Ergonomics

Ergonomics sometimes called as human engineering is an engineering parallel to a field generally referred to as either Industrial psychology or experimental psychology. Ergon means work and nomos means Natural laws. It is the scientific study of the relationship between man and his working environment.

Ergonomics commonly refers to designing work environments for maximizing safety and efficiency. a safe work environment can result in greater efficiency and productivity. Ergonomics, also known as human factors, is the scientific discipline that seeks to understand and improve human interactions with products, equipment, environments and systems. Drawing upon human biology, psychology, engineering and design, ergonomics aims to develop and apply knowledge and techniques to optimize system performance, whilst protecting the health, safety and well-being of individuals involved.

Ergonomics impacts our daily lives and influences the design of tools at work, appliances in our homes, and computer workstations, including monitors, keyboard and seating. Ergonomics emphasizes designing the workplace to fit the employee rather than the employee fitting the workplace. The goal of an ergonomic program is to minimize injury and illnesses due to chronic physical and psychological stresses, while maximizing comfort, productivity, and efficiency.

Application of Ergonomics Ergonomics, in practice is found to be applied over the whole field of the working environment and deals with such aspects as : Anatomical factors in the layout of the workplace, including the design of seats and the arrangement of components and equipment to suit human body measurements. The layout and presentation of all types of instrument dials and display panels to help accurate perception.

Ergonomics also contributes to the study of energy expenditure, rest pauses and factors influencing fatigue and this helps ensure that knowledge useful in work measurement is kept up to date. In many cases where critical approach of work study has made an important contribution to the physical or mental well being of people at work, ergonomics offers a refinement of approach and a body of new scientific knowledge that enables this contribution to be enhanced.

Work study and ergonomics are in this sense complimentary. The design of such diverse systems as automobiles production machinery, computers, town planning, housing etc, are presently being investigated to test their ergonomics suitability.

Objectives of Ergonomics The objective of the study of ergonomics is to optimize the integration of man and machine in order to increase work and accuracy. It involves the design of : A workplace befitting the needs and requirements of the worker. Equipment, machinery and controls in such a manner as to minimize mental and physical strain on the worker thereby increasing the efficiency. A conductive environment for executing the task most effectively.

The goal of ergonomics in the workplace is to prevent injuries and illnesses (work-related musculoskeletal disorders or WMDs) by reducing or eliminating worker exposure to occupational hazards.this can be done by controlling the risk factors such as force, repetition, posture and vibration that can cause injuries to develop.

The aim of ergonomics are therefore to enhance Functional effectiveness while maintaining or improving human welfare. Ergonomic measures may also be defined as those that go beyond the mere protection of the workers physical integrity and aim at ensuring their well being through appropriate working conditions and the most suitable use of their physical characteristics and physiological capabilities.thus, ergonomics is human centered.

Though,both work study and ergonomics are complementary and try to fit the job to the workers, however ergonomics adequately takes care of the factors governing physical and mental strain. For ergonomics, the task is to develop the most comfortable conditions for the worker as regards to lighting, climate and noise level, to reduce the physical workload, to facilitate psycho-sensorial functions in reading instrument displays, to make handling of machine levers and controls easier, to make better use of spontaneous and stereotypes responses to avoid unneccessary information recall efforts and so on.

Occupational loads and stress Occupational loads and stresses have a profound effect on : Job design Productivity Quality of working life. While at work, a worker may experience : Physical loads Mental loads Perpetual loads

Physical, mental and perpetual loads may be further classified as : Static loads Dynamic loads

LOADSTATICDYNAMIC Physical Holding a casting in handWorking with a hand hacksaw Mental Solving a mathematical problem Carrying out frame by frame analysis as in micro motion study Perpetual Hearing a continuous sound of a machine tool under operationHearing a siren

Perpetual loads come into picture when some information is given to a worker in the form of sensory input. A worker may receive sensory information by seeing ( visual ), hearing and smelling or by touch. Mental workload relates to that part of the task invoking predominantly decision making processes. Physical load is the result of physical effort on the part of a worker. Occupational stresses result because of physical, mental and perpetual loads which a worker experiences while being engaged in a particular occupation or job.

