Ergonomics: Introduction book notes

UNIT 19A

Ergonomics: Introduction

Work Environment & Human Factors

Enhanced & Integrated Study Notes

Scope of these notes

•  Definitions, history, and disciplinary foundations of ergonomics •  FJM vs FMJ design philosophy and workplace problem-solving method •  Applied guidelines — seating, lifting, tool and wrist posture •  Biomechanical model of spinal loading (L5/S1) with NIOSH criteria

 

Contents

 

 

1. Meaning and Core Definition

Ergonomics derives from the Greek ergon (work) and nomos (law) — literally, the "Law of Work." It is concerned with achieving the optimal relationship between people and their work environment, treating the human operator, the machine, and the work environment as one interacting system.

ILO Definition •  Ergonomics is the application of human and biological sciences, together with engineering, to improve the work environment and simultaneously enhance productivity.

Ergonomics is inherently multidisciplinary: it studies the person, the machine, and the work environment together, with the objective of achieving optimal performance without physiological or psychological discomfort.

1.1 The Human – Machine – Environment Triad

Component	Representative Factors
Human	Muscle strength, physical dimensions, body build, age, sex
Work environment	Heat, noise, vibration, light, acceleration
Machine / task	Equipment, tools, workstation layout, job design
Poor match produces	Job injury, work stress, human error, poor performance

2. Historical Development

Ergonomic thinking is not new — even Stone Age tool-makers shaped implements to fit the user and the task. What is recent is its formalisation as a distinct discipline.

Period / Region	Key Development
Stone Age	Hand tools shaped to fit the user and the task
Industrial Revolution	Human-centred design: interesting jobs to humans, repetitive tasks to machines
Post-WWII, UK	Focus on equipment and workspace design; drew on anatomy, physiology, industrial medicine, architecture, illumination engineering
1950, Britain	Ergonomics Research Society established
Continental Europe	France, Germany, Netherlands, Scandinavia: discipline well established; labour unions actively promote it for safety, health, comfort, convenience
USA, early 1950s	Human Factors emerges as a parallel discipline
USA — aerospace	Major success in large-system design (NASA, space programmes)
Industry	Eastman-Kodak and IBM among the earliest substantial industrial adopters, often led by industrial engineers and company nurses
Recent	Human Factors Society (USA) renamed the Human Factors and Ergonomics Society

A unifying thread across both traditions: both human factors and ergonomics take the FJM approach — jobs should be made appropriate for people, not the reverse.

3. Major Focus of Ergonomics

1.     Designing and engineering human–machine systems.

2.     Applying science to people performing in working environments.

3.     Studying humans' limited capabilities as they relate to safe job operation.

4.     Improving knowledge of work and work-related stress.

5.     Studying the interface between people and equipment/environment.

4. Basic Design Approaches: FMJ vs FJM

Approach	Meaning	Application
FMJ — Fit the Man to the Job	Change or train the worker to suit the job	Justified only under extreme, unavoidable circumstances (e.g., acclimatisation to unavoidable heat)
FJM — Fit the Job to the Man	Design the job around human characteristics	Almost always the superior approach

The FJM approach assumes that a suitable set of operator characteristics can be specified, and that a job can be designed around them for virtually any task. Ergonomics content is therefore directed at describing these characteristics at the anatomical, physiological, and psychological levels, and at explaining their design implications. Where FMJ is unavoidable — such as workers who must acclimatise to fixed hot conditions — FJM-style mitigations (better work–rest schedules, protective clothing) remain preferable wherever possible.

5. Purpose, Rationale, and Benefits

5.1 Purpose

To identify and remove work stresses that adversely affect the health, safety, and efficiency of workers.

5.2 Why Ergonomics?

●    Provide a safe and productive workplace.

●    Comply with regulatory bodies.

●    Achieve better productivity.

5.3 Benefits

Benefit	Organisational Impact
More production output	Higher throughput
Reduced lost time	Less downtime
Lower medical cost	Reduced healthcare burden
Reduced absenteeism	Better attendance
High-quality work	Fewer defects
Safe workplace	Fewer accidents
Reduced labour turnover	A more stable workforce

6. Contributing Disciplines

Discipline	Study Area
Anthropometry	Human capabilities, limitations, and body dimensions
Biomechanics	Forces and stresses acting on the human body
Work physiology	Body functions affected by muscular stress
Industrial psychology	Human behaviour
Epidemiology	Incidence of disease and injury
Bioengineering	Engineering applied to designing work tools for human use

Ergonomics also draws more broadly on mathematics, physics, chemistry, engineering and technology, and the biological sciences — reflecting its position at the intersection of multiple fields.

