NBCOT Biomechanics, Kinesiology, and Musculoskeletal Function — Questions and Answers
Question 1: During manual muscle testing (MMT), a muscle grade of 3/5 indicates the muscle can:
- Move through partial ROM against gravity with some added resistance
- Move through full ROM against gravity with no added resistance (Correct answer)
- Move through full ROM only with gravity eliminated
- Show a visible or palpable contraction but produce no joint movement
Correct answer: Move through full ROM against gravity with no added resistance
MMT grade 3 (Fair) means the muscle moves the segment through full ROM against gravity but cannot sustain any additional resistance. Grade 2 requires gravity eliminated; grade 4 moves against some resistance; grade 1 is trace contraction only.
Question 2: The glenohumeral (shoulder) joint is classified as which type of synovial joint, allowing movement in multiple planes?
- Hinge joint
- Pivot joint
- Ball-and-socket joint (Correct answer)
- Condyloid joint
Correct answer: Ball-and-socket joint
The glenohumeral joint is a ball-and-socket (spheroidal) joint, permitting flexion/extension, abduction/adduction, and internal/external rotation. Hinge joints (e.g., elbow) allow only flexion/extension; pivot joints allow axial rotation; condyloid joints allow movement in two planes.
Question 3: A client demonstrates wrist drop following a radial nerve injury. Which muscle group is MOST affected?
- Wrist flexors
- Wrist extensors (Correct answer)
- Intrinsic hand muscles
- Finger flexors
Correct answer: Wrist extensors
The radial nerve innervates wrist and finger extensors. Injury results in wrist drop (inability to extend the wrist) due to paralysis of the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris. Wrist flexors are innervated by the median and ulnar nerves.
Question 4: When teaching body mechanics to a client with low back pain, the OT instructs the client to pivot the feet when changing direction rather than twisting the trunk. This primarily addresses which biomechanical principle?
- Reducing compressive forces on spinal discs
- Eliminating rotational/torsional forces on the lumbar spine (Correct answer)
- Maximizing mechanical advantage of the erector spinae
- Increasing base of support during lifting
Correct answer: Eliminating rotational/torsional forces on the lumbar spine
Trunk rotation applies torsional stress to intervertebral discs and facet joints, which is particularly damaging to the lumbar spine. Pivoting the feet eliminates rotational forces while keeping the trunk in a protected neutral alignment.
Question 5: Passive range of motion (PROM) differs from active range of motion (AROM) in that PROM:
- Requires greater muscle strength to perform
- Is produced entirely by an external force without voluntary muscle contraction (Correct answer)
- Results in greater joint mobility than AROM in healthy individuals
- Is contraindicated whenever joint inflammation is present
Correct answer: Is produced entirely by an external force without voluntary muscle contraction
PROM is movement produced entirely by an external force (therapist, gravity, or mechanical device) without active muscle contraction. AROM requires voluntary muscle activation. In healthy individuals PROM and AROM are approximately equal; PROM may actually be indicated in certain inflamed joints.
Question 6: A client has a weak serratus anterior muscle. Which functional deficit would the OT MOST likely observe during an activity requiring arm elevation?
- Inability to supinate the forearm
- Winging of the scapula during arm elevation (Correct answer)
- Reduced elbow flexion strength
- Difficulty with wrist extension against resistance
Correct answer: Winging of the scapula during arm elevation
The serratus anterior protracts and upwardly rotates the scapula, holding its medial border flat against the thorax. Weakness causes the medial border to lift away from the thorax during arm elevation — a condition called scapular winging — which also impairs overhead reaching ability.
NBCOT Biomechanics, Kinesiology, and Musculoskeletal Function
During manual muscle testing (MMT), a muscle grade of 3/5 indicates the muscle can: