Research conducted forest ergonomics in the southeastern United States between 1980 and 1982 under the auspices of the Southern Forest Experiment Station Forest Service of the United States. The similarity of the environmental conditions of this region with those of other humid tropics would apply the results in a larger scale.

Placing a heart rate recorder

The timber industry is an activity that employs more people in the southern United States. In the extraction of wood is used a multitude of workers in manual, semi-mechanized and fully mechanized. These activities have always been physically strenuous and danger associated with frequent accidents and injuries of some severity. In this region, the operation is usually entrusted to many small independent contractors, although some of the largest timber companies have crews of loggers themselves. The extraction was rapidly mechanizing machinery based on very expensive, but still requires heavy manual labor. It is essential to carry out the removal of economic and productive way, and efectuarla without excessive fatigue, injury or sickness of staff.

During the past decade, the Department of Industrial Engineering at Auburn University, in cooperation with the engineering experiment station of the university and experiment station (Southern Forest Experiment Station) Forest Service of the United States, conducted a program ergonomic research aimed to increase the productivity of mining activities. Here are the results of major studies conducted as part of this program.

Evaluation of the physiological demands

In order to obtain basic data on the physical demands of logging activities, there was a study on the physiological stress – measured by heart rate level – due to different types of worker for normal activities and place that are out, paying particular attention to fatigue imposed by the heat in summer (Smith, Wilson and Sirois, 1982, 1983). During the summer of 1981, in the middle – eastern Alabama, collected data from four different combinations of employee and workplace, relating to persons engaged in simple tasks with chainsaw felling, stripping wire, parting and cutting, and management loader articulated mechanical arm length. In one of the places were also obtained data on mechanized felling and the use of arrastraderas claw (grapple skidder).

The data obtained indicate that the tasks performed in summer timber workers have physiological demands equal or exceed the maximum values ​​generally considered tolerable. According to figures from the tasks can be described in the following descending order of physiological requirements: parting and cutting (heavy duty) chainsaw felling (medium to heavy work), drag cable (light duty); mechanized felling (light duty) , loaded with long articulated arm machine (light work). The study also resulted in an important observation that led to further studies of heat stress: the beating heart means not accelerated as much as might be expected when the work is done with heat exposure, compared with the rate at which lot when working under normal conditions.

Bucking and delimbing at the landing

This suggests that the employee does his work without becoming fatigued to the point that he considers unacceptable. This means less muscle work that may be imperceptible to the observer, and can even be done unconsciously. For example, it was noted that with increasing temperature were recorded more undercover rest periods, such as crash interrupts the chain saw, etc.. Obviously these episodes fatigue limit but also lower productivity. As a result of this observation was later made investigations to determine the relationship between fatigue caused by heat and productivity.

Evaluation of fatigue caused by heat

Productivity versus heat

They conducted a study to assess the relationship between worker productivity and the level of ambient heat present at work for common tasks of logging (Smith, Seay and Sirois, 1985). The tasks evaluated were: chainsaw felling, stripping wire, bucking at the landing, handling a mechanical apeadora a multiple braiding. We reviewed archival data covering a period of 806 days of a gang, and supplemented by personal observations, totaling more than 20000 data.

Productivity in the first set of data measured in pounds came drawn by man – hours worked. By direct observation we determined the percentage of unproductive activities dependent on such factors as operator control, level of effort of the worker, the worker’s performance, percentage of risky activities and percentage of cases that did not use safety equipment.

The results indicate that the productivity of the whole band of felling, and in particular the productivity of the chain saw operators streamer cable and descends in a 5 to 15 percent when the temperature measured by the test and the temperature Oxford Index wet bulb exceeds 25 ° C and 26 ° C, respectively. None of the activities of parting was affected by increasing temperature, perhaps because they are not fully taking advantage of relevant staff in crews observed. Apeadoras mechanical operators experienced a loss of productivity from 2 to 3 percent with increasing temperature. The two companies collaborated in this study were in office safety programs at work that encouraged not to incur unnecessary risks. None of the workers had observed a dangerous behavior index greater than 2 percent. Although about half of workers exposed to hazards more with increasing temperature, reached not significantly change their behavior. However, the saws, which are most exposed to the sun, most often forget safety measures when it was hot. Those responsible for the short should be alert to this possibility and implement controls and supervision.

Guide to prevent fatigue due to heat

Another study (Smith and Rummer, 1988), taking into account the data of the study described above and an investigation of the impact on productivity in the use of air conditioning in harvesting machinery (Rummer and Smith, 1990), issued a guide to prevent fatigue caused by heat in logging activities, for use by those responsible for removal. This guide, entitled Guide to the prevention of heat stress in forest harvesting tasks, to assess the danger of consultation fatigue about appropriate boxes, the guide covers manual tasks, semi-mechanized and fully mechanized includes some suggestions for practices that reduce the risk of fatigue; discusses special situations where the danger may be greater than suggested by the weather, disease is caused by heat and measures to be taken if symptoms appear, and analyzes the effects of a hot working environment on safety. The guide needs field testing by managers to verify the extraction efficiency.

Assessment of exposure to vibration

The body’s exposure to vibrations can be partial or total. From the point of view of occupational exposure is the most dangerous part of the hand and arm of the operators of power tools, including chainsaws. The total exposure takes place through the building structure that is installed machinery vibration generating or through the bodywork of motor vehicles, among which include many machines used in the extraction timber. The total body exposure causes discomfort, reduced performance and a range of physical symptoms, including nausea and microfractures of the bone.