7. Workplace Problems and the Ergonomics Method

Workplace problems relate to four interacting elements:

1.     The work or task to be performed.

2.     The humans responsible for the work.

3.     The environment in which humans work.

4.     The interfaces between work, humans, and environment.

Because technology changes continuously and no two people perform identical work in exactly the same way, such problems can never be eliminated completely — only continuously managed. Addressing them calls for interdisciplinary knowledge (work physiology, biomechanics, psychology, engineering, systems design, cybernetics) to formulate system goals, understand functional requirements, analyse the system, design improvements, and implement them.

Long-run outcomes of ergonomic solutions •  Increased productivity and efficiency of resources •  Safer working methods •  Improved health with minimised hazards •  A comfortable, well-maintained work environment •  Minimum cost, maximum quality, and an acceptable quality of work life

Despite this potential, ergonomics remains under-implemented outside some developed Western economies, and awareness of its importance remains limited among non-specialists. As technology and human–machine interfaces grow more complex, the need for systematic ergonomic design is expected to intensify.

8. Steps to Identify and Solve Ergonomic Problems

1.     Become aware of the problem.

2.     Analyse the task and the conditions — drawing on expert knowledge, operator suggestions, performance data, dissatisfaction or turnover trends, health records, and accident reports.

3.     Identify the specific problem.

4.     State the needs and the goal.

5.     Select a candidate solution.

6.     Apply engineering control or managerial control.

7.     Implement the solution.

8.     Check for success — if solved, close out; if not, return to steps 2–5.

9. Applied Ergonomic Guidelines

9.1 Chair Design

An ergonomically correct chair enables the user to maintain an erect sitting posture. The ideal chair provides:

●    Adjustable lower back (lumbar) support.

●    A soft or curved front edge to the seat bucket.

●    Easily adjustable height.

●    Five legs with rollers for safe, easy manoeuvrability.

If the feet cannot fully reach the floor after height adjustment, a footrest or foot stool should be used — pressing the feet against the floor or stool helps counterbalance the forces exerted on the lower back while sitting.

9.2 Correct Sitting Posture

●    Torso upright, upper arms vertical.

●    Cushioned backrest supporting the inward lumbar curve.

●    Cushioned seat; thighs horizontal and supported.

●    Lower legs vertical, feet flat on the floor.

9.3 Limiting Strain While Sitting

●    Use lumbar support pads and adjustable chairs.

●    Increase leg and foot room; adjust work-surface height.

●    Use a foot rest.

●    Stand up every 45–60 minutes.

9.4 Tool and Workstation Design

●    Use a tool on a horizontal surface at elbow height, or on a vertical surface below knuckle height.

●    Tool suspension aids a better grip.

●    Good lighting on stairs and in corridors prevents accidents and reduces product damage.

●    Proper workstation design prevents awkward wrist postures.

●    Carry thin items in a cupped hand rather than a pinch grip, which strains the hand.

●    Where work is needed from both sides of an item, allow free worker movement or free rotation of the item so work is always done in front of the body.

9.5 Manual Material Handling

●    Keep the load close to the body.

●    Keep the back straight; use stable foot positions.

●    Lift using the power of the legs, not the back.

●    Move materials along surfaces of the same height — the best arrangement.

●    Lifting from a platform is preferable to lifting from the floor.

●    Use cut-out handholds that allow gripping with bent fingers, reducing the force required, and position them so the container can be carried in front of the body.

●    Minimise the distance between the worker and the work item.

9.6 Pushing, Pulling, and Contact Stress

Non-back-related strains can arise from pushing and pulling tasks, driven by the push or pull force applied. Contact stress at sharp or hard edges can be reduced through padding and improved workstation-edge design.

10. Biomechanics of Lifting: The L5/S1 Spinal Loading Model

Manual lifting guidelines can be formalised as a single-equivalent-muscle biomechanical model of the low back, taken about the L5/S1 lumbosacral joint — the point of greatest mechanical disadvantage in the spine during forward-bent lifting.

10.1 Variables

Symbol	Meaning
W_torso, W_load	Weight of the upper body and weight of the load being lifted
d_torso, d_load	Moment arms — horizontal distance from the L5/S1 joint to the centre of mass of the torso and of the load
d_muscle	Moment arm of the erector spinae muscles about L5/S1 (≈ 5 cm)

10.2 Moment Equilibrium and Muscle Force

Taking moments about the L5/S1 joint, the erector spinae muscles must generate a counter-moment equal to the moment produced by the torso and load:

F_muscle × d_muscle = W_torso × d_torso + W_load × d_load

Rearranged, the required muscle force is:

F_muscle = (W_torso × d_torso + W_load × d_load) ÷ d_muscle

Because d_muscle is small (about 5 cm) relative to d_torso and d_load, the erector spinae must generate a muscle force many times larger than the actual weight of the torso and load combined — this mechanical disadvantage is the central reason manual lifting is so damaging to the low back.

