Industrial Erg

CHAPTER 2 THE BASICS OF ERGONOMICS

LEARNING OBJECTIVES

At the end of this module, students will be able to identify the basic principles of ergonomics, which will include a working definition of the term, and a brief history of ergonomics will be provided. Students will also be able to recognize the physical workplace risk factors and other contributors to the development of work-related musculoskeletal disorders (WMSDs) as well as potential resolutions to reduce or control workplace risk.

INTRODUCTION

Ergonomics is a field of study that involves the application of knowledge about physiological, psychological, and biomechanical capacities and limitations of the human (Butterworth, 1974). This knowledge is applied in the planning, design, and evaluation of work environments, jobs, tools, and equipment to enhance worker performance, safety, and health. Ergonomics is essentially fitting the workplace to the worker.

Ergonomics seeks to prevent WMSDs by applying principles to identify, evaluate, and control physical workplace risk factors.

History of Ergonomics

Wojciech Jastrzębowski, a Polish biologist, coined the word “ergonomics” as the science of work in 1857 in a philosophical narrative “based upon the truths drawn from the Science of Nature.” The term ergonomics – er·go·nom·ics \,ûrg-go-'näm-iks\ – is derived from two Greek words, Ergon meaning work and Nomos meaning principles or laws. Jasterzebowis understood the human and economic impacts of the industrial revolution during a time when a society of farmers traded in their hoes for 14-hour days in factories, growing iron and steel in lieu of wheat and potatoes. Factories brought people, process, and power together like never before.

A more commonly used definition of ergonomics today, as defined by one of the fathers of modern ergonomics Étienne Grandjean, is “fitting the work to the worker.” Ergonomics is an applied science combining various disciplines that cater to the special needs of humans and is a goal-oriented science that seeks to reduce or eliminate injuries and disorders, increase productivity, and improve life quality.

Ergonomics, as defined by the Board of Certification for Professional Ergonomists (BCPE), “is a body of knowledge about human abilities, human limitations and human characteristics that are relevant to design. Ergonomic design is the application of this body of knowledge to the design of tools, machines, systems, tasks, jobs, and environments for safe, comfortable and effective human use” (Ergonomics).

The profession has two major branches with considerable overlap. One area of the discipline referred to as “industrial ergonomics,” or “occupational biomechanics,” concentrates on the physical aspects of work and human capabilities such as force, posture, and repetition. The second branch, referred to as “human factors,” is oriented to the psychological aspects of work such as mental loading and decision making.

Bernardino Ramazzini was born in Carpi, Italy, in 1633. While he was still a medical student at Parma University, his attention was drawn to diseases suffered by workers. In 1682, when he was appointed chair of theory of medicine at the University of Modena, Ramazzini focused on workers' health problems in a systematic and scholarly way (Brauer, 2005). He visited workplaces, observed workers' activities, and discussed their illnesses with them. The medicine courses he taught were dedicated to the diseases of workers.

Primarily on the basis of this work, Ramazzini is called “the father of occupational medicine” (Report, 2012). Ramazzini systematized the existing knowledge and made a large personal contribution to the field by collecting his observations in De Morbis Artificum Diatriba (Diseases of Workers); the first edition was printed in Modena in 1700 and the second in Padua in 1713.

Each chapter of the De Morbis Artificum Diatriba contains a description of the disease associated with a particular work activity followed by a literature analysis, workplace description, questions for workers, disease description, remedies, and advice. The clinical picture was directly observed by Ramazzini, who questioned workers about their complaints. He regularly asked his patients about the kind of work they did and suggested that all physicians do the same expanding on the list by Hippocrates (Giluliano Franco, 2009).

Ramazzini realized that not all workers' diseases were attributable to the working environment (chemical or physical agents).

The first and most potent is the harmful character of the material that they handle, for these emit noxious vapors and very fine particles … and induce particular diseases (in humans).

The second cause I ascribe to certain violent and irregular motions and unnatural posture of the body, by reason of which the natural structure of the vital machine is so impaired that serious disease gradually develop…

Ramazzini observed that a variety of common workers' diseases appeared to be due to prolonged, violent, and irregular motions and prolonged postures. Such cumulative trauma and repetitive motion injuries have recently been called the occupational epidemic of the 1990s (Giluliano Franco, 2009).

A good deal of evidence indicates that Greek civilization in the 5th century bc used ergonomic principles in the design of their tools, jobs, and workplaces. One outstanding example of this can be found in the description Hippocrates gave of how a surgeon's workplace should be designed and how the tools he uses should be arranged. Hippocrates also suggested to physicians that they inquire as to one's profession during examination.

