11 Ergonomics in Osh

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Occupational Safety Management and Engineering: Ergonomics in OSH 11-1

© E. R. Vaidogas, Lecture Notes on OSH, VGTU, 2009

11 ERGONOMICS IN OSH

The history of workplace development in the industrial world is characterised by jobs and technologies de-

signed to improve processes and productivity. All too often in the past, little or no concern was given to the

impact of the job process or technology on workers. As a result, work processes and machines have some-

times been unnecessarily dangerous. Another result has been that new technologies have sometimes failed to

live up to expectations. This is because, even in the age of high technology, human involvement in work processes is still the key to the most significant and enduring productivity improvements. If a machine or

system is uncomfortable, difficult, overly complicated, or dangerous to use, human workers will not be able

to derive its full benefit.

The proliferation of uncomfortable and dangerous workplace conditions, whether created by job design

or unfriendly technologies, is now widely recognised as a harmful to productivity, quality, and worker safety

and health. The advent of the science of ergonomics is making the workplace more physically friendly. This,

in turn, is making the workplace a safer and healthier place.

Safety fact*

Pain, discomfort, and loss of function in the back, neck, and extremities are commonamong working people. Within 27 countries of the European Union, about 25% of work-

ers complain of backache and about 23% report muscular pain. Available cost estimates

of these disorders put the cost at 0,5% to 2% of GDP.

* EASHW (2007)

11.1 T HE SCIENCE OF ERGONOMICS

Briefly, ergonomics is defined as the science of fitting the job to the worker (Hammer and Price 2001: 145).

Minimising the amount of physical stress in the workplace requires continuous study of the ways in which

people and technology interact. The insight learned from this study must then be used to improve the interac-

tion. This is a wider description of the science of ergonomics. Thus ergonomics is a multidisciplinary science

that seeks to conform the workplace and all of its physiological aspects to the worker. Ergonomics involves

the following (Goetsch 2002: 147):

Using special design and evaluation techniques to make tasks, objects, and environments more compati-

ble with human abilities and limitations;

Seeking to improve productivity and quality by reducing workplace stressors, reducing the risk of inju-

ries and illnesses and increasing efficiency.

The field of ergonomics is also called human engineering and human factors. The word “ergonomics” is

derived from the Greek language. “Ergon” is Greek for “work”; “nomos” means “laws”. Therefore, in a lit-

eral sense, ergonomics means work of laws. In practice, it consists of the scientific principles (laws) applied

in minimising the physical stress associated with the workplace (work). The widely accepted benefits of er-

gonomics are:

Improved health and safety for workers,

Higher morale throughout the workplace,

Improved quality,

Improved productivity,

Improved competitiveness,

Decreased absenteeism,

Fewer workplace injuries/health problems.

There are benefits to be derived from ergonomics. There are also problems, both financial and health-related,

that can result from giving too little attention to ergonomics. The matter is complicated further because

health problems tend to multiply company’s financial problems.

Common indicators of the existence of ergonomic problems include the following:

Occupational health problems collectively known as musculoskeletal disorders,





Trends in accidents and injuries,

Absenteeism,

High turnover rates,

Employee complaints,

Employee generated changes,

Poor quality, and

High incidence of manual material handling.

11.2 D OMAINS OF ERGONOMICS

The International Ergonomics Association (IEA1) divides ergonomics broadly into three domains:

Physical ergonomics. It is concerned with human anatomical, anthropometric, physiological and

biomechanical characteristics as they relate to physical activity (Relevant topics include working

postures, materials handling, repetitive movements, work related musculoskeletal disorders, workplace

layout, safety and health).

Cognitive ergonomis. It is concerned with mental processes, such as perception, memory, reasoning, and

motor response, as they affect interactions among humans and other elements of a system (Relevanttopics include mental workload, decision-making, skilled performance, human-computer interaction,

human reliability, work stress and training as these may relate to human-system design).

Organizational ergonomics. It is concerned with the optimization of sociotechnical systems, including

their organizational structures, policies, and processes(Relevant topics include communication, crew

resource management, work design, design of working times, teamwork, participatory design,

community ergonomics, cooperative work, new work paradigms, virtual organizations, telework, and

quality management).