Review of the machinery for the analysis of vibration to the operator is subject

Rummer, Smith and Stokes (1985) compared exposure to vibration and noise of single-cylinder two models of chainsaws with a new two-cylinder model. Static tests were made in a test, and dynamic, cutting the field. The results show that the twin model has a lower vibration level. There was a calculation of the period during which there is a 50 percent chance for accumulation of damage to the body and concluded that, with four hours of use of the chainsaw twin, the period would be 26 years, while for single-cylinder would be less than 12 years. The noise emitted by chain saws all exceed the recommended limit. The less noisy, a constant speed, is the two-cylinder, but, if allowed the operator to choose the operating speed, the noise level is equivalent in both, as apparently operators speed calculated based on the chainsaw noise. If it were possible to generalize this result would have a substantial impact on training programs.

Most of the studies done on human exposure to whole-body vibration exposure levels measured and compared with existing models. Rummer (1988) examined the attitudes of forest workers to the total exposure and built a computer model that simulates all the possibilities and can be used to improve existing forestry machinery, the study surveyed a representative sample of 26 forest machine operators and examined subjective appreciation of vibration as a source of environmental stress.

Although the study revealed that total exposure is prolonged source of injury, the answers indicate that operators is one of the more unpleasant aspects of their work. According to the study, a significant proportion of the working day (1.5 hours) takes place aboard a truck, pit road. The vibration in the same is therefore a significant element of the total time of exposure to vibration.

Equipment design

When designing forest machinery engineers never attributed much importance to ergonomics, always giving precedence to parameters more directly related to profits, as capacity, durability and cost. The Southern Forest Experiment Station of the United States has sponsored studies on the application of ergonomics to the design of equipment.

Design of personal protective equipment

The chainsaw is involved in a high percentage of accidents timber. There are several types of protection for the legs of the chainsaw, which used properly are effective in preventing or mitigating injuries, but are rarely used in South America. Smith, Helm and Rummer (1988) investigated the factors that most affect the selection and use by operators of such equipment: protection capacity, appearance, cost, shelter, mobility, durability and style.

Five workers evaluated in the laboratory and field efficacy of leggings, protective pants, pants with normal work protective patch insertion, and chaps, compared with simple regular work pants. Were obtained and subjective views on the protection of the legs. In the laboratory, a computer used to simulate different conditions at 23 ° C and 35 ° C, and measured the temperature of the skin and restrictions of movement with each protection; also subjective impressions were obtained with a questionnaire. Finally, we asked the workers who participated in the tests take place protective gear for a week and then others who answered questionnaires with their own impressions.

The results suggest that the ability of protection and thermal comfort are the two factors that affect the decision of the operators, is mobility. Noteworthy is the fact that even declaring as less important factors of all the look, regardless of the test all operators discussed it more than any other factor, ie, showed more importance than stated. The test results are contradictory mobility, which could mean that different types of protection affect the mobility of different people in different ways. In short, the study suggests that to promote the use of protective material of the leg between the chainsaw should offer it in several colors to choose, demonstrate that the protection is effective, and test that does not harbor too, or hinders movement.

Ergonomic analysis of forestry machinery

Smith, Adsit and Rummer (1990) developed a model to facilitate ergonomic analysis of forestry machinery, so that can be done without the need to gather as much data as compiled in the literature. The model was then applied to the study of mobile shredders.

The model assumed the form of a checklist, which covers issues such as access to the cabins, interior dimensions of these, seat position controls, the force required to move these controls, instruments, visibility, climate inside the cabin, air quality, noise, vibration and maintenance. In addition to the list above, a questionnaire was drafted for submission to the operators to obtain subjective information.

Camera automatically records the positions of the operator

We evaluated six models of mobile shredders and the results indicate that the six are defective from the ergonomic point of view. The most notable defects were in the dimension of access to cars and the characteristics of the seat. In unequal measure the different models were weak visibility, cab climate and noise insulation. The answers to the questionnaire cited subjectively corroborated those objective results.

Operation of a claw arrastradora

Thomas and Smith (1991) found that operators of drag-nets of claws go from 27 to 57 percent (41 percent on average) of their work shift in contorted positions causing back pain. It was clear that the position of commander of the claws was a major cause of twisting of the positions adopted operators, and the vibration of the seat, on all machines tested, lowered the performance of operators. Anthropometric measurements showed that the operators of these machines in the southern United States were generally more bulky than the population samples to establish measures SAE standards and ILO officials, and were also more severe than the provisions of the SAE .

Conclusions

Research sponsored by the Southern ergonomic Forest Experiment Station have focused on the extraction systems of wood which have an important element of manual work. Workers use little or no protective equipment and work in environmental conditions characterized by wet bulb temperatures between 20 ° C and 35 ° C. The results of these investigations are somewhat relevant to other regions that have exhaust systems and similar environmental characteristics.

