identification of three levels of MAPO index corresponding with increasing probabilities of being affected by acute low back pain. In accordance with the well-known traffic light model, for MAPO index values between 0 and 1.5 the risk is considered to be absent or negligible. For values between 1.51 and 5.00 the risk is considered to be moderate. For values exceeding 5.00 the risk is considered to be high. In view of the limitations of the previous study, the results needed confirmation and so, in 2000-2001, another cross-sectional study was carried out, which included 191 hospital wards for acute and chronic patients and 2603 exposed subjects. This paper presents the analytical results of the association between the MAPO index and acute low back pain in this new data sample.The agreement between results of the two studies indicates that the MAPO index can be used as a risk index, although with some caution, as detailed in the paper. It can assess the risk exposure level of patient manual handling in wards and can be a useful tool for planning effective preventive actions to reduce the risk of work-related musculoskeletal disorders in health-care workers looking after disabled patients.     

Reliability and validity of self-reported assessment of exposure and outcome variables for manual lifting tasks: a preliminary investigation

The reliability and validity of self-reported assessment of exposure and outcome variables were examined for manual lifting activities among ten physiotherapists. In this study, the participants evaluated the effects of five lifting variables on perceived effort, twice separated by a one-week period. One hundred and sixty-two lifting conditions were evaluated by each subject. The exposure and outcome lifting variables were described in linguistic terms. Intra-class correlation coefficient (ICC(1,1)) analysis revealed a mean value of 0.62 for all lifting activities. The self-reported assessment was cross-validated with the NIOSH lifting index by mapping the linguistic variables into numerical ranges. Moderate correlations (r = 0.54 and 0.53, p<0.01) were obtained between perceived physical exertion/perceived risk and lifting index. The findings of this study provide preliminary indications that human-based methodologies may be further explored on experienced workers.     

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n = 1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.     

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n=1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.     

Design of a six-axis wrist force/moment sensor using FEM and its fabrication for an intelligent robot

This paper describes the design of a six-axis force/moment sensor using FEM (finite element method) and its fabrication. In order to safely grasp an unknown object using an intelligent hand in robot, the hand has to perceive the weight of it. The weight is calculated by forces F_x, F_y, F_z measured from the six-axis wrist force/moment sensor attached to an intelligent robot's hand. And, in order to accurately push and pull an object, forces and moments should be measured. Also, the position of the robot's finger contacted on an object are calculated by forces F_x, F_y and F_z, and moments M_x, M_y and M_z measured from the six-axis wrist force/moment sensor. Therefore, an intelligent robot's hand should get a six-axis wrist force/moment sensor that can measure forces F_x, F_y and F_z, and moments M_x, M_y and M_z simultaneously. The size of the six-axis force/moment sensor for an intelligent robot’ wrist is very important. If its diameter is larger or its thickness (length) is longer, it cannot be mounted in robot's wrist or it will break down under the applied moment M_x or M_y. So, its size is similar to that of the wrist of human being, that is, the diameter is about 60–80 mm and the thickness (length) about 20–40 mm. But the manufactured sensors are not proper in size for the intelligent robot's wrist. Thus, the six-axis force/moment sensor should be developed for the intelligent robot's wrist.In this paper, the structure of a six-axis wrist force/moment sensor was modeled for an intelligent hand in robot newly. And the sensing elements of it were designed by using FEM and were fabricated by attaching strain-gages on the sensing elements. And, the characteristic test of the developed sensor was carried out. The rated outputs from FEM analysis agree well with the results from the experiments. The interference error of the sensor is less than 2.85%.     

Developing a diagnosis system of work‐related capabilities for students: A computer‐assisted assessment

A gap exists between students' employment needs and higher education offerings. Thus, developing the capability to meet the learning needs of students in supporting their future aspirations should be facilitated. To bridge this gap in practice, this study uses multiple methods (i.e., nominal group technique and instructional systems development) and robust tests (e.g., reliability and validity) to develop a diagnosis system of work‐related capabilities. The research participants are twofold. At the early stage, this study invites three professors and three senior Human Resources managers to join the panel and help this study develop required capabilities. At the design and implementation stages, the research participants are freshman students at a famous university in Taiwan. This system enables college students to evaluate their capability scores by comparing themselves with the performances of prior students. The diagnosis results not only help students make learning plans during their university education, but also assist educators in adjusting the structure of the curriculum. Future studies are invited to use or adapt the assessment of work‐related capabilities, as well as proposed system procedure and architecture this study developed.     

Construction of a supermicro sense of force feedback and vision for micro-objects: development of a haptic device

This research aims to develop a combined sense system that uses both the force feedback and visual feedback to establish the shape of microscopic features of a microsample. It is thought that the efficiency of minute procedures would be improved if the operator could obtain a sense of force while using a manipulator. We used a cantilever to touch a minute object and obtain a reaction force from the degree of bending. We made a haptic device which gives a sense of that force to the operator, who can feel the force when a user touches a sample with a cantilever. In addition, when the haptic device is used in simulations, the user can feel a force just as if the user had touched a sample.     

Evaluating causes and consequences of turnover intention among IT workers: the development of a questionnaire survey

In this paper we describe the process of developing a questionnaire survey that evaluates the causes and consequences of turnover intention among information technology (IT) workers, with specific attention to issues of importance to women and minorities within the IT workforce. The questionnaire development process consisted of four steps:

1. Creation of the initial questionnaire from a literature review of existing scales
2. Pilot study using interviews to test the questionnaire
3. Modifications to the questionnaire based on feedback from the pilot study
4. Implementation of the revised questionnaire survey.

The process used for the development of the questionnaire survey is systematic and addresses issues specific to the IT workforce, in particular the underrepresentation of women and minorities in the IT workforce. The questionnaire survey allows the collection of reliable and valid data on causes and effects of retention and intention to turnover, thus making it possible to better understand the reasons for the underrepresentation of women and minorities in the IT workforce.     

Evaluating causes and consequences of turnover intention among IT workers: the development of a questionnaire survey

Abstract

In this paper we describe the process of developing a questionnaire survey that evaluates the causes and consequences of turnover intention among information technology (IT) workers, with specific attention to issues of importance to women and minorities within the IT workforce. The questionnaire development process consisted of four steps:

1. Creation of the initial questionnaire from a literature review of existing scales

2. Pilot study using interviews to test the questionnaire

3. Modifications to the questionnaire based on feedback from the pilot study

4. Implementation of the revised questionnaire survey.

The process used for the development of the questionnaire survey is systematic and addresses issues specific to the IT workforce, in particular the underrepresentation of women and minorities in the IT workforce. The questionnaire survey allows the collection of reliable and valid data on causes and effects of retention and intention to turnover, thus making it possible to better understand the reasons for the underrepresentation of women and minorities in the IT workforce.