CHST Ergonomics and Musculoskeletal Disorder (MSD) Prevention — Questions and Answers
Question 1: Which ergonomic risk factor most directly contributes to rotator cuff injuries among construction workers performing overhead tasks?
- Contact stress on the palms
- Sustained or repeated shoulder elevation above 60 degrees (Correct answer)
- High-frequency hand-arm vibration
- Whole-body vibration from equipment
Correct answer: Sustained or repeated shoulder elevation above 60 degrees
Sustained or repeated work with the shoulder elevated above 60° increases mechanical loading on the rotator cuff tendons and reduces blood flow, leading to tendinopathy and tears. This is a well-documented awkward-posture risk factor specific to overhead construction tasks.
Question 2: The NIOSH Lifting Equation Recommended Weight Limit (RWL) accounts for which combination of lifting variables?
- Load weight, worker height, and shift length only
- Horizontal distance, vertical height, travel distance, asymmetry, frequency, and coupling (Correct answer)
- Body weight of the lifter, load center of gravity, and temperature
- Grip strength, shoe traction, and floor coefficient of friction
Correct answer: Horizontal distance, vertical height, travel distance, asymmetry, frequency, and coupling
The NIOSH Lifting Equation multipliers include: horizontal distance (H), vertical height (V), vertical travel distance (D), trunk asymmetry angle (A), lifting frequency (F), and hand-to-object coupling (C). These six task variables determine how much the maximum 23 kg ideal load must be reduced.
Question 3: A safety technician observes masons repeatedly bending at the waist to pick up bricks from ground-level pallets. The most effective ergonomic intervention is:
- Issuing the workers lumbar support belts
- Training workers on proper lifting technique
- Raising the pallet to knuckle height using a pallet jack or adjustable scaffold (Correct answer)
- Limiting each worker to lifting no more than 50 lbs per lift
Correct answer: Raising the pallet to knuckle height using a pallet jack or adjustable scaffold
Engineering controls — here, repositioning the work at knuckle height — eliminate the awkward posture at the source. Back belts (PPE) and training (administrative) are lower-order controls that do not change the physical demands of the task. Weight limits without posture correction still allow repetitive bending.
Question 4: Hand-arm vibration syndrome (HAVS) is most associated with prolonged use of which type of construction tool?
- Powder-actuated nail guns
- Chipping hammers and grinders (Correct answer)
- Hydraulic man-lifts
- Electric conduit benders
Correct answer: Chipping hammers and grinders
HAVS (also called vibration white finger) results from chronic exposure to hand-transmitted vibration typically above 2.5 m/s² A(8). Chipping hammers, grinders, jackhammers, and similar vibratory hand tools are the primary sources in construction. Powder-actuated tools fire too briefly; lifts and benders transmit minimal hand-arm vibration.
Question 5: Which administrative control is most effective for reducing cumulative trauma disorders among workers performing repetitive tasks?
- Requiring anti-vibration gloves at all times
- Implementing job rotation so no single muscle group is overloaded continuously (Correct answer)
- Posting MSD hazard warning signs near workstations
- Scheduling quarterly ergonomic assessments
Correct answer: Implementing job rotation so no single muscle group is overloaded continuously
Job rotation distributes repetitive loading across different muscle groups, allowing recovery time and reducing cumulative exposure for any single tissue. Anti-vibration gloves (PPE) have limited effectiveness and don't reduce posture or force demands. Signs and periodic assessments are informational — they don't reduce the physical stress directly.
Question 6: When conducting a Site-level MSD risk assessment, the SAFETY technician should prioritize which data source first?
- Workers' compensation claim costs by department
- OSHA 300 log entries for musculoskeletal injuries and disorders
- Worker symptom surveys and near-miss reports from the affected crews (Correct answer)
- Published industry MSD incidence rates for comparable construction trades
Correct answer: Worker symptom surveys and near-miss reports from the affected crews
Worker symptom surveys and near-miss reports capture early-stage discomfort before it becomes a recordable injury, enabling proactive intervention. OSHA 300 logs and WC data are lagging indicators — they record harm already done. Industry benchmarks reflect average conditions, not site-specific exposures.
CHST Ergonomics and Musculoskeletal Disorder (MSD) Prevention
Which ergonomic risk factor most directly contributes to rotator cuff injuries among construction workers performing overhead tasks?