Ergonomics and its application in the company

Industrial ergonomics is a field of knowledge that intervenes in production, it is relatively new in our country, due to the little knowledge of it and its application, but it has been developing and being applied in some companies. However, every day through the dissemination in congresses, meetings and courses, it begins to have demand and results in its application.

Ergonomics is defined as a body of knowledge about human abilities, their limitations, and characteristics that are relevant to design. Ergonomic design is the application of this knowledge for the design of tools, machines, systems, tasks, jobs and environments that are safe, comfortable and for effective human use.

The term ergonomics is derived from the Greek words ergos, work; we are not natural laws or knowledge or study. Literally work study.

Ergonomics has two main branches: one refers to industrial ergonomics, occupational biomechanics, which focuses on the physical aspects of work and human capacities such as strength, posture and repetitions.

A second discipline, sometimes referred to as "Human Factors," which is oriented to the psychological aspects of work such as mental load and decision making.

1. Anthropometry

There is no official definition of ergonomics. Murruel defined it as "The scientific study of man's relationships and his work environment."

Ergonomics is considered a technology; Technology is the practice, description and terminology of applied sciences, which, in their entirety or in certain aspects, consider to have a commercial value.

Ergonomics uses sciences such as occupational medicine, physiology, and anthropometry.

Occupational medicine was defined in 1950 by the ILO as:

“The branch of medicine that aims to promote and maintain the highest degree of physical, mental and social well-being of workers in all professions; prevent all damage to your health caused by working conditions; protect them against the risks derived from the presence of agents harmful to their health; place and keep the worker in a job suitable to her physiological and psychological aptitudes; in short, adapting work to man and each man to his work "

The physiology of work is the science that deals with analyzing and explaining the modifications and alterations that occur in the human organism as a result of the work carried out, thus determining the maximum capacities of the operators for various activities and the highest performance of the organism based scientifically. The field of study of work psychology covers issues such as reaction time, memory, the use of information theory, task analysis, the nature of activities, in accordance with the mental capacity of workers, the feeling of having done a good job, the persecution that the worker is duly appreciated, relationships with colleagues and superiors.

The sociology of work investigates the problem of work adaptation, handling variables such as age, level of education, salary, room, family environment, transportation and journeys, using interviews, surveys and observations.

Ergonomics falls within various professions and academic careers such as engineering, industrial hygiene, physical therapy, occupational therapists, nurses, chiropractors, occupational physicians, and sometimes with specialties in ergonomics.

The following points are among the general objectives of ergonomics:

Reduction of occupational injuries and illnesses Reduction of workers' disability costs Increased production Improved quality of work Decreased absenteeism Enforcement of existing standards Decreased loss of raw materials

These methods by which the objectives are obtained are:

Appreciation of the risks in the workplace, identification and quantification of risk conditions in the workplace, recommendation of engineering and administrative controls to reduce the identified risk conditions, education of supervisors and workers about the conditions of risk.

According to the Mexican Institute of Social Security in 1979, work risks increased enormously. During the 1974-1978 period, their index was 11.8%, which went to 18.9% in 1979.

In that year, 58,500 workers who were victims of a professional risk were treated; 1,600 deaths were registered (sic); 13,000 cases of permanent disabilities, and more than 10 million pesos were paid in subsidies for temporary disability.

It is estimated that in Mexico a work accident occurs every 58 seconds.

Every source of work must carry out activities aimed at preventing occupational risks in order to carry out loss control, with the consequent advantages of production and productivity, thus achieving greater social well-being, which is reflected in the economy of the company itself.

The need to protect workers against the causes of occupational diseases and accidents at work is an unobjectionable issue.

These problems, which are typical of labor legislation, are projected in ergonomics towards a more radical situation: the adaptation of the methods, instruments and working conditions, to the anatomy, physiology and psychology of the worker.

Avoiding fatigue, caused by the work performed, prevents the worker from enjoying his free time; suppresses the boredom associated with monotonous activity; Protecting workers and employees against premature aging, fatigue and overload is an extremely complex task.