11.3 M USCULOSKELETAL DISORDERS

Musculoskeletal disorders cause more than 30% of all occupational injuries and diseases in the United States

(Goetsch 2002: 150). In the European Union, musculoskeletal disorders are the cause of about 50% of work-

related health problems (Figure 11.1) (European Social Statistics 2002: 104).

Musculoskeletal disorder (MSD) is an umbrella term that covers a number of injuries caused by awk-

ward movements repeated frequently over time. Other aggravating factors include poor posture, an improp-

erly designed workstation, poor tool design, and work stress. MSDs occur to the muscles, nerves, and ten-

dons of the hands, arms, shoulders, and neck. Box 11.1 shows a classification of musculoskeletal disorder.

MSDs are also called by names such as occupational overuse disorders, cumulative trauma disorders, and

repetitive stress injuries.

Muscle and tendon disorders

Tendons connect muscles to bones. They can accommodate very little in the way of stretching and are

prone to injury when overused. Overworking a tendon can cause small tears in it. These tears can becomeinflamed and cause intense pain. This condition is known as tenditis. Shoulder tenditis occurs in the muscles

of a shoulder. Forearm tenditis causes pain in fingers, wrist, and muscles in the top of the hand.

Overexertion can cause myofacial muscle damage. The symptom of this disorder is soreness that persists

even when resting. Muscles may burn and be sensitive to the touch. When the muscles become inflamed and

swell, the symptoms are aggravated even further by nerve compression.

1See URL http://www.iea.cc





0 5 10 15 20 25 30 35 40 45 50 55

Percentage

Musculoskeletal disorders, 52%

Stress depression, anxiety, 18%

Lung disorders, 8%

Cardiovascular disorders, 4%

Headaches, visual fatigue, 3%

Hearing disorders, 3%

Infectious diseases, 3%

Skin problems, 3%

Other, 6%

Figure 11.1 Work-related health problems by diagnosis group (the old 15 countries of the European Union, 1999; seri-

ous health problem only, with or without days’ absence from work, %, source European Social Statistics (2002: 108))

Box 11.1: classification of musculoskeletal disorders (MSDs)*

Muscle and tendon disorders

Tendinitis:

– Shoulder tendinitis,

– Bicipital tendinitis,

– Rotator cuff tendinitis,Muscle damage,

Tenosynovitis,

Stenosing tenosynovitis:

– DeQuervain’s disease,

– Trigger finger (flexor tenosynovitis),

Forearm tendinitis:

– Flexor carpi radials tendinitis,

– Extensor tendinitis,

– Flexor tendinitis,

Epicondylitis,

Ganglion cysts.

Cervical Radiculopathy

Tunnel syndromes

Carpal tunnel syndrome,

Radial tunnel syndrome,

Sulcus ulnaris syndrome,

Cubital tunnel syndrome,

Guyons canal syndrome.

Nerve and circulation disorders

Thoracic outlet syndrome,

Raynaud’s disease,

* Goetsch (2002: 175)





Tendons which curve around bones are encased in protective coverings called sheaths. Sheaths contain a

lubricated substance known as synovial fluid. When tendons rub against the sheath too frequently, friction is

produced. The body responds by producing additional synovial fluid. Excess build-up of this fluid can cause

swelling which, in turn, causes pressure on the surrounding nerves. This condition is known as tenosynovitis.

Chronic tenosynovitis is known as stenosing tenosynovitis.

Epicondilitis and ganglion cysts are two muscle and tendon disorders. Epicondilitis affects an elbow.

The common term for this disorder is “tennis elbow”. Ganglion cysts grow on the tendon, tendon sheath, or

synovial lining, typically on the top of the hand, on the nail bed, above the wrist, or on the inside of the wrist.

Cervical radiculopathy

This disorder is most commonly associated with holding a telephone receiver on an upraised shoulder when

typing. This widely practised act can cause compression of the cervical discs in the neck making it painful to

turn the head. Putting the body in an unnatural posture while using the hands is always dangerous.

Tunnel syndromes

Tunnels are conduits for nerves that are formed by ligaments and other soft tissues. Damage to the soft tis-

sues can cause swelling that compresses the nerves that pass through the tunnel. These nerves are the medial,

radial, and ulnar nerves that pass through the tunnel in the forearm and wrist. Pain experienced with tunnel

injuries can be constant and intense. In addition to pain, people with a tunnel injury might experience numb-ness, tingling, and a loss of gripping power.

