CIEE Repetitive Motion & CTD Prevention 3 — Questions and Answers
Question 1: A keyboard operator reports tingling in the thumb, index, and middle fingers that worsens at night. The MOST likely CTD diagnosis is:
- Ulnar nerve entrapment at the elbow
- Carpal tunnel syndrome (Correct answer)
- Thoracic outlet syndrome
- Lateral epicondylitis
Correct answer: Carpal tunnel syndrome
Nocturnal tingling in the median nerve distribution (thumb, index, middle finger) is a hallmark presentation of carpal tunnel syndrome.
Question 2: Job rotation is used as an administrative control for CTDs. For rotation to be effective, the alternate job must primarily differ in which characteristic?
- Shift timing and break schedule
- The specific muscle groups and joints loaded (Correct answer)
- Pay grade and productivity standard
- Ambient temperature of the workstation
Correct answer: The specific muscle groups and joints loaded
Effective job rotation requires that the alternate task loads different muscle groups and joints, preventing cumulative exposure on the same tissues.
Question 3: Which tool feature BEST reduces ulnar deviation during a repetitive assembly task?
- Increased handle diameter
- Angled or bent handle that keeps the wrist in neutral (Correct answer)
- Heavier tool weight to dampen vibration
- Textured grip tape to increase friction
Correct answer: Angled or bent handle that keeps the wrist in neutral
An angled handle (pistol-grip or bent) allows the wrist to remain straight/neutral while the tool axis aligns with the work, eliminating chronic ulnar deviation.
Question 4: In the context of CTD prevention, the term 'recovery time ratio' refers to the proportion of:
- Total shift time spent in medical treatment
- Work-rest cycle dedicated to low-load or no-load recovery relative to exertion time (Correct answer)
- Overtime hours relative to base schedule
- Time between CTD diagnosis and return to full duty
Correct answer: Work-rest cycle dedicated to low-load or no-load recovery relative to exertion time
Recovery time ratio describes how much of the work cycle is devoted to tissue recovery (low force/rest) versus active exertion, with higher ratios reducing cumulative strain.
Question 5: Lateral epicondylitis (tennis elbow) in industrial workers is MOST closely associated with which job demand?
- Sustained cervical flexion greater than 20°
- Repetitive wrist extension combined with forearm pronation (Correct answer)
- Static shoulder abduction above 90°
- Whole-body vibration from seated driving tasks
Correct answer: Repetitive wrist extension combined with forearm pronation
Lateral epicondylitis involves overload of the wrist extensor muscles that originate at the lateral epicondyle, commonly caused by repetitive wrist extension and forearm pronation.
Question 6: Which factor is captured by the 'duty cycle' metric when assessing repetitive work exposure?
- Number of different tasks in a job rotation schedule
- Percentage of time a muscle group is actively loaded within a given period (Correct answer)
- Total weight handled per shift
- Frequency of ergonomic assessments per year
Correct answer: Percentage of time a muscle group is actively loaded within a given period
Duty cycle expresses the fraction of time a muscle or joint is under load, helping quantify cumulative exposure beyond simple repetition counts.
Question 7: An ergonomist wants to estimate cumulative trauma exposure across a full shift using the Hand Activity Level (HAL) tool. Which two inputs are required?
- Grip span and handle material
- Hand activity level (frequency/duty cycle) and peak force (Correct answer)
- Wrist angle and forearm rotation angle
- Tool weight and vibration magnitude
Correct answer: Hand activity level (frequency/duty cycle) and peak force
The ACGIH HAL method plots Peak Force (normalized as % MVC) against Hand Activity Level (a composite of exertion frequency and duty cycle) to determine TLV exceedance.
CIEE Repetitive Motion & CTD Prevention 3
A keyboard operator reports tingling in the thumb, index, and middle fingers that worsens at night.
The MOST likely CTD diagnosis is: