Human Factors Test 1

The equivalent expressions used primarily in the United States? In the rest of the world the science is called '________."

-Human factors or human factors engineering or Ergonomics -Ergonomics

1. Occupational lung disease 2. Musculoskeletal injuries 3. Occupational cancers 4. Amputations, fractures, eye loss, lacerations, and traumatic deaths 5. Cardiovascular diseases 6. Diseases of reproduction 7. Neurotoxic disorders 8. Noise-induced loss of hearing 9. Dermatologic conditions 10. Psychologic disorders

10 Leading Work Related Diseases & Injuries in the US

Under sufficient oxygen supply, the pyruvic acid is broken down into water and carbon dioxide, releasing large amounts of ATP. This is a more efficient reaction than anaerobic reaction

Aerobic Work

-Structural dimensions These are taken with the body in various standard and still positions. Another term is static anthropometry. -Functional dimensions These are obtained with the body in various work postures. Another term for this category is dynamic anthropometry. Crawling height, kneeling height in mines and airplanes are important.

Anthropometric Data

-Determine the body dimensions important in the design. -Define the user population. -Select the percentage of the population to be accommodated. -Each body dimension identified: Look up the value from data tables. Apply the data. Make adjustments in the data if necessary (slump, clothing, etc).

Application Methodology

related to either information overload or underload under information processing requirements (short-term and long-term memory requirements, etc.).

Cognitive

Factors that contribute to boredom 1. Short cycle times 2. Few opportunities for bodily movement 3. Warm conditions 4. No contacts with fellow workers 5. People with low motivation 6. People with high abilities, eager to excel 7. Dimly lighted work environments The remedies for boredom 1. Job expansion 2. Job enrichment 3. Job rotation 4. Proper amount of stress 5. Optimal environmental conditions 6. Personal attention to one's job 7. Good social contacts

Cognitive factors: Boredom

Measuring methods 1. Psycho physiological indexes - Heart rate variability, electroencephalogram 2. Behavioral timesharing methods - Dual task method 3. Subjective ratings

Cognitive factors: Mental Workload

-The overstressed muscle will develop a painful phenomenon called the muscular fatigue. This condition is acute and localized. -On the other hand, with overburdened cognitive functions, human beings develop mental fatigue, accompanied by a general sensation of weariness. -We feel impaired, heavy, and overworked. Both monotony and excessive use of mental functions may cause these symptoms. -Mental fatigue requires a general state of rest for recovery. Physical exercise also helps. Several of the mental load measurement techniques may also be applied to measure mental fatigue.

Cognitive factors: Mental fatigue

respond to light levels equivalent to light falling on a white paper 30 cm (1 ft) away from a standard candle, and above. Cones are responsible for daylight vision (photopic vision). There are 7,000,000 cones.

Cones

1. Less production output 2. Increased lost time 3. Higher medical costs 4. Higher material costs 5. Increased absenteeism 6. Low-quality work 7. Injuries, strains 8. Increased probability of accidents and errors 9. Increased labor turnover 10. Less spare capacity to deal with emergencies

Cost of Ignoring Ergonomics

-People can maintain their maximum effort only briefly. -Static effort can be maintained at only 20% of its peak over times, whereas 30% of peak forces can be maintained over extended periods in dynamic work.

Endurance

Measurement Devices and Techniques Human Variability Is There an Average Human? Factors that Affect Anthropometric Data Anthropometric Data Structural Data Functional Dimensions Application Methodology -Anthropometry is the study of human body dimensions. -The most recent standardization occurred in the 1980s by the International Standards Organization (ISO) Technical Committee 159. -Primary areas of application of anthropometric data are: Clothing design Workspace design Environment design Design of equipment, tools, and machinery Consumer product design -The designer should accommodate the body dimensions of the population that will be using the equipment. -Universal operability is desired within a population category. 90 to 95% of the population within a target user group must be able to use the design. -Universal operability objectives can be achieved by adjustable designs (car seats, etc.) -Certain aspects of design may call for only one set of dimensions to be used. Clearances usually call for designs based on 95th percentile values, since most everybody will then be able to fit in the clearance.

Engineering Anthropometry

the five classic senses (vision, audition, smell, taste, and touch).

Exteroceptors

-Age Body dimensions increase from birth to the early or late 20s We begin to shrink in body height at around age 40. -Gender Men are in general larger than women except for hip, thigh, skin fold thickness. -Body position Posture affects body size (standard position for measurement) Restraints also affect data applicability. -Clothing Clothing adds to body size and restricts movement. Gloves allowance must be made for gloves if the operator is expected to be wearing them during work.