In the 19th century, Frederick Winslow Taylor pioneered the “scientific management” method, which proposed a way to find the optimum method of carrying out a given task by maximizing human performance. Occupational ergonomics today seeks to decrease injury while enhancing performance. Taylor found, for example, you could triple the amount of coal workers were shoveling by incrementally reducing the size and weight of coal or ore in shovels until the fastest shoveling rate was reached, thus, literally matching the task and tools to the worker. Frank and Lillian Gilbreth expanded Taylor's methods in the early 1900s to develop the “time and motion study.” They aimed to improve efficiency by eliminating unnecessary steps and actions. By applying this approach, the Gilbreths reduced the number of motions in bricklaying from 18 to 4.5, allowing bricklayers to increase their productivity from 120 to 350 bricks/h. The elimination of repetitive motions and extended reaching are methods of controlling WMSDs due to cumulative exposure to the same muscle group.

Prior to World War I (1914), the focus of aviation psychology or human factors was on the aviator himself, but the war shifted the focus onto the aircraft, in particular, the design of controls and displays, the size and shape of the aviator within the cockpit to reach and activate controls, and the effects of altitude and environmental factors on the pilot. The war witnessed the emergence of aeromedical research and the need for repeatable testing and measurement methods to ensure, as much as possible, a pilot's cognitive and physical capacities were maximized but not exceeded.

Studies on driver behavior started gaining momentum during this period as well as with Henry Ford (1920) providing millions of Americans with an automobile. Henry Ford was also concerned with efficiency of motion to decrease the cost of making an automobile while increasing its quality. Henry Ford stated, “The work must be brought to the man waist-high. No worker must ever have to stoop to attach a wheel, a bolt, a screw or anything else to the moving chassis (Ford).”

World War II (1940) marked the development of new and complex machines and weaponry, and these made new demands on operators' cognition and physical capacity. Now the design of equipment had to take into account human limitations and take advantage of human capabilities. It was observed that fully functional aircraft, flown by the best-trained pilots, still crashed. In 1943, Alphonse Chapanis, a lieutenant in the U.S. Army, showed that this so-called “pilot error” could be greatly reduced when more logical and differentiable controls replaced confusing designs in airplane cockpits. After the war, the Army Air Force published 19 volumes summarizing what had been established from research during the war. Research covered areas such as:

· Muscle force required to perform manual tasks

· Compressive low back disk force when lifting

· Cardiovascular response when performing heavy labor

· Perceived maximum load that can be carried, pushed, or pulled.

The beginning of the Cold War led to a major expansion of defense supported research laboratories in the areas of human factors and ergonomics. While most of the research following the war was military-sponsored, the scope of the research broadened from small equipment to entire workstations, and systems benefited the industrial sector as well as in defense. Concurrently, private opportunities started opening up in the civilian industry for improvements in workstation and task design. The focus shifted from research to participation through advice to engineers in the design of equipment, facilities, and processes.

The Human Factors Society, the main professional organization for human factors and ergonomics practitioners in the United States, was formed in 1957 with approximately 90 people attending the first annual meeting. The name was changed to the Human Factors and Ergonomics Society in 1992. Today the society has more than 4500 members (Society) and is the benchmark for an internationally recognized designation in the practice of ergonomics.

Starting in the mid-1960s, the discipline continued to grow and develop in previously established areas. Moreover, it expanded into computer hardware (1960s); computer software (1970s); nuclear power plants and weapon systems (1980s); the Internet and automation (1990s), and adaptive technology (2000s) just to name a few. Most recently, new areas of interest have emerged including neuro-ergonomics and nano-ergonomics.

A consistent theme influencing human factors and ergonomics has sought to grow over the years as an ever-expanding sphere and has emerged too, in order to keep pace with scientific advances. With the rapid advances in science and technology today, it's interesting to speculate on what newly discovered challenges human factors and ergonomics will be called upon to solve. Exoskeletons are being used to perform tasks and lighten the burden on the human today. As it was at its inception, human factors and ergonomics remain multidisciplinary professions.

Contributors to ergonomics and human factors concepts include industrial engineers, industrial psychologists, occupational medicine physicians, industrial hygienists, and safety engineers. Professions that use ergonomics/human factors information include architects, occupational therapists, physical therapists, industrial hygienists, designers, safety engineers, general engineering, occupational medicine professionals, and insurance loss control specialists.

