CIEE Biomechanics & Musculoskeletal Disorder Mechanisms 2 — Questions and Answers
Question 1: Which condition is characterized by inflammation of the tendons attaching the forearm muscles to the lateral epicondyle of the elbow?
- Carpal tunnel syndrome
- Lateral epicondylitis (tennis elbow) (Correct answer)
- De Quervain's tenosynovitis
- Trigger finger (stenosing tenosynovitis)
Correct answer: Lateral epicondylitis (tennis elbow)
Lateral epicondylitis involves repetitive strain of the wrist extensor tendons at their attachment to the lateral epicondyle, causing pain and inflammation from cumulative micro-trauma.
Question 2: What effect does maintaining a forward-flexed trunk posture have on spinal disc pressure compared to standing upright?
- Decreases disc pressure by approximately 50%
- Increases disc pressure significantly due to greater moment arm (Correct answer)
- Has no clinically significant effect on disc pressure
- Reduces compressive forces by activating abdominal muscles
Correct answer: Increases disc pressure significantly due to greater moment arm
Forward trunk flexion increases the moment arm of the upper body weight relative to the lumbar spine, substantially increasing compressive disc pressure beyond that of upright standing.
Question 3: Which nerve is compressed in carpal tunnel syndrome, causing numbness and tingling in the hand?
- Ulnar nerve
- Radial nerve
- Median nerve (Correct answer)
- Musculocutaneous nerve
Correct answer: Median nerve
Carpal tunnel syndrome results from compression of the median nerve as it passes through the carpal tunnel, causing sensory and motor symptoms on the palm-side of the hand.
Question 4: What does the NIOSH lifting equation directly calculate as its primary output for assessing a lifting task?
- Recommended Weight Limit (RWL) (Correct answer)
- Maximum Moment Load (MML)
- Acceptable Compression Index (ACI)
- Biomechanical Strain Ratio (BSR)
Correct answer: Recommended Weight Limit (RWL)
The NIOSH lifting equation calculates the Recommended Weight Limit (RWL) based on task variables; the Lifting Index (LI) is then determined by dividing the actual load by the RWL.
Question 5: What is the primary biomechanical mechanism by which intra-abdominal pressure (IAP) assists the spine during heavy lifting?
- It increases heart rate to supply more oxygen to spinal muscles
- It creates an internal pressure cylinder that reduces net spinal compressive loading (Correct answer)
- It directly strengthens quadriceps and hip extensor muscles
- It decreases the perceived weight of the object being lifted
Correct answer: It creates an internal pressure cylinder that reduces net spinal compressive loading
Increased intra-abdominal pressure creates an internal hydraulic cylinder effect in the abdominal cavity that helps support the trunk and reduce net compressive forces on the lumbar spine.
Question 6: Which type of muscle contraction occurs when a muscle develops tension while its length remains constant, such as holding a part stationary?
- Isotonic concentric contraction
- Isotonic eccentric contraction
- Isometric contraction (Correct answer)
- Isokinetic contraction
Correct answer: Isometric contraction
Isometric contractions involve muscle tension generation without change in muscle length, commonly occurring during static holding tasks such as maintaining a fixed work posture.
Question 7: What is the primary risk factor for developing rotator cuff disorders in workers performing sustained overhead tasks?
- High ambient temperature above 85°F
- Sustained shoulder elevation above 60 degrees causing subacromial impingement (Correct answer)
- Insufficient workplace lighting below 50 foot-candles
- High ambient noise levels above 85 dB
Correct answer: Sustained shoulder elevation above 60 degrees causing subacromial impingement
Sustained elevation of the shoulder above 60 degrees compresses supraspinatus tendons in the subacromial space, increasing risk of rotator cuff impingement and cumulative tears.
CIEE Biomechanics & Musculoskeletal Disorder Mechanisms 2
Which condition is characterized by inflammation of the tendons attaching the forearm muscles to the lateral epicondyle of the elbow?