CIEE Ergonomic Principles & Evaluation Techniques 3 — Questions and Answers
Question 1: Which evaluation method uses time-lapse or video-based observation to code worker postures at predetermined intervals for exposure assessment?
- RULA
- OWAS (Ovako Working Posture Analysis System) (Correct answer)
- Borg CR10 Scale
- Snook Tables
Correct answer: OWAS (Ovako Working Posture Analysis System)
OWAS was developed for steel industry use and codes trunk, arm, and leg postures from video observations to quantify awkward posture exposure.
Question 2: In the context of ergonomic risk assessment, 'force coupling' refers to:
- The combination of high force and high repetition as compounding risk factors (Correct answer)
- The use of two workers to share a single high-force task
- The mechanical advantage gained when two muscles act on the same joint
- A technique for measuring grip force using a dynamometer
Correct answer: The combination of high force and high repetition as compounding risk factors
Force coupling (or the interaction of force and repetition) compounds musculoskeletal injury risk beyond what either factor alone would cause.
Question 3: An ergonomic evaluator is assessing a packaging line where workers perform 12,000 hand motions per shift. Which metric would best quantify the repetitiveness risk for this task?
- Metabolic equivalent of task (MET)
- Strain Index score based on frequency of exertions per minute (Correct answer)
- REBA action level
- Noise dose percentage
Correct answer: Strain Index score based on frequency of exertions per minute
The Strain Index uses frequency of exertions per minute as a primary input to quantify the repetitiveness component of upper extremity risk.
Question 4: According to the NIOSH Work Practices Guide, which factor does NOT reduce the Recommended Weight Limit (RWL) when present?
- Horizontal distance greater than 25 cm from the body
- Vertical origin height at knuckle level (75 cm) (Correct answer)
- Asymmetric twisting during the lift
- High frequency of lifting (more than 15 lifts/hour)
Correct answer: Vertical origin height at knuckle level (75 cm)
A vertical origin of 75 cm (knuckle height) is the optimal lift origin and yields a vertical multiplier of 1.0, meaning it does not reduce the RWL.
Question 5: A worker reports hand-arm vibration exposure from operating a pneumatic grinder for 4 hours daily. The most appropriate first step in managing this hazard is to:
- Provide anti-vibration gloves as PPE
- Quantify vibration exposure by measuring tool vibration magnitude and daily exposure A(8) (Correct answer)
- Limit tool use to 30-minute intervals
- Request a medical examination for the worker
Correct answer: Quantify vibration exposure by measuring tool vibration magnitude and daily exposure A(8)
Quantifying vibration magnitude and daily exposure A(8) is the necessary first step to assess whether exposure exceeds action or limit values and to prioritize controls.
Question 6: In ergonomic workstation design, the recommended elbow height for precision work performed while seated is:
- 5–10 cm below elbow height
- At elbow height or slightly above (Correct answer)
- 15–20 cm above elbow height
- At mid-thigh height to reduce shoulder load
Correct answer: At elbow height or slightly above
Precision work surfaces should be at or slightly above elbow height to allow visual proximity to the work without excessive neck or trunk flexion.
Question 7: Which of the following describes the 'zone of convenient reach' for a standing worker at a workbench?
- The full arm's length in any direction from the body
- The area swept by the forearm pivoting at the elbow without trunk movement (Correct answer)
- The reach zone defined by lateral shoulder width only
- Any area accessible without lifting the shoulder above 45 degrees
Correct answer: The area swept by the forearm pivoting at the elbow without trunk movement
The zone of convenient reach is the arc swept by the forearm when the elbow remains bent and close to the body, minimizing shoulder loading.
CIEE Ergonomic Principles & Evaluation Techniques 3
Which evaluation method uses time-lapse or video-based observation to code worker postures at predetermined intervals for exposure assessment?