10.3 Compressive Force at L5/S1

Vertical force equilibrium at the disc gives the net compressive force on the spine as the sum of the muscle force and the weights being supported:

F_compression = F_muscle + W_torso + W_load

This compressive force acts on the intervertebral disc and vertebral end-plates and is the quantity used in occupational risk assessment.

10.4 NIOSH Evidence Threshold

NIOSH Action Limit •  The National Institute for Occupational Safety and Health (NIOSH) sets 3,400 N (≈ 770 lb) of L5/S1 compressive force as the Action Limit. •  Forces above this threshold are associated with increased risk of spinal disc micro-fractures, disc herniation, and severe low-back pain.

10.5 Safe Lifting Protocol (derived from the model)

●    Load position: keep the object as close to the body as possible — this minimises d_load and therefore F_muscle and F_compression.

●    Posture: keep the back straight and erect; bend at the knees and hips rather than the spine.

●    Foot stance: maintain a stable, wide base of support.

●    Muscle utilisation: lift using the powerful quadriceps and gluteal muscles rather than the lumbar erector spinae.

●    Platform usage: store materials at knuckle or hip height to avoid lifting directly from floor level.

●    Container handholds: use cut-out, recessed handholds that allow power gripping with bent fingers instead of pinch grips.

Every element of the classical "lift with your legs, not your back" instruction reduces one of the terms in the moment-equilibrium equation above — the model is the mechanism behind the rule of thumb.

11. Back Loading and Back Pain

The back is loaded by four interacting forces: torso and arm weight, the load held in the hands, the resultant erector-spinae muscle force, and the resulting compressive force on the spine (formalised above in Section 10).

Work-related factors	Factors not work-related
Poor equipment design and layout	Previous history of back problems
Lifting	Age
Pushing and pulling	Fitness (or lack of it)
Prolonged sitting or standing	Outside activities: sports, hobbies, yard work
Sudden high-level exertions
Extended working hours (over eight hours a day)

12. Hand, Wrist, Arm, and Shoulder Issues

Activity	Affected Part
Bending or twisting the wrist	Wrist, elbow
Forceful finger grips	Hand, wrist, elbow
Pinches	Hand, wrist
Resting the arm on a sharp edge	Forearm, elbow, wrist
Hand hammering	Contact point on the hand; posture and force may also affect wrist, forearm, elbow

Shoulder and upper-back strain is associated with raising the elbows, reaching too far, shrugging the shoulders, and reaching backward behind the mid-torso line.

13. Wrist Position, Grip Strength, and WMSDs

13.1 Wrist Posture vs. Grip Strength

Wrist position directly changes the biomechanical efficiency of the flexor tendons as they pass through the carpal tunnel. Any deviation away from the neutral (0°) axis reduces maximum voluntary contraction (MVC) grip strength, because the tendons lose their straight line of pull and the finger flexors must work at a mechanical disadvantage.

Wrist Position	Grip Strength (% of maximum)
Neutral (0°)	100%
25° radial deviation	80%
40° ulnar deviation	75%
45° extension	75%
45° flexion	60%
65° flexion	45%

Key point: the neutral position is the strongest and most stable. Deviation weakens grip and requires more force to accomplish the same task — repeated forceful gripping in a deviated posture is a primary contributor to cumulative trauma at the wrist.

13.2 Wrist Motions

●    Extension — bending the hand backward.

●    Flexion — bending the hand down.

●    Radial deviation — bending the hand toward the thumb.

●    Ulnar deviation — bending the hand toward the little finger.

●    Neutral — hand in line with the forearm.

13.3 Power Grip

●    The hand closes around the object; the thumb touches or overlaps the fingers.

●    Strongest and most stable when the hand is in line with the forearm.

●    Bending the wrist weakens the grip.

13.4 Work-Related Musculoskeletal Disorders (WMSDs)

WMSDs are also referred to as cumulative trauma disorders, repetitive stress injuries, repetitive motion injuries, or occupational overuse syndromes. They result from repeated strain, awkward postures, forceful exertions, and poor workstation design acting cumulatively over time — rather than from a single traumatic event.

14. The Cumulative Trauma "Mountain" Analogy

Symptom progression is often depicted as an ascent up a mountain that is partly obscured by fog — the fog representing the level of perception and awareness of symptoms at each stage:

1.     Fatigue, tiredness, uneasiness, and discomfort — commonly accepted as "normal" after a full day’s work.

2.     Occasional movement or posture problems; intermittent discomfort, fatigue, small aches.

3.     Soreness and persistent pain and ache affecting well-being and performance.

4.     Pronounced symptoms that make it difficult to continue usual activities.

5.     Disorders, injuries, and diseases requiring medical intervention.

6.     Disability.

Because early stages sit "in the fog," workers and supervisors often normalise symptoms that are, in fact, early warning signs — reinforcing the case for proactive ergonomic assessment rather than waiting for injury to appear.

15. Quick-Revision: Key Exam Points

●    Ergonomics = "Law of Work"; studies the Human–Machine–Work Environment triad.

●    ILO definition: human + biological sciences + engineering → improved work environment + enhanced productivity.

●    FJM (fit the job to the man) is almost always superior to FMJ (fit the man to the job).

●    Contributing disciplines: anthropometry, biomechanics, work physiology, industrial psychology, epidemiology, bioengineering.

●    Ergonomics Research Society founded in Britain, 1950; Human Factors Society (USA) later renamed the Human Factors and Ergonomics Society.

●    Problem-solving cycle: aware → analyse → identify → state goal → select solution → control → implement → check.

●    Ideal chair: adjustable lumbar support, curved seat-front edge, adjustable height, five legs with rollers.

●    Manual lifting: keep load close, back straight, stable feet, use leg power — all reduce moment arms in the L5/S1 model.

●    NIOSH Action Limit for L5/S1 compressive force: 3,400 N (≈ 770 lb).

●    Neutral wrist position = 100% grip strength; any deviation reduces grip strength and raises WMSD risk.

●    WMSDs = cumulative trauma disorders / repetitive stress injuries / repetitive motion injuries / occupational overuse syndromes.

19A Ergonomics: Introduction — Integrated Study Notes

1. Meaning & Definition

· Ergonomics = Greek ergon = work + nomos = law → Law of Work.
· Deals with interaction of Human + Machine + Work Environment.
· Concerned with achieving the optimal relationship between people and their work environment.
· ILO definition: Application of human and biological sciences and engineering to improve the work environment and at the same time enhance productivity.
· It is a multidisciplinary science studying men, machine, and work environment to achieve optimal performance without physiological and psychological discomfort.

2. Human–Machine–Environment Model

Component Factors
Human Muscle strength, physical dimensions, body build, age, sex
Work environment Heat, noise, vibration, light, acceleration
Machine/task Equipment, tools, workstation, job design
Poor match causes Job injury, work stress, human errors, poor performance

3. History of Ergonomics

· Ancient/Stone Age: hand tools designed to fit user and task.
· Industrial Revolution: human-centred design; interesting jobs to humans, repetitive tasks to machines.
· After WWII, UK: focus on equipment and workspace design.
· Related subjects: anatomy, physiology, industrial medicine, design, architecture, illumination engineering.
· Ergonomics Research Society established in 1950.
· Europe: France, Germany, Netherlands, Scandinavia — well-established; labour unions promote safety, health, comfort, convenience.
· USA: Human Factors emerged in early 1950s.
· Success in aerospace/NASA.
· Manufacturing applications recent — Eastman-Kodak, IBM.
· Human Factors Society renamed Human Factors and Ergonomics Society.

4. Major Focus of Ergonomics

· Designing and engineering human-machine systems.
· Applying science to people performing in working environments.
· Studying human limited capabilities related to safe job operation.
· Improving knowledge of work and stress.
· Studying interface between people and equipment.

5. Basic Approaches: FMJ vs FJM

Approach Meaning Remarks
FMJ Fit the Man to the Job Only under extreme circumstances, e.g. unavoidable hot conditions; use acclimatization, better work-rest schedule, protective clothing.
FJM Fit the Job to the Man Superior and preferred approach. Assumes operator characteristics can be specified and job designed around them.

Ergonomics describes operator characteristics at anatomical, physiological, and psychological levels and explains design implications.

6. Purpose, Why Ergonomics, Benefits

Purpose: Identify and remove work stresses that adversely affect health, safety, and efficiency.

Why Ergonomics?

· Safe and productive workplace.
· Comply with regulatory bodies.
· Better productivity.