During the next decade will intensify the mechanization of logging activities is adopted as new machinery to perform tasks traditionally manual, or as they are implemented – as a large-scale thinning or fuel particle production – only are rewarding executed mechanically. It also enacted new mandatory standards of protection, therefore, the next phase of ergonomics research program of the Forest Service of the United States and Auburn University will focus on mechanized logging systems and promote the manufacture and use of equipment protector. These new research will be an extension of the existing studies on fatigue caused by heat and vibration, to continue accumulating data and to devise systems that minimize negative impacts on safety, health and productivity operators. It will increase and correct the database available anthropometric equipment makers and will continue with an ergonomic evaluation of existing machines to improve the livability and maintenance. Research on personal protective equipment complete sets that lead to effective protection with minimum negative effects on comfort and mobility of the operator. It will also examine some currently popular devices such as belts that “support” the lower back, and wrist guards to protect the forearm, whose efficacy has not been demonstrated.

By LA Smith and RE Thomas, Jr.
Leo A. Smith and Robert E. Thomas Jr. belong to the Department of Industrial Engineering at Auburn University, Auburn, Alabama, USA.

Literature

• Axelson, O. 1974. Heat stress in forest work. Rome, FAO.
• Rummer, RB 1988. Whole-body Vibration Exposure of forest equipment in the southeastern OPERATORS United States. PhD thesis. Auburn, Alabama Department of Industrial Engineering, Auburn University.
• Rummer, RB and Smith, L A. 1990. Utilization of air-conditioned feller / Bunchers. Int J. of Industrial Ergonomics, 5: 93-302.
• Rummer, RB, Smith, LA and Stokes, BJ 1985. Two-cylinder chainsaw vibration and noise test. Technical Release 85-R-13. American Pulpwood Association, Inc.
• Smith, LA 1980. Final Report No. 19-353. New Orleans, Forest Service, Department of Agriculture (USDA).
• Smith, LA and Rummer, RB 1988. Development of a heat stress prevention activity guide for use by southern forest harvesting managers. Final Report No. 1987-065. New Orleans, USDA Forest Service.
• Smith, LA and Sirois, DL 1982. Ergonomic research: review and Needs in southern forest harvesting. Forest Prod J., 32 (4): 44-49.
• Smith, LA and Wilson, GD 1982. Equipment note: an inexpensive system for remote monitoring of work heart rate. Ergonomics, 26 (7): 719-722.
• Smith, LA, Adsit, DA and Rummer, RB 1990. An ergonomic evaluation of forest machines: development of an evaluation protocol and case-study of mobile chippers. Final Report No. 19-88-074. New Orleans, USDA Forest Service.
• Smith, L A., Helm, AM and Rummer, RB 1988. Evaluation of Factors Affecting the selection and use of chainsaw leg protection Final Report No. 19-86-048. New Orleans, USDA Forest Service.
• Smith, LA, Seay, MS and Sirois, DL 1985. Evaluation of the effect of heat stress on worker Productivity for selected southern forest harvesting tasks. Final Report No. 19-82-082. New Orleans, USDA Forest Service.
• Smith, LA, Wilson, GD and Sirois, DL 1982. Assessment of the Physiological stress of selected forest harvesting Activities in the southeastern United States. Final Report N °. 19-80-407. New Orleans, USDA Forest Service.
• Smith, L A., Wilson, GD and Sirois, DL 1983. Work physiology evaluation of southern forest harvesting tasks. Forest Prod J., 33 (9): 38-44.
• Thomas, RE and Smith, L A. 1991. Reducing Injuries in grapple skidder back OPERATORS-through ergonomic design. Project No. 1991-033. New Orleans, USDA Forest Service.

One pathway by which exposure to occupational stress results in pain may be through changes in musculoskeletal activity or reactivity.

Increases in muscular activity have been associated with tasks involving greater psychological demands. It has also been observed that muscle activation can be triggered by mental stress independent of physical effort. Spectral changes in forearm EMG, increased forearm tremor, and increased musculoskeletal discomfort have been observed in response to stress. In the absence of a quantifiable increase in work demands, the perception of an increase in work demands is sufficient to increase forearm muscular tension during task performance. When exposure to psychological stressors co-occurs with physical stressors, levels of EMG, blood pressure, and self-reported stress tend to be greater than in response to either exposure alone. An individual’s psychological style, or how he or she characteristically responds to a challenge, has been related to the degree of muscle coactivation during completion of a simple motor task. This finding suggests that muscle activation can vary depending on how one characteristically perceives his or her environment. Taken as a whole, these studies suggest that while a perception of work as demanding is sufficient to increase musculoskeletal activity, the addition of physical exposures and a certain style or personality can further increase this activity. It is possible that such recurrent or chronic forearm muscle tension, secondary to psychosocial stressors, places sustained loads on the tendons in the wrist and elbow.

The fatiguing of low-level motor neurons in the upper trapezius and forearm, secondary to stress-induced muscle contraction, may also lead to musculoskeletal discomfort or injury via the fatiguing of small motor units. This discomfort or injury may encourage alternative muscle recruitment and exposure to increased biomechanical risks.

Another potential pathway linking occupational stress to work-related upper extremity disorders may involve the biochemical consequences of the stress response, specifically the release of catecholamines and cortisol. Although serum levels of cortisol, epinephrine, and norepinephrine typically rise and fall throughout the day, investigations of psychological and environmental correlates of stress hormone levels have determined that the sympathetic nervous system stimulates the release of these hormones differentially, based on the qualitative interpretation of the exposure to stress. On one hand, in general, it has been reported that the catecholamines appear to be related to the “positive” mental and physical demands of a stressor. On the other hand, cortisol appears to be generally related to negative aspects of the stress response, including negative emotions, the anticipation of negative consequences, and the perception of events as novel, uncontrollable, or unpredictable.