Nerve and circulation disorders

When friction or inflammation cause swelling, both nerves and arteries can be compressed and so restrict the

flow of blood to muscles. This can cause a disorder known as thoracic outlet syndrome. The symptoms of

this disorder are pain in the entire arm, numbness, coldness, and weakness in the arm, hand, and fingers.

If the blood vessels in the hands are restricted, Raynaud’s disease can result. Symptoms include painful

sensitivity, tingling, numbness, coldness, and paleness in the fingers. It can affect one or both hands. This

disorder is also known as vibration syndrome because it is associated with vibrating tools.

11.4 R ISK FACTORS FOR MSD S

Identification of ergonomic hazards is based on ergonomic risk factors: conditions of the work process,workstations, or work method which contribute to the likelihood of developing MSDs. Not all of these risk

factors will be present in every MSD probe occupational activity, nor is the existence of one of these factors

necessarily sufficient to cause a MSD. Some of the risk factors for MSDs of the upper extremities include the

following:

Repetitive and/or prolonged activities;

Forceful exertions usually with the hands (including pinch grips);

Prolonged static pressures;

Awkward postures of the upper body, including reaching above the shoulders or behind the back and

twisting the wrists and other joints to perform tasks;

Continued physical contact with work surfaces (soft tissue compression);

Excessive vibration from the power tools; Cool temperatures;

Inappropriate or inadequate tool design;

High wrist acceleration;

Fatigue (inadequate recovery time);

Use of gloves.

Risk factors for back disorders include items such as the following:

Bad body mechanics such as continued bending over the waist, continued lifting from below the knees

or above the shoulders, and twisting at the waist, especially while lifting (see Figure 11.2);

Lifting or moving objects of excessive weight or asymmetric size;

Prolonged sitting, especially with poor posture;

Lack of adjustable chairs, footrests, body supports, and work surfaces at workstations;

Poor grips on handles;





Slippery footing.

Safety fact*

Almost all of us will experience back pain at sometime in our life. It is normal and a fact

of life. All epidemiology studies indicate that up to 90% of persons between the ages of

18-55 years (i.e., of working age) will recall an episode of low back pain that interfered

with their ability to function for at least 24 hours at some time. All social and occupa-

tional groups are the same. Approximately 40% of us will experience recurring problems

with our backs.

Most primary care patients who seek treatment for back pain will improve considerably

over the first 4 weeks, but only 30% will be pain free. At one year 70-80% will still re-

port some recurring back symptoms; one third will have intermittent or persistent pain of

at least moderate intensity, and about 15-20% will have a poor functional outcome. The

period prevalence of neck and arm pain in the population is similar to low back pain but

not as frequently disabling.

* Gardiner and Harrington (2005: 42)

Works, operations, or workstations that have multiple risk factors have a higher probability of MSDs.

The combined effect of several risk factors in the development of MSD is sometimes referred to as multiple

causation.

Figure 11.2 Workstation in a pharmaceutical plant: before and after adjustments were made to the workstation(EASHW 2007)

11.5 P REVENTION OF MSD S

MSDs can occur across all types of jobs and work sectors. However, some types of employment groups seem

to be particularly at risk. Specific industries (occupations) with high exposures and groups at high risk in-

clude (EASHW 2008: 17):

Agriculture, forestry and fisheries;

Manufacturing, mining;

Machine operators;

Craft workers, tailors;

Construction;

Wholesale, retail and repairs;

Hotels, restaurants and catering;

Secretaries, typists;

Loaders and unloaders.

Evidence suggests that MSDs affect women more than men largely because of the type of work they do than

because of any gender or other personal factors.Physical causes of MSD include manual handling, loads, poor posture and awkward movements, highly

repetitive movements, forceful hand applications, direct mechanical pressure on body tissues, vibrations, and

cold work environments. Causes in the organisation of work include pace of work, repetitive work, time pat-





terns, payment systems, monotonous work, and also psychosocial work factors. Some types of disorders are

associated with particular tasks or occupations.

To prevent musculoskeletal disorders effectively, the risk factors in the workplace must be identified

and then practical measures taken to prevent or reduce the risks. Eight variables that can influence the

amount of physical stress experienced on the job are as follows (Goetsch 2002: 147):

Sitting versus standing.

Stationary versus movable/mobile.