Factors Affecting Anthropometric Data

-Fatigue is result of work that is physically and mentally demanding. -Feelings of fatigue occur during or after work (from slight tiredness to complete exhaustion). -Measures can be subjective and objective measures such as accumulation of lactate in the blood.

Fatigue

rich in cones, is a shallow pit centered within the yellow spot. The yellow spot contains many cones, increasing in number toward the center of the spot. The fovea is the region of maximum visual acuity under sufficient illumination.

Fovea

Prone length and height Squatting height Crawling length and height

Functional Dimensions

Internal Environment Input Sensing Identifying Interpreting External Environment Decision Making Responding and Manipulating Output Feedback Circuits Information Storage Short term memory Long term memory

Functional Structure

symbolize attention to the human being from start of finish in the design cycle. ____is replaced by "design," "manufacturing," "test," or other. ____ stands for "human integrated."

HIX "X" "HI"

-Human beings vary with respect to body measurements. -Different ethnic groups, tribes, and nationalities possess varying physiological characteristics that make them different. -Differences exist even within the same group, due to gene characteristics. -Is There an Average Human? No. Probably there is no single person that is an average on all accounts of anthropometry.

Human Variability

refers to systems designed with human capabilities and limitations in mind so that the resultant design can be used effectively by people.

Human-integrated design (HID)

refers to the systems where human operators can work effectively with the design. Consider HIM when designing for manufacture.

Human-integrated manufacturing (HIM)

Note- short-term memory can handle 6 bits at a time

Information Input Process

Theories of information processing 1. Broadbent's filter theory an audio filter exists between the sensory buffer and short-term store (what is now called working memory) that prevents overloading memory 2. Bills' blocking theory Human beings are limited in the amount of information they can learn. Work must be interspersed with interruption 3. Donders' stage model One can measure the time required to process information based on mental processes Includes sensing, recognition, and action

Information Processing

Information processing- H= log2n where n is # of choices and H is the number of bits.

Information processing

In 1961, ____________ was founded which works as an umbrella association and has at least 15 societies from different countries.

International Ergonomics Association (IEA)

-Simple devices Spreading and sliding calipers to measure short distances Anthropometers: straight rods with one fixed and one movable arm with the distance between the two arms indicated on a ruler Tapes to measure circumferences and contours Simple scales for weight measurements Cones and boards with holes for grip circumference and finger-size measurement -Morant technique: A set of grids is used to aid in the measurements. The projections of body landmarks on grids are used for measurements. -Other methods include photographic methods, videotaping, use of mirrors, holography, & stereophotometry.

Measurement Devices & Techniques

-supplies the necessary energy to the musculoskeletal system. -It is the chemical process of conversion of food into mechanical work and heat. -Energy conversion in the muscle

Metabolism

-During WW I, US and Great Britain, exercised selection and training -During and right after WW II, optimal design parameters for display and control were studied.

Military (Brief history of ergonomics)

related to the problems that train muscular and skeletal system (single incident or cumulative trauma).

Musculoskeletal

the resulting change in the body

Strain

-Static strength is measured at static postures, such as standing or seated. -Dynamic strength is measured during work. -Posture and duration are important factors. -Characteristics of Strength -Strength is at its peak by the late twenties, and shows continuous decline from then on. At age 65, one has only 75% of the strength of a youth. -On the average, women have two-thirds the strength of men. -Exercise can increase strength and endurance by as much as 50%. -Peak grip strength occurs with shoulder abducted 0 degrees, elbow flexed 135 degrees, and the waist at neutral posture. Deviations in elbow and wrist angles may result in up to 36% decrement in grip strength.

Strength

the maximum force that one can exert voluntarily. It can be measured in kilograms using a dynamometer.

Strength

Weight Stature Sitting height Head length Knee height (sitting) Popliteal height (sitting) Elbow rest height (sitting) Hip breadth (sitting) Elbow-to-elbow breadth (sitting) Thigh clearance (sitting) Eye height (sitting) Arm reach Hand length Foot length

Structural Data

1. Natural Anthills 2. Man-made 3. Open Systems 4. Closed Systems 5. Open Loop Systems 6. Closed Loop Systems 7. Manual Systems 8. Semi-Automatic 9. Automatic Systems 10. Adaptive Systems and Non-Adaptive Systems

System Classification

-Light is visually evaluated radiant energy. -The human organ that is sensitive to light is the eye. -The eye is a globe about 2.5 cm (1 in.) in diameter. -Six muscles attach to the eyeball by means of ligaments.