The psychosocial characteristics of the work environment, such as task repetitiveness and rigid work arrangements, also appear to affect circulating catecholamines. Lundberg et al reported that “deactivation” of catecholamines, especially epinephrine, was slower after a repetitive data entry task than after a stimulating, self-learning task. Melin et al reported that catecholamine levels in male and female assembly workers who were given the opportunity to work in autonomous groups and to influence their work pace decreased more rapidly after work than did catecholamine levels in individuals who worked in the “traditional” work organization (with fixed workstations and short, repetitive work cycles). In this study, the pattern of heightened reactivity and delayed recovery was observed in female workers in contrast to males and the pattern was even more marked in female workers who had children at home. Luecken et al reported that 24-hour cortisol secretion was higher in women with at least one child living at home than in women without children. These cortisol levels were not affected by marital status or social support. These studies suggest a potential interaction among gender, paid and unpaid work demands, and stress reactivity and recovery.

Chronic elicitation of the stress response, and the concomitant increases in catecholamine and cortisol release, could also directly affect the structure and function of muscles, tendons, and ligaments. In addition to the direct effect these substances can exert on soft tissues, norepinephrine release can, theoretically, affect behavior, resulting in an increased rate at which an individual performs tasks under stress. This, in turn, could result in more rapid and forceful responses during work tasks, thereby potentially increasing exposure to biomechanical risks.

Release of neurotransmitters may also play a role in the exacerbation of muscle pain. It has been observed that serotonin, which is released in response to stress, potentiates the effects of endogenous pain mediators, such as bradykinin (Babenko et al., 1999). The infusion of both serotonin and bradykinin into the tibialis anterior muscle in humans has been associated with elevated pain intensity and prolonged pain in response to mechanical stimulation. This preliminary evidence suggests that exposure to stress could exert a nociceptor sensitization effect on muscle. In addition to the peripheral effect of stress on pain, data exist to support a direct role of the central nervous system. This may help explain how psychological processes, such as attention and emotion, influence pain and pain tolerance. In addition, the peripheral vasoconstriction induced by circulating catecholamines could further inhibit blood flow to a potentially compromised nerve in the case of carpal tunnel syndrome.

It has also been shown that exposure to stress exerts an inhibitory effect on inflammatory or immune responses. Glucocorticoids (cortisol) decrease the production of cytokines and other mediators of inflammation and inhibit the effects of these agents on target tissues. It is possible that the repeated elicitation of the stress response does not allow for the pain-sensitive tissues to recover following mechanical insult. Although the exact mechanism of injury differs from most work-related upper extremity disorders, it has recently been demonstrated that recovery from an oral puncture wound is significantly delayed following exposure to stress. Production of interleukin-1ρ, a proinflammatory cytokine important in cell recruitment and activation of fibroblasts, was noted to decrease by 68 percent following exposure to a stressor.

As indicated earlier, the potential pathways described above are speculative and represent a series of hypotheses that require rigorous scientific scrutiny. A critical element in validating these models is the determination of the time course between job stressor exposure, physiological changes, and symptom expression. Given the role that job stress plays in work-related symptoms in both the back and upper extremities, it is critical to identify the biobehavioral pathways underlying this effect, in order to understand how job stress can result in the symptom expressions characteristic of these disorders and in order to develop effective prevention and management strategies. The models reviewed need to be carefully tested using both laboratory and workplace studies.

Well-being at work? Is not that a bit exaggerated claims? No, because being healthy is more than not being sick.

There is a sense of well-being includes both physical as well as emotionally and psychologically. This ultimately provides the basis for motivation and performance dar.

What is health?

Who is not sick, should not automatically be healthy. Whether someone is sick, is determined by the measurement of blood pressure, sugar, etc., but many “ailments” such as nervousness, fatigue and insomnia to escape such findings. And yet these are often the harbingers of insidious symptoms of serious illnesses. For this reason, good health is much more than just the absence of disease.
Well-being: Being healthy is more than not being sick

The World Health Organization (WHO) has developed a concept of health that is holistic and based on human physical and psychological him as a social being and understands that in shaping his work and living conditions. It defines health as:

WHO definition of health
“Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.”

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The ISO 9241-2 for humane work design seeks to promote the well-being including in the workplace.

WHO sets new criteria

In November 1987 was the first international conference on health promotion. There, the Ottawa Charter was adopted, which relates to the comprehensive concept of health by the WHO. Moreover, it stressed the importance of the statement of work for health:

“Health promotion is the process of enabling all people to increase control over, their health and thus to enable them to strengthen their health. (…) The evolution of life, work and leisure have a significant impact on health . The way in which a society work, working conditions and leisure organized, should be a source of health and not the disease. health promotion creates safe, stimulating, satisfying and pleasant working and living conditions. ”

In plain language this means that it is not just about disease prevention and prevention , but about the health-promoting organization of labor and environmental conditions.

Comprehensive understanding of health

In the 50s and 60s aimed at health education to be provided through health education and knowledge-friendly behaviors. health promotion , however, is a relatively new concept. In relation to the workplace, it means that this is not only the place where it is to avoid accidents and diseases. A well-designed and content satisfactory work but makes an active contribution to promoting the health and personality.

