CIH Ergonomics and Biomechanics 3 — Questions and Answers
Question 1: Which segment of the spine bears the greatest compressive load during forward bending with a load in the hands?
- Cervical C5-C6
- Thoracic T6-T7
- Lumbar L4-L5 (Correct answer)
- Sacral S1-S2
Correct answer: Lumbar L4-L5
The L4-L5 disc is subjected to the highest compressive forces during lumbar flexion with external loads.
Question 2: The RULA (Rapid Upper Limb Assessment) tool was primarily designed to evaluate risk in which type of work?
- Whole-body exertion tasks involving leg strength
- Sedentary tasks with sustained upper limb postures (Correct answer)
- Manual material handling requiring team lifts
- Tasks involving full-body dynamic movement
Correct answer: Sedentary tasks with sustained upper limb postures
RULA assesses upper limb posture, force, and repetition in sedentary tasks such as office and assembly work.
Question 3: What is the primary biomechanical disadvantage of a wide grip span (>2 inches) when using a power hand tool?
- Increases trigger finger force required
- Reduces tool torque output
- Increases grip strength requirement by raising internal joint forces (Correct answer)
- Shifts load to proximal muscle groups only
Correct answer: Increases grip strength requirement by raising internal joint forces
A grip span exceeding the optimal 1.75–2 inches requires greater muscle force, increasing tendon and joint loading.
Question 4: During a job demands analysis, a task requires exerting 15 lbs of push force with both hands. This best represents which ergonomic risk factor?
- Sustained posture
- Contact stress
- Forceful exertion (Correct answer)
- Vibration exposure
Correct answer: Forceful exertion
Applying 15 lbs of push force constitutes forceful exertion, a primary ergonomic risk factor for upper extremity MSDs.
Question 5: Which workplace intervention is considered the most effective (highest hierarchy) for reducing MSD risk?
- Job rotation among workers
- Personal protective equipment such as wrist splints
- Administrative controls and rest breaks
- Engineering controls that eliminate the hazardous task (Correct answer)
Correct answer: Engineering controls that eliminate the hazardous task
Engineering controls rank highest in the hierarchy of controls, addressing hazards at the source rather than managing exposure.
Question 6: A forklift operator reports low back pain after long shifts. Which vibration frequency range is most harmful to the lumbar spine?
- 0.5–2 Hz
- 4–8 Hz (Correct answer)
- 20–50 Hz
- 100–200 Hz
Correct answer: 4–8 Hz
The lumbar spine resonates at approximately 4–8 Hz, making this frequency range most damaging during whole-body vibration.
Question 7: The term 'static load' in occupational biomechanics refers to:
- Dynamic forces exceeding maximal voluntary contraction
- Sustained muscle contraction without movement over time (Correct answer)
- Intermittent high-force exertions during lifting
- Sudden impact forces applied to the skeletal system
Correct answer: Sustained muscle contraction without movement over time
Static loading occurs when muscles maintain continuous contraction to hold a posture, reducing blood flow and accelerating fatigue.
CIH Ergonomics and Biomechanics 3
Which segment of the spine bears the greatest compressive load during forward bending with a load in the hands?