Occupational heat stress assessment by the Predicted Heat Strain model.

The work of the main European research teams in the field of thermal factors was coordinated in order to improve significantly the Required Sweat Rate model published as an international standard. Many significant modifications were brought, in particular concerning the effects of forced convection, body movements and exercise and the prediction of the skin temperature as a function of the rectal temperature and in case of severe conditions of radiation, humidity and clothing. The criteria for acceptable work durations in hot environments were updated concerning the maximum increase in core temperature and the acceptable water loss. The revised model, called Predicted Heat Strain model, was validated through a set of lab and field experiments involving stable and fluctuating conditions with high and low radiation, humidity and air velocity. It is meanwhile adopted as an ISO and CEN standard. In addition, a strategy was developed to assess the risks of heat disorders in any working situation. It is based on the three highest stages of the SOBANE strategy: an "Observation" method for improving simply the thermal conditions of work; an "Analysis" method to evaluate the magnitude of the problem and optimise the choice of solutions and an "Expert" method for in depth analysis of the working situation when needed.

Participative management strategy for occupational health, safety and well-being risks.

The article discusses the principles that underlie a coherent and efficient prevention program for occupational health, safety and well-being: the need of a global approach of these problems not only at the workplace but for the whole of the living conditions at work; a clear understanding of the complementarity between the different partners of this prevention; the role of actor of the workers and therefore the absolute necessity of a participative approach; the real usefulness of measurements and of risk quantification in general; the differences between risk assessment and risk management and the specificities of small and medium size enterprises. On the basis of these principles, the various steps and levels of intervention are defined. The SOBANE prevention strategy is introduced and its 4 levels (Screening, Observation, Analysis and Expertise) are described as well as the consultation guide Déparis for the Screening level. The strategy proved to make it possible to approach the work situations progressively in small as well as in large companies, to coordinate the cooperation between the workers, the technical staff and the occupational health practitioners and to prevent the problems more rapidly, more efficiently and more economically. The paper describes the role of a 'facilitator' to introduce the philosophy and the tools of the SOBANE strategy in the company, to monitor its application and insure the continuity and the efficiency of the participatory approach.

The SOBANE risk management strategy and the Déparis method for the participatory screening of the risks.

INTRODUCTION: The first section of the document describes a risk-prevention strategy, called SOBANE, in four levels: screening, observation, analysis and expertise. The aim is to make risk prevention faster, more cost effective, and more effective in coordinating the contributions of the workers themselves, their management, the internal and external occupational health (OH) practitioners and the experts. These four levels are: screening, where the risk factors are detected by the workers and their management, and obvious solutions are implemented; observation, where the remaining problems are studied in more detail, one by one, and the reasons and the solutions are discussed in detail; analysis, where, when necessary, an OH practitioner is called upon to carry out appropriate measurements to develop specific solutions; expertise, where, in very sophisticated and rare cases, the assistance of an expert is called upon to solve a particular problem. METHOD: The method for the participatory screening of the risks (in French: Dépistage Participatif des Risques), Déparis, is proposed for the first level screening of the SOBANE strategy. The work situation is systematically reviewed and all the aspects conditioning the easiness, the effectiveness and the satisfaction at work are discussed, in search of practical prevention measures. The points to be studied more in detail at level 2, observation, are identified. The method is carried out during a meeting of key workers and technical staff. CONCLUSION: The method proves to be simple, sparing in time and means and playing a significant role in the development of a dynamic plan of risk management and of a culture of dialogue in the company.

Co-ordinated strategy of prevention and control of the biomechanical factors associated with the risk of musculoskeletal disorders.