Workplace health promotion includes

• Environmental prevention by creating health-promoting working conditions,
• Behavioral prevention through appropriate behaviors.

Workplace health promotion is based on the fact remain under what conditions people are not only healthy but also develop their personality and social skills and daily living skills. The opportunity to influence and change the working and everyday life, is one of the Ottawa Charter for additional terms.

The main objective of the study of accidents at work is prevention. Discipline does not care, responsible for the protection of workers against accidents at work is industrial safety, which raises substantive task identified as possible risk factors for correction and amendment with the intention of eliminating them.

An important element that makes their study is the high frequency with which they occur. The International Labour Office (ILO), according to their statistics reports that are reported annually on average 120 million workplace accidents worldwide, of these, 210,000 are registered as defunciones.1 Given the wide range of perspectives from which can approach the study of accidents at work, it is not possible in a single definition fully describe the meaning of a work accident and its implications in the field of health, social, the economic, etc. In recent years, knowledge about accidents at work has evolved considerably.

Previously, they were defined from a simple model that divided the accidents unsafe acts and conditions, and generally considered the accident as a result of error in worker behavior and / or conditions laborales.

The ILO considers the accident as the result of a chain of factors in which something went wrong and has not come to fruition. It is argued that accidents are a result of human activity, and that human intervention can prevent the occurrence of that string sucesos.1 Today, with the aim of reducing accidents at work, the emphasis is on improve working conditions, more complex models, trying to understand what the underlying causes in order to be able to set you correctiedigraphic.com measures, analyze working conditions and the risks to which the worker is exposed. 1

However, depending on the interest you have, there are different ways of approaching the problem as a result of working conditions, including direct and indirect costs such as lost days as compensation cost.

Also, accidents can also be classified according to the risk of labor or the type of damage they cause.

While the accidents involved a large number of publications, criteria and / or variables that are studied they are diverse. In order to have a general outline about what were the criteria used and results obtained in studies on accidents at work was a review of studies reported in the last 10 years.

Material and methods

We searched Medline and the base of infoSMART Avantel, we identified studies published between the year 1993 to year 2003. To avoid bias the literature search, this was based on some general keywords such as: Work Injuries, occupational Injuries, occupational accidents, work accidents, work revile security, occupational accidents, occupational accidents, work health and occupational health. We only included those that were being studied accidents at work, we excluded articles on diseases related to occupation. For the selection of the work is not interested in the economic sector in which they were made.

To explore how the study was conducted on occupational accidents were identified with the aim of the study, and the variables used as economic sector, completion date, age, sex, health and safety strategies in place, type of injury , the body part affected, severity of damage from considering whether caused partial disability, permanent, or death, characteristics of the activity and causes and promoting factors of the accident.

Results

From the research done, we selected 30 items, of which most (75%) were secondary sector and of these, five were performed in the construction industry, 5% of the studies were made in the tertiary sector and 10% were in the primary sector. We found that a third of the studies addressed the problem from the perspective of implementing health and safety strategies; in 12, analyzed the causes and promoting factors accidents. Only seven, it was found that the type of activity undertaken by injured workers was the focal point for the analysis of the accident. As for the damage resulting from accident, mention was made of seven articles of the type of injury. It was found that two thirds of articles stressing the damage classification as disabling or fatal accident.

A fundamental consideration for the designer is the size of the body – its spatial requirements. Measurements of population dimensions come from an area of study called “anthropometry.” These findings are relevant to such design tasks as selecting furniture, allocating space or placing equipment.

Anthropometry can provide the dimensions of an entire population or a target range within that population. Manufacturers often target measurements to the 50th percentile, or so-called “average” user. All this means is that 50% of the population are larger and 50% are smaller. By this definition, “average” does not really exist, and it is dangerous to design to this standard alone.

In more cases, it is necessary to design for an entire range of a population, from the smallest to the largest of those likely to use the particular space or equipment over time. For example, the height of cabinets or storage space might be set so that 90 percent of a typical office population can reach it, whereas a doorway may be designed so that 99 percent of the entire population can pass through it without stooping.

As a point of departure, the interior designer should consider criteria that cover the size of the fifth percentile of the adult female population through the 90th percentile of the adult male population. At left are some frequently used measurements.

It is also important to understand the inherent limitations of anthropometric data, and why they should be used as guidelines rather than hard and fast mandates. First, there is no one set of data that has been universally agreed upon. It is not uncommon to find values listed in different sources that vary by several inches for the same measurement.

Also, it should be obvious that the applicability of any measurements used in a design solution depends upon the similarity between the population studied and the population who will be performing the task or using the product.

The designer should also refer to the provisions of the Americans with Disabilities Act (ADA) to ensure that reasonable accommodation of the disabled is taken into consideration. An informed designer will be able to achieve the best fit between the individual and his or her environment.

The selection and placement of furniture and equipment will also determine the postural requirements in a workplace. Ergonomic research used to stress the importance of maintaining the body in a “neutral” position for as long as possible to minimize the stress on muscles and joints. Current research indicates that in addition to maintaining healthful posture, it is important for the individual to vary or alternate pressure points and body positions at will. This will allow the body to increase its available strength, postpone fatigue, and minimize the likelihood of injury. Whenever possible, a design scheme should accommodate this need for the body to change positions. Providing spaces for people to walk short distances, adjust their chairs or to alternate between seated and standing tasks can have a healthful effect.

