Biomechanical Consequences of Hand's Action on Unstable Handle Stefan Kornecki, 199-207 Perceived Discomfort and Electromyographic Activity of the Upper Trapezius While Working at a VDT-Station Veerle Hermans, Arthur Spaepen, 208-214 A Distributed Signal Detection Theory Model: Implications for the Design of Warnings Jason D. Papastavrou, Mark R. Lehto, 215-234 Physiological Method of Evaluating Protective Clothing for Work in a Cold Environmen Anna Marszałek, Krzysztof Sołtyński, Alicja Sawickat, 235-243 Some Aspects of Vehicle Active Safety Jerzy Wicher, 244-251 Role Stress, Job Anxiety, Job Involvement, and Job Satisfaction among Three Groups of Organizational Employees: a Factor Analytic Study Sanjay Srivastava, Arun K. Sen, 252-261 Handling Techniques: The Influence of Weight and Height for Experts and Novices Marie Authier, Micheline Gagnon,Monique Lortie, 262-275 Issues of the Human Reliability Analysis in the Context of Probabilistic Safety Studies Kazimierz T. Kosmowski, 276-293 Lifting Belts: A Review Margaret J. Rys, Stephan A. Konz, 294-303

Notes:

The Influence of Alcohol on Industrial Accidents in the Czech Republic Miloš Paleček, 304-307 The Organisation of the WASP Scheme in the U.K. Barry Tylee, 308-310

Biomechanical Consequences of Hand's Action on Unstable Handle
Stefan Kornecki, 199-207

The concept of muscular stabilization refers to imposing active muscular constraints on the joint degrees of freedom (DOFs) which are not used in a given motor task, and the stabilization of unstable working objects. The human organism bears considerable cost due to the realization of the above process, which in the case of muscular static force developed in relation to an unstable working object reaches approximately 24%. The aim of this paper is two-fold: (1) to determine the useful efficiency of the hand-working object system with an unstable handle in relation to the released muscular force and power dynamics, and (2) to identify the relative contribution of the upper extremity muscles engaged in the realization of motor or stabilizing functions in the electromyography (EMG) sphere.
Twelve male students of physical education took part in the experiment. The experimental set-up consisted of a 3.08-meter-long physical pendulum with the inertia moment of 574 kg m2, with an exchangeable handle. Three handles with zero, one, and two degrees of freedom in relation to the pendulum shaft were used. The subjects were asked to push the pendulum handle with a hand utilizing maximum force in order to develop high kinetic energy irrespective of its state of equilibrium and mobility. In the course of the experiment, the muscles straightening the upper extremity and stabilizing the wrist joint were subjected to EMG measurements. It was found that the useful efficiency of the human organism in relation to developed muscular force and power decreases to 80% and 60% respectively, if the handle of a driven working object is unstable.
When the stabilization of the handle is the condition of setting a working object in motion, the contribution of the muscles fulfilling stabilization functions is comparable to the participation of the muscles realizing motor activities.

Perceived Discomfort and Electromyographic Activity of the Upper Trapezius While Working at a VDT Station
Veerle Hermans, Arthur Spaepen, 208-214

Ten female participants performed work at a video display terminal (VDT) station over a whole working day. Subjective local muscular fatigue was evaluated by means of the Category Ratio 10 scale. Electromyographic activity of the upper right and left trapezius was measured. A comparison was made between five participants who had previous complaints and five participants who reported no musculoskeletal problems in the shoulder-neck region. The subjective scores for the shoulder differed significantly between the two groups, being higher for the group with complaints. Both groups showed a decrease in discomfort after the lunch break. The activity of the trapezius increased significantly for both groups, in a more pronounced way for the group with disorders. Although it is found in literature that VDT work is a task with very low static loads, it seems from this study that the EMG activity increase can be an indication of muscle fatigue: more effort was required to accomplish the same VDT task at the end of the day.

A Distributed Signal Detection Theory Model: Implications for the Design of Warnings
Jason D. Papastavrou, Mark R. Lehto, 215-234

A distributed signal detection theory model is employed to analyze the effectiveness of warnings under different operating conditions. In particular, the following two cases are examined: the warning on a product is always present, and the warning on a product is administered selectively. The comparative effects of warning versus no warning are described. It is established that selectivity always increase effectiveness. The implications to optimal warning design of intermittent hazard versus continuous hazard are discussed. Furthermore, a series of experiments is conducted to compare the behavior of human subjects with the prescriptive behavior of the normative model. The changes in the behavior of the human subjects in response to changes in the warning levels are consistent with the predictions of the model. These changes should be taken into consideration in the design of warnings.