OBJECTIVES: To propose a cost-effective set of methods (strategy) to improve biomechanical working conditions and prevent the development of musculoskeletal disorders. METHODS: The strategy was developed according to the philosophy already used for other aspects of working conditions. It was then tested in ten industrial situations with various characteristics, to check its understanding, its usability, and its efficiency. RESULTS: The strategy includes a five-page leaflet ( screening) aimed at motivating the operators to check the problems and bring about immediate solutions if possible. A stage-2 observation checklist is then proposed to guide the discussions during a meeting of the protagonists (workers and management). The assistance of an occupational health practitioner might become indispensable at stage 3 to deepen the analysis of the remaining problems, while experts are requested only in exceptional cases (stage 4, expertise). This strategy was positively judged by the users and proved to be effective in motivating and co-ordinating the protagonists. CONCLUSION: The strategy proved to consider effectively all biomechanical aspects that might contribute to the development of musculoskeletal disorders (MSDs). It proved also to be participatory, placing the operators and their management at the centre of the intervention as the main actors, and organising when to turn to an occupational health practitioner or an expert for assistance.

Musculoskeletal complaints, functional capacity, personality and psychosocial factors.

OBJECTIVES: The aim of the research was to study the association between psychosocial and personality factors, and neck and wrist-hand musculoskeletal complaints, taking account of the occupational factors of force, posture and repetitiveness, and non-occupational risk factors such as sport, hobbies, medical history. METHODS: During personal interviews 133 women from seven different companies, working at constraining workplaces (very repetitive work), answered several questionnaires. These concerned: personal characteristics and history; work characteristics; psychosocial factors (perception and appreciation of the work situation, satisfaction at work, stress symptoms, Karasek questionnaire) and personality factors (neuroticism, conscientiousness, type-A behavior). They also undertook functional and psychomotor tests (wrist angles, grip strength and a dexterity test). Logistic regression models were calculated. RESULTS: Wrist-hand complaints appear to be associated with some personal characteristics (smoking habits, fewer hobbies), work constraints (fewer breaks, heavy lifting efforts) and some personality (introversion) and psychosocial factors (worse appreciation of work). Neck complaints are also associated with some personal characteristics (young people, small, bad health, hormonal problems, fewer hobbies), some personality (urgency of time) and psychosocial factors (constraints as seen by the supervisor). CONCLUSION: The study confirms the multifactorial character of the musculoskeletal disorders and underlines the need for a global ergonomic approach to work situations, taking into account all their physical, psychological and social components.

Relation between functional characteristics of the trunk and the occurrence of low back pain. Associated risk factors.

STUDY DESIGN: A 2-year prospective study relating a set of subject characteristics (professional and extraprofessional constraints, personal and anthropometric characteristics, and static and dynamic performance of the trunk) and incidence of low back pain in a population of male Belgian steel workers. OBJECTIVES: To investigate the relation between occurrence of new cases of low back pain and prior personal, anthropometric, or functional characteristics. SUMMARY OF BACKGROUND DATA: Some functional characteristics--in particular, dynamic parameters of the trunk such as the velocity--have been shown to be significantly reduced for low back pain in workers in cross-sectional studies. The question remained as to whether modifications of these parameters preceded the development of low back pain. METHODS: The protocol included a questionnaire, a clinical examination, anthropometric measurements, and a set of functional tests on an isoinertial dynamometer. It was carried out twice, after a 1-year interval, on a sample of 215 workers without any history of low back pain. The reports of low back pain were again investigated 1 year later. RESULTS: The development of low back pain is related to frontal plane imbalance of the trunk, lower body weight, and perception of heavy lifting efforts at the workplace. Individuals performing dynamic tests at higher velocities appear also to be at a greater risk of low back pain. CONCLUSIONS: Although workers with a history of low back pain performed dynamic tests at significantly lower velocities, the probability for development of low back pain in the following year is greater for workers performing such tests at greater velocities.

Prevalence of musculoskeletal disorders at the wrist as a function of angles, forces, repetitiveness and movement velocities.