Industrial ergonomics as a new field of knowledge that intervenes in the field of production, is relatively new in our country, new due to the little knowledge of it and its application. However, its method and techniques that if applied offer benefits to the worker, supervisor and especially in savings to the company, resulting in an improvement in the quality of life of all workers and the company.Anthropometry is the study of the proportions and measurements of the different parts of the human body, such as the length of the arms, the weight, the height of the shoulders, the stature, the ratio between the length of the legs and that of the trunk, taking into account the diversity of individual measurements around the average; analysis alsothe operation of the various muscle levers and investigates the forces that can be applied depending on the position of different muscle groups.

Anthropometric factors

If the structure of the human body and its dynamic characteristics are not taken into account when making the layout of the workplace, there may be adverse effects on the efficiency of the operator, his health and his well-being. Both static and dynamic anthropometric data are detailed in the standards manuals; the text by Damon et al. deals specifically and extensively with the subject. The designer must be familiar with the data available and imposed on their applications, their implications and their intelligent use.

Static anthropometry. In a workplace layout problem, measurements of the human body, indicated in the following figure, may be involved. The usual practice to use the 5th and 95th percentiles as a guideline for a given working population.

It must be accepted that there is no average man. An average person in one dimension may be very far from the average in another, and therefore it is virtually impossible to design the distribution of a job taking into account all the extreme cases of the problem. Only in a few situations, such as the height of the workbench surface, is it designed for a reasonable middle man. When considering control facilities, the 5th percentile for arm or leg reach should be used to ensure that operators can reach the controls. Seat heights will be adjustable from the 5th to the 95th percentile. Clearances will be based on the 95th percentile dimensions.

Anthropometric data are also useful in the design of personnel equipment (cases, goggles, masks, headphones, gloves), escape doors, work tables and desks, vehicles, prosthetic devices, furniture, utensils, office equipment, and passenger seats Dynamic anthropometry. Dynamic anthropometry deals with the movements of the body, its functional range, and the operations that can be done with the limbs in various positions. The dynamic data for kneeling, crawling and prone position, have application only when the work has special restrictions, as if the frequent case with mechanics, plumbers or repairmen. The range of action of a limb, for example grasping and operating a control and a torso movement,They can be studied by analyzing slow-moving photographs. The silhouette of the movement of the elements of the body can then be drawn in each of the three dimensions, and conclusions can be drawn regarding the optimal control situation, distribution of effort, etc.

2. Capabilities of the human body

There is a direct relationship between the amount of work being done and certain physiological phenomena, such as the heart rhythm oxygen consumption. There is also a similar relationship between other physiological functions, such as blood pressure, respiration, body temperature, and the rate of perspiration. Measurements from these can certainly give information about the man in a job. Like heart rate and oxygen consumption, Brouha and others have found that they are directly related to how much energy is being expended. Furthermore, these two functions can be measured quite easily to make practical use of them in the workplace or in the laboratory. For these reasons, the rhythm of the heart,oxygen consumption and total respiration are measurements most commonly made to determine the true physiological demands of certain jobs.

In the dynamic activity of the whole body, the demands on the cardiovascular system and the respiratory system are the greatest. The respiratory system must supply an adequate amount of oxygen to the circulatory system, which in turn must transport this oxygen to the working muscles. The result is a higher level of oxygen consumption and a faster heart rate.

For example, if the heart rate of an individual is measured at rest, it can be around 75 beats per minute. This is represented in section A in the curve of the following figure:

Then if the individual begins to walk at a pace of 6 km per hour, his heart rate will increase rapidly and after 2 or 3 minutes the heart rate will rise to more than 110 beats per minute. This is represented in section B of the curve. Section C shows how the heart rate returns to its original level when it is returned to rest. Therefore, the difference between the heart rate at work and at rest is represented by the distance Y. As stated above.

Measurement techniques.- These physiological principles can easily be used to determine the level of activity in certain work situations. Of the two physiological functions, the rhythm of the heart is somewhat easier to measure. The general principle of the electrocardiogram is used. Small electrodes are placed on the chest of the individual to be studied and the very small electrical current generated each time the heart beats is transmitted to the recording instrument, either by means of cables or by radio waves. Then the individual's heartbeat can be counted directly or electronically converted into beats per minute and recorded as a continuous curve of the heart's rhythm.