Benefits

· More production output
· Reduced lost time
· Lower medical cost
· Reduced absenteeism
· High quality work
· Safe workplace
· Reduced labour turnover

7. Contributing Disciplines

Discipline Study Area
Anthropometry Human capabilities, limitations, body dimensions
Biomechanics Forces and stresses on human body
Work physiology Body functions affected by muscular stress
Industrial psychology Human behaviour
Epidemiology Incidences of disease/injury
Bioengineering Engineering in design of work tools for human use
Other Mathematics, physics, chemistry, engineering & technology, biological sciences, psychology

8. Workplace Problems & Ergonomics Method

Problems relate to:

1. Work/task to be performed.
2. Humans responsible for work.
3. Environment where humans work.
4. Interfaces between work, humans, and environment.

No two persons work exactly the same; technology changes continuously. Problems cannot be completely eliminated.

Interdisciplinary knowledge needed to:

· Formulate systems goals.
· Understand functional requirements.
· Analyze the system.
· Design a new system.
· Implement the system.

Ergonomics solutions lead to:

· Increased productivity and efficiency.
· Safe working methods.
· Improved health and minimized hazards.
· Comfortable work environment.
· Long run: minimum cost, maximum quality, acceptable quality of work life.

9. Steps to Identify and Solve Ergonomic Problems

10. Become aware of the problem.

11. Analyze task and condition.
    · Use expert knowledge, operator suggestions, performance problems, dissatisfaction, turnover, health effects, accidents.

12. Identify problem.

13. State needs and goal.

14. Select candidate solution.

15. Engineering control / Managerial control.

16. Implement solution.

17. Check success.
    · Yes → problem solved.
    · No → go back to steps 2–5.

18. Ergonomic Guidelines

Chair Design

Ideal chair:

· Adjustable lower back (lumbar) support.
· Soft or curved front edge of seat bucket.
· Easily adjustable height.
· Five legs with rollers for easy and safe manoeuverability.

If feet cannot reach floor: use footrest/foot stool. Pressing feet against floor/stool helps counterbalance lower-back forces.

Sitting Posture

· Torso upright.
· Upper arms vertical.
· Cushioned backrest supporting inward lumbar curve.
· Cushioned seat.
· Thighs horizontal and supported.
· Lower legs vertical.
· Feet flat on floor.

Ways to Limit Strains While Sitting

· Use lumbar support pads.
· Use adjustable chairs.
· Increase leg and foot room.
· Adjust work surface height.
· Use a foot rest.
· Stand every 45–60 minutes.

Tool & Workstation Design

· Use tool on horizontal surface at elbow height.
· Use on vertical surface below knuckle height.
· Tool suspension helps better grip.
· Good lighting on staircases/corridors prevents accidents and reduces product damage.
· Proper workstation design prevents awkward wrist postures.
· Carry thin item in a cupped hand, not pinch grip.
· If work needed from both sides, arrange free movement or rotation so work is done in front.

Manual Material Handling

· Keep load close to body.
· Keep back straight.
· Stable foot positions.
· Use power of legs.
· Move materials along surfaces of same height — best arrangement.
· Lifting from platform is better than lifting from floor.
· Cut-out handholds allow gripping by bent fingers, reducing force.
· Locate handholds so box/container can be carried in front of body.
· Minimize distance between worker and work item.

11. Back Loading & Back Pain

How back is loaded:

· Torso and arm weight
· Load in hands
· Resultant muscle force
· Compressive force on spine

Work-related back pain factors:

· Poor equipment design and layout
· Lifting
· Pushing and pulling
· Prolonged sitting or standing
· Sudden high-level exertions
· Extended working hours (over 8 hours/day)

Non-work factors:

· Previous history of back problem
· Age
· Fitness or lack of it
· Outside activities: sports, hobbies, yard work

12. Hand, Wrist, Arm & Shoulder Issues

Activity Affected Part
Bending wrist / twisting motions Wrist, elbow
Forceful finger grips Hand, wrist, elbow
Pinches Hand/wrist
Resting arms on sharp edge Forearm, elbow, wrist
Hand hammering Contact point on hand; posture/force may affect wrist, forearm, elbow

Shoulder/upper back affected by:

· Raising elbows
· Reaching too far
· Shrugging shoulders
· Reaching backwards behind mid-torso line

Work-Related Musculoskeletal Disorders (WMSDs) terms:

· Cumulative trauma disorders
· Repetitive stress injuries
· Repetitive motion injuries
· Occupational overuse syndromes

13. Wrist Position & Grip Strength

Wrist Position Grip Strength
Neutral 0° 100%
25° radial deviation 80%
40° ulnar deviation 75%
45° extension 75%
45° flexion 60%
65° flexion 45%

· Neutral position = strongest and most stable.
· Wrist deviation weakens grip and requires more force.
· Motions: extension, neutral, flexion; radial deviation, ulnar deviation.

