Ergonomics Exam 1
The average employer-sponsored premium for a family of four costs close to ___________ a year.
$13,000
Anatomical concerns
*wrist movement, *grip types, *static muscle loading
symptons associated with CTDs
-pain -restriction joint movement -soft tissue swelling
portable power tool controls
-start switch lockout
hazard controls for hand tools
-the right tool for the right job -know the hazards of the tool
Job Analysis step 1
1) break the job down into tasks and subtasks. Goald is to link excessive job demands to specific aspect of the job or work environment.
Estimated total costs for low back pain is approximately ___________________ annually.
16 billion
BMI Overweight
25-29.9
Optimum shovel angle is
32 degrees
zombie zone
3am to 6am
CO at rest
5-6 L/min
In just three years Medicare and Medicaid will account for ____% of all national health spending.
50
Approximately what percentage of Americans will suffer back pain in their lifetime?
80%
Fahrenheit conversion equation
9/5(X) + 32
BMI underweight
<18.5
Calculate the body surface area for an individual of 82 kg body weight and 180 cm height.
= 0.007184 * Wt0.425 * Ht0.725 =2.02 m^2
Obese
>30
Joint articulations
A junction between two or more bones.
Ganglionic cyst
A noncancerous lump, often on the tendons or joints of wrists and hands.
Biomechanics
A study that uses principals of physics to quantitatively study how forces interact within a living body.
Celsius conversion equation
(X-32) * 5/9
F = 9/5*C+32
C= 5/9(F-32)
non rotary force equation
F*Cos of the angle
M = -E (-+) R(-+) C (-+) S
S = change in heat body content C= convection heat exchange R= radiative heat exchange E= evaporative heat loss
zone B
Time limited compensation, increase in heart rate and body core temp
The Astrand nomogram is used as an indirect assessment of aerobic capacity.
True
A work space is
a three dimensional region surrounding the worker
kinetic energy (KE)
ability of a body to do work because of its motion
circadian rhythm
activity cycle based on 24 hour interval
Avoid static loads, but when it can't be avoided, employee should
assume a posture that gives them the best mechanical advantage
Acclamation
at least 5 days needed. Training, Medical Surveillance, Emergency Response Plan
Raynaud's phenomenon
bouts of white finger and painful sensations
Causes of trips and missteps
changes in elevation or levels, irregularities in walking surfaces, rumpled or rolled up carpets/ mats, carpets with curled edges, missing or uneven floor tiles and bricks
work practices
changes that minimize risks associated with their jobs
health status
chronic disease and acute illness should adjust schedule
heat stress PPE
circulating air systems ice cooling garments liquid cooling systems
prolonged work
continuous work; lactic acid does not accumulate fuel source: carbs and fats
The insertion bone generally moves when the muscle
contracts
Cardiac Index (CI) defined
correlation between resting CO and BSA
Common factors in flooring selection
cost, maintenance, load bearing, aesthetics
hyaline cartilage
cover where bones join
arc
curvilinear distance between points
strain injuries
damage to myofibers increased intracellur calcium release of pro and anti-inflammatory factors
anthropometry
data on body size and range of joint motion can be used to assess the appropriatness of workplace, equipment and product designs relative to workforce capacities for reach, grasp, and clearance.
kinematics
describes motions of the body w/o considering the forces causing the motion
Non rotary component
directed toward the fulcrum, parallel to the lever, and not contributing to the lever movement
Type 2a: fast oxidative
fast twitch, fatigue resistent
long bones
femar, fibia, humerous,
Cannon
fight or flight theory (1926)
Work equation
force * distance
Diarthrosis
freely movable: shoulder joint
Selye
general adaptation theory (1956)
Sylvia burwell
health and human services secretary
Heat stress symptoms
heat cramps heat rash heat exhaustion heat stroke
convection
heat gain or loss: from air
Synarthrosis
immovable: skull
Synarthrosis (joint articulation)
immovable; skull
Health and physical condition can...
impair a person's vision, judgment, and balance. for example: Age, Physical state, fatigue, Stress, illness, Medications, alcohol, drug effects, Blood sugar
Tenosynovitis
inflammation of tendon sheath
tendinitis
inflammation of the tendons
Circadian clock
internal clock
shift work
irregular hours
taking measurements
labels and drawing dimensions of workstations.
Static analyses
looking at the body at rest
static forces
looking at the body at rest
dynamic analyses
looking at the body in motion
dynamic forces
looking at the body in motion
Effects of slips, trips and falls to the employer
loss in productivity and business, increased industrial insurance premiums, costs associated with training replacement worker
circadian clock night
lowers body temp, slows heart, and changing hormone levels
According to the U. S. Department of Labor, slips, trips, and falls...
make up the majority of general industry accidents.
hypothalamus
manages body temp, release of hormones into the blood, wakefulness and sleepiness
PE equation
mass *gravity or weight * height
momentum
mass*velocity
Effort =
moment *time
do workers ever adjust to the night shift?
no
Thoracic outlet syndrome
occurs due to compression, injury, or irritation involving *subclavian vein, subclavian artery, and lower trunks of the brachial plexus
workplace hazards
physical hazards chemical biological
Biomechanics
physics, anthropometry, biology and physiology
What guidelines went into the lifting equation?
physiological; biomechanical psychophysical epidemiological
Niosh finding on job stress
poses a threat to the health and workers
managing work stress
primary prevention secondary prevention tertiary prevention
prime movers
producing desired movement
engineering controls
provide better light
Proprioceptors
provide information about the musculoskeletal system
Heat rash
red bumps from sweat, ex. belt line
circadian rhythm cycle
regular biological rhythm with a period of 24 hours
exposure to light
resets the circadian clock most effective
ear measurement
sensitive to environmental conditions
Ampiarthrosis
slightly movable
neglecting circadian rhythm
susceptible to colds and flu, chronic fatigue, neg effects on female reproduction, obesity, heart disease, accidents, stomach problems, depression, sleep problems
Intermittent Work
sustained effort for short periods of time followed by periods of rest. lactic acid build up. fuel: carbs
Energy
the ability of a body to do work
Class 1: Lever system
the joint (fulcrum) lies between the force point and the resistance point
Endurance
the length of time a person can exert a specified force
endurance
the length of time a person can exert a specified force
Calorimetry
the process of measuring the heat generated by an energy source.