WORK-RELATED MUSCULOSKELETAL DISORDERS

Ergonomics seeks to prevent Work-Related Musculoskeletal Disorders (WMSDs) by applying principles to identify, evaluate, and control physical workplace risk factors.

Musculoskeletal disorders (MSDs) are a class of disorders involving damage to muscles, tendons, ligaments, peripheral nerves, joints, cartilage (including vertebral discs), bones, and/or supporting blood vessels. WMSDs are MSDs aggravated by working conditions. WMSDs are not typically due to acute events but occur slowly over time due to repeated wear and tear or microtraumas to the tissue. For example, dental hygienists tend to develop hand-related tendon damage due to repeated gripping of small diameter tools while applying force.

Micro-trauma is a small, minor, limited area tissue damage or tear. Cumulative trauma occurs when rest or overnight sleep fails completely to heal the micro-trauma, and the residual trauma carries over to the next day. Damage continues to proliferate if the exposure or dose remains unchanged (Labor, 1999).

WMSDs are also known as cumulative trauma disorders (CTDs), repetitive strain injuries (RSIs), repetitive motion trauma (RMT), or occupational overuse syndrome. Examples of WMSDs include epicondylitis (tennis elbow), tendinitis, DeQuervain's disease (tenosynovitis of the thumb), trigger finger, and Reynaud's syndrome (vibration white finger), Carpal tunnel syndrome (CTS) is a commonly known WMSD as is back strain. Occupational Safety and Health Association (OSHA) uses the term MSD.

OSHA defines MSD as a disorder of the muscles, nerves, tendons, ligaments, joints, cartilage or spinal discs that was not caused by a slip, trip, fall, motor vehicle accident or similar accident (OSHA).

Researchers have identified specific physical workplace risk factors involved in the development of WMSDs. Exposure to these risk factors can result in

· decreased blood flow to muscles, nerves, and joints;

· nerve compression;

· tendon or tendon sheath damage;

· muscle, tendon, or ligament sprain or strain; and

· joint damage.

Prolonged exposure to the physical workplace risk factors can lead to permanent damage and a debilitating condition. Stages of WMSD development and specific WMSDs are discussed in Chapter 14.

When present for sufficient duration, frequency, or magnitude, physical workplace risk factors may contribute to the development of WMSDs. In addition, personal risk factors, such as physical conditioning, existing health problems, gender, age, work technique, hobbies, and organizational factors (e.g., job autonomy, quotas, deadlines) contribute to, but do not cause the development of WMSDs. Applying ergonomic principles to reduce a worker's exposure to the physical workplace risk factors decreases the chance of injury and illness. Figure 2.1 is an example of a task with a combination of physical workplace risk factors.

Figure 2.1  Awkward posture of the back, high spinal forces, and hand compression are found with emergency transport

PHYSICAL WORKPLACE RISK FACTORS – OVERVIEW

Physical workplace risk factors are those aspects of a job or task that impose biomechanical stress on a worker. Researchers have identified specific physical workplace risk factors that can cause or contribute to the development of WMSDs. Ergonomic principles are commonly used to mitigate the exposure. The following will be covered in detail.

· Postures – both awkward (nonneutral) and static

· Forces-including heavy, frequent, or awkward lifting

· Compression

· Repetition

· Vibration.

Force, repetition, and awkward postures, especially when occurring at high levels or in combination, are most often associated with the occurrence of WMSDs. While exposure to one risk factor may be enough to cause injury, typically physical workplace risk factors act in combination to cause injury. An example is the position of the wrist a waiter or waitress uses when carrying a tray (with hand bent back, wrist at almost a 90° angle). This position causes severe hand extension. When this extreme awkward posture is combined with the gravitational force created by a heavy tray and the position is repeated over a long shift, multiple risk factors are present that place the employee at risk of injury, Posture + Force + Duration + Repetition. Dialing down or decreasing any single risk factor will ultimately decrease the risk of injury. Other workplace conditions can contribute to but do not cause WMSDs. They can however cause other undesirable health conditions. These conditions can include the following:

· Duration

· Intensity

· Temperature

· Workplace

· Stress

· Organizational issues.

Personal risk factors can also contribute to the development of WMSDs, for example:

· Age

· Gender

· Hobbies

· Previous injuries

· Physical or medical conditions

· Smoking

· Fatigue.