Power Grip

· Hand closed around object.
· Thumb touches or overlaps fingers.
· Strongest and most stable when hands are in line with forearm.
· Bending wrist weakens grip.

14. Cumulative Trauma Mountain Analogy

Progression from normal to severe:

1. Fatigue, tiredness, uneasiness, discomfort considered “normal” after a full day’s work.
2. Occasional movement or posture problems; intermittent discomfort, fatigue, small aches.
3. Soreness, pain, persistent pains and aches affecting well-being and performance.
4. Pronounced symptoms make it difficult to continue usual activities.
5. Disorders, injuries, diseases requiring medical intervention.
6. Disability.

“Fog” = level of perception and awareness of symptoms.

15. Key Exam Points

· Ergonomics = Law of Work.
· FJM > FMJ.
· ILO definition: human + biological sciences + engineering → improve work environment + productivity.
· Ergonomics is multidisciplinary.
· Neutral wrist = 100% grip strength.
· Manual lifting: load close, back straight, stable feet, leg power.
· Chair: lumbar support, adjustable height, curved front edge, five legs with rollers.
· WMSDs = cumulative trauma, repetitive stress/motion injuries, occupational overuse syndromes.
Sub section 1.2
19A ERGONOMICS: INTRODUCTION — COMPLETE, WELL-ORGANISED STUDY NOTES

1. Definition and Core Concept

Ergonomics comes from Greek:

· Ergon = work
· Nomos = law
→ Ergonomics = Law of Work

Core definition:

· Ergonomics is concerned with achieving the optimal relationship between humans and their work environment.
· It studies the interaction of Human – Machine – Work Environment.
· ILO definition: Application of human, biological sciences, and engineering to improve the work environment and at the same time enhance productivity.
· It is a multidisciplinary science dealing with men, machine, and work environment to achieve optimal performance without causing physiological and psychological discomfort.

Core triad:
HUMAN ↔ MACHINE ↔ WORK ENVIRONMENT

---

2. Historical Development

Period / Region Key Developments
Stone Age Hand tools designed to fit the user and the task
Industrial Revolution “Human-centred design”; interesting jobs to humans, repetitive tasks to machines
After World War II, UK Focus on equipment and workspace design; anatomy, physiology, industrial medicine, design, architecture, illumination engineering
1950, Britain Ergonomics Research Society established
Europe France, Germany, Netherlands, Scandinavia: ergonomics well-established; labour unions active for safety, health, comfort, convenience
USA, early 1950s Human factors emerged as a discipline
USA aerospace Success in large systems design, NASA and space programmes
Industry Eastman-Kodak and IBM applied ergonomics substantially
Recent Human Factors Society, USA renamed Human Factors and Ergonomics Society

Key point: Both human factors and ergonomics take the FJM approach — jobs should be made appropriate for people, not people forced to fit jobs.

---

3. Major Focus of Ergonomics

Ergonomics involves:

1. Designing and engineering human-machine systems.
2. Applying science to people performing in working environments.
3. Studying human limited capabilities related to safe job operation.
4. Improving knowledge on work and human performance.
5. Studying the interface between people and equipment/environment.

---

4. Basic Approaches: FMJ vs FJM

Approach Meaning Suitability
FMJ — Fit the Man to the Job Change or train the worker to fit the job Only under extreme circumstances
FJM — Fit the Job to the Man Design the job around human characteristics Almost always superior

FJM assumptions:

· Suitable operator/human characteristics can be specified.
· A job can be designed around those characteristics.
· This can be done for any job.

Ergonomics describes these characteristics at:

· Anatomical level
· Physiological level
· Psychological level

FMJ example: Workers requiring acclimatization to hot conditions that cannot be changed.
FJM alternatives: Better work-rest schedule, protective clothing, etc.

---

5. Purpose and Benefits of Ergonomics

Purpose

· Identify and remove work stresses that adversely affect health, safety, and efficiency of workers.

Why Ergonomics?

· Provide safe and productive workplace.
· Comply with regulatory bodies.
· Achieve better productivity.

Benefits

Benefit Impact
More production output Higher productivity
Reduced lost time Less downtime
Lower medical cost Reduced healthcare burden
Reduced absenteeism Better attendance
High quality work Improved quality
Safe workplace Fewer accidents
Reduced labour turnover Stable workforce

---

6. Ergonomics System Models

6.1 Main Task–Environment System

Components:

· Work Environment: heat, noise, vibration, light, acceleration, etc.
· Man: muscles, strength, physical dimensions, body build, age, sex, etc.