Class 2: lever system
the resistance is between the joint and the force point
Stroke Volume (SV)
the volume of blood ml/hr ejected from the left ventricle during a contraction
Work input
useful work output + against friction
circadian clock morning
wakes most people up
Anatomical Concerns (static muscle loading)
- Situations where arms are elevated or held for extended periods of time -results in fatigue, reduced work capacity, and soreness
take home message hand tools
- it is possible to quantitatively determine which tools minimize exertions -important tool parameters include: Mechanical advantage; balance and handle location; screw head; tool geometry; posture and work location; tool speed and reaction force build up time. -the best tools are the ones best matched to the task.
principles of tool design
- must perform effectively for intended purpose - must be properly proportional to body dimension of the operator - designed to match strength and work capacity of operator -it should not cause undue fatigue -it must provide sensory feedback to the user -its capital and maintenance costs should be reasonable
hand tool hazards
- using tools correctly -maintaining tools
Which of the following is the most likely reason that reported occupational musculoskeletal disorders have increased significantly since the mid-1980's?
-Changing economic base: heavy manufacturing to light manufacturing -Greater percentage of females working than before -Increase in citations in the mid 1980s by OSHA -Courts have decided that work-related musculoskeletal disorders are compensable
Anatomical Concerns (tissue compression)
-Compressive forces on palm or fingers results in ischemia, with resulting numbness and tingling of the fingers. -handles should have large contact surfaces. -finger grooves or recesses in tool handles should be avoided
Handle Properties
-Diameter: handle diameter should be 31-50 mm, with upper end for torque and lower end for dexterity and speed. -length: minimum of 100 mm, with 125mm being ideal -shape: optimal shape may depend upon task performed. T-handles have more torque than straight handles -grip surface, texture, materials -angulation: should be angled to maintain straight wrist
General Anatomical Concerns
-Gender: female grip strength ranges from 50-67% of male grip strength -handedness: 90% of population is right handed -Posture: torque exertion not significantly affected unless extreme postures. -repetitive finger action: trigger forces should be low, under 10N. 2 or 3 finger control operations preferred.
types of screw heads
-Phillips head screws require more force to keep the blade seated -flat head screws need less feed force, but there is a greater tendency to slip sideways -torx heads have advantages of Phillips and flat head screws -holds for manual and power tools.
Anatomical Concerns (awkward wrist position)
-Pronation decreases grip strength 12% -Flexion/extension decreases strength 25% -radial/ulnar deviation decreases strength 15%
Anatomical concerns (wrist)
-Radial deviation (bent horizontal in) - neutral - ulnar deviation (bent horizontal out) -Dorsiflexion (bent vertical out) -neutral -Palmar flexion (bent vertical in)
Seated workstation recommendations (circumstances)
-all items needed for routine task can be easily supplied and handled within the seated workstation. -job being performed does not require more than 40 cm forward or higher than 15cm above work surface -doesnt require handling large forces greater than 10 pounds -writing or light assembly -precision or fine manipulative movements need a level of stability
Ball peen hammer
-ball side made to flatten rivets -drive steel chisels, masonry chisels, nail pullers or concrete nails -used to shape metal and working rivets
Advantages of prediction metabolic rate
-does not interfere with workers job - can be used in the design stage of the job
effort reward imbalance (ERI) model
-effort given given at work and the rewards of the effort -imbalance can result in health risks - high ERI associated with high BMI
Take home message pliers
-ergonomic because the task to squeeze pliers and create strong compressive forces in the jaws is easier. -tasks requiring precise manipulation, fine motor control and little force may be better the other way.
Cylindrical handle grip
-grip strength (G) is sum of forces exerted to the handle surface -when turning handle, maximum torque is T=SD, where T-torque (N-M); S-shear/friction force (N); D-Handle diameter (m) (S=muG, where mu-coefficient of friction, G=grip (N)
Saws
-heavy sawing requires a power grip and repeated flexion /extension, where light sawing uses a precision grip and wrist manipulation. -a pistol grip is used for the heavy sawing power grip, while a cylindrical handle used for precision grip -Western saws usually cut while pushed through wood, while japanese cut on the pull. Jap saves more energy.
maintaining tools
-inspecting tools regularly to make sure they are in good condition. -replace tools that are worn, damaged or broken -sharpen edges of cutting tools so that they work more efficiently and pose less hazard to the workers
sit-stand workstations important considerations
-job requires frequent reaches more than 16 inches forward and more than 6 inches above the work surface -job consists of multiple tasks, some best performed in the sitting while others stand
Workplace designer should keep design factors in mind
-large variability in size of people in the work force population -understand the user population
take home message screwdrivers
-longer screwdrivers need less feed force than shorter ones when used with one hand -screwdriver length may accessibility challenges -feed force is also reduced by using two hands or using a nut driver.
