Ergonomic conditions of work
Abstract: Knowledge of ergonomic conditions prevents employee discomfort, fatigue, and physical injury. Injury related to poor ergonomic conditions can be prevented by designing the physical work environment around the physical needs of individual employees. Therefore, it is necessary to know the physiological, psycho-sociological conditions, and anthropometric ergonomic conditions.
Key words: physiology, motivation, fatigue, monotony, stress, anthropometric, bio- mechanical
disease. So today, except for the impact of physical work on the organism, physiology studies the following:
1. Substances that exist in the workplace or are manipulated with 2. Working time, regime of work and rest
3. Design and construction of equipment for work, workplace and work space
4. Relationships in a working group or by hierarchy
5. Responsibility and fear for success in production and careers 6. Alienation from one’s own work
7. Computerization and management of technological systems
Physiology of work studies the work quality and physiological abilities of a man to overcome its various forms and their mutual relations. Work is performed in the interaction of three interrelated factors:
1. The work itself – which by its content, regime and organization, is a burden to a man.
2. Work environment – which can be the meeting place of various aggravating, risk or even harmful factors.
3. The man who performs the work – who must make an effort to overcome the burden of work and hazards in the working environment.
At the same time he uses his abilities, knowledge and skills.
When the requirements of work are such that a man can overcome them by making an effort, the functional abilities of his body and his health are not endangered and there is ergonomic balance. In that sense, the physiology of work deals with (Arandjelovic and Jovanovic, 2009):
1. Defi ning the workload.
2. Defi ning the requirements of work.
3. Studying human physiological abilities and the amount of physiological effort he can make to respond to the requirements of work.
(1) Defi ning the workload
Performing any kind of work is a kind of a burden for the body. The type, intensity and duration of the load depend on the work. Physiological workloads should be such that the body can respond to them through physi- ological functions, i.e. to maintain homeostasis when working. The load that cannot be overcome leads to disorders of homeostasis (the balance in the body is lost), which is an overload that causes fatigue. In case of further
increasing the intensity of overload, there is a pathological response of the body, i.e. fatigue.
Loads can be physical, mental, and sensory.
Physical work (the work of skeletal muscles) is a major cause of physical load because of work. Physical work means the work that a man does while overcoming burden and resistance. Physical work can be dynamic and static work.
(a) Dynamic work: It is the work in which there is a change in the position of the bones to which muscle is attached and which is, from the me- chanical aspect, characterized by the change of body position in space.
Fatigue rarely occurs in dynamic work because constant contraction and de-contraction of muscles acts as a pump, which accelerates blood circulation (it enables the fl ow of nutrients and elimination of decay products). At the beginning of dynamic work (because of the energy needs), oxygen consumption and heart rate suddenly increase. After a few minutes they reach the level that is maintained steadily as long as the work is performed (steady state). Upon termination of work, the curve of oxygen consumption and heart rate gradually drops to a value at rest.
Each work is characterized by a degree of diffi culty. A particular work should not be more diffi cult than the one that a man can perform. The evaluation of work in physiology is carried out in order to standardize the workload, program the regime of work and rest and carry out a professional selection.
Each physical activity requires a specifi c energy necessary for muscle contraction.
The evaluation of how diffi cult the work is can be done by determining the energy consumption during work. Energy consumption ranges from 4 to 6 kJ/
min at rest, and from 50 to 80 kJ/min during extremely heavy physical work.
Energy consumption is affected by gender, age, and the level of how trained the workers are. According to energy consumption, work can be:
1. Easy work 10.9–15.5 kJ/min 2. Moderate work 15.5–20.5 kJ/min 3. Hard work 20.5–26.0 kJ/min 4. Very hard work 26.0–32.7 kJ/min
(b) Static work: It is the work of muscles without moving in space. It is also called a static effort because the external mechanical effect equals to zero. During static, work consumes the energy to tighten certain
muscle groups, and they are necessary to maintain the body position in space (standing long, lifting tools, holding a burden, etc.).
Static work is characterized by lower energy consumption compared to dynamic work, but it causes fatigue and tiredness more rapidly. There is an increase in the tone of muscles that perform the compression of blood vessels in static work; hence, circulation is more diffi cult, the supply of nutrients is reduced (oxygen, glucose), the outfl ow of decay products of metabolism is reduced (lactic acid) and fatigue occurs more quickly. After completing the work, oxygen consumption continues to increase and returns to the value at rest very slowly.
In evaluating psychological workload three groups of factors are taken into consideration: unfavorable working environment; job requirements and its organizational-technical characteristics; and social changes and problems in everyday life.