To measure oxygen consumption, the individual to be studied must put on a mask connected by a 25 mm flexible tube to a small gas meter (respirometer) that he keeps on his back. This passes around 3 kilos and measures the total volume of expired air and at the same time collects a sample of that air. The percentage of oxygen in the sample is measured by means of an oxygen analyzer. The oxygen content of the sample is then compared with that of the room. Knowing these percentages and the total volume of air breathed, the oxygen consumption can be calculated and converted into calories of energy consumed by means of a simple formula.

Work risk factors

Certain characteristics of the work environment have been associated with injuries, these characteristics are called work risk factors and include:

Physical characteristics of the task (the primary interaction between the worker and the work environment).

Postures force repetitions speed / acceleration duration recovery time dynamic load segment vibration.

The posture

It is the position that the body adopts when carrying out work. Crouching posture is associated with an increased risk of injury.

It is generally considered that more than one joint that deviates from the neutral position produces a high risk of injury.

Specific postures that are associated with injuries. Examples:

On the wrist

In the shoulder

A 30 degree flexion position takes 300 minutes to produce acute pain symptoms, with a 60 degree flexion it takes 120 minutes to produce the same symptoms.Extension with the raised arm has been linked to neck-shoulder pain and numbness, the Pain in the shoulder muscles decreases movement of the neck In the lower back: The sagittal angle in the trunk has been associated with occupational disturbances in the lower back.

Posture can be the result of work methods (bending over and twisting to lift a box, bending the wrist to assemble a part) or workstation dimensions (reaching for and getting a part on a one-piece worktable). high location; kneel in warehouse in confined space).

Three common conditions of workspace dimensions have been studied such as video workstations, standing workstations and electron microscopy stations.

Standing work station

According to Grandjean, the optimal height of the work surface where the manufacturing work is performed depends on the elbow height of the workers and the nature of the work.

For precision work, the height of the work surface should be 5-10 cm below the elbow, which provides support by reducing static loads on the shoulders. For light work, the height of the work surface should be 10 to 15 cm below the elbow for materials and small tools. For heavy duty work, the height of the work surface should be 15 to 40 cm below the elbow to allow good muscle work of the upper extremity.

Force

Tasks that require force can be seen as the effect of an extension on the internal tissues of the body, for example, compression on a spinal disc from loading, tension around a muscle and tendon from a small grip with the fingers, or so on. physical characteristics associated with an object external to the body, such as the weight of a box, the pressure required to activate a tool, or the pressure applied to join two pieces. Generally, the greater the force, the greater the degree of risk. Large forces have been associated with risk of injury to the shoulder and neck, lower back, and forearm, wrist, and hand.

It is important to note that the relationship between strength and the degree of risk of injury is modified by other risk factors, such as posture, acceleration, speed, repetition and duration.

Two examples of the interrelationship of strength, posture, speed, acceleration, repetition, and duration are as follows:

A 9 kg load on a flat slowly and gently directly in front of the body from a 71 cm shelf to a 81 cm shelf may be less risky than a 9 kg weight loaded quickly 60 times in 10 minutes of floor to a 1.52 m cabinet

A 45-degree neck flexion for one minute may be less risky than a 45-degree flexion for 30 minutes.

A good analysis of the tools (see the revised 1991 NIOSH load equation) recognizes the interrelationships of force with other risk factors related to overstress hazards.

There are five risk conditions added with force, which have been studied extensively by ergonomists. These are not rudimentary risks, they are job conditions that represent a combination of risk factors with significant components. The common appearance in the workplace and the strong association with the injury is seen below.

Static force

This has been defined in different ways, static force is generally the performance of a task in a postural position for a long time. This condition is a combination of strength, posture, and duration.

The degree of risk is the combined ratio of the magnitude and the external resistance; the difficult thing about the posture is the time and the duration.

Grip

The grip is the conformation of the hand to an object accompanied by the application of a force to manipulate it, therefore, it is the combination of a force with a position. Grip is applied to tools, parts and objects in the workplace during the performance of a task.

To generate a specific force, the fine grip with the fingers requires greater muscle force than a powerful grip (object in the palm of the hand), therefore, a grip with the fingers has a higher risk of causing injury.

The relationship between the size of the hand and the object influences the risk of injury. Physical force is reduced when the grip is one centimeter or less than the diameter of the finger grip.