Repetitive tasks
-low force, extended muscle action -injuries generally rapid pain and fatigue
carpenters hammer
-made for driving and pulling nails -not all purpose hammer -not heavy enough to drive hardened masonry nails
grip span
-maximum grip achieved at 45-50 mm with parallel sides, and 75-80 mm with inward angled handles. -Maximum grip requirements should be less than 90 N.
what are the 4 thermodynamic processes
-metabolism -evaporation -radiation -convection
pliers
-most commonly used where the jaw is on the radial side of the hand -inverted grip allows greater span between thumb and index finger.
Anatomical concerns (grip)
-power grip -two point pinch -hook grip -lateral pinch -internal precision -external precision
minimize pressure on the forearms
-rounding and padding the edge -changing the work-surface height or the seat -providing arm rests -redesigning the job.
Standing workstation recommendations (circumstances)
-suitable leg room -involve handling objects weighing more than 10 pounds -job requires high, low or extended reaches frequently -requires frequent movement from one station to others -job requires the exertion of downward forces as in packaging and wrapping operations.
sit-stand workstation advantages
-taking body weight off legs -ability to avoid unnatural body postures -lower energy consumption ->reduce fatigue -less demand on the cardiovascular system -more stability for precision tasks or fine manipulative movements -ability to operate foot controls more easily, precisely and safely while maintaining good working postures
Shovels
-the blade is attached to the shaft through a socket -Handles have traditionally been a T-form but more recently a D-form -Leverage provided by the angle of the shaft from horizontal- called lift. (Optimal angle 32 deg) -blade size depends upon density of material to be shoveled. -optimum shovel rate of 18-21 scoops/min, with loads from 5-11kg
hand tool safeguards
-tool guards -handle design
hand tools
-tools are extensions of human hands -they enhance the capability and productivity of users performing tasks -poorly designed tools or using the wrong tools for the job can result in injuries, reduced productivity for the worker.
Factors leading to development of CTDs
-use of excess force during normal motions -awkward or extreme joint motions -high repetition of same movement -lack of sufficient rest
General principles for workstation design to think about
-what must the worker see while on the job? -what must the worker hear? -what must the worker perform? -what is the sequence of job activities? -what clearance are required? -what storage is required?
Constant numbers of BSA
0.007184 0.425(WT) 0.725(HT)
KE equation
1/2mass*velocity^2
Basal metabolism is
1/5th to 1/3 of a liter of oxygen consumed per minute, or 1.0 to 1.5 kcal of energy expenditure per minute.
MSD Cost
10 billion dolla
Over the last decade, employer-sponsored health insurance premiums have increased ____%
119 (4x the rate of inflation)
Slips, trips and falls make up
15 percent of all accidental deaths
Back injury cost
16 billion annually 25% of low back cases account for 95% of the costs
BMI normal
18.5-24.9
When did healthcare spending begin to rise at a very high level?
1980s
1Pa=
1N*m^-2
What is the maximum recommended energy expenditure that can be expected to continue for months or years
2,000 kcal
Basal Metabolism
2/3 energy consumed by fat; O2 level between 1/5 and 1/3 of a liter of O2/min
Bones
206 bones -long bones -short bones - flat bones -irregular bones
maximum heart rate
220-age
CO during heavy work
25-30 L/min
During work
25-30 l/min
The foot
26 total bones, 14 Phalanges, 5 Metatarsals, 3 Cuneiforms, 1 Navicular, 1 Cuboid, 1 Talus,1 Clacaneus
The hand
28 total bones, 12 phalanges in the fingers, 2 phalanges in the thumb, 5 metacarpal bones in the palm of the hand, 8 carpal bones in the wrist, 1 Sesamoid bone located near the head of the thumb metacarpal.
zombie zone
3 am - 6 am notorious industrial accidents
Heart rate recovery, as an indicator of fatigue, is measured how soon after work stops
3 minutes
Back injuries
30 mil exp low back pain 80% will suffer from low back pain
Between 2008 and 2018, the GDP is expected to increase ___% per year.
4.1
1 pound =
4.45 N = 0.45kg
Between 2008 and 2018, average increase in national health expenditures is expected to be ____% per year.
6.2
Anatomical Concern, handedness:
90% of population is right handed.
Force equation
= mass * acceleration F-N M-kg A-m*s^-2
Body surface formula
=0.007184*Wt^0.425*Ht^0.725
The given parameters are, F = 250N and R= 600N Mechanical advantage formula is
=2.4N
Ergonomics
A branch of science that focuses on the achievement of optimal relationships between workers and their work Environment.
Hypothalamus
A neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion
force
A physical quantity that can accelerate and/or deform a body
Homeostasis
A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level
scoliosis
Abnormal lateral curvature of the spine
About ____% of low back cases account for about ____% of low back compensation costs.
About 25% of low back injuries accounts for about 90% of low back costs.
Main objective of ergonomics
Achieve an optimal relationship between people and their work environment.
What occurred in the 80s to cause the steep increase of occupational musculoskeletal disorders?
Aging population More females in the workplace Changing economic base Increase in citations (OSHA) Court decision that MSDs are covered by workman's comp
Sprain
An injury in which the ligaments holding bones together are stretched too far and tear.
DAvid michaels
Assistant secretary of labor
Ergonomics
Biomechanics & anthropometry; physiology & psychology; Epidemiology; physics; engineer tech; chemistry biological sciences math
thomas frieden
CDC director
CI equals
CO/BSA
At rest
Cardiac Output is 5-6 l/min
Heat stress PPE
Circulating air systems, liquid cooling systems, ice cooling garments
Circumference
Closed curvilinear surface around a body part.