The Eye

The consideration of human beings in the design of objects, machinery, and environments.

The central focus

The ___ and the ____ separate two chambers of the eyeball.

iris and lens

A ______ is an integrated assembly of interacting elements designed to carry out cooperatively a pre-determined function.

system

ergon and nomos

work and laws

the minimum steady energy consumption to maintain involuntary activity (circulation, etc.). Basal: 0.3 kcal/min for 70kg male Digestive: 1700 kcal/day for 70kg male 1400 kcal/day for 60kg female

Basal Metabolism (kcal)

-Research studies started at about the same time including work physiology and human physical resources. -In 1971 ERGOLAB was founded, primarily concentrated on human psychology. -In the 1970s, researches played practical roles dealing with real-life situations

Scandinavia (brief history in ergonomics)

-Justifying ergonomics projects -Production increase -Social responsibility -Planning the presentation -Making the presentation

Selling the Idea to the Management

Considerations for job design 1. To the extent possible, separate the signal + noise distribution from the noise distribution (increase signal-to-noise ratio) 2. If an overlap is inevitable, the criterion line can be set based on the expected magnitude of damage due to each type of wrong decision.

Signal Detection

-Arrangement of workplace (dimensions, relative locations, etc.) -Work content (speed and accuracy requirements, etc.) -Work organization (work-rest cycles, start-stop times, etc.) -Work environment (co-workers, supervision, heat, cold, etc.) -Other (financial problems, family problems, etc.)

Sources of Stress

the outside effector

Stress

-Circulatory system carries oxygen from the lungs and nutrients from the GI tract to the cells, muscles, etc. -It also returns metabolic byproducts (carbon dioxide, heat, water, and waste) to be dissipated. -The heart acts as the double pump for the system.

Supporting systems: Circulation

-Nutrition process involves ingestion, digestion, absorption, and utilization of nutrient substances. -The foundation of physical activity providing the necessary fuel and the chemicals. -Proteins, carbohydrates, and fat are the main nutrients that supply energy for muscular work. Certain vitamins and inorganic compounds are also necessary for nutritional balance and efficient energy transfer. -The body cannot make use of the ingested food directly. It has to be converted into a usable form by digestion. This takes the form of a combination of mechanical and chemical processes. -Involves many organs including mouth, stomach, small intestine, and large intestine.

Supporting systems: Nutrition

The _____________ is systematic application of available data on human characteristics (capabilities, limitations) to the design of such systems or procedures.

central approach

The ________ of ergonomics is fitting the task to the person.

central theme

External stimuli provide the ____that are sensed by the human. Perception differs from sensation in that perception involves attaching meaning to the stimuli. Just as there is a difference between "data" and "information," there is a difference between what is sensed and what is perceived.

data

The ________ are to increase the effectiveness of the resulting human-machine system while maintaining human well being.

objectives

a variable aperture that gets larger in dark surroundings and smaller in bright environments. The aperture of pupil ranges from 3-5mm in daylight and 7-8mm at night.

pupil

is an outgrowth of the brain that is composed of a complex structure of nervous tissue.

Retina

respond to low illumination levels equivalent to light impinging on earth in full moon, or below. Primary receptors used in low illumination (scotopic vision) are the rods. There are 130,000,000 rods.

Rods

Representative of the population and randomly selected and not biased

Sampling of data

Types of ergonomics problems

1. Anthropometric 2. Cognitive 3. Musculoskeletal 4. Cardiovascular 5. Psychomotor

If sufficient oxygen is not being supplied to the muscle, pyruvic acid is converted into lactic acid while ATP is regenerated. Lactic acid accumulation between muscle fibers causes muscular fatigue and pain.

Anaerobic Work

related to the conflict between functional space geometry and human dimensions (reach distances, sitting eye height, etc.).

Anthropometric.

-Epidemiological Approach: job-work place characterization, historical records, etc/ -Biomechanical Approach: forces-moments on body parts, considers less than 4 lifts per minute -Psychophysical Methods: subjects adjust load and task characteristics -Physiological Approach: considers heart rate, oxygen consumption, lactic acid accumulation, etc.