Contact trauma

There are two types of contact trauma:

Local mechanical stress that is generated by having contact between the body and the external object, such as occurs in the forearm against the edge of the work area. Local mechanical stress generated by blows of the hand against an object.

Grip is applied to tools, parts and objects in the workplace during the performance of a task.

The relationship between the size of the hand and the object influences the risk of injury. Physical force is reduced when the grip is one centimeter or less than the diameter of the finger grip.

Contact trauma

There are two types of contact trauma:

Local mechanical stress that is generated by having contact between the body and the external object, such as occurs in the forearm against the edge of the work area. Local mechanical stress generated by blows of the hand against an object.

The degree of risk of injury is in proportion to the magnitude of the force, duration of contact, and the shape of the object.

Recovery time

It is the quantification of the time of rest, performing a low-stress activity or an activity that is done by another part of the body rested.

Short work breaks tend to reduce perceived fatigue and rest periods between forces tend to reduce performance.

The recovery time required to reduce the risk of injury increases with the duration of the risk factors. The specific minimum recovery time has not been established.

Dynamic force

The cardiovascular system provides oxygen and metabolites to muscle tissue. The body's response is to increase the respiratory and heart rate.

When the muscular demands of metabolites are not satisfied or when the need for energy exceeds the consumption, lactic acid is produced, producing fatigue.

If this occurs in one area of the body (shoulder muscles from repetitions during long periods of abduction), the fatigue is localized and characterized by tiredness and inflammation.

If it occurs at the general level of the body (due to heavy carrying, loading, climbing stairs, fatigue occurs throughout the body and can cause a cardiovascular accident).

Also an increase in ambient temperature can cause an increase in heart rate, contrary to when the temperature decreases. Therefore, for a given job, metabolic stress can be influenced by ambient heat.

Segmental vibration

Vibration can cause vascular insufficiency of the hand and fingers (Raynaud's disease or white finger vibration), also this can interfere with sensory feedback receptors to increase the grip strength with the fingers of the tools.

Furthermore, a strong association has been reported between carpal tunnel syndrome and segmental vibration.

3. Measurement and control of the physical environment

Harmful environmental factors, in general, adversely affect performance. Man has learned to adapt and accept a number of stresses in our complex urban-industrial world. A distinction can and should be made between the discomfort and discomfort of a job, for which a worker can be compensated, and the extreme stress that can cause physical injury and impairment. Certainly, high noise levels can damage the hearing mechanism and must be controlled. However, moderate noise levels are an inseparable part of the industry and a common source of worker complaints.

Environmental characteristics (the primary interaction between the worker and the work environment).

heat stress cold stress vibration towards the body lighting noise

Heat stress

Heat stress is the body load that the body must adapt to. This is generated extensively from the ambient temperature and internally from the body's metabolism.

Excessive heat can cause shock, a life-threatening condition resulting in irreversible damage. A less serious condition associated with excessive heat includes fatigue, cramps, and heat stroke-related disorders, eg, dehydration, fluid and electrolyte imbalance, loss of physical and mental capacity during work.

Cold stress

It is the body's exposure to cold. Systemic symptoms that the worker may present when exposed to cold include shivering, loss of consciousness, severe pain, dilated pupils, and ventricular fibrillation.

Cold can reduce grip strength with the fingers and loss of coordination.

Vibration throughout the body

Exposure of the whole body to vibration, usually the feet, buttocks when operating a vehicle results in occupational hazards. The prevalence of reports of lower back pain may be higher in tractor drivers than in workers more exposed to vibrations, thus increasing back pain with vibration. Power shovel operators with at least 10 years of exposure to whole body vibration showed morphological changes in the lumbar spine and it is more frequent than in unexposed people.

illumination

With industrialization, lighting has become important to have adequate lighting levels. This offers risks around certain work environments such as glare problems and eye symptoms associated with levels above 100 lux. The differences in visual function over the course of a workday between computer terminal operators and tellers working in illuminated environments are striking, to note one case.

The lighting recommendations in offices are 300 to 700 lux so that they do not reflect. Work that requires high visual acuity and contrast sensitivity requires high levels of illumination. Fine and delicate work should have an illumination of 1,000 to 10,000 lux.