Interaction between men and machine One relevant characteristics of any machine is the way that it conveys information to the operator. The information in provided thru displays. Controls and displays play a critical part in 2 way communication if there has to be effective use by the persons of the VDUs ( visual display units ), machinery, tools and equipment.

The interaction involves perception, cognition ( processing the information ), decision making and action or response usually through the psychomotor system i.e., brain - nerve – muscles. The way information is presented can affect the way we perceive it and so the interpretation we put on it.

Displays could be: Visual Auditory Many ergonomic design aspects of these devices should be considered by work study practitioner when studying the current working method. The main aim of the displays is to establish a communication link between the machine and the worker and that this process can be enhanced or degraded depending upon the quality of the displays selected.

An analogne display ( white needle on black circular dial) of vehicle speed is easily interpreted at a glance while a display in digit form with digits anywhere between 57 and 62 during the observation takes more efforts. As far as controls are concerned, some are easier to adjust than others.Rotating controls on vloume are easier to set then linear controls or push button digital controls.

General principles concerning displays : Display design must be based on a clear definition of the task and on an understanding of the way in which the particular kind of operator performs it. There are three kinds of display : pictorial, qualitative and quantitative. Quantitative displays are only used when numbers are essential to the task. In most tasks the operator receives information both from real work process and from artificial display representing it. The artificial display must be so designed as to be compatible with the real display in terms of patterns and relative movements.

 In designing displays for maximum speed and minimum attention, use the kinasthetic channel.  For maximum attention, use auditory channel.  For maximum precision and agreement between operators, use the visual channel.

Ergonomics is also concerned with the way a worker is able to control the running of the operations.Basically, there are two factors involved, time and space. Time is … the time is takes for a worker to exert control or react to a system out of control which could be matched with the motor skills of the worker. Space is … space available to permit freedom of movement when exerting control. The space needed is generally underestimated by the systems designer.

If work tasks and equipment do not include ergonomic principles in their design, workers may have exposure to undue physical stress, strain and overexertion,including vibration, awkward postures, forceful exertions, repetitive motion and heavy lifting. Ergonomists, industrial engineers, occupational safety and health professionals and other trained individuals believe that reducing physical stress in the workplace could eliminate upto half of the serious injuries each year.

Ergonomics in the Textile and Apparel Industries Improving Ergonomic Conditions Can Improve Productivity and Safety - Enhance Competitiveness Reduce Worker Compensation Costs Provide More Reliable Workforce May Include Allocating High Risk Jobs to Machines Where Possible

Injuries and Illnesses Among Textile and Apparel Workers 70% of Sewing Machine Operators Using Foot Controls Report Back Pain 35% Report Persistent Low Back Pain 25% Have Suffered a Compensable Cumulative Trauma Disorder (CTD) –81% of CTDs Were to the Wrist –14% of CTDs to the Elbow –5% of CTDs to the Shoulder

49% of Workers Experience Pain in the Neck Absenteeism Increases as Working Conditions Worsen Loss of Workers Due to Injuries or Turnover is Associated With Working Conditions

Tasks Associated With Injuries and Illnesses Hand Sewing and Trimming are Stressful to All Upper Limbs Stitching Tasks are Associated With Pain in the Shoulders, Wrists, and Hands Ironing by Hand is Associated With Elbow Pain Garment Assembly Tasks are Associated With CTDs of the Hands and Wrists Foot Operated Sewing is Associated With Pain in the Back

Static Postures and CTDs Analysis Reveals That 40% of Operators at Sewing Machines Stoop Forward > 20 o Throughout the Machine Cycle 60% Tilt Their Heads Forward > 20 o Throughout the Machine Cycle - Why? –Visual Demands of the Work –Geometry of the Work Station –Inadequate Seating

Postural Stress and Lighting  Precise Stitching Tasks are Visually Demanding  Thread and Fabric Often Offer Little or No Visual Contrast  36% of Operators Feel Lighting is Inadequate  Surveys Found Light Levels at Less Than 60% of Recommended Levels  Operators Lean Forward to See Their Work