Posture

The neutral posture is the optimal body position in order to minimize stress and provide the greatest strength and control as seen in Figure 2.2. The neutral posture is the body position in which there is the least amount of tension or pressure on the nerves, tendons, muscles, joints, and spinal discs. It is also the position in which muscles are at their resting length, neither contracted nor stretched. Muscles at this length can develop and maintain maximum force most efficiently. The neutral posture in the workplace can be recognized by the proper alignment of body landmarks. Neck, shoulders, and arms should be relaxed with elbows by the sides. The elbow should be open at an angle that is no less than 90°. The ears are roughly over the shoulders, shoulders over hips, hips over knees, and knees over ankles. The spine should have a slight S shape with the lower back slightly concaved.

Figure 2.2  Standing neutral postures (Adapted with permission from The Ergonomics Image Gallery)

The benefits of proper spinal alignment are discussed in Chapters 13 and 7. The seated neutral posture is discussed in Chapter 4as well as the guide “Standing up on the Job” found in Appendix B.

Awkward Postures

Awkward postures or nonneutral postures are those outside of the neutral posture. Awkward or unsupported postures can stretch the body's physical limits and can compress nerves and irritate tendons. Awkward postures are often significant contributors to MSDs because they increase the work and the muscle force required (OSHA).

Examples of awkward postures include the following:

· Raising hands above the head or elbows above the shoulders, a common awkward posture in manufacturing and manual material handling

· Kneeling or squatting, common in maintenance operations

· Working with back, neck, and/or wrist bent, for example, when using a microscope

· Sitting with feet unsupported that can cause blood to pool in the feet and flatten the natural curve in the lumbar spine. This problem is common among laboratory technicians who work at high benches.

Awkward postures are more fatiguing than neutral postures because the muscles, tendons, and ligaments are actively working to maintain the posture; the greater the posture deviations from neutral, the higher the stress on the human and resultant risk of injury.

In Figure 2.3, before, the worker had to bend and reach to gather parts for eyeglass assembly. After, an automatic storage system delivers parts at elbow height, reducing awkward postures and improving quality control through an automated inventory stem.

Figure 2.3  (a) Workers are exposed to long reaches above the shoulders and below the knees. (b) Automated retrieval system delivers parts at elbow height reducing the repeated and frequent awkward postures

Static Postures

Holding a posture for extended periods of time is known as a static posture or static muscle loading. Static postures prevent the flow of blood. These types of exertions put increased load or forces on the muscles or tendons, which contribute to fatigue (OSHA). Blood flow brings nutrients to the muscles and carries away waste products. Holding a muscle in contraction causes waste products to build up and leads to fatigue. Fatigue is considered a precursor to injury. For more information on fatigue, see the administrative chapter.

Examples of static postures include the following:

· Gripping tools that cannot be put down

· Holding arms out or up to perform tasks

· Standing in one place for prolonged periods.

Repetition

Repetition is a physical risk factor that occurs when the same motion or group of motions is performed over and over again. Different tasks may still utilize the same muscle groups and, therefore, not allow the muscles to rest leading to overuse. Repetition alone is not typically a problem, but when it occurs with other risk factors it magnifies the exposure.

Force

Force refers to the amount of physical effort that is required to accomplish a task or motion. Tasks or motions that require application of higher force place higher mechanical loads on muscles, tendons, and joints (OSHA) and can quickly lead to fatigue.

The force required to complete a movement increases when other risk factors are also involved. For example, more physical effort may be needed to perform a task when speed is increased or vibration present. Performing forceful exertions requires the application of muscle contraction that may cause them to fatigue quickly. The more force that must be applied, the more quickly the muscles fatigue. Excessive or prolonged exposure also leads to overuse of the muscles and may result in muscle strain or damage.

The power zone for lifting, with the greatest strength, endurance and control, and lowest risk of injury is holding the load close to the body between the knuckle and shoulder height.

Compression

Compression or contact stress is a concentrated force on a small surface area. Contact stress can reduce blood flow or cause tissue (e.g. tendon) irritation due to the constant pressure.

One of the most common sources of compression is a sharp or hard desk edge creating a compressive force on the forearm or elbows as we rest to stabilize the joint. Nerves in the forearm are close to the skin surface; compression of the forearm impedes nerve conduction.

Vibration

There are two types of vibration, single point and whole body. More information can be found in Chapter 10.

Single Point Vibration

Single point vibration is exposure to a single body part such as the upper extremity. This type of vibration is common with tool use.