(a) Unfavorable conditions of working environment such as noise, vibra- tion, temperature, humidity, brightness, etc. act negatively on the ef- fi ciency and sense of comfort at work. In certain circumstances, their impact can be subjectively perceived in a different way. For example, monotonous jobs with moderate-intensity noise activate the body and have a positive effect on performance. If many factors act at the same time the ultimate effect can be different, i.e. they can cause:
1. Accumulation: total harmful effect equals the sum of individual adverse effects.
2. Compensation: mutual cancellation of a number of factors so that the ultimate effect is less adverse than if only one factor were to act.
3. Multiplication: total adverse effect is bigger than the sum of individual adverse effects, which can result in very harmful consequences for human health.
(b) Job requirements and its organizational-technical characteristics, i.e.
direct effects of psychological factors related to job characteristics lead to psychosensory and psychomobility workload, as well as intel- lectual and emotional ones.
Dangerous, risky, complex, stressful, and responsible jobs require appropriate abilities, knowledge and skills of workers, i.e. high degree of engagement of psychophysical capacities of workers. Psychological factors that infl uence these jobs lead to psychophysiological effort, the size of which depends primarily on job characteristics (terms and conditions), but also on personality traits. If these factors act longer, psychophysiological tension occurs (the state between the normal, physiological and pathological one, with a tendency to take the form of pathology, i.e. a disease).
Emotional state has an important role in decision making, problem solving, communication, negotiation and adaptation to the environment and changes.
According to Damasio (1999), emotions may be as follows: happiness, sadness, fear, anger, surprise, disgust, discomfort, jealousy, guilt, pride, serenity, or tension.
Personal characteristics of an individual (the characteristics of worker’s personality), which are defi ned hereditarily by constitutionary characteristics, together with the risks that arise from the work environment, can favor the occurrence of a strain and its negative effects on the health of workers.
Emotional stability, resistance to stress and frustration, anxiety, neurotic personality traits, depressive reactions, self-confi dence, etc. are of particular importance. Poor coordination between individual traits and abilities and job requirements can lead to the following: stress, mental fatigue, unruly behavior (alcoholism, lack of discipline, etc.), psychiatric disorders (depression, anxiety), and psychosomatic illnesses (hypertension, asthma, endocrine disorders, etc.). On the other hand, a good psychosocial adaptation has positive effects on the satisfaction of workers with their life and work and on the overall state of his health.
(c) Social changes and problems in everyday life include the following:
family problems, divorce, death in the family, family obligations, housing problems, problems at work, confl icts in production–busi- ness system (PBS), diffi culties in interpersonal communication and bad corporate and economic situation in the country. Estimates of psy- chological strain are based on the practical experience and researches of psychologists and doctors of work medicine, and what follows are three possible approaches:
1. professional-graphical: it is based on the description and standard- ization of characteristics of work.
2. individual psychological: it is based on determining the personality profi le, health status and behavior of workers.
3. epidemiological: it is based on monitoring the health consequences of psycho-physiological workload in certain jobs.
(2) Defi ning the requirements of work
Requirements of work defi ne what the workload and adverse effects require of the workers and can be the following:
• Requests for certain functions of the organism. In addition to general health conditions, the work requires some particularly preserved functions of organs and systems or some particularly preserved or marked morphological features of a man. For example, working with
the microscope, quality control of textiles, sewing and so on require certain visual functions.
• Requests for certain age limits of a worker. Depending on the age, some functions are established, some are changed, some disappear or are reduced, so that the same work shall not place the same demands on quite young, middle-aged or older workers. For example, workers in the night shift should not be older than 55 years.
• Requests for a specifi c sex of a worker. These requirements are not common, and are based on specifi c differences in the physiology of female and male body. Different requirements for men and women are set by the night work, working with heavy loads (carrying and setting up of textile materials on the table for cutting).
(3) Size of physiological effort
A man must make an effort to deal with the load imposed by a certain work.
The analysis of work can specify which functions of the body will be exposed to the infl uence of that work. So the individual workplace should always be analyzed, not the occupation.
The bigger the load is, the bigger the effort is, although not all the people make the same effort to deal with the same load. In determining the effort, the following has to be determined:
• the limit of physiological strain at rest
• the level of physiological response to work impact and
• the boundary between physiological and pathological responses Physiology of work therefore studies both the work and the man who works.
If one knows the physiological processes of human organism, it is possible to predict and prevent the occurrence of defects and damage caused by unnatural environmental conditions. By proper professional orientation, arrangement of work space in accordance with hygiene standards and production of clothing, especially adapted equipment designed to affect normal physiological activities as little as possible, ergonomics becomes an indispensable ‘‘ally in the fi ght’’ against professional diseases.