Day 1 Ergonomics
What is the guiding principle of ergonomics?
maintain D<C (demand<capacity)
Why are lifting activities bad?
Lifting activities can place large metabolic demands on workers, leading to fatigue. Fatigue is bad because it is a decrease in strength and an increased likelihood of injury.
List the potential uses of Epidemiology (M)
- record keeping of injuries
- job screening (identify at risk workers or high risk jobs)
- ergonomics process
When drawing a free body diagram the muscle should be included as a moment and a force? (True or False)
FALSE: When drawing a free body diagram the muscle should be included as EITHER a moment or a force, not both
Why evaluate task demands?
(1) to compare task demands with worker capacity (D<C)
(2) contribute to general understanding of risk factors that affect task demands
Why do we care about ergonomics?
(1) costs
(2) acute or chronic musculoskeletal disorders
What do psychophysical methods assume?
assume that people have the ability to be self-limiting or self-protecting in terms of the risk of musculoskeletal injury
Describe the difference between RULA vs REBA
RULA - assess postures of neck, trunk, and upper limbs; best for seated tasks
REBA - whole body
Always report the moment as a what?
A positive number with direction
What are the disadvantages of checklists?
- may require some level of training or knowledge
- some have not been formally evaluated or validated
What are the three general areas of ergonomics?
(1) physical
(2) cognitive
(3) organizational
What are the four main task demands?
(1) Muscle Strength Demands
(2) Tissue Strength Demands
(3) Metabolic Demands
(4) Cognitive Demands
List the top 4 most important checklists for Ergonomics?
(1) OSHA's ergonomic assessment checklist
(2) RULA (rapid upper limb assessment)
(3) REBA (rapid entire body assessment)
(4) Job strain index
Statics Question 1
Statics Question 1
What does RULA analyze?
analyzes posture at a moment in the work cycle; postures selected for evaluation may be:
- held for the longest period of time
- where the highest force occurs
- most awk/ext
What are the 4 types of PHYSICAL ergonomics problems?
(1) anthropometric
(2) musculoskeletal
(3) metabolic
(4) environmental
What are Snook Tables and what are Liberty Mutual Tables?
Snook Tables: existing psychophysical data; can be used to estimate MAWL for lifting, lowering, pushing, pulling, and carrying
Liberty Mutual Tables: existing psychophysical data; can be used to estimate the population percentage that an complete tasks of lifting, lowering, pushing, pulling, and carrying
List the pitfalls and precautions with these ratios and some examples for each?
(1) bias
- healthy worker survivor effect
- confounding variables
- hawthorne effect
(2) chance
- sampling variability
Statics problem 2
Statics problem 2
What are the inputs included in the NIOSH equation (by year)?
1981: horizontal position, vertical position, vertical distance moved, frequency
1991: asymmetry and coupling
What is ergonomics (word-for-word)?
the process of designing or evaluating products, tasks, environments, and systems to improve performance and reduce risk of injury
List 6 assumptions and limitations of the NIOSH equation?
(1) assumes lifting task is two-handed and in sagittal plane
(2) biomechanical criterion assumes only low back loads are of importance and not loads at other joints
(3) assumes moderate environmental work condition
(4) assumes lifting and lowering have the same level of risk
(5) assumes sufficient coefficient of friction between the shoes and the work surface
(6) does not account for individual differences or psychosocial risk factors
What are the four questions to ask when selecting a job analysis tool or checklist?
(1) what are the most likely risk factors involved?
(2) what body parts are involved?
(3) what can we measure or reasonably estimate in this task?
(4) what do you need from job analysis?
statics problem 3
statics problem 3
List and describe the three injury risk criteria that the NIOSH equation predicts the recommended weight limit for lifting based on?
(1) biomechanical criterion: joint loading
(2) physiological criterion: energy/calories required during repetitive lifting
(3) psychophysical criterion: max acceptable weigh limit