Noise

Noise is an unwanted sound. In the industrial environment, this can be continuous or intermittent and appear in various forms such as the pressure of a die, hum of an electric motor. Exposure to noise can result in temporary or permanent ringing in the ears, decreased auditory perception.

If the noise lasts longer, there is a greater risk of hearing loss or decreased hearing. Also noise below threshold limits can cause hearing loss because it interferes with some people's ability to concentrate.

Other risks of the job

The occupational hazards indicated by industrial ergonomics are a list of injuries present in the work environment. Others include:

Work stress Work monotony Cognitive demands Work organization Workload Work hours (load, overtime) Sign and control panels Slip and fall Fire Electrical exposure Chemical exposure Biological exposure Ionizing radiation Radio frequency and microwave radiation

Professionals of industrial hygiene and safety, ergonomics and human factors, occupational doctors, occupational nurses must assess and control these risks. The ergonomist needs to recognize the capabilities of individuals and work relationships in order to achieve a safe and appropriate workplace.

4. Human-machine interaction

In countries like ours, which is not self-sufficient in the production of machinery, it is imported, the worker having to deal with instruments whose dimensions do not coincide with their characteristics, since they were designed for subjects with other proportions.

Estimation of the workplace for ergonomic risk conditions

This evaluation is carried out in two steps: 1) identification of the existence of ergonomic risks and, 2) quantification of the degrees of ergonomic risk.

Identification of ergonomic risks

There are several approaches that can be applied to identify the existence of ergonomic hazards. The method used depends on the philosophy of the company (participation of workers in decision-making), level of analysis (evaluating a position or the entire company) and personal preference.

Examples of approaches to identifying ergonomic hazard conditions include:

Review of Hygiene and safety regulations. Analyze the frequency and incidence of cumulative trauma injuries (carpal tunnel syndrome, upper extremity tendonitis, lower back or lumbar pain) Symptom investigation analysis: information on the type, location, duration and exacerbation of symptoms suggestive of conditions associated with ergonomic risk factors, such as neck, shoulder, elbow and wrist pain. Interview with workers, supervisors. Questions about the work process (what? How and why?) That can reveal the presence of risk factors. Also questions about work methods (is it difficult to do the job?) Can reveal unsafe conditions.

Facilities around work such as movements or walking. With knowledge of the process and work schedules, the job site should be observed for the presence of hazardous conditions.

Quantification of ergonomic risks

When the presence of ergonomic hazards has been established, the degree of risk associated with all factors must be evaluated. For this, it is necessary to apply ergonomic analytical tools and the use of specific guides.

Ergonomic analysis tools

There are a wide variety of tools for ergonomic analysis, these are frequently oriented to a specific type of work. For example, manual handling of materials; or from a particular area of the body such as the wrist, elbow, or shoulder.

These techniques can also vary in their conclusions, they can prioritize work by quantifying activities associated with increased risk of injury or recommended weight limits for lifting.

The analyst determines what type of evaluation and technique is best to evaluate the risks of occupational injuries based on a knowledge of the applications of a certain tool, taste or ease for any of it.

A good technique can provide a good approximation of the degrees of risk. Variations in individual physiology, injury history, work methods, and other factors that influence a person to present an injury. In addition, many tools have not been adequately tested to implement and validate them, this reflects the progress and increasingly better knowledge of ergonomics towards aspects that are more difficult to find in the worker and his job.

Despite these comments, these ergonomic tools offer a standard method of reasonably and objectively analyzing workplace hazards.

Description of the job

The work environment is characterized by the interaction between the following elements:

The worker with the attributes of height, width, strength, ranges of motion, intellect, education, expectations, and other physical and mental characteristics.

The workstation comprising: tools, furniture, dashboards and controls and other work objects.

The work environment that includes temperature, lighting, noise, vibrations and other atmospheric qualities.

The interaction of these aspects determines the way in which a task is performed and its physical demands. For example, a 72.5 kg load at 1.77 m, the male worker loads 15.9 kg from the floor generating 272 kg of force from the lower back muscles.

When the physical demand of the tasks increases, the risk of injury also, when the physical demand of a task exceeds the capabilities of a worker an injury can occur.

Bibliography

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