What does NIOSH do?
Conducts research and makes recommendations for work-related injury prevention.
Job demand- control theory
Considers the psychological job demands and characteristics of the job related to decision making and skill usage.
Intermittent work
Consists of sustained effort for short periods of time followed by periods of rest. Fat plays a minor role, proteins are negligible. Energy supply is anaerobic. Lactic acid results.
Prolonged work
Continuous work typically involves sub-maximal efforts for a several hours. Energy comes from carbohydrates and fats, Lactic acid does not accumulate, Anaerobic glycolysis is not needed during steady state work activities.
Workplace redesign
Correct working posture by adjusting the workstation to the height of the worker - manual crank or power lift
CTD's
Cumulative Trauma Disorders
Arc
Curvilinear distance between points.
secondary prevention to stress
Detecting stress and improving stress management, Relaxation techniques, Stress education Stress management, Health promotion
Work Physiologists
Devise work systems that allow individuals to accomplish their work without developing excessive fatigue, on a day to day basis.
Reach
Dimensions that determine the maximum space allowable for the human who operates equipment in the workspace.
Clearance
Dimensions that determine the minimum space required for a human to perform work activities in the workspace.
Height
Distance along Z-axis, from floor or seat to a specific point on the body.
Depth
Distance between landmarks in the anteriorposterior surface, along X-axis.
Breadth
Distance between points on left and right sides of body.
Length
Distance between two points on a single body segment.
primary prevention to stress
Eliminate the sources of stress, Redesign job/work environment, Flexible work scheduling, Fair work policies, Participative management, Reward sharing
Person Environment fit model (theory)
Emphasizes interaction between the individual and their environment, as well as their perception of the environment. Lack of fit results in stress.
What is the General Duty Clause 5A(1)?
Employers must keep their workplaces free from recognized serious hazards.
Thoracic Outlet syndrome
Entrapment of the brachial plexus/subclavian vessels passing from base of neck through the armpit.
Ergonomics
Europe
Kyphosis
Exaggerated over-curvature of thoracic area of vertebral column
Rotary force equation
F*sin of the angle
There is currently a federal law, which places strict requirements on employers to help eliminate musculoskeletal disorders, called the Ergonomics Standard.
False - the ergonomics standard was rescinded by the Congressional Review Act in 2001
Ergonomics is a fairly new study that began in the early 2000s.
False, Ramazzini studied the health of workers in the 1700s.
What is FICA?
Federal Insurance Contributions Act- tax supporting social security and Medicare; taken out of employee and employer pay
Anatomical concern, gender:
Female grip strength generally ranges from 50-67% of male grip strength
Which of the following is the most important application of Ergonomics?
Fitting the task to the person, not fitting the person to the task.
MA=
Force Arm Resistance Arm
Stress
Force applied to one unit of surface area. 1 Pa = 1 N * m-2
Mechanical Advantage is calculated is the
Force arm / Resistance arm
Friction
Force exerted tangentially by surface of one object on another and resists motion of either surface relative to the other.
impulse =
Force*time
Tissue compression
Forces on palm or fingers results in ischemia, with resulting numbness and tingling of the fingers. Handles should have large contact surfaces. Finger grooves or recesses in tool handles should be avoided
National health expenditures 6.2%/yr increase
GDP 4.2%/yr increase
Body size Variability
Gender Age Race/Ethnicity
Excess junk food...
Gives you a temporary sugar-high, can leave you tired and fatigued
The root origin of the word "Ergonomics" comes from...
Greek, meaning Laws of Work
Heat stress index
HSI = (M +\- C +\- R) / Emax, 2 Factors: Temperature and Humidity
Handle properties
Handle diameter should be 31-50mm, with upper end for torque and lower end for dexterity and speed. Length: minimum of 100mm, with 125mm being ideal. Shape: optimal shape may depend upon task performed. T-handles have more torque than straight screw driver handles.
_________________________ are the fastest growing expense for employers.
Health insurance costs
Economists have found that rising health care costs correlate with significant drops in ____________________________.
Health insurance coverage
The formula for cardiac output is:
Heart rate x Stroke volume
Radiation
Heat gain or heat loss
Metabolism
Heat gain; physical activity of the worker, depends on the job or as paced by the worker
Evaporation
Heat loss
How did the workforce change in the 80s?
Heavy manufacturing ---> light manufacturing service, knowledge-based economy
Seven of the most Common Work Risk Factors for Developing CTDs.
High Rates of Manual Repetition, Excessive Manual Force, Awkward Posture, Insufficient Recovery Time, Sustained Muscle Loading, Vibration, Temperature
Heat stroke
Hot dry skin, with rectal temp, > 104 F
Phalen's test
In this test the patient is asked to put the backs of his/her two hands together and acutely flex his/her wrists for one minute. Development of tingling in the fingers is a positive sign of CTS.
most qualified persons for shift work
Independent workers, More adjustable to changes in working conditions, High self-esteem, Young, Healthy
Arthritis
Inflammation of a joint
Myosotis
Inflammation of muscle
Physical work capacity
Is the maximum capabilities of the physiological systems to produce energy for muscular work.
Effort
Is the product of torque (moment) times time duration in which force is sustained. = M * t = F * dv * t
Work Physiology
Is the study of the functions of the human affected by muscular work stresses.