The main outcome of prolonged exposure is a decrease in blood volume to the extremities. Vibrating tools can cause vascular spasms or a constriction of blood vessels in the fingers, which then appear white or pale. More information is provided in Chapter 9 of the book.

Whole Body Vibration

Whole body vibration is exposure to vibration through the entire body. This type of vibration can be found from vehicles such as forklifts, cranes, trucks, buses, ocean vessels, and aircrafts.

The main effect is usually to the spine, but studies indicate that high exposure can reduce circulation and cause disorientation and motion sickness.

High or prolonged exposure to whole body vibration can affect the skeletal muscles and digestive system and can cause lower back pain and pregnancy complications.

Contributing Factors

Contributing risk factors contribute to but do not cause WMSDs. Contributing factors, when personal in nature, can be outside of a safety professional's realm to mitigate without an active wellness program.

Duration and Magnitude

Duration is the time period in which an action continues or lasts. Continuous exposure to any risk factor may not allow sufficient recovery time for muscles, tendons, and nerves. Duration magnifies the risk factors as does intensity or magnitude.

Temperature Extremes

Temperature extreme are a contributing factor to the development of WMSDs. Working in cold environments places a greater aerobic demand on the worker, which means they fatigue faster. The cold also reduces dexterity and causes you to grip harder or apply more muscle force. Cold temperatures are especially problematic when present with vibration because both risk factors contract blood vessels.

Radiant heat from furnaces or direct exposure from the sun should be considered for warm temperature exposure. Workers move more slowly when hot, so simple tasks can take longer, thus increasing the duration of exposure to temperature extremes and other risk factors.

Note that personal protective equipment (PPE) can decrease evaporation from the skin thus reducing the body's ability to cool itself adding to thermal gain.

Inadequate Recovery

Working without rest can cause fatigue and contribute to injury. Muscles need time to rest to re-oxygenate and remove the waste products of muscle metabolism. There are many ways to rest a muscle group. Stretching, alternating tasks, and taking microbreaks (brief pause) can aid in muscle recovery and readiness. Refer to the administrative controls, Chapter 5, more information on stretching programs and WMSDs, Chapter 13, for disease etiology.

Personal Risk Factors

Personal risk factors can also contribute to the development of workplace injury and illness.

· Age – as we age, the repair process in our body takes longer.

· Gender – due to anatomical and hormonal differences, certain WMSDs are more prevalent in women.

· Hobbies – knitting, crocheting, bowling, and computer gaming.

· Smoking – linked to back pain because smokers tend to heal more slowly due to the decrease in oxygen in the blood stream.

· Obesity and pregnancy – linked to carpal tunnel syndrome (CTS). Even a low level of exposure to workplace risk factors can create CTS in a pregnant worker. The symptoms usually disappear after the baby is born. Obesity impacts are lack of flexibility, fluid buildup, and increased pressure on the disks.

· Previous injury – puts a worker at risk of an MSD in the same place.

· Medications – can cause dehydration, swelling, decreased/increased metabolic rates, and a change in electrolyte levels.

· Fatigue – cause a reduction in performance due to a period of excessive activity followed by inadequate recovery time. Muscle fatigue is accompanied by a buildup of lactic acid in the working muscle.

· Physical conditions – poor fitness, particularly when combined with a body weight above the “ideal,” is a prime cause of weariness and fatigue, which are commonly recognized to be factors that can contribute to the onset of musculoskeletal injuries.

WMSD SIGNS, SYMPTOMS, PREVENTION

Early identification of signs and symptoms of WMSDs can eliminate risk or reduce the severity of an injury. Reporting allows the occupational safety and health professional the opportunity correct issues before an employee is injured. Refer to Chapter 13 for more information.

Some signs and symptoms are as follows:

· Painful aching joints, muscles

· Pain, tingling or numbness

· Shooting or stabbing pains

· Swelling or inflammation

· Warmth

· Stiffness or difficulty moving

· Burning sensation

· Pain during the night

· Loss of strength and mobility.

Pain and discomfort are usually precursors to injury and should be considered warning signs or an indicator of a need for improvement.

SUMMARY

Understanding and applying ergonomics principles in the workplace will reduce the physical stress on the body and eliminate potentially serious, disabling WMSDs through matching jobs, tasks, and work environment to the worker. Ergonomics is also good economics. Other benefits include the following:

· Improved comfort, morale and job satisfaction, and worker health

· Improved productivity and reduced workers' compensation costs and employee turnover.

