CIH Ergonomics and Biomechanics 4 — Questions and Answers
Question 1: A warehouse worker lifts boxes from floor level 60 times per hour for an 8-hour shift. According to NIOSH guidelines, the frequency multiplier (FM) would be:
- Relatively high, minimally reducing the RWL
- Substantially reduced, significantly lowering allowable load weight (Correct answer)
- Equal to 1.0 with no effect on the RWL
- Not applicable since frequency above 15 lifts/min is not addressed
Correct answer: Substantially reduced, significantly lowering allowable load weight
High lift frequency (1 lift/minute for 8 hours) results in a low FM, substantially reducing the RWL below the 51-lb load constant.
Question 2: Which measure of work pace is most directly associated with increased carpal tunnel syndrome risk in assembly workers?
- Metabolic equivalent (MET) level above 5
- Wrist repetition rate exceeding 30 cycles per minute (Correct answer)
- Shoulder abduction beyond 60 degrees
- Trunk flexion angle greater than 20 degrees
Correct answer: Wrist repetition rate exceeding 30 cycles per minute
High wrist repetition rates compress the median nerve through repeated tendon movements within the carpal tunnel.
Question 3: Ergonomic design using the 5th percentile female for minimum reach distance ensures that:
- Taller workers will find the workstation too cramped
- The smallest users can reach all required controls (Correct answer)
- The average worker requires accommodations
- Maximum clearance is provided for all users
Correct answer: The smallest users can reach all required controls
Designing reach envelopes for the 5th percentile female ensures that the smallest users can access controls without overreaching.
Question 4: Contact stress on the wrist from a hard tool handle edge is classified as which type of ergonomic risk factor?
- Forceful exertion
- Awkward posture
- Localized mechanical stress (Correct answer)
- Whole-body vibration
Correct answer: Localized mechanical stress
Localized mechanical stress (contact stress) occurs when a hard surface compresses soft tissue, impairing blood flow and nerve conduction.
Question 5: The Borg CR10 scale is used in ergonomics primarily to quantify:
- Maximum acceptable weight of lift
- Perceived exertion or discomfort rating from workers (Correct answer)
- Vibration exposure in hand-arm assessments
- Postural deviation angle from neutral
Correct answer: Perceived exertion or discomfort rating from workers
The Borg CR10 scale measures subjective perception of physical effort or discomfort, ranging from 0 (nothing at all) to 10 (extremely strong).
Question 6: A task analysis reveals that an assembly worker reaches 28 inches horizontally from the body to pick up a part. This primarily increases risk by:
- Reducing the NIOSH horizontal multiplier, lowering the safe lift limit (Correct answer)
- Increasing muscle velocity requirements
- Decreasing trunk rotation angle
- Elevating the coupling multiplier value
Correct answer: Reducing the NIOSH horizontal multiplier, lowering the safe lift limit
Greater horizontal distance reduces the NIOSH horizontal multiplier (HM), decreasing the Recommended Weight Limit.
Question 7: Which ergonomic tool specifically assesses both upper and lower body posture and is commonly used in manufacturing?
- RULA
- OWAS (Ovako Working Posture Analysis System) (Correct answer)
- HAL (Hand Activity Level)
- ANSI Z365
Correct answer: OWAS (Ovako Working Posture Analysis System)
OWAS was developed in the Finnish steel industry to assess whole-body working postures across back, arms, and legs.
CIH Ergonomics and Biomechanics 4
A warehouse worker lifts boxes from floor level 60 times per hour for an 8-hour shift.
According to NIOSH guidelines, the frequency multiplier (FM) would be: