Test 2(biomechanics, material handling, epidemiology) Flashcards
What are 3 types of task demands?
1,) physical
- ) metabolic
- ) cognitive
What are physical demands
muscle strength demands (joint moments required to perform a task), tissue strength demand (aka joint or tissue forces required to perform a given task)
What are some biomechanical analyses
2-D/3-D, single or mult-segment, or static/dynamic
What are we using biomechanical analysis for?
- Calculate muscle strength demands and tissue strength demands for a given task to compare with worker capacity (D vs C)
- Predict these demands over different variations of a task to find the one with the lowest demands
What is NMM
net muscle moment
What can “load” refer to?
moment or force
What kind of supports do we assume joints to be?
Pin, therefore they have x and y reactions
What are the two options to compare capacity of the worker?
- ) compare NMM with an individual’s measured strength.
2. )compare NMM with population statistics (obtains percentiles)
NOT A QUESTION JUST A FACT:
In these problems for the free-body diagram, you will either draw a moment or muscle force. NEVER BOTH
Muscle strength demand = draw a _______
moment
Muscle force in a single muscle = draw a ____
force
General Duty Clause
Section 5a of the OSHA of 1970, states that employers are required to provide their employees with a place of employment that is free from recognized hazards that are causing or are likely to cause death or serious physical harm.
WISHA Lifting calculator
Developed by Washington State Dept of Labor and Industries. Simplified NIOSH LE, applies to manual lifting and lowering, used as a screening tool to identify lifting tasks that should be further analyzed using NIOSHLE
MMH stands for
manual material handling
MMH examples
lifting, pulling, carrying, pushing, holding, throwing
psychophysical METHODS in MH
use existing dat of maximum acceptable weight limit, measure MAWL directly, assess physical stress or discomfort
What are psychophysical methods?
formalized way of subjectively determining maximum acceptable loads for a prolonged MMH task. It assumes people have the ability to be “self-limiting” in terms of the risk of injury.
What are Snook Tables
used to estimate MAWL for lifting, lowering, pushing, pulling and carrying
What are liberty mutual tables?
used to estimate the population percentage that can complete tasks of lifting, lowering, pushing, pulling, and carrying.
What are ways to measure MAWL directly?
procedures and instructions
What scale is used to measure RPE?
The Borg Scales
What is the NIOSH LE?
provide a quantitative method for determining the amount of weight that can be lifted for specific conditions.
What does NIOSHLE predict?
Recommended weight limit for lifting when either a biomechanical, physiological, or psychophysical criterion would be exceeded.
Lifting Equation
RWL = LCHMVMDMAMFMCM
Where the appreviations are
Load constant, horizontal, vertical, distance, asymmetric, frequency and coupling
What is the criterion level for compressive force at L5/S1?
3400N
Advantages of NIOSHLE
Easy to apply and widely used guideline, requires no special equipment
Disadvantages of NIOSHLE (also called assumptions and limitations)
Several assumptions and limitations, doesn’t include MMH activities other than lifting, assumes lifting task ideal, biomechanical criterion focuses only on low back loads, assumes moderate work conditions, assumes that lifting and lowering have the same level of risk, shoes don’t slip, doesn’t account for individual differences, typically underestimates risk
examples of engineering controls for MMH
abdominal belt
Ex. of elimination for MMH
Using a machine to lift or forklift
Ex. of substitution for MMH
Using tools like a conveyor to grab at waist level and carry shorter differences, dollies, etc.
Examples of administrative controls for MMH
Scheduling, training. worker selection
What are two techniques for picking up and object, and which is better?
Stoop and squat. Neither has been proven to be better
What size affect do task-related and individual risk factors have on risk
Task-related: large
individual: moderate
How do engineering controls address affects of risk factors?
Lowering task demands
How do administrative controls address affects of risk factors?
Using worker selection to ensure workers have high capacity.
epidemiology definition
study of the frequency, distribution, risk factors, and possible control of health problems
Epidemiology uses
record keeping, job screening, steps 1,2 and 4 of ergo process
incidence definition
number of individuals who develop an injury or disease during a period of time within a population at risk
Prevalence definition
number of individuals who have an injury or disease during a period of time or at a point in time.
Risk ratios: (what does >< or =1 mean?)
increased risk >1, did not affect risk = 1, reduced the risk <1
Borg Scale 6-20 represents:
RPE, whole body and it is GLOBAL
Borg Scale 0-10 represents:
RPE, large-muscle-group and it is LOCAL
What is the site of greatest stress during lifting, and what force at this joint is considered critical?
L5/S1, and compressive force
What is the physiological/metabolic criterion for NIOSHLE?
fixed percentage of maximum aerobic capacity
What is the psychophysical criterion for NIOSHLE?
fixed percentage of maximum acceptable weight of lift
How do we interpret NIOSHLE?
Using Lift index. <1 ok, =1 borderline, 1 to 3 may have increased risk, >3 likely to have increased risk
How is NIOSHLE enforced?
OSHA can levy penalties against employers that violate General Duty Clause.
General Duty Clause
Requires that employers provide their employees a place of employment that is free from recognized hazards that are causing or are likely to cause death or serious physical harm.
Advantages of using abdominal belts
reduces low back pain, increases intra-abdominal pressure, reduces spinal shrinkage, reduces perceived exertion, reduces back muscle activation level, may restrict unnecessary flexion or twisting, and may remind to lift cautiously.
How to design MMH tasks to be safe
- ) Leverage the job analysis tools (provide guidance)
- ) knowledge of task-related risk factors
- ) follow hierarchy of hazard controls
- ) general guidelines
Relative Risk definiton
a ratio of two probabilities, risk in exposed group divided by risk in unexposed group.
RR equation
(yes-yes/(yes-yes+yes-no)/(no-yes/(no-yes+no-no)) or risk of pain in exposed group/risk of pain in non-exposed group
Odd-Ratio
Ratio of two odds, the odds of an event is the number of event/number of non-events
Pitfall and Precautions of RR/OR
Healthy worker survivor effect, sampling variability and confounding variables
Advantages to checklists
easy to administer and inexpensive
- ) potentially demonstrate causal relationship b/w exposure and injury
- )designed to be used in the workplace/minimal interference
- )many to choose from
Disadv to checklists
- ) some require training or expert knowledge
- ) fuzzy lines between classifying high/low risk tasks
- ) can have subjective measures that depend on rater
- ) many have not been formally evaluated or validated
OSHA’s ergonomics assessment checklist evaluates:
high repetition, high force exertions, awkward/extreme postures, contact mechanical stress, vibration
Body areas addressed in RULA
wrist, forearms, elbows, shoulders, neck and trunk
Which postures are evaluated in RULA
held for the longest period of time, where the highest force occurs, most difficult posture or tasks based on worker interview, only one limb assessed at a time.
Postures selected for REBA evaluation may be
held for longest period of time, where the highest force occurs, most difficult/extreme/awkward posture
SI evaluates which body parts?
hand, wrist, forearm or elbow
What tool for: Varied task
biomechanical analysis or OSHA ergonomic assessment checklist
What tool for: entire body posture
REBA
What tool for: lifting, lowering, pushing, pulling carrying
Snook tables, liberty mutual tables, psychophysical measurments
What tool for: lifting or lowering
NIOSHLE or WISHA
What tool for upper body posture:
RULA