Large demand for strength/power versus small demand for strength/power.

Good horizontal work area versus bad horizontal work area.

Good vertical work area versus bad vertical work area.

Non-repetitive motion versus repetitive motion.

Low surface versus high surface.

No negative environmental factors versus negative environmental factors.

For the prevention of MSDs, attention needs to be paid to: risk assessment; health surveillance; training;

employee information and consultation; ergonomic work systems (i.e., looking at the effect of the whole

workplace, equipment, work methods, and work organisation, etc. to identify problems and solutions); and

prevention of fatigue. These components of MSD prevention are already recognised in the European practice(EASHW 2008). Solutions of the MSD problem include:

1 Administrative solutions:

A reduction in daily working hours, modification of work, and job rotation may reduce MSDs;

The introduction of additional breaks into repetitive work may be achievable without the loss of produc-

tivity.

2 Engineering solutions:

Technical ergonomic measures can reduce the workload on the back and upper limbs (e.g., in the case of ergonomic hand tools), and thus the occurrence of MSDs, without the loss of productivity;

Technical interventions may also include redesign of physical environment, introduction of lifting and

transfer aids, etc. (Figure 11.3).

3 Behavioural modification:

Training on working methods in manual handling is not effective if it is used as the only measure to pre-

vent low back pain;

Physical training can reduce the recurrence of back pain and neck-shoulder pain. But to be effective, the

training should include vigorous exercise and be repeated at least three times a week.

4 Implementation strategies:

A combination of several kinds of interventions (multidisciplinary approach) – including organisational,

technical and personal measures – is needed to prevent MSDs. Interventions based on single measures

are unlikely to prevent MSDs;

A participative approach that includes the workers in the process of change may have a positive effect

on the success of an intervention.





Figure 11.3 Hand-guided pneumatic balancer and folding trolley used as lifting and transfer aids

11.6 T HE R OLE OF ERGONOMICS IN ACCIDENT PREVENTION

Besides improving the ease with which workers can undertake tasks such as reading dials, good ergonomics

will reduce fatigue, erroneous actions, and wrong decisions (Figure 11.4). Ergonomics has resulted in the

design of better tools, controls for equipment, seats and chairs, and many other items that affect comfort and

safety. Investigation of the accident in the nuclear power plant at Three Mile Island cited two principal

causes: human error and bad ergonomics. Much of the operator error occurred in making decisions and re-

sponses required because of inadequate designs.

Ergonomics

Better workplaces and workprocesses

Minimizing the work-related stress and fatigue

Reduces the possibility of human error andwrong decisions

Contributes to the prevention of workplace

accidents and industrial accidents

Prevents occupational diseases,first of all, muscular-skeletal

disorders (MSDs)

Figure 11.4 The role of ergonomics in prevention of accidents and occupational diseases

Ergonomics attempts to obtain maximum effectiveness in any human-machine operation by integrating

the best capabilities of both. It is concerned with the design of equipment so that it can be operated easily and

rapidly with a minimum of undue effort or strain. A control panel designed for operation by a single personcan overwhelm the worker’s mental and physical capabilities, if an overabundance of data from instruments

must be monitored or its controls operated at one time. Should the instruments on a panel be widely sepa-

rated, an operator would either quickly be exhausted trying to perform an almost impossible task, make er-

rors or ignore some of the instruments, possibly leading to an accident. Much work has been done in the pre-

vious decades in the development of ergonomics. An ergonomic analysis of a very common operation is

given in Table 11.1.





Safety fact*

It often takes a major accident to get the attention of management and the engineering

community regarding the lack of good ergonomics. Such an event occurred on 28 March

1979 at the Three Mile Island nuclear plant in Pennsylvania. Accident investigations

disclosed that this catastrophe was due to a variety of factors:

inadequate training,

a control room poorly designed for people,

questionable emergency operating procedures, and

inadequate provisions for the monitoring of the basic parameters of plant function-

ing.

The event was a turning point for the nuclear power industry because it emphasized the

central importance of ergonomics to safe plant operation. The President’s Commission

on the Accident at Three-Mile Island stated that: “There are many examples in our report

that indicate the lack of attention to the ergonomics in nuclear safety. The control room,

through which the operation of the Three Mile Island plant is carried out, is lacking in

many ways. The control panel is huge, with hundreds of alarms, and there are some key

indicators placed in locations where the operators cannot see them. There is little evi-dence of the impact of modern information technology within the control room … it is

seriously deficient under accident conditions.”