Seating Straight Backed Wooden or Metal Chairs are Typical in the Industry Chairs Often Lack Cushioning Chairs Often Lack Adjustable Back Rests Chairs Often Lack Height Adjustability Improved Seating is Readily Available

PsychoSocial Considerations  Psychomotor Demands are High (Speed, Accuracy, Coordination)  Positive Attitudes Toward Work are Inversely Related to Increased Monotony and Fatigue  Positive Attitudes Toward Work are Directly Related to Job Satisfaction

Work Organization  As Many as 100% of Piecework Operators in High Manipulation Jobs Have Symptoms of CTDs  Workers in Piecework are 4 Times as Likely to Develop Severe Disabilities as Hourly Workers  Workers in Piecework are 9 Times as Likely to Develop Arthritic and Osteoarticular Disorders as Hourly Workers  As Duration of Employment in Piecework Increases, So Does Severe Disabilities

Duration of Exposure  Machine Operators Experience Cumulative Damage to the Neck and Shoulders Over Time  Risk for Persistent Neck and Shoulder Pain Increases With Years of Employment as a Machine Operator  Work for More Than Eight Years as Machine Operator Increases Risks For Neck and Shoulder Pain

1)Static work: musculoskeletal effort required to hold a certain position, even a comfortable one. Example: sit & work at computers; keeping head and torso upright requires small or great amounts of static work depending on the efficiency of the body positions we chose. What two elements are at work?

Elements at work (cont) Force: amount of tension our muscles generate Example: tilting your head forward or backward from a neutral, vertical position quadruples the amount of force acting on your lower neck vertebrae Increased force is d/t increase in muscular tension needed to support head in a tilted position

Three Main Ergonomic Principles: 1.Work activities should permit worker to adopt several different healthy and safe postures. 2.Muscle forces should be done by the largest appropriate muscle groups available 3.Work activities s/b performed with joints at about mid- point of their ROM (esp. head,trunk,UE)

What are MSDs ? MSD --- Musculoskeletal disorders Are injuries and disorders of the soft tissues ( muscles, tendons, ligaments,joints and cartilage) and nervous system. They can affect nearly all tissues, including the nerves and tendon sheaths and most frequently involve the arms and back.

What causes Nerve Compression or Entrapment? 1)Repeated motions 2)Tight muscles 3)Inflammation of surrounding tissues 4)Misalignment of the nerve

What are 4 Common Nerve injuries? I.Thoracic Outlet Syndrome: brachial plexus compression d/t muscle tightness side of neck from poor head position or slumped posture. S/Sx: numbness/tingling in hand, made worse w/overhead activities or cradling phone b/w ear and shoulder

Nerve injuries (cont) II.Radial tunnel syndrome: compressed radial outside of elbow d/t repetitive wrist & finger extension or turning of forearm S/Sx: Sensations from elbow to base of thumb w/ wrist weakness a common sx

Nerve injuries (cont) III.Cubital tunnel syndrome: ulnar nerve compression inside of the elbow d/t repetitive bending of elbow or resting your elbow on a hard surface S/Sx: numbness or tingling and inside of arm w/ tingling to ring & little fingers

Nerve injuries (cont) IV.Carpal tunnel syndrome: compression of median nerve at level of carpal tunnel Where is carpal tunnel? wrist by ligament over the carpal bones in hand S/Sx: numbness or tingling in thumb, index, or middle finger & ½ of ring finger; often night by hand “falling asleep” Sx increased by driving or attempting to hold objects; dropping objects is a common complaint

Tendons and Tendonitis Tendons are connective tissue that attach muscle to bone; have little stretch or rebound Tendon overuse, static or prolonged position=inflammation or tendonitis Tendons of wrist & hand very high risk for injury w/ overuse “Tennis elbow” or lateral epicondylitis affects finger extensor tendons outside of elbow “Golfer’s elbow” or medical epicondylitis affects finger flexor tendons inside of elbow

Parts of body affected by MSDs Arms Hands Fingers Neck Back Wrists Legs Shoulders

Occupational safety and health professionals have called these disorders a variety of names, including cumulative trauma disorders, repeated trauma, repetitive stress injuries and occupational overexertion syndrome. These painful and often disabling injuries generally develop gradually over weeks, months and years.