Approaches for manual material handling evaluation

related to the problems place stress on the circulatory system (blood pressure, oxygen requirements, etc.).

Cardiovascular

1. The system is man-made from equipment or hardware. 2. The system has integrity - all components are contributing to a set of optimum outputs from the given inputs. 3. The system is complex - a change in one variable will affect many other variables in the system. 4. The system is semi-automatic - machines perform some of the functions of the system and human beings perform some of the functions of the system. 5. The system inputs are stochastic - the exact load or performance at any given instance is not predictable. 6. Most systems, and specially the most difficult systems, are competitive, military of business.

Characteristics of a System

-Similar to vigilance, attention requires that certain aspects of the environment must be given high priority during performance. -Also requires processing of incoming information. -Two types of attention need to be mentioned. -Selective attention allows one to focus on one particular aspect of the environment despite other distractions. -Divided attention allows one to focus on several tasks simultaneously while ignoring others.

Cognitive factors: Attention

-refers to the case where a person is asked to watch for a signal of interest and make correct calls in all conditions [i.e., catch the signal (target) and let nonsignals go by]. -Relative improvements in vigilance performance can be achieved if: 1. The frequency of signals increases. 2. The signals are stronger. 3. The signals can be discriminated more easily from non- signals. 4. Periodic feedback is provided to the subject on his or her performance. -Performance gets worse if: 1. The watch period increases. 2. The between-signal interval shows high variability. 3. The subject is already under stress.

Cognitive factors: Vigilance

Bursitis Tendonitis Synovitis Tenosynovitis Stenosing-tenosynovitis Stenosing-tenosynovitis-crepitans Ganglionic cyst Trigger finger DeQuervain's disease Raynaud's phenomenon Ischemia Carpal tunnel syndrome Neuritis Guyon's canal syndrome Intersection syndrome Other Lateral epicondylitis, also known as "tennis elbow" Medial epicondylitis, also Known as "golfer's elbow" Telephone operator's elbow Radial tunnel syndrome Frequently reported shoulder disorders Bicipital tenosynovitis or bursitis Subdeltoid bursitis Rotator cuff irritation, and tear

Common CTDs

admits light through the anterior chamber and then the pupil, the aperture within the iris.

Cornea

-Cumulative Trauma Disorders (CTD) -CTDs are disorders of the softer tissue due primarily to repeated use (a.k.a. repetitive-motion disorders, overuse, cumulative-effect trauma, and cumulative-effect disorders). -CTDs are commonly reported in the tendons and in the nerves of the upper extremities, including the fingers, the wrist, the forearm and the upper arm, and the shoulder. Joints, muscles, blood vessels, and bursas may also be effected. -Reasons Unnatural Posture Forceful application Repetition of activity Pounding/Jerking Contorted body joints Others Extreme positions Working with objects causing vibrations of a part or whole body -Prevention Techniques Administrative controls Engineering Controls Therapeutic approaches

Cumulative Trauma Disorders (CTD)

Mode Median Mean Standard deviation Correlation Coefficient Criteria Subject related: 1. Human Performance 2. Physiological 3. Subjective response 4. Accident or injury frequently and severity. System related: lifetime, ease of operation, maintainability, reliability, Operating cost, human resource requirement. Judgment Task Data Empirical Task Data Reliability 1. Component in series R system = ∏ Ri 2. In parallel R system = 1 - ∏ (1 - Ri) 3. n-components, m-parallel Source of Information Human Physical Components Environment

Data Analysis

can be estimated as 10% of the sum of basal and activity metabolisms.

Digestive metabolism .

the ability to maintain activity over time. In the content of physical activity, endurance refers to the maintenance of effort.

Endurance

-Measured in kilocalories. -Energy consumption of work can be measured indirectly by oxygen consumption. For every liter of oxygen consumed, there is an average of 4.8 kcal of energy expended. -Amount of calories expended on a task depends on age, sex, postures, body weight, and the intensity of activity. -A task that affects the center of gravity least is also the least energy consuming. -As the rate of activity increases, there is elevated energy cost. -With increasing body weight, there is increasing energy cost. -It is estimated that a healthy occupation should require 3000 to 3500 kcal for a man and 2500 to 3000 kcal for a woman each day. -In general, women expend fewer calories than men and thus require fewer calories. -At the age of 65, one can spend 75% of the calories that can be spent at age 25. -Daily energy expenditure due to specific activities is the sum of the product of time spent on each activity and the energy cost of work for that activity, summed across all activities. Naturally, the total daily energy requirement must also include the needs for basal and digestive metabolism. -Keeping energy cost of work within acceptable limits -For men: -A max time-weighted average of 5 kcal/min due to activity energy cost of work -A max time-weighted heart rate average of 100 beats/min. -For women: -A max time-weighted average of 4 kcal/min due to activity energy cost of work -A max time-weighted heart rate average of 90 beats/min.

Energy Cost of Activities

-With physical work, energy demands increase. -The amount of increase depends on several factors, such as physical conditioning of the body, intensity of activity, sex, and body weight. -To provide the needed oxygen and remove the accumulated waste, vascular activity in the muscles increases. -More blood is pumped to affected areas. -Oxygen consumption increases. -Breathing accelerates to oxygenate more blood per unit time in the lungs. -Heart rate increases since more blood is processed in this organ per unit time. -Sweating occurs to dissipate the excess heat. -Blood pressure increases. -Oxygen consumption and heart rate is used to measure physical strain that the body is undergoing. -Portable devices exist to measure HR and oxygen consumption. -Both static effort and dynamic load on limited muscle groups can be analyzed with the help of electromyogram (EMG).

Energy Cost of Work

the design of the work, workplace, work environment, and tools to match the physical, physiological, and mental capability of the workers to provide a safe and productive workplace.

Ergonomics

Total metabolism for heavy washing per min. Activity metabolism for heavy washing is 5kcal/min (table 3.2 p 38). Digestive metabolism = 10%(0.3 + 5)= 0.53kcal/min. Therefore total metabolism/min= 0.3+0.53+5=5.83kcal

Example problem

Worker Characteristics Task Characteristics Material Characteristics Work Organization

Factors Affecting Manual Material Handling

Internal factors - relate to the human's physiological characteristics 1. Visual acuity. 2. Depth perception. 3. Near point accommodation. 4. Phorias. 5. Color discrimination. 6. Dark adaptation. 7. Age. 8. Purkinje shift. 9. Blind spot. 10. Peripheral vision. 11. Night blindness. 12. Normal line of sight (NLS). External factors 1. Brightness contrast 2. Color contrast 3. Amount of light 4. Duration and movement of target 5. Glare 6. Surrounding brightness 7. Color 8. Size 9. Position of target in the visual field. NOTE-The eye can adapt to dark/light environment. The ability of the eyes to adapt from dark to light environment takes less time than adapting from light to dark. The cones take up to 40min to adjust to a darker environment.

Factors Affecting Visual Function

-In 1915, Industrial Fatigue Research Board (later became Industrial Health Research Board) -Before WW I, areas of environmental factors and performance were studied -No work related studies between WW I and II. -After WW II, study areas include anatomy, physiology, psychology, industrial medicine, design engineering, architecture, and illumination engineering. -In 1949, Ergonomics Research Society (later became Ergonomics Society (ES))

Great Britain (brief history in ergonomics)

-During rest, the HR averages around some value between 60 and 85 -At the onset of work, the HR starts to rise. -For some time HR lags the energy cost of work, using locally available high-energy phosphates, while developing oxygen debt. -At some point it levels off, indicating that the amount of blood supply to the muscles is sufficient to meet the demand (steady state). -If work is stopped suddenly, a gradual decline in HR occurs until it again levels off at the resting rate. HR does not immediately drop back to resting level, indicating that the oxygen debt initially developed is being paid back possibly faith interest. -Note- Because of breathing the heart changes from beat to beat. this variation is called Arrhythmia. At each inspiration the H.R. rises and at each expiration it slows down. -The difference between HRR and HRT is a measure of the intensity of physical stress (T2 is more stressful than T1). -HR recovery time is longer in more stressful work. -HR recovery time may also be used as a measure of task intensity. -With physical conditioning, one can attain lower elevated heart rates than otherwise -At the age of 65, one can attain only about 60% of the heart rate at the age 20. -Linear relationship between heart rate and oxygen consumption has also been demonstrated in field studies. -Oxygen uptake can be estimated from recorded heart rate, with some error.