* with modifications from Korwowski (2001: 76)

Table 11.1 Ergonomic analysis of a straight ladder (Hammer and Price 2001:147)

Misuse mode Behavioural factors Design consideration

User sets ladder at angle too near

vertical so that it tips backward as

he ascends or gets near top

Lack of experience, user doesn’t

know proper erection-angle limits;

doesn’t know or realise his bodyneeds to remain close to rungs; not

familiar with centre of gravity fac-

tor

Warning-use instruction label con-

spicuously located (consider use of

alternate orientation of ladder);built-in safe-angle indicator; design

instruction with “pictures”

User sets ladder at shallow angle so

that ladder bends or bounces when

he is near centre of span

Same as above Same as above; over design struc-

turally; minimise bending charac-

teristics

Ladder is too short for situation souser stands on upper rungs with no

hard support

Doesn’t think ahead or recognisepotential hazards; tries to “make

do” – takes a chance

Warning - use instruction

Due to uneven surface, ladder is not

set up properly (e.g., it lists right or

left causing ladder to twist, shift

c.g.(1)

, or introduce structuralstress); feet of ladder slip or pene-trate surface unevenly

Not conscious of support surface

condition; poor judge of verticality;

too lazy or too much in a hurry to

prepare surface; willing to takechance due to inexperience; doesn’tconsider which end of ladder

should be down or up

Self-levelling, broad-footprint foot

design; conspicuous warning; built-

in vertical level indication

… … …

User doesn’t pick ladder up at c.g.(1)

for carrying, causing him to drop it

or dig one end into ground

Lack of experience; doesn’t know

where c.g. is

Warning; mark pick up point

User injuries himself picking up

ladder which is too heavy to carry

Doesn’t know ladder too heavy;

doesn’t think about it before he tries

to pick up; doesn’t pick up properly

Warning – indicate weight

User foot slips off rung or misses

and slips between rungs

Climbs without looking at feet; puts

them where he thinks rungs should

be

Use non-skid surface; use standard

rung spacing and vertical separation

… … …

Metal ladder comes in contact with Unaware of hazard User materials which will not carry





high-tension electrical wire or com-

ponent; may cause shock or burn as

user touches ladder

electrical current

In backing off roof or high place,

misses rung with foot; may kick

ladder and change its orientation,

causing it to be unsteady

Can’t see where he is putting foot;

unsteady; preoccupied with holding

on to structure; in awkward position

for determining orientation

Maximise ladder width; point out

hazard in operation instruction

(1)

c.g. = centre of gravity

References

EASHW (2007) Prevention of Work-Related MSDs in Practice. Bilbao: European Agency for Safety and Health at

Work.

EASHW (2008) Work-related musculoskeletal disorders: Prevention report, EN 4. Bilbao: European Agency for Safety

and Health at Work.

European social statistics (2002) Accidents at work and work related health problems. Data 1994-2000. European

Communities, 2002. Retrieved October, 2007, from http://epp.eurostat.cec.eu.int/cache/ITY_OFFPUB/KS-BP-02-

002-3A/EN/KS-BP-02-002-3A-EN.PDFGardiner, K.; Harrington, J. M. (Eds.) (2005) Occupational Hygiene. 3rd

ed. Malden: Blackwell Publishing.

Goetsch, D. L. (2002) Occupational Safety and Health for Technologists, Engineers, and Managers. 4th ed. Upper Side

River, New Jersey: Prentice Hall.

Hammer, W. & Proce, D. (2001) Occupational Safety Management and Engineering. 5th Ed., New Jersy: Prentice

Hall.

Korwowski, W. (2001) International Encyclopedia on Ergonomics and Human Factors. Vol. I. London and New York:Taylor and Francis.

Examination questions

1 Define the term “ergonomics”. Explain benefits of ergonomics.

2 What is the main cause of occupational injuries and diseases in the European Union?

3 What is the approximate percentage of MSDs among serious work-related health problems?

4 List five risk factors associated with MSDs.5 Which industries and occupations have an increased risk of MSDs?

6 Explain four possible solutions of the MSD problem. Provide one or two examples of each solution.

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11 Ergonomics in Osh