We know that maintaining any posture or performing any movement exerts force on, or stresses, the body. These stresses exist somewhat in any situation, although they are not necessarily hazardous. Whether or not they have a negative effect depends upon the amount of demand imposed on the individual through exertion, intensity, duration or repetition. It can also be a combination of these factors which produces dramatic increases in work effort, fatigue, pain, discomfort and injury.

An example of a stressor is the amount of force required in moving or lifting an object, such as opening a file cabinet or raising a flipper to retrieve an item from overhead. It is important that the strength requirements are within the level of the capabilities of the population who will be performing the task.

Some stressors can be reduced by simple rearrangement once the ergonomic risk has been identified. In other cases, it is necessary to replace furniture or products that are dated or dangerous with newer, more ergonomically designed products. One example is the selection of overhead storage units with a hydraulic assist on the flipper. The unit can be the same size as the one it replaces, but the amount of effort required to operate it is much lower. Consider user ease and access when making purchasing or placement decisions.

They facilitate the development of occupational health and safety in operation in terms of a management task: planning, a systematic, targeted and controlled.

These design principles can be the basis of regulations, Occupational Safety regulations (safety regulations) and the rules of the art concrete for the various tasks and jobs.

Design Principle 1: preventive

The Labour Protection Act contains a model of occupational safety and health, as it were a basic philosophy. First there is the avoidance of health hazards, the prevention or The preventive action. This requires a planned approach and the inclusion of occupational health and safety at all levels of the company, executives and employees.

• The work must be designed so that any risk to life and health is avoided and the remaining risk is as low as possible.
• Employees must fulfill their obligation to cooperate, protective measures and codes of conduct must be observed.
• Hazards should be controlled at the source. It follows that technical and organizational protection measures have priority over personal protection equipment.

Design Principle 2: business related

The measures for the health and safety in operation, the more effectively and more efficiently, the more all predictors of the respective specific operational circumstances are taken into account. Therefore urges the OSH Act:

• The necessary measures must take into account the circumstances of the workplace, the work situation and operations that affect the health and safety.

Design Principle 3: holistic

Not just the technology or operations have influence on potential health hazards, but also social and psychological components. This may include, for example, unclear responsibilities and job descriptions, lack of qualifications of the persons concerned or a bad work environment include.

Measures should be planned with the aim of technology, work organization, other working conditions, social relationships and link the influence of environment on the job properly

The work system as a basis

A step towards holistic coverage of all factors and elements of a work situation or in a workplace, and their mutual influence on the consideration of the work situation is as a working system.

Health and safety should be ensured in a working system, the system must be designed according to its individual elements and in its entire interaction. The detection of specific work system is the preparation and systematization of the risk assessment. These may be process-oriented and make work tasks and work processes at the center as required. You may also be object-oriented and look at individual elements of the work system. Approaches to design are basically always the technology, people and organization.

Design Principle 4: current

The development of measures for occupational health and safety is not an act. New technical equipment, materials and new working methods, new discoveries in medicine require an adjustment of labor protection measures ever necessary.

• The prior art and secure working scientific knowledge – and the generally accepted rules in the professional world of technology – the specification of protective measures must be taken into account. Such expertise to bring the consultant to the employer, as the experts on occupational safety with one.

Design Principle 5: A continuous process

The measures of occupational health and safety must withstand a review of efficacy. The Labour Protection Act calls for a continuous quality assurance process.

• The safeguard measures shall be reviewed for effectiveness and modified if necessary, the conditions are matched.
• An improvement of health and safety is desirable.

Design Principle 6: participation-oriented

Without the active involvement and a piece of personal responsibility as it gets. So says the Occupational Safety Act, the training of employees. You have a duty to follow the instructions and support to employers for health protection. You have the right to information and may make suggestions for improvement.

Involvement and participation in health and safety promotes thinking, preventive action and Aktzeptanz.

• The employer shall instruct sufficient and appropriate.
• Employees are entitled to the employer proposals on all issues of safety and health to make.
• Vulnerable groups such as pregnant women need or Mitigated performance are also considered in the design of protective measures.

The literature provides strong evidence for the role, in low back disorders, of job satisfaction, monotonous work, social support at work, high work demands, job stress, and emotional effort at work. The perception of one’s ability to return to work was also positively associated with future back pain.

While the literature on upper extremity work disorders is not so extensive as with back disorders, higher levels of perceived job demands and job stress were the psychosocial factors most consistently linked to upper extremity work disorders. The reviews of the epidemiologic literature also indicated that certain psychosocial factors that are not work-specific (e.g., general worry/psychological tension, depression/anxiety, general coping style, and response to pain) were also associated with both back and upper extremity disorders. Nonwork-related variables tend to be more commonly related to back than to upper extremity disorders.

Given that the emphasis of this report is on work-related factors, this chapter reviews various models of occupational stress and discusses how exposure to stresses at work can impact the physiology of musculoskeletal pain in the spine and upper extremities work disorders. Nonworkplace psychosocial stressors can exert similar effects, but are not discussed here.

The study of work disorders and occupational stress is a difficult endeavor because of the many factors that can influence the development, exacerbation, and maintenance of job stress and the highly subjective nature of measures of exposure and outcomes used in this area. In addition, the various biological correlates of stress exposure and, more specifically, the proposed models of how job stress may affect occupational musculoskeletal disorders, are speculative.

Also, if biological pathways linking job stress to work-related musculoskeletal disorders exist, it is currently unknown whether they are specific to these disorders or, more likely, represent the final common pathway by which exposure to both work-related and nonwork-related stressors exert an effect on a number of health disorders (e.g., cardiovascular disease). That is, the specificity of these pathways is unknown. It is generally accepted that musculoskeletal pain can be experienced in the absence of evident physiological change or tissue damage (Melzack, 1999) and that such pain is modulated primarily by cognitive processes.

This chapter reviews general models of occupational stress, biological correlates of stress exposure, selected theories related to how occupational stress might impact musculoskeletal disorders, and hypothesized pathways that may account for the relationship.

Approximately 43.6 percent of the reports of the injury or illnesses associated with overexertion from lifting and 49.7 percent associated with repetitive motion come from employees working in jobs in the operator/fabricator/laborer category. The next highest categories for lifting were service (18.3 percent) and technical/sales/administrative support (17.7 percent). For repetitive motion, the next highest categories were technical/sales/administrative support (21.6 percent) and precision/production/craft/repair (12.3 percent).

It is interesting to note that overall the percentage of injuries or illnesses reported from lifting declined by 25 percent between 1992 and 1997; those attributed to repetitive motion declined by 16 percent. Since jobs in manual materials handling are a major source of reported musculoskeletal injuries and illnesses, we take the analysis another step and examine the types of workers’ compensation claims resulting from work in jobs involving manual materials handling. This analysis is supplemented by data collected from a large number of companies on various features of manual materials handling tasks.

Jobs involving such materials handling tasks as construction, meatpacking, parcel package delivery, transportation, and moving were the source of the greatest number of workers’ compensation claims filed in the state of Washington between 1990 and 1997 for musculoskeletal injury or illnesses of the low back and upper extremities (Silverstein and Kalat, 1999). Another occupation with a significant number of claims was nursing home work that involved lifting and moving patients.

According to an analysis performed at the Liberty Mutual Insurance Company (Dempsey and Hashemi, 1999), 36 percent of these claims, over a 6-year period, were associated with manual materials handling jobs. Of these, approximately 70 percent were for problems with the low back and upper extremities. As for the nature of the injury or illnesses (as classified by these authors), the highest category was strain (62 percent) followed by fracture (12.8 percent) and laceration (11.6 percent); sprains accounted for 6 percent.

Ciriello and Snook (1999) conducted a study summarizing typical manual materials handling tasks performed at 2,442 locations across the country. They collected and analyzed data on lifting, lowering, pushing, pulling, and carrying activities covering a 13-year period. The results show that lifting tasks were acceptable for 81 percent of the men but for only 10 percent of the women; for lowering tasks, the percentages were 89 and 14; and for carrying tasks, they were 88 and 36 percent, respectively.

Moreover, the median weights for the lifting and lowering tasks were significantly higher than the weight limits recommended by the National Institute for Occupational Safety and Health (NIOSH). The authors concluded that additional work was needed to reduce the risks of the injury or illnesses in industry associated with manual lifting tasks. With the growing number of women in the workforce, these data are of particular interest.

The data from Ciriello and Snook (1999) can also be analyzed for time trends to determine whether jobs have become easier or more difficult over the 12 years of data collection. The authors did not conduct a random survey of all jobs, but rather analyzed the jobs that had been submitted to them by insurance agents in their capacity as reducers of potential insurance claims. The authors claim that the jobs are representative of industrial practice, although they acknowledge that sample sizes have decreased over the time period covered. In fact, they probably represent more demanding jobs, as their median weights for lifting and lowering were about 20 kg, well above the 9.1 kg reported by Drury, Law, and Pawenski (1982) in a survey of about 2,000 box-handling jobs in industry.

When analyzed for linear time trends, Ciriello and Snook’s data show significant changes over 1981 to 1993, with jobs becoming less demanding over time. The changes were quite large in some cases; for example, there was a mean decrease in lifted weight of about 0.5 kg per year and an improvement in both lift distance and height (at the start of the lift) of over 10 mm per year. These trends, coupled with the continued promise of automation of heavy industrial tasks, suggest a decrease in workplace risk factors associated with manual lifting tasks.

The central theme of work both now and in the future is diversity in workers, jobs, workplace design, and work location. At the level of industries and occupations, changes have been occurring for a number of years. For example, there has been a shift from blue-collar work to service work, a trend toward teamwork, and an increasing need for all levels of employees to develop new skills for working with technology.

Current trends also indicate continuing part-time employment, outsourcing, mobility of workers among jobs both within and between occupations, and an aging workforce with an increasing number of women and minorities. Furthermore, it has been suggested that the current trend in work outside the traditional work setting will continue to expand.

The scholarly treatment of workplace trends has focused almost exclusively on organizational issues and personnel policies rather than on changes in the content of specific jobs and occupations. In this chapter, we attempt to piece together a description of the current and projected content of work and the implications for the occurrence of musculoskeletal disorders.

We begin the discussion with an overview of the growth and decline of occupations in the past and the projected trends for the future. This discussion focuses on the types of jobs that have produced the highest percentage of musculoskeletal disorders injury reports in the last decade—those associated with materials handling—and the expected changes anticipated in these jobs in the next decade.