Outputs / Problems:

· Job injury
· Work stress
· Human errors
· Poor performance

Fig. 19A.2: Main-task environment system shows how environment and human factors combine to produce injury, stress, errors, and poor performance.

6.2 Cumulative Trauma “Mountain” Analogy

Symptoms progress upward like a mountain, partly hidden by fog:

1. Fatigue, tiredness, uneasiness, discomfort — considered “normal” after a full day’s work.
2. Occasional movement or posture problems; intermittent discomfort, fatigue, small aches.
3. Soreness, pain, persistent pains and aches affecting well-being and performance.
4. Pronounced symptoms make it difficult to continue usual activities.
5. Disability, disorders, injuries, diseases requiring medical intervention.

· Fog = level of perception and awareness of symptoms.

6.3 Person–Task–Workstation Interaction

Integrated model:

· Person + Task + Workstation Design
· Furniture
· Equipment
· Environment
· ↓
· Work Posture + Work Activities
· ↓
· Person’s Well-being + Performance Output

Good design improves posture, activity, well-being, and output. Poor design causes strain, errors, and injury.

---

7. Contributing Disciplines to Ergonomics

Discipline Study Area
Anthropometry Human capabilities and limitations
Biomechanics Forces and stresses on human body
Work Physiology Functions of human organism affected by muscular stress
Industrial Psychology Human behaviour
Epidemiology Incidence of diseases/disorders
Bioengineering Application of engineering in design of work tools and equipment for human use

Other contributing fields: mathematics, physics, chemistry, engineering and technology, biological sciences.

---

8. Problems at the Workplace and Ergonomics

Problems relate to:

1. The work or task to be performed.
2. The humans responsible for the work.
3. The environment where humans work.
4. The interfaces between work, humans, and environment.

These affect and determine the level of human performance and output production.

Why problems cannot be eliminated completely:

· Technology in use is continuously assessed.
· No two persons can work exactly the same job because responses to work environment and work systems vary among humans.

Primary concern of ergonomics:

· Design the workplace as a system to achieve the best-possible performance from humans consistently and continuously.

Interdisciplinary knowledge needed:

· Work physiology, biomechanics, psychology, engineering, systems design, cybernetics.

To:

1. Formulate systems goals.
2. Understand functional requirements.
3. Analyze the system.
4. Design a new system.
5. Implement the system.

Ergonomics offers a set of solutions leading to:

1. Increase in productivity of resources and efficiency in production equipment.
2. Safe working methods.
3. Improved health of humans with minimization of hazards.
4. Design and maintenance of a comfortable work environment.

Long-run goal:

· Minimum cost and maximum quality of products/services.
· Acceptable and standard quality of work life for humans.

Current status:

· Potential of ergonomics not fully explored.
· Except in some developed Western countries, industries in developing countries have hardly implemented ergonomics.
· People outside the field are hardly aware of its importance.
· As technology becomes complex, the need for ergonomics at the workplace is expected to grow.

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9. Problem-Solving Methodology in Ergonomics

Steps to identify and preempt or solve ergonomic problems:

1. Become aware of the problem.
2. Analyze task and condition.
3. Identify problem.
4. State needs and goal.
5. Select candidate solution.
6. Apply:
   · Engineering control
   · Managerial control
7. Implement success.
8. Check success:
   · If yes → problem solved.
   · If no → go to step 2 to 5.

Sources of problem awareness:

· Expert knowledge
· Operator suggestion
· Performance problem
· Dissatisfaction
· Turnover
· Well-being or health affected
· Nurse records
· Accidents

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10. Ergonomic Guidelines and Applications

10.1 Chair Design

An ergonomically correct chair enables the user to maintain an erect sitting posture.

Ideal chair has:

1. Adjustable lower back (lumbar) support.
2. Soft or curved front edge of seat bucket.
3. Easily adjustable height.
4. Five legs with rollers for easy and safe manoeuverability.

· If feet cannot fully reach floor after adjusting chair height, use a footrest or footstool.
· Pressing feet against floor/stool helps counterbalance forces on lower back when sitting.

Correct sitting posture:

· Torso upright
· Upper arms vertical
· Cushioned backrest supporting inward lumbar curve
· Cushioned seat
· Thighs horizontal and supported
· Lower legs vertical
· Feet flat on floor

10.2 Tool and Work Surface Design

· Use tool on a horizontal surface at elbow height, or on a vertical surface below knuckle height.
· Tool suspension can help get a better grip.
· Good lighting on staircases and corridors prevents accidents and reduces product damage.
· Avoid direct/glare lighting problems.