HR, O2 Consumption & Work

-Design of complex man-machine systems -Based on research concerned with man's behavior in complex man-machine environments -Physical Environment -Personal and protective items

Human Factors Engineering

1. There is an unacceptably large numbers of rejects on the operation 2. Operators are making frequent mistakes on the job 3. There is high material waste 4. Labor turnover on the job is excessive 5. Employees frequently complain about job requirements 6. Production output is unacceptably low 7. Absenteeism is unacceptably high 8. There are accidents or near accidents on the job 9. Employees frequently visit the infirmary 10. Product quality is low 11. Training time is unacceptably long 12. Employees take frequent rest periods 13. Personal and fatigue allowances are too high 14. Operator assignment to the job is limited by size, gender, sex , age, or physique 15. There is interference with verbal communication 16. There are requests for transfers to the other jobs 17. Employees can not meet production standards 18. Employees are frequently away from the workplace 19. Breaks seem excessively long

Indicators of Need for Ergonomics Attention

The oxidation of pyruvic acid in aerobic work is a very complex process involving enzymes, co-enzymes, and fatty acids. This process cycle is known as the Kerbs cycle.

Kerbs Cycle

-Frank B. GILBRETH, Engineer, Lillian M. GILBRETH, Psychologist -Lillian Gilbreth developed motion study, concerned with the manipulations or movements, which an operator must make in performing any job. It usually included an analysis of movements in an attempt to get at the best way of doing a particular job.

Motion Study

focuses on: -Methods Improvement - Based on common sense and rule of thumb principles of movement -Setting fair rates of pay

Motion and Time Study

1. Plan it in advance 2. Run a pilot study 3. Construct and use forms 4. Have back-up systems, subject-equipment, maintain

Murphy's Law

-Composed of bundled muscle fibers. -The skeletal muscles (voluntary muscles) are of most concern to an ergonomist. -Muscles contract to generate forces. -Muscles can generate maximum force in extended state. -Contracted muscles can generate very little force. -Muscle generates mechanical work by converting chemical energy into mechanical energy.

Musculoskeletal System: Muscles

Below AL - 99% of men, 75% of women can lift safely Between MPL and AL - administrative controls are required Over MPL - lifting conditions are not acceptable

NIOSH Lifting Guide 1981

-Nervous system coordinates and regulates body activities. It is responsible for the initiation and control of muscular activity. -Neuron is composed of a nerve cell along with a minimum of two nerve fibers. -A nerve fiber that brings messages to a nerve cell is known as a dendrite. -A nerve fiber that takes messages to another cell is known as the axon. -The nerve fibers are coated with a substance called myelin, which serves to protect one nerve fiber's messages from another. -Impulse of the preceding neuron is passed to the succeeding one unaltered in one thousandth of a second. -The nervous system is divided into three major parts -The Autonomic Nervous System - balance of nervous control -The Peripheral Nervous System - controls voluntary activity -The Central Nervous System - brain and spinal cord

Nervous System

-Occupational biomechanics deals with the mechanical and motion characteristics of the human body and its elements. -Occupational biomechanics can be defined as a field of science that studies the interrelationships between workers and their tools, workplaces, and so on, in order to enhance performance while minimizing the possibility of musculoskeletal injury. -Anthropometry provides the human body and segment dimension, including masses and centers of gravity. -Kinesiology covers the area of human motion (body segment motions, muscle actions). -Bioinstrumentation deals with process of data acquisition and analysis. -Data collected via force platforms, electromyography, goniometry, and linear distance measuring devices. -Biomechanical modeling is based on three theories (Newton's) 1. A mass will remain or rest or in uniform motion unless an unbalanced external force acts on it. 2. Force is proportional to the acceleration of mass. 3. Any action will be opposed by reaction of equal magnitude. -Standard anatomical posture - standing erect, face forward, holding arms down at the sides with palms facing forward. -Kinesiological terms that describes movement -Flexion: decreasing angle between body parts -Extension: increasing angle between body parts -Adduction: movement toward the middle of the body -Abduction: moving away from the midbody -Pronation: face-down, or palm-down position -Supination: face-up, or palm-up position

Occupational biomechanics

EPA - Environmental Protection Agency OSHA - Occupational Safety and Health Administration NIOSH - The National Institute for Occupational Health and Safety MSHA - Mine Safety and Health Administration HFES - Human Factors and Ergonomics Society IIE - Institute of Industrial Engineers, Ergonomics Division ASSE - American Society of Safety Engineers AIHA - American Industrial Hygiene Association IEEE - Institute of Electrical and Electronics Engineers-Systems, Man and Cybernetics APA - American Psychological Association-Division 21 ES - Ergonomics Society ILO - International Labor Organization WHO - World Health Organization IEA - International Ergonomics Association NRC-NEC - National Research Council CPSC - Consumer Product Safety Commission NHTSA - National Highway Traffic Safety Administration NLCPI - National Legal Center for Public Interest NSC - National Safety Council

Organizations

the key to efficient work. This requires more blood to be pumped to the muscle per unit time and heavier breathing.