OBJECTIVES: The purpose of this investigation was to study the relationship between the prevalence of musculoskeletal disorders at the wrists and the characteristics of the work conditions in terms of angles, forces, repetitiveness, and movement velocities. METHODS: Nine workplaces were selected and the prevalence of wrist disorders was determined by means of a questionnaire for both arms separately, along with characteristics of the 335 subjects (age, weight, height, seniority). A work analysis was performed on subjects selected at random from each workplace by recording, for both wrists during a representative number of work cycles, the angles both in radial and ulnar deviations and in flexion-extension and the surface electromyogram on the hand flexors of the forearm. Repetitiveness (defined as the number of transitions per minute) and movement velocities (in deviation and flexion-extension) were derived from the recordings of the angles. RESULTS: All the derived variables were highly correlated, greater angles and greater forces being associated with greater velocities and higher repetitiveness. A multivariate linear regression model for the prediction of the prevalence of musculoskeletal disorders of the wrist was constructed (R = 0.904). Height, weight, seniority, angles in radial-ulnar deviation, and forces were significant and independent predictors of the prevalence. CONCLUSIONS: The prevalence of wrist disorders is significantly linked to wrist angles in deviation and to forces exerted. Due to their high correlation with force, the repetitiveness indices and velocities, as defined, do not appear to play an additional role. Further research is needed to find alternative ways of characterizing repetitiveness.

Isometric and dynamic performances of the trunk and associated factors.

STUDY DESIGN: Static and dynamic performances of the trunk were measured on an isoinertial device and data were collected regarding the working conditions and the anthropometric and psychosocial characteristics of the workers. OBJECTIVES: To describe the difference in static and dynamic performances of the trunk between workers with and without low back pain and to investigate the anthropometric, personal, and occupational factors associated with these performances. SUMMARY OF BACKGROUND DATA: The isometric torque and the parameters of displacement, velocity, and torque during dynamic tests were chosen to describe the isoinertial performances of the trunk. Dynamic characteristics in particular were investigated because it has been suggested in the literature that these discriminate best between workers with and without low back pain. METHODS: The protocol included a 52-item questionnaire, a clinical examination with a series of anthropometric measurements, and the isometric and dynamic tests (against 25% and 50% of the isometric values) on the isostation. RESULTS: The variables significantly associated with the trunk performances were weight, height, muscularity, sports, and leisure activities as positive factors, and linearity, health problems, and vehicle driving as negative factors. When these covariates were taken into consideration, the significant differences between subjects with and without low back pain were related only to the velocities during dynamic tests, which were reduced by 5.9%. CONCLUSIONS: The performances of the trunk are associated mainly with the anthropometric characteristics of the subjects but also with factors such as lumbar status, health, working conditions, and leisure activities.

Evaluation of the physical work load of bricklayers in the steel industry.

A study was made of work conditions suspected of being responsible for a greater prevalence of musculoskeletal disorders among 33 bricklayers. A standardized questionnaire was used to confirm a high 12-month prevalence of 73% for the low back and about 20% for the upper limbs. Physical work load was studied with the use of heart rate recordings and posture analyses. According to the heart rate data, the work load was "moderately heavy" (300 W). A diagnostic analysis identified work postures that could be considered as imposing a heavy strain on the musculoskeletal system. The risk associated with these postures was investigated with biomechanical models. This analysis procedure made possible elaborate ergonomic solutions that reduced the work load in general and the biomechanical constraints in particular.

Predicted sweat rate in fluctuating thermal conditions.

The ISO 7933 Required Sweat Rate Index is inappropriate under conditions of fluctuating exposure. Time weighted average values can introduce large underestimations as, for hot conditions, the relationship between physical stress and physiological strain is not linear. Mean skin temperature and sweat rate vary as a first order system, that is, according to an exponential averaging system, in response to a step function of the primary parameters. A very simple algorithm has been derived to take into account this exponential averaging and to predict the sweat rate at any time, taking into account the past exposure of the subject. It is based on time constants of 3 min for the mean skin temperature and of 25 min (up to a sweat rate of 50 W.m-2) and 10 min for the sweat rate. The correlation coefficient is 0.780 between observed and predicted sweat rates in independent experiments used for the validation of the model. This emphasises the necessity for exponential averaging as differences between individuals are very important and the precision of the observed data in these experiments was lower than for laboratory experimental data.