Types of muscle contraction
Isometric concentric eccentric
Engineering solutions
Job redesign; repetitive tasks performed in awkward postures. Enlarge tasks requiring different movements; Design fast-paced tasks with work cycles longer than 30 seconds; Avoid keeping the same posture
Sit-stand work stations
Job requires frequent reaches more than 41 cm (16") forward or more than 15 cm (6") above the work-surface & Job consists of multiple tasks, some best performed in the sitting position, and others while standing.
Niosh model of job stress
Job stress leads to injury and illness
Commonly effected body parts
Knee, Ankle, Foot, Wrist, Elbow, Back, Shoulder, Hip, Head
Most work related injuries occur in the lumbar spine
L5-S1 most common L4-L5 second most common
Ergonomics
Laws of work (greek)
Shovel lift
Leverage provided by the angle of the shaft from horizontal
Lifting index (LI)
Load weight (L)/ RWL
__________________________ has increased significantly over the past 30 years, while the incidence of low back pain has stayed the same.
Lost time from work
Most work-related injuries occur in the
Lumbar spine, vertebrae L5 to S4
MA = R/F Thus MA = Force Arm/ Resistance arm
MA = Mechanical Advantage R = resistance overcome F = force exterted
Mechanical advantage equation
MA= R/F Where: MA = mechanical advantage R = resistance overcome F = force exerted
high strain jobs associated with highest risk of
MSD's and stress related health issues
Evaluation of Muscular fatigue
Manifested by aches and pains followed by reduced movement and weakening of the muscle(s).
Grip span
Maximum grip achieved at 45-50mm with parallel sides, and 75-80mm with inward angled handles. Maximum grip requirements should be less than 90N.
Which nerve passes through the carpal tunnel and produces the symptoms of carpal tunnel syndrome upon impingement of this nerve?
Median
L5-S1(lower back)
Most common site of work related back injuries
Abduction
Movement away from the midline of the body
Adduction
Movement toward the midline of the body
Principles of tool design
Must perform effectively for intended purpose, be properly proportional to body, dimensions of the operator, Designed to match strength and work capacity of operator, It should not cause undue fatigue, It must provide sensory feedback to the user, capital and maintenance costs should be reasonable
John howard
NIOSH Director
NIOSH
National Institute for Occupational Safety and Health; under US Department of Health and Human Sciences
Footwear
Needs to be suitable for the environment
Raynaud's disease
No symptoms due to other underlying diseases, Laboratory evaluation is normal, normally no strucutural changes in vessels, trophic changes are uncommon
__________________________ are the leading cause of work disability.
Occupational MSDs
OSHA
Occupational Safety and Health Administration; under US Department of Labor
Fall
Occurs when you are too far off your center of balance.
Symptoms associated with CTDs
Pain, Restriction of joint movement, Soft tissue swelling
Heat cramps
Painful spasms of the muscles. Heavy sweat during work
Heart rate recovery
Phase 1 = 1 min phase 2 = 2 mins phase 3 = 3 mins
Administration controls
Planned work time, self-determination, recovery allowances, scheduling work
RWL = LC*HM*VM*DM*AM*FM*CM
RWL = recommended weight limit LC = Load Constant HM = Horizontal VM = Vertical DM = Distance AM = Asymmetric FM = Frequency CM = Coupling Multipliers are not greater than 1.0
Roots of ergonomics
Ramazzini (1700s) vapors and irregular motions
Basal metabolism
Rate of metabolic activity of a subject after 12 hours fasting and 8 hours resting. The basal rate is generally considered the level of energy expenditure required to keep an individual alive and functioning but not performing external work
Energy expenditure
Recommended total energy expenditure of 2000 kcal during work as a maximum that can be expected for work to continue for months or years.
Engineering controls
Reduce metabolic rate, change clothing requirements, reduce temperature and humidity, increase air motion, control radiant heat(insulation)
The weight of the lever, surrounding tissues and counterforce is defined as?
Resistance
Which of the following is a flat bone?
Ribs
Heat Stress Hygiene
Self determination fluids lifestyle and diet health status training
Intervertebral disks
Separate the vertebrae, Are composed of a tough, fibrous ring, Is filled with a viscous fluid (consistency not like jelly, more like crab meat) Act as shock absorbers between vertebrae, Provide flexibility for vertebrae, Most fragile parts of the spine (especially the Lumbar region)
static muscle loading
Situations where arms are elevated or held for extended periods of time, Results in fatigue, reduced work capacity, and soreness. Optimum work posture is when elbow is at 90 degrees.
Amphiarthrosis (joint articulation)
Slightly movable: intervertebral joints
Reach (static measurement)
Special arm-hand distance in particular posture.
Common types of injuries
Sprains, strains, Bruises, contusions, Fractures, Abrasions, lacerations
Work rest scheduling
Standard workload in United Kingdom and USA is equivalent to the workload generated by a man of average physique walking without carrying a load in a straight line on level ground at a speed of 4 mph
Cardiac Output (CO)
Stroke Volume* Heart Rate
Cartilage
Supports body structure and is avascular
Raynaud's phenomenon
Symptoms due to other underlying diseases, Laboratory evaluation is abnormal, structural changes often present, trophic changes are common
Wet Bulb Globe Temperature
Takes into account radiated heat, therm wrapped with wet cloth
Anatomy
That branch of science which deals with the body's structures, including muscles, bones, tendons, ligaments, and other structures.