Oxygen

-Worker's capacity for energy output is referred to as physical work capacity. -It is a function of the energy available to the person in the form of food, oxygen, and the sum of the energy provided by the aerobic and anaerobic processes. -Age limits the maximum increase in heart rate and oxygen consumption. -Working at more than 30 to 40% of one's maximum aerobic power in an eight-hour shift causes notable muscular fatigue.

Physical Work Capacity

_______are stimulated by the actions of the body itself, such as a reach or a sudden turn. ______ are embedded within the subcutaneous tissue, such as in the muscles and tendons, around the joints, and in the inner ear.

Proprioceptors

related to the problems that strain the psychomotor system due to job requirements, human capabilities, and performance aids (manipulative work, extreme visual demands, etc.).

Psychomotor

It's the right thing to do OSHA ADA You'll have to do it anyway Improve productivity Improve quality Improve labor relations Attract quality workers Retain quality workers Improve safety and health Reduce medical & compensation costs Improve company image Improved marketing Sell program to other companies Total quality management TQM This is an opportunity

Reasons for Implementing an Ergonomics Program

-Classification Content 1. Descriptive Studies 2. Experimental Research 3. Evaluation Research Location 1. Field 2. Laboratory 3. Simulation Variable Type 1. Independent Variable a. Task related b. Environment related c. Subject related 2. Dependent Variable (Criterion) -Sampling of data

Research Methods

-Respiration denotes interrelated processes: absorption of oxygen and elimination of carbon dioxide, transportation of oxygen and carbon dioxide, use of oxygen and release of carbon dioxide by cells and the interstitial fluid, and lastly it denotes the roles of these two gasses in the metabolic processes. -Composed of many organs, including the nose and mouth, pharynx, larynx and trachea; and the lungs, consisting of bronchi, bronchioles, alveolar ducts, alveolar sacs, and alveoli. -Primary function is to expose a large volume of water-saturated air to a large volume of blood to facilitate rapid exchange of gasses between blood and the inhaled air. -Linked to the circulatory system, which carries gasses, water, electrolytes, etc. to tissues and cells.

Supporting systems: Respiration

-The tactual and the olfactory senses are not as important as vision and audition in efficient human functioning in industrial environments. -Skin is sensitive to pressure, pain, cold and warmth. -The olfactory (smell) sense is simple in anatomical structure but complex in its functioning. The smell sense organ is a patch of cells located in the upper part of each nostril. -The olfactory hairs in these cells actually carry out the function of detecting different odors. Foul odors in industry (chemical, metallurgical, leather, etc.) may indicate unusual events.

Tactual & Olfactory Senses

-A combination of rods and cones are used during in-between levels of light (mesopic vision). -Among the neurons that make up most of the retina are the photoreceptors rods and cones. -The tissue layer between the retina and the external sheathing of the eyeball is called the choroid membrane. It is dark in color to absorb the light that is not taken up by the retina. The sclera, the outer layer of the eyeball, is a rather tough tissue protecting the structure. -Curvature of the lens is controlled by the ciliary muscle and the suspensory ligament. The thickening of the lens is accomplished by the relaxation of the muscles, with shortening of the focal length to bring the nearby objects into proper focus on the retina.

The Eye

-206 bones in body. -Bones give body its structure, and with muscles provide mobility. -Some bones simply cover the vital organs (skull, ribs, etc.). -Others provide activity (upper and lower extremities, etc.). -Ligaments connect bone to bone. -Tendons connect bones to muscles. -Bones are connected to each other at joints. -Hinge joints (wrist). -Pivot joints (elbow). -Ball and socket joints (shoulder) larger forces compared to hinge joints. -Bones change their shape, size, and structure depending on the mechanical demands placed on them over time.