The second part of the chapter examines the external variables that influence changes in work, including: (1) workforce demographics, (2) technology, (3) the globalization of markets, and (4) organizational structures, policies, and procedures. The final section presents a summary of the implications of anticipated trends in work on the occurrence of musculoskeletal disorders.

At the end of the nineteenth century, Frederick Winslow Taylor went to work at Bethlehem Steel. Upon observing the workers shoveling coal, Taylor had an idea. He assigned each worker a shovel that was of a size and weight ideally suited to the worker’s own body structure. With the new shovels, the workers became triply effective, Bethlehem Steel was able to reduce its cost by half, and get the same amount of work out of 140 employees that it once got out of 400.

Today, few businesses need concern themselves with optimizing their employees’ coal-shoveling potentialities, but workers are breaking their backs at a whole new kind of grind, spending up to fourteen hours a day at a desk in front of a computer. That is why ergonomics, the study and integration of human well-being principles into systems designs, has become an integral part of the creation of modern workspaces.

There are several areas of ergonomics to consider when designing or redesigning an office space. Arguably the most important of these is the physical aspect. The average worker pushes his or her body to the limit every day simply by sitting in a chair, motionless save for fingers flashing over the keyboard, and hands and arms controlling the mouse.

It doesn’t seem like a punishing physical task, but according to the Bureau of Labor Statistics, Repetitive Stress Injuries (RSIs), such as Carpel Tunnel Syndrome, are the single fastest-growing work-related illness, costing businesses as much as 30 billion dollars a year, and all due to just sitting at a desk typing.

Physical ergonomics, then, is concerned with office tools and supplies geared towards allowing people to work efficiently, productively, and painlessly. The major product issues in this category surround chairs, keyboards, and mice. There are many of these type of ‘ergonomic’ products on the market, but experts say that virtually none of these actually do the job right..

A huge demand for ergonomic office furniture and supplies has led to an unfortunate wave of products being advertised as ‘ergonomic,’ when they are anything but. At this point, there is absolutely no system in place regulating what can or cannot be marketed as such, so it’s wise to shop around. Ergonomists suggest that businesses consult – surprise, surprise – ergonomists, before overhauling a work environment.

However, without resorting to a process of drastic remodeling, employers can vastly improve physical ergonomics by providing free classes in which workers can learn to use their own bodies ergonomically. After all, you can have the best office chair in the world, but if you don’t know how to sit in it, you will always be uncomfortable. Classes in the Alexander Technique, Tai Chi, and yoga can do huge things for physical health in the workplace, and lead to a reduction in work-related injuries, which in turn shrinks the cost to businesses of paying out for sick days and sick workers.

Another crucial area of ergonomics is engineering psychology, or cognitive ergonomics. This area is born out of the philosophy that a happy worker is a productive worker, and to be happy, a worker has to not dread going in to the office every day. Cluttered, messy, overwhelming, or generally unpleasant workstations are the cause of this ennui for more than 50% of all office employees in the US, according to a recent Logitech survey.

The word of the day in ergonomic workspace design is to say goodbye to those cubicles! In practice, open, dynamic work areas are proving to be hotbeds of employee creativity and productivity. It is true that privacy is often cited as a workplace must-have, but the benefits of a spatially unrestricted environment in which workers are able to easily collaborate, communicate, and problem-solve are far greater.

A ‘war room’ style workspace, or what is called ‘radical collocation’ is gaining in popularity amongst fast-growing IT businesses. This environment normally involves a large, open space with tables around the center for collaborative work, and more enclosed spaces around the edge of the room for solo projects and private conferences.

Ideally, these workspaces will be furnished as dynamically as possible, with lightweight, easily movable furniture that can be regularly reconfigured to meet the needs of the day. Studies show that employees who are given the opportunity to contribute to the shaping of their work environment demonstrate high levels of commitment to their jobs, which translates into increased productivity, low turnover rates, fewer sick days, and even increased neatness and conscientious behavior.

This sort of open, flexible environment also provides ample opportunity for workers to move around, which has both cognitive and physical ergonomic benefits. Staying in the same position, at the same desk, day after day, is not conducive in allowing human beings to function at their best.

Rather than assigning desks, ergonomic workspace design involves employees being able to move freely from workstation to workstation, library to hot desk to breakout room, depending on what they need to do. This strategy works best in a wireless environment, and overall leads to reduced clutter, increased creativity and job commitment, and better employee health.

For a new business, beginning ergonomically is a must. It is an investment in cutting future costs by ensuring the on-site well-being of employees. When starting from scratch, ergonomic design can actually be cheaper than creating a conventional office environment, because it eliminates many of the expensive borders and limitations – everything from walls to wiring – that so many drab, gray, airless office spaces labor under.

For an established business, coming around to ergonomics can prove to be a great expense, and with so many products and services out there pushing themselves as the ergo-solution of the day, it can be hard not to go over-budget. However, the time of the isolated, burnt-out cubicle employee is drawing to a close, and to compete with the satisfied, energized workers found in modern office spaces, traditional businesses are going to have to come around eventually.

In the end, it’s just a matter of identifying the point at which the costs of dealing with unhappy, uncomfortable workers begins to be outweighed by the benefits of making the change in favor of better quality work, lower absenteeism, consistently met deadlines, and fewer errors. Yes, the transition to ergonomic workspace design can be expensive, but ultimately, it could save your business.