MSDs usually result from exposure to multiple risk factors that can cause the disorders. MSD’s can cause a number of conditions, including pain, numbness, tingling, stiff joints, difficulty in moving, muscle loss, and sometimes paralysis. These disorders include Carpal tunnel syndrome, tendinitis, sciatica, herniated discs, and low back pain. MSD’s do not include injuries resulting from slips, trips, falls or similar accidents.

Causes of work related MSDs Occur when the physical capabilities of the worker do not match the physical requirements of the job. Prolonged exposure to ergonomic risk factors can cause damage to a worker’s body and lead to MSDs.

Conditions that are likely to cause work related MSDs Exerting excessive force Excessive repetition of movements that can irritate tendons and increase pressure on the nerves. Awkward postures, or unsupported positions that stretch physical limits, can compress nerves and irritate tendons. Static postures or positions that a worker must hold for long periods of time, can restrict blood flow and damage muscles. Motion such as increased speed or acceleration when bending and twisting, can increase the amount of force exerted on the body.

Compression from grasping sharp edges like tool handles, can concentrate force on small areas of the body, reduce blood flow and nerve transmission and damage tendons and tendon sheaths. Inadequate recovery time due to overtime, lack of breaks and failure to vary tasks can leave insufficient time for tissue repair. Excessive vibration, usually from vibrating tools, can decrease blood flow, damage nerves and contribute to muscle fatigue.

MSD risk factors Force Repetition Awkward postures Static postures Quick motions Compression or contact stress Vibration Cold temperatures

What type of work are most likely to pose ergonomic hazards ? Manual handling Manufacturing and production Heavy lifting Twisting movements Long hours of working in awkward positions.

Examples of Musculoskeletal disorders

Solutions - A Comprehensive Ergonomics Program Training for Supervisors and Managers Awareness Training for Employees Job Analyses and Implementation of Controls Worker Involvement and Participation Medical Management

To make something ergonomically sound you need to understand three things. Body mechanics the tool, and the task being performed.

Some fundamental ergonomic principles to keep in mind : 1.Use proper tools 2.Keep repetitive motions to minimum. 3. Avoid awkward postions 4. Use safe lifting procedures 5. Get proper rest

How to control ergonomic risk factors. Appropriate engineering contorls, such as work station, tool and equipment design or re-design. Work practices such as proper lifting techniques and keeping work areas clean. Administrative controls, such as worker rotation, more task variety and increased rest breaks. Personal protective equipment such as knee pads, vibration gloves and similar devices. Work tools and equipment should be ergonomically designed. Tools should be light weight and handles designed to allow relaxed grip so the wrists can remain straight.

Tools should be designed for use with either hand and be of various sizes so they are appropriate for all workers. Tool handles should be shaped so that they contact the largest possible surface of the inner hand and fingers. Use power tools to reduce the amount of human force and repetition required. Purchase low vibration tools to reduce tool vibration and if necessary, fit absorbent rubber sleeves over tool handles.

WorkStation Redesign - Sewing Machines  30” Fixed TableTop Height  Point of Operation Between 4-7” Above TableTop  Sewing Machine Tilted 11 o Toward Operator  For Jobs of Longer Duration Sewing - Bench Mounted Arm Rests  Adjustable Chair  Adjustable Foot Rest With Movable Machine Control

Work Enhancements  Foam Padded Edges to Sharp Table Edges  Provide Cloth Upholstered Adjustable Chairs  Angle Packing Boxes to Workers With Tilt Equipment  Provide Anti-Fatigue Matting for Standing Workers  Improved Lighting  Require Rest Periods  Job Rotations

Automated Materials Handling  Eliminates Heavy Lifting by Operators or “Bundle Boys”  Uses Pre-Programmed Hanging Conveyor  Moves Only One or a Few Work Pieces Per Hanger  Computer Controlled - Movement Tracked by Bar- Coded Hangers and Series of Scanners  Delivers Work to Queue Near Operator