Cardiac output
The amount of blood (in liters per minute) ejected into the main artery by the left ventricle per unit time
The Carpal bones and the tunnel
The carpal bones form a small u-shaped "tunnel" on the palmer side of the wrist. This tunnel is covered by a transverse carpal ligament. Between the bones and transverse carpal ligament passes all the flexor tendons, blood vessels, major nerves (including the median nerve), and related tissue, that operate the hand.
Torque
The effect of a force producing rotation about an axis. Measured by product of the force and perpendicular distance form the axis of rotation to the line of action of the force.
Class 3: lever system
The force point lies between the join and the resistance
Lever system class 3
The force point lies between the joint (fulcrum) and the resistance
Basal metabolism
The minimal amount of energy needed for sustaining life.
Domino effect
The more people work during the night the more people have to work during the night
Anaerobic threshold
The point at which lactic acid (from anaerobic glycolysis) begins to accumulate in the blood at levels above the basal rate of lactic acid production.
Respiration
The process of exchanging carbon dioxide and oxygen between the body and the environment.
What's OSHA's primary goal?
The reduction of injuries and illnesses in the workplace.
Physiology
The science of the body's functions, including metabolism, muscle mechanics, oxygen and nutrient distribution, temperature regulation, nerve transmission, cognition, and other functional activities.
Anthropometry
The study of the dimensions and physical characteristics of the human body.
rotating shifts
The work schedule requires the employee to work more than one shift, that is, employees switch from one to another according to a certain cyclic pattern of shift rotation.
Tinnel's test
This methods is performed by tapping the median nerve at the wrist. Tapping a compressed median nerve induces tingling in one or more fingers in the hand afflicted with CTS
Causes of trips
Transitioning from one type of flooring to another with less traction, freshly waxed surfaces, highly polished floors
Tertiary prevention to stress
Treatment and recovery from stress related illnesses, Counseling services, Employee assistance programs
Anatomical concern, repetitive finger action:
Trigger forces should be low, under 10N. Two or 3 finger control operations preferred.
Human factors
US and Canada
Factors leading to development of CTDs
Use of excess force during normal motions, Awkward or extreme joint motions, High repetition of same movement, Lack of sufficient rest
Slip
When there is too little friction or traction between your feet (footwear) and the walking or working surface, and you lose your balance.
Fall to lower level
When you fall to a level below the one on which you are walking, working, or standing.
Fall at the same level
When you fall to the surface you are walking or standing on, or fall into or against objects at or above the surface.
Trip
When you step down unexpectedly to a lower surface (Misstep) and lose your balance, e.g., stepping off a curb
Trip
When your foot (or lower leg) hits an object and your upper body continues moving, throwing you off balance.
Physiological demand on workers theory
Workers should not exceed 50% of their energy expenditure capacity during the work day to avoid becoming physiologically strained during the work day. Margin of safety is that workers should not exceed 33% of their expenditure capacity for the work day
STAT basis of Anthropometry
Xp(pth percentile of value of the variable X) = X(sample mean) + Zp(standard normal value corresponding to the pth percentile of value X) *S(sample standard deviation)
Sweating rate
[BWi-BWf+ingestion (kg) ]/ Time (hr)
De Quervain's syndrome
abductor pollicis longus and extensor pollicis brevis tendons
potential energy (PE)
ability of a body to do work because of its position or state
Behaviour's
actions you choose and control (e.g., working safely) - can contribute to a slip, trip, and fall injury if you set yourself up for one.
fluid replacement
adequate hydration
Two processes in which the muscles get energy
aerobic and anaerobic
Job analysis step 2
after the job is broken into tasks determine if work methods, the workstation, tools and equipment required to perform each task may cause a musculoskeletal injury or illness
increase of MSD since 1980
aging work population greater % females heavy to light manufacturing increase of citations by OSHA MSD covered worker comp
axial skeleton
all bones except legs and arms
Maximize muscle efficiency and skillfulness in performing heavy workload
allow as much "range of motion" as possible
administrative controls
allow for shorter shifts additional days off for 3rd shift have workers get home before sunrise always rotate shifts in a clockwise direction provide equal benefits provide training and counseling
Step test
alternative method for estimating VO2max (VO2[L/min] = mL*body weight*1000mL)
Muscle Fatigue
amount of lactic acid plays a part in localized fatigue
Shiftwork
anything outside of regular 9 to 5, usually nights
appendicular skeleton
arms and legs
Heart rate stability
average for a workday should be less than 110 bpm, peak less than 90% mass HR
Effort-Reward imbalance model
balance between what what someone is putting into a job compared to what they are getting out of the job
skeletal system consists of
bones cartilages
Expert assessment
can quickly perform a needs assessment and provide quick and accurate recommendations
increased metabolic rate
can work at lower temperatures
short bones
carpals, tarsals
Peritendinitis
central region of the tendon
circumference
closed curvilinear surface around a body part
secondary prevention
detecting stress and improving management of stress -stress education -stress management -health promotion
non rotary force
directed toward the fulcrum, parallel to the lever, and not contributing to the lever movement
Height
distance along z-axis from floor to specific point on the body
depth
distance between landmarks in the anterior posterior surface
breadth
distance between points on the left and right sides of body
Length
distance between two points on a single body segment
Ideal mechanical advantge
distance moved by force/ distance moved by load force arm/ resistance arm
oral measurement
do not eat or drink 15 min before measurement, have mouth closed
elastic cartilage
ears and nose
Greatest damage occurs to muscles during
eccentric contraction
stress creates larger amounts of cortisol (a stress hormone) that can in turn reduce the body's ability to
effectively fight off sickness and disease
primary prevention
eliminate source of stress -redesign environment -flexibe work schedule -participative management -reward sharing
BMI equation
english = weight/h(in)^2 *703 metric= weight/h(cm)^2
Work stress prevention
ensure workload in workers capabilities and resources design jobs to provide meaning, stimulation and opportunites to use their skill clearly define worker roles and responsibilities
Hand tools
extent of human hands, enhance the capability and productivity of users performing tasks
Type 2b Muscle Fiber
fast glycolytic: fast twitch fatigable
Type 2a Muscle Fiber
fast oxidative - fast twitch fatigue resistant
Type 2b: fast glycolytic
fast twitch, fatigable
Whole muscles contain a mixture of
fiber types
The segment between the point of force exertion and fulcrum is called the
force arm
Ideal mechanical Advantage
force arm/resistance arm
Actual mechanical advantage
force exerted by machine or load/force used to operate machine
job analysis specific tasks
force, posture, frequency, duration or work and recovery period, and vibration and cold temperature.
Actual mechanical advantage
forced exerted by load/ force used to operate machine resistance/effort
Biomechanics used to analyze
forces and torques; strength limitation; to predict stressful work postures and conditions
Internal forces
forces generated by or acting on muscle, ligaments, etc
internal forces
forces generated by or acting on muscles, ligaments, and joints
Kinetics
forces that act on the body that cause movement
kinetics
forces that act on the body that cause movement
things to look for in an ergonomic tool
forces, movements, thermal and vibration exposure
1.5 million families subject to ___________ due to rising healthcare costs
foreclosure
Pushing and pulling forces are the same order of magnitude whether the arms are held out sideways or
forward
Diarthrosis (joint articulation)
freely movable; shoulder joint
zone A
full compensation, steady state, steady heart rate
least qualified for shift work
gastrointestinal problems, respiratory disorders, nervous disorders, Abnormal fatigue after short work exposure, Past the age of 45, especially if they have health problems, Pregnant
external forces
gravitational or from objects lifted, lowered, pushed, or pulled
Injury to muscles
greatest damage during eccentric contraction -strain injuries -repetitive task
Of the total spending for the US, the largest percentage of money is spent on _________________.
healthcare
Heart rate recovery from Brouha Phase 1
heart rate (in bpm) during the second 30 s of the first minute
Heart rate recovery from Brouha Phase 2
heart rate during the second 30 s of the second minute
Heart rate recovery from Brouha Phase 3
heart rate during the third 30 s of the third minute
radiation
heat gain or loss: from objects
Convection
heat gain or loss; by ambient air flow
metabolism
heat gain: physical activity
Evaporation
heat loss: relative humidity and air velocity across the skin
active jobs
high demand and high control
active jobs
high demands and high control
High strain jobs
high demands and low control
iso strain model
high strained and low social support
high strain jobs
highest risk of MSDs high demand and low control
Worst candidates for shift work
history of: gastrointestinal problems; respiratory disorders; nervous disorders, pregnant >45 abnormal fatigue after short exposure
health insurance premiums
increased 119% over the based decade
Best candidate for shift work
independent workers more adjustable to changes in working conditions high self esteem young healthy
Bursitis
inflammation of a bursa, often characterized by difficulty of movement in body joints
Bursa disorders
inflammation of synovial sacs in elbow, shoulder, knee
sweating rate
initial bw- final bw + ingestion (kg)/time (h)
Each tendon is attached to an origin bone and an
insertion bone
person environment fit model
interaction between the individual and their environment as well as their perception of the environment - lack of fitness results in stress and psychological and physical symptoms
Strain index
job demand/ worker capacity
When you are stuck in a job and unable to leave due to the benefits; inability to move throughout the job market
job lock
Radial tunnel syndrome
lateral elbow
Lever system class 1: the joint
lies between the force point (where the muscle pulls on the lever) and the resistance point (the weight to be lifted)
External forces
lifting, lowering, push, pull
passive jobs
low demand and low control
low strain jobs
low demands and high control
passive jobs
low demands and low control
low strain jobs
low demands high control
Grip strength
maximum momentary squeeze force exerted on a hand dynamometer
Body Mass Index (BMI)
measure of body fat based on height and weight
Direct calorimetry
measurement of heat generated by a person in a box chamber
direct calorimety
measurement of heat generated by a person in a box chamber.
Indirect calorimetry
measurement of metabolic rate usually by oxygen consumption rate.
indirect calorimety
measurement of metabolic rate usually by oxygen consumption rate.
Arthritis of joints is due to
mechanical stress
Carpal tunnel syndrome
median nerve
Back injury stats
most frequently injured; account for nearly 20% of all injuries and illness in the workplace
Kinematics
motions of the body w/o considering force
synergist
muscle that contract at the same time as the prime mover (muscle assist)
Myotendinitis
muscle-tendon junction
Synergists
muscles that contract at the same time as the prime mover
Antagonists
muscles that relax or counteract to slow the action of a prime mover
Prime movers
muscles whose contraction is the primary agent in producing desired movement
Antagonist
muslce that relax or counteract to slow the action of a prime mover
Muscle disorders
myalgia, trigger points
Body temperature measurements
oral and ear
Bones and cartilage
osteoarthritis
Wet bulb globe temperature (WBGT)
outdoor = 0.7 NWB + 0.2GT +0.1DB Indoor = 0.7 NWB + 0.3GT
Effects of slips, trips and falls to the worker
pain, lost wages, temporary or permanent disability, reduced quality of life, depression
Rotary component
perpendicular to the lever and contributing to the lever's movement
Rotary Force
perpendicular to the lever and contributing to the levers movement
heat stress administrative controls
planned work time self determination recovery allowances scheduling work
_______________ is defined as the muscle that has the most influence in one direction on the joint it acts on. For example the _____________ in flexion of the forearm is the bicep.