The Musculoskeletal System: Bones

-The ear is sensitive to variations in air pressure caused by vibrating objects. 15 to 19% of information is acquired by the auditory channel -Frequency is the number of alternations in sound pressure per unit time caused by changes in density of air molecules. Measure of frequency in cycles per second is expressed in hertz (Hz). -The human ear is sensitive to frequencies between 20 and 20,000 Hz. -Intensity is associated with the human sensation of loudness. It can be measured in bels (B) or decibels (dB). -OSHA requires manufacturers to expose workers to no more than 90 dB measured on the A-scale, on a time-weighted average basis across an 8-hour shift. -Instantaneous sound intensity can be measured by a sound-level meter. -Outer ear collects variations in air pressure. They are then funneled to the eardrum (tympanic membrane) via the ear canal. -In middle ear are three bones in succession: the malleus, the incus, and the stapes collectively called the ossicles. -Their joint purpose is to transmit vibrations from the eardrum to the oval window of inner ear. Since the area of the eardrum is about 22 times the area of the oval window, by the time it is transmitted to the inner ear, the sound energy is amplified 22 times. When tightened, muscles attached to the ossicles act to protect the inner ear against very intense sounds.

The ear

-Frederick W. TAYLOR originated time study techniques in 1881. -Time Study is concerned with the time relations of motions and sequences of motions. Its findings are typically used to establish performance standards.

Time Study

Basal Met. (kcal) + Digestive Met. (kcal) + Activity Met. (kcal)

Total Metabolism (kcal)

-Characterized by a prolonged state of contraction, which restricts blood flow to the muscle tissue. -Neither oxygen supply nor waste removal needs can be met (Example: holding a box in static posture, applying continuous pressure on a part to maintaining position). -The muscle bulk experiencing static loading still quickly depletes the reserve ATP and creatine phosphate. Since no oxygen or glucose is being received, this tape of activity will not last long. Severe muscular pain will also develop due to waste products, including lactic acid, accumulating in the muscle tissue. -Compared to dynamic loading, static effort will require longer rest periods. It will also result in more employee complaints and turnover.

Types of Muscular effort: Static effort

-Rhythmic contraction and relaxation of the muscles -Example: turning a hand wheel to open a valve -Alternated tension and relaxation allow more blood to be circulated through the muscle than when in the resting state. -Both oxygen needs and waste removal needs are met effectively.

Types of muscular effort: Dynamic effort

-In 1949, first book dealing with ergonomics -In the 1950s, non-military applications including areas of manufacturing, communications, and transportation started. -In 1957, Human Factors Society (HFS) of US in Tulsa, Oklahoma -In 1986, International Foundation of Industrial Ergonomics and Safety Research formed. -In 1992, HFS became Human Factors and Ergonomics Society (HFES), in Santa Monica, California

United States (Brief history of ergonomics)

-Employees are being injured -Production volume is high -Labor turnover is high -The work place is utilized for more than one shift Note- A high percentage of OSHA recordable injuries are musculoskeletal. Ergonomics deals with preventing these injuries as well as improves productivity and quality.

When is significant ergonomic involvement Necessary?

Founded ergonomics

Wojciech Jastrzebowski (1950s), K. F. H. Murrell (1949)

-Human beings cannot maintain an activity level that is physically demanding for long periods. They need rest periodically to recover from the effects of the task. -Rest allowances due to physical activity may be evaluated through extensive time studies or physiological methods. These methods may be strain based or metabolic energy expenditure based. -Accepted norm in work-rest cycles due to physical activity, using the metabolic energy expenditure method, is that no work-related rest allowance is necessary for jobs that demand energy expenditure of less than the standard (4 or 5 kcal/min). However, it is a common practice to allow for rest when energy demands exceed accepted standards. -An age allowance is necessary to consider after the Rt calculation (as a multiplier). -Experience suggests that the most effective relief muscular fatigue is through small periods of rest taken several times during the duration of work rather than all taken at one time. -This can be reflected in the standard time for an operation, based on less than 60 minutes in an hour. (Example: a 10-minute fatigue allowance every hour means that one expects only 50 minutes of effective work each hour. Thus the operator can take 10 minutes of break every hour or 5 minutes of rest every 30 minutes.) -It is customary in industry to allow for a 15- to 20-minute coffee break 2 hours after start in the morning and after lunch. These periods may be counted in the total rest duration.

Work-Rest Cycles

-First major thrust for worker safety and health came during and after the industrial revolution, primarily in Europe between the 1850s and 1900s. -Power tool designs for increased productivity rather than human interference. Therefore, many worker injuries and fatalities occurred. -Facing the social problem, countries passed laws to protect workers (England, France, US)

Worker Safety and Health (brief history of ergonomics)