10.3 Wrist and Hand Posture

· Proper workstation design prevents awkward wrist postures.
· Carry a thin item in a cupped hand rather than a pinch grip between thumb and fingers.
· Pinch grip causes more strain.

10.4 Work Arrangement

· Minimize distance between worker and work item.
· If work is needed from both sides of the work item, arrange free movement of worker or free rotation of the work item so work is done in front of the worker.
· Move materials along surfaces of the same height — best arrangement.

10.5 Manual Lifting

· Lift or lower heavy load in front of body.
· Keep back straight.
· Use stable foot positions.
· Use power of the legs.
· Keep object as close to the body as possible.
· Lifting from a platform is better than lifting from the floor.
· Use handholds adapted to the object.
· Cut-out handholds allow gripping by bent fingers and reduce force needed.
· Locate handholds so box/container can be carried in front of the body.

10.6 Pushing and Pulling

· Non-back related strains can occur from pushing and pulling tasks.
· Push force and pull force affect the body.
· Contact stress can be reduced by padding and improved design.

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11. How the Back is Loaded

Loads on the back:

· Torso and arm weight
· Load in hands
· Resultant muscle force
· Compressive force on spine

Ways to Limit Strains While Sitting

· Use lumbar support pads.
· Use adjustable chairs.
· Increase leg and foot room.
· Adjust work surface height.
· Use a footrest.
· Make a point of standing every 45 to 60 minutes.

Back Pain Factors

Work-Related Not Work-Related
Poor equipment design and layout Previous history of back problem
Lifting Age
Pushing and pulling Fitness (or lack of it)
Prolonged sitting or standing Outside activities: sports, hobbies, yard work
Sudden high-level exertions
Extended working hours (over 8 hours/day)

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12. Effects of Hand, Arm, and Shoulder Activities

Action Affected Part
Bending the wrist Wrist, elbow
Twisting motions Wrist, elbow
Forceful finger grips Hand, wrist, elbow
Pinches Hand, wrist, elbow
Resting arm(s) on a sharp edge Forearm, elbow, wrist
Hand hammering Contact point on hand; posture and force may affect wrist, forearm, elbow

Activities Affecting Shoulders and Upper Back

· Raising the elbows
· Reaching too far
· Shrugging the shoulders
· Reaching backwards behind mid-torso line

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13. Wrist Position and Grip Strength

Wrist Position Grip Strength
Neutral 0° 100%
25° radial deviation 80%
40° ulnar deviation 75%
45° extension 75%
45° flexion 60%
65° flexion 45%

Key point:

· Neutral position is strongest and most stable.
· Deviation of wrist causes weaker grip and requires more force to use it.

Wrist Motions

· Extension: bending hand backward
· Flexion: bending hand down
· Radial deviation: bending hand toward thumb
· Ulnar deviation: bending hand toward little finger
· Neutral: hand in line with forearm

Grip Postures

Power Grip:

· Hand closed around object.
· Thumb touches or overlaps fingers.
· Strongest and most stable when hands are in line with forearm.
· Bending wrist weakens grip.

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14. Work-Related Musculoskeletal Disorders (WRMSDs)

Also called:

· Cumulative trauma disorders
· Repetitive stress injuries
· Repetitive motion injuries
· Occupational overuse syndromes

These result from repeated strain, awkward postures, forceful exertions, and poor workstation design.

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15. Integrated Summary and Key Takeaways

16. Ergonomics = Law of Work — studies human–machine–work environment interaction.

17. Goal: Fit the job to the man (FJM) rather than fit the man to the job (FMJ).

18. Multidisciplinary: Uses anthropometry, biomechanics, work physiology, industrial psychology, epidemiology, bioengineering, and engineering.

19. Benefits: Higher productivity, better quality, fewer injuries, lower costs, reduced absenteeism, safer workplace.

20. Problem-solving: Identify → Analyze → Design → Implement → Check → Improve.

21. Design guidelines: Proper chair, tool height, wrist posture, lifting technique, work arrangement, and lighting.

22. Health focus: Prevent cumulative trauma, back pain, wrist strain, and musculoskeletal disorders.

23. Future need: As technology becomes complex, ergonomics will become increasingly essential for safe, productive, and sustainable work.

Final integrated formula:
Good Ergonomics = Human Well-being + Safe Work + High Productivity + Quality Work Life