prime movers
Classification of skeletal muscles
prime movers antagonists synergists
pushing force > than
pulling force
lever system
pulling on the involved insertion bone acts as a lever and the join as a fulcrum of the lever
Muscle spindles
receptors sensitive to change in length of the muscle and the rate of that change
heat stress engineering controls
reduce metabolic rate change clothes req reduce temp and humidity increase air motion control radiant heat
The segment between the resistance and fulcrum is called the
resistance arm
fibrous cartilage
ribcage and intervertebral disks
Flat bones
ribs, skull
Waist Circumf
risk increase when: >40 inches men >35 inches women
physiology
science of body's functions including metabolism
anatomy
science which deals with the body's structures
thomas e perez
secretary of labor
In all the other areas of ergonomics we have been taught to make engineering, work practice, or administrative changes, not to discriminate against workers - except
shift-work
Heat exhaustion
skins feels clammy and moist, complexion is pale and muddy. Symptoms; fatigue, nausea, headache, giddiness
what can be done for those that must work 3rd shift
sleep having a life away from work immune system healthy digestive system diet and exercise healthy heart playing it safe
lifestyle and food consumption
sleep, alcohol and diet
Ergonomic factors in flooring selection
slip resistant, trip potentials, standing fatigue, shoe/floor interactions, noise reduction
Type 1 Muscle fiber
slow twitch oxidative (maintain posture; long duration; low intensity)
reach
special arm hand distance in particular posture
Rigid bodies
static and dynamic analyses
Tension neck syndrome
static trapezius contraction in precision work
self determination
stop when uncomfortable
Anthropometry
study of the dimension and physical characteristics of the human body.
Cartilage
supports body structure Avascular
Neglecting circadian hygiene
susceptible to colds and flu chronic fatigue negative effects on the female reproductive system greater tendency of obesity heart disease accidents stomach problems depression sleep problems
health effects of stess
symptoms: headache; sleep disturbance; upset stomach diseases states: cardio musculo psycholo increased injury
Insertional tendinitis
tendon-bone interface, eg. Lateral epicondylitis
Muscles are attached to the bones by
tendons
Isometric contraction
tension generated during muscle activity, but no change in length
Isometric
tension generated during muscle activity; no change in length
Concentric
tension generated in muscle while shortening
Concentric contraction
tension generated in muscle while shortening
Eccentric
tension generated while muscle is lengthening
Eccentric contraction
tension generated while muscle is lengthening
potential energy
the ability of a body to do work because of its position or state. ( = m * g = W * h) where m=mass, h = vertical distance, g = acceleration due to gravity, W = weight lifted .
Kinetic energy
the ability of a body to do work because of its motion. ( = 1/2m * v^2) where m = mass, v = velocity
Metabolism
the collective chemical process of the conversion of foodstuffs and oxygen into mechanical work and heat.
Cardiac index
the correlation between resting cardiac output and body surface area.
Aerobic capacity
the maximum level of oxygen uptake (VO2max) in liters per minute or milliliters of oxygen per kilogram body weight per minute.
grip strength
the maximum momentary squeeze force exerted on a hand dynamometer
Calorimetry
the process of measuring heat generated by an energy source
job demand control theory
the psychological job demands and characteristics of the job related to decision making and skill usage.
Lever system class 2
the resistance is between the joint (fulcrum) and the force (insertion) point
over 17% of all disabling work injuries are...
the result of falls
velocity
the time rate of change in displacement (Km*h^-1)
acceleration
the time rate of change in velocity (m*s^2)
resistance
the weight of the lever and its surrounding counter force (antagonist muscle) and the external load
A work space is a-
three dimensional region surrounding the worker
When the spine is in a natural position, it forms
three natural curvatures in a double-S shape
Anatomical concern, posture:
torque exertion not significantly affected unless extreme postures.
Tertiary prevention
treatment and recovery from stress related illness -counseling services -employee assistance programs
Cubital tunnel syndrome
ulnar nerve at elbow
Guyon's canal syndrome
ulnar nerve at wrist
zone C
uncompensated heat storage, Steady rate fatigue and failure, high increase in core temperature
Minimize pinch grips
use whole hand; Hold an object near to the center of gravity for better balance; Provide flanged support on handles; Avoid excessive forces; Minimize exposure to vibration and cold temperatures; Automate repetitive tasks when technologically and economically feasible.
Type 1: slow twitch oxidative
used to maintain posture long duration low intensity tasks often found at work.
physiological data
useful if jobs involve repetitive lifting, load carrying and general use of large muscle groups. data: maximum aerobic capacity declines with age
Strength data
various populations and muscle groups have been published and can be found in several sources
Hand/arm vibration syndrome
vasoconstriction in the hands and fingers "white finger" syndrome
irregular bones
vertebrea
Calculate BMI for an individual of 68 kg body weight and 165 cm.
weight (kg) / [height (m)]2 =24.98
efficiency equat
work output/ work input
Xp=x +Zp*s
x = sample mean s = sample std dev Xp = pth %tile value of the variable X Zp = standard normal value corresponding to the pth %tile value of X
Statistical Basis of Anthropometry
xp = x + zp* s where: x = sample mean s = Sample standard deviation Xp = pth percentile value of the variable X Zp = standard normal value corresponding to the pth percentile value of X