Ergonomics is essentially fitting the work to the worker and is effective in preventing MSDs that are caused or aggravated by the work environment. Physical ergonomics risk factors that can cause injury (when occurring in combination) are force, posture, duration, repetition, vibration, and compression. Other workplace risk factors (e.g., temperature and quotas) along with personal factors can contribute to but do not cause WMSDs.

KEY POINTS

· Ergonomics is not a new science; it was founded in the 1700s along with other occupational medicine disciplines. The ill effects have been documented since 1857 on work and health.

· Ergonomics seeks to prevent injuries before they occur.

· Early studies in ergonomics focused on productivity improvements.

· The US Military's involvement in flying technology in the 1940s, followed by the personal computer boom in the 1990s, brought ergonomics into the forefront of safety and health.

· Microtrauma is a small, minor, limited area tissue damage or tear. Cumulative trauma occurs when rest or overnight sleep fails to completely heal the microtrauma, and residual trauma carries over to the next day, adding to the total system trauma.

· Physical workplace risk factors that can cause WMSDs can be changed. Personal and contributing risk factors that do not cause WMSDs typically cannot be changed.

· Standing neutral posture:

· Ears over shoulders

· Shoulders over hips

· Hips over knees

· Knees over ankles

· Elbows by the sides.

In Figure 2.4a, firefighters were required to lift an 86-lb smoke ejector fan from above the cab on the fire apparatus, walk across hoses, and lower it to others below. In Figure 2.4b, smoke ejector fan is mounted to bumper, greatly reducing awkward postures during lifting. The task resulted in physical workplace risk factor exposure, as well other safety risks. The fan was mounted to the rear bumper of the truck, virtually eliminating the physical workplace risk factors by placing the lift to within the workers power zone.

Figure 2.4  (a) Firefighters carried a heavy fan over unstable footing and lowered it to workers below. (b) Mounting the fan on the bumper eliminated the hazards

REVIEW QUESTIONS

1. Define ergonomics.

2. Define WMSD.

3. List and briefly describe the physical workplace risk factors.

4. List at least three personal risk factors that contribute to but do not cause WMSDs.

5. List at least two workplace risk factors that contribute to but do not cause WMSDs.

6. What are the two differences between physical workplace risk factors and contributing factors for the development of WMSDs?

7. What is the difference between ergonomics and human factors?

8. Describe the contribution of Frederick W. Taylor to the advancement of ergonomics.

9. Describe the contribution of Dr. Ramazzini to the practice of occupational medicine.

EXERCISES

1. Students research a historic WMSD, such as musicians' nerve, and relate how it was caused in historic times to current times.

1. Students submit a personal biography highlighting their work or educational experience as well as exposure to occupational ergonomics. Students should list one goal they hope to meet by completing the course.

2. Students submit an assignment or verbally discuss an area in their work or home life, where they are already practicing ergonomics.

REFERENCES

1. Brauer, R. (2005). Safety and Health for Engineers 2nd edn. Hoboken: John Wiley & Sons Inc..

2. Butterworth (1974). Applied Ergonomics Handbook. London.

3. Ergonomics, B. o. (n.d.). About BCPE. Retrieved 2012, from Board of Certification in Professional Ergonomics: http://www.bcpe.org/.

4. Giluliano Franco, M. (2009). Bernardino Ramazzini: The Father of Occupational Medicine. Retrieved December 29, 2013, from National Center for Biotechnology Information: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1446786/.

5. Labor, U. S. (1999). Occupational Safety and Health Administration Federal Register Proposed Rule. Retrieved December 8, 2001, from Occupational Safety and Health Administration: https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=federal_register&p_id=16305.

6. Report, T. E. (2012). Revisiting the Roots of Ergonomics. Retrieved January 4, 2013, from ErgoWed: https://ergoweb.com/revisiting-the-roots-of-ergonomics/.

ADDITIONAL SOURCES

Health, N. Y. (n.d.). Work Place Hazards. Retrieved December 26, 2013, from NYCOSH: http://nycosh.org/index.php?page=Hierarchy-of-Hazard-Controls.

Henry Ford Quotes. (n.d.). Retrieved March 5, 2015, from The Henry Ford: https://www.thehenryford.org/research/henryFordQuotes.aspx.

OSHA. (1999). Federal Register V 64 No. 225 Proposed Rule. OSHA.

Society, H. F. (n.d.). Membership. Retrieved December 26, 2013, from Human Factors and Ergonomics Society: https://www.hfes.org//Web/Membership/membership.html.