Physiological Method of Evaluating Protective Clothing for Work in a Cold Environment
Anna Marszałek, Krzysztof Sołtyński, Alicja Sawicka, 235-243

The purpose of this study was to determine the usefulness of physiological studies in the evaluation of protective clothing for work in a cold environment. The study included the examination of the dynamics of changes in chosen physiological parameters (core and skin temperatures, heart rate, pulmonary minute ventilation) as well as physical ones (the temperature and relative humidity under the clothes) during work in protective clothing with unknown thermal insulation. The experiment was conducted in extreme environmental conditions (-10 and -15° C) at a work load defined by the clothing manufacturer as moderate.
Results show that thermal equilibrium was achieved and maintained throughout the investigated work time (60 min) and that the protective clothing ensures safety on the time scale of a regular 8-hour work day.
It was also shown that the dynamics of thermal stress physiological parameters can be used to determine the maximum duration of exposure for cold protective clothing with unknown thermal insulation.

Some Aspects of Vehicle Active Safety
Jerzy Wicher, 244-251

Three selected aspects of vehicle active safety are presented in this paper: (1) modeling the driver and the vehicle-driver-environment system, (2) the dynamic aspects of vehicle rollover, and (3) an analysis of the process of overtaking. Sample solutions and results show the need for further research in the field of vehicle safety, in order to lower the probability of drivers, passengers, and other road traffic users being involved in road accidents.

Role Stress, Job Anxiety, Job Involvement, and Job Satisfaction Among Three Groups of Organizational Employees: A Factor Analytic Study
Sanjay Srivastava, Arun K. Sen, 252-261

The study is an attempt to compare organizational role stress, job involvement, job anxiety, and job satisfaction among three groups of employees in a private sector organization. The sample consisted of 50 top managers, 50 middle managers, and 50 workers. The Organizational Role Stress developed by Pareek (1983), the Job Involvement scale by Lodhal and Kejner (1965), the Job Anxiety scale by Srivastava and Sinha (1977), and the Job Descriptive Index developed by Smith, Yulin, and Kendall (1969) were administered to all three groups of employees. The results were analyzed both by the Factor Analytic Technique and by Discriminant Function Analysis. The Factor Analysis yielded three important factors which are discussed. The Discriminant Function Analysis separated the three groups on ten out of the twenty-three variables considered in the study. The findings are discussed in the light of other relevant studies.

Handling Techniques: The Influence of Weight and Height for Experts and Novices
Marie Authier, Micheline Gagnon,Monique Lortie, 262-275

The purpose of the study was to evaluate the influence of the weight of the load (12 kg, 22 kg) and of the height of the grasp (high: 126 cm; middle: 64 cm and 95 cm; low: 33 cm) on the handling techniques adopted by six experienced handlers and six novices having only limited handling experience during a free box-handling task. Each subject had to transfer two sets of 16 boxes from a platform to a four-wheel cart. The observations dealt with the position of the subject at the beginning of transfer and at deposit (position of the back, knees and feet, pelvic orientation, position of the hands), his way of moving during the transfer (position of the feet) and his way of positioning and moving the box during handling (tilt of the box, impulse given to the box, grip change). The results show that the weight and the height of grasp/deposit had an influence on the techniques adopted by expert handlers and novices. Some of these variations are common to both groups but many of them are not, such as the position of the knees, the grips and the position of the box. This study suggests that there is not one method that is suitable for all situations, and that expert handlers may have learned how to adjust their methods to the working environment. A better understanding of the experts' techniques could help in redesigning efficient training programs.

Issues of the Human Reliability Analysis in the Context of Probabilistic Safety Studies
Kazimierz T. Kosmowski, 276-293

This article addresses methodological issues of the human reliability analysis (HRA) in the context of probabilistic safety studies. Several conventional HRA techniques, more often used for the evaluation of the human error probabilities (HEPs), have been classified. A taxonomy of human actions, failure events, and related factors is outlined in order to distinguish actions phases, human behavior types and incorrect outputs (errors of omission or commission), error types (slips, lapses, and mistakes), and performance-shaping factors (PSFs) influencing the human performance. A tree is proposed to facilitate the selection of a specific method for the evaluation of human reliability with regard to attributes of the situation analyzed. A software system based on the expert system technology to facilitate and document PSA and HRA is outlined. At the end of the paper some research challenges in the domain are discussed.

Lifting Belts: A Review
Margaret J. Rys, Stephan A. Konz, 294-303

This article reviews and evaluates the literature related to the effectiveness of protective restraints on abdominal strength, low-back injuries and workers' discomfort. The studies indicate that back belts have potential disadvantages as well as advantages. Belts seem to reduce lifting stress. They may, however, lead to a false sense of security while being worn and may weaken the body, too, so injury occurs when they are not being worn. There also seems to be comfort problems with some belts. More scientific research is needed before any conclusions can be drawn about positive, negative, or long-term effects of lifting belts.