CEA Manual Material Handling 3 — Questions and Answers
Question 1: What is the primary purpose of the asymmetry multiplier (AM) in the NIOSH lifting equation?
- To account for the weight distribution of irregularly shaped loads
- To reduce the RWL when lifts involve trunk rotation from the sagittal plane (Correct answer)
- To estimate cumulative spinal compression over a shift
- To adjust for worker height differences
Correct answer: To reduce the RWL when lifts involve trunk rotation from the sagittal plane
The asymmetry multiplier penalizes lifts that require trunk twisting, which adds torsional and shear stress to lumbar structures.
Question 2: Which handle coupling type yields the highest coupling multiplier (CM = 1.0) in the NIOSH equation?
- Poor coupling — no handles, irregular shape
- Fair coupling — fingers flexed 90 degrees
- Good coupling — optimal handles within the power grasp zone (Correct answer)
- No coupling — load rests on forearms
Correct answer: Good coupling — optimal handles within the power grasp zone
Good coupling (CM = 1.0) means handles allow a full power grasp without requiring deviated or awkward wrist positions.
Question 3: A worker carries a 30 lb tote 150 feet to a workstation 20 times per shift. Which engineering control would MOST effectively reduce cumulative lumbar load?
- Provide anti-fatigue matting along the route
- Replace the carry task with a wheeled cart or conveyor (Correct answer)
- Issue a back support belt
- Train the worker in neutral spine posture
Correct answer: Replace the carry task with a wheeled cart or conveyor
Eliminating the carrying task by substituting mechanical transport (cart or conveyor) removes cumulative lumbar loading entirely.
Question 4: Snook psychophysical tables are used primarily to determine which of the following?
- Acceptable force limits for lifting, lowering, pushing, pulling, and carrying based on worker self-selection (Correct answer)
- Spinal compression values during dynamic lifting
- OSHA-mandated weight limits for warehouse tasks
- Biomechanical joint torques during material handling
Correct answer: Acceptable force limits for lifting, lowering, pushing, pulling, and carrying based on worker self-selection
Snook tables present maximum acceptable weights and forces based on psychophysical studies where workers self-selected loads they could sustain without excessive strain.
Question 5: A load's center of gravity is shifted unexpectedly during a lift. Which immediate injury mechanism is most likely?
- Repetitive strain of the finger flexors
- Sudden asymmetric spinal loading causing disc herniation (Correct answer)
- Contact stress on the forearms from a sharp edge
- Thermal injury from a hot surface
Correct answer: Sudden asymmetric spinal loading causing disc herniation
Unexpected load shifts create sudden uncontrolled torques on the lumbar spine, substantially increasing the risk of acute disc herniation.
Question 6: When a worker must lower a heavy box from an overhead shelf, the NIOSH equation destination multipliers apply to the:
- Origin of the lift only
- Destination of the lift only
- Both origin and destination, with the lower RWL governing the task (Correct answer)
- The midpoint of the vertical travel path
Correct answer: Both origin and destination, with the lower RWL governing the task
The NIOSH equation is applied at both the origin and destination; the more restrictive (lower) RWL controls task design.
Question 7: Which measure best quantifies spinal compressive force during a manual lift for biomechanical analysis?
- L4/L5 compression force in Newtons (Correct answer)
- Grip strength in kilograms
- Metabolic energy expenditure in kcal/min
- Heart rate reserve percentage
Correct answer: L4/L5 compression force in Newtons
L4/L5 compression force (N) is the standard biomechanical criterion used to quantify spinal loading risk during lifting tasks.
CEA Manual Material Handling 3
What is the primary purpose of the asymmetry multiplier (AM) in the NIOSH lifting equation?