CIEE Biomechanics & Musculoskeletal Disorder Mechanisms 1 — Questions and Answers
Question 1: What term best describes the scientific study of forces and their effects on the human musculoskeletal system during work tasks?
- Kinesiology
- Biomechanics (Correct answer)
- Anthropometry
- Physiology
Correct answer: Biomechanics
Biomechanics applies principles of mechanics to study how forces act on and within the human body during work activities.
Question 2: Which region of the spine is most frequently injured in work-related musculoskeletal disorders?
- Cervical
- Thoracic
- Lumbar (Correct answer)
- Sacral
Correct answer: Lumbar
The lumbar spine bears the greatest compressive loads during lifting and bending, making it the most common site for work-related spinal injuries.
Question 3: In biomechanics, what is the 'moment arm' (lever arm)?
- The weight of the load being lifted
- The perpendicular distance from the axis of rotation to the line of force action (Correct answer)
- The speed at which a joint moves through range of motion
- The total force applied by a contracting muscle
Correct answer: The perpendicular distance from the axis of rotation to the line of force action
The moment arm is the perpendicular distance from the axis of rotation to the line of action of the force, which determines the torque produced at a joint.
Question 4: What is the NIOSH recommended action limit for compressive force at the L5/S1 lumbar joint?
- 1,000 N
- 3,400 N (Correct answer)
- 6,800 N
- 500 N
Correct answer: 3,400 N
NIOSH established 3,400 N as the action limit for L5/S1 compressive force, above which the risk of low back injury increases significantly for most workers.
Question 5: Which soft tissue is most prone to cumulative damage from repetitive loading due to its relatively poor blood supply?
- Skeletal muscle
- Cortical bone
- Tendon (Correct answer)
- Epidermis
Correct answer: Tendon
Tendons have a relatively poor blood supply, which limits their ability to repair micro-damage from repetitive loading, making them highly susceptible to cumulative trauma disorders.
Question 6: What does the term 'torque' mean in ergonomic biomechanical analysis?
- The speed of muscle contraction during a task
- The rotational force produced by a moment arm and applied force (Correct answer)
- The compressive force transmitted through a vertebral disc
- The friction coefficient between a tool handle and the hand
Correct answer: The rotational force produced by a moment arm and applied force
Torque is calculated as force multiplied by moment arm and represents the rotational effect of a force about a joint axis, which is central to assessing musculoskeletal loading.
Question 7: During a lifting task, increasing the horizontal distance of the load from the body primarily increases which biomechanical factor at the lumbar spine?
- Intra-abdominal pressure
- Lumbar compressive and shear forces (Correct answer)
- Grip force required to hold the object
- Metabolic heart rate demand
Correct answer: Lumbar compressive and shear forces
As horizontal distance increases, the moment arm for the load increases substantially, which increases the torque and compressive forces at the lumbar spine.
CIEE Biomechanics & Musculoskeletal Disorder Mechanisms 1
What term best describes the scientific study of forces and their effects on the human musculoskeletal system during work tasks?