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 degrees 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.     

A comparison of risk assessment of single and combination manual handling tasks: 3. Biomechanical measures

Anecdotal evidence suggests organisations experience difficulty assessing the risk in manual handling tasks. One reason for this difficulty may be that many common tasks are a combination of lift, lower, push, pull and carry tasks. No prior reports of attempts to assess the risk in combination tasks using biomechanical measures could be found. The aim of the study was to compare the risks assessed in single manual handling tasks with those in combination tasks. Nine male and nine female students performed combination and single handling tasks. The force applied by subjects to a box was recorded and, together with kinematic data on subject posture collected via video, used in a twodimensional dynamic model to estimate the lumbar compression force and lumbar shear force. The hand force, peak lumbar compression force and peak lumbar shear force for each combination task were each compared with the same variable for the single tasks which comprised the combination, using repeated measured analysis of variance with specific contrasts. In at least one of the twelve comparisons performed for each dependent variable, the combination task value was significantly different to the single task value. It is concluded that the risk in combination manual handling tasks can not be accurately assessed by using estimates based on biomechanical measures of single tasks.     

A hand-ergonomics training kit: development and evaluation of a package to support improved awareness and critical thinking

A need for a hand-ergonomics training kit has been identified to increase critical thinking concerning choice of hand tools. This study deals with the design, use and evaluation of a hand-ergonomics training kit for use in ergonomics training programmes. The effects on awareness of hand ergonomics among training course participants have been evaluated by means of a questionnaire and interviews at a car production plant in Sweden. The evaluation was carried out about one and a half years after training with the hand-ergonomics training kit. The training kit consists of a guide to practical exercises, equipment for measuring hand size and strength, examples of hand tools for use in practical exercises, equipment for testing and evaluating the hand tools and checklists and judgement forms for qualitative evaluation. In addition, the kit contains relevant scientifically based reference reports on hand ergonomics. The evaluation showed that the practical exercises with the hand-ergonomic training kit had, to a remarkable extent, increased individuals' awareness of anthropometric differences and of the importance of ergonomically well-designed hand tools. After the practical exercises with the training kit, communication within the plant when choosing hand tools seems to be based on objective criteria to a higher degree, however, the results indicate that this communication could be further improved.     

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.     

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.