PAS Biomechanical Analysis & Movement 3 — Questions and Answers
Question 1: In biomechanical analysis, what does the term 'moment arm' refer to?
- The length of the muscle belly
- The perpendicular distance from the joint axis to the line of force (Correct answer)
- The velocity of limb movement
- The angle of the joint at peak force
Correct answer: The perpendicular distance from the joint axis to the line of force
The moment arm is the perpendicular distance from the joint's axis of rotation to the line of action of a force, determining torque magnitude.
Question 2: Which postural deviation is characterized by an exaggerated thoracic kyphosis combined with a flattened lumbar curve?
- Lordosis
- Flat-back posture
- Sway-back posture (Correct answer)
- Scoliosis
Correct answer: Sway-back posture
Sway-back posture features increased thoracic kyphosis, a posteriorly shifted pelvis, and a flattened lumbar spine.
Question 3: The 'Q-angle' is a measurement used to assess alignment of which joint?
- Hip
- Ankle
- Knee (Correct answer)
- Shoulder
Correct answer: Knee
The Q-angle measures the quadriceps angle at the knee, formed between the line from the ASIS to the patella and the patellar tendon to the tibial tubercle.
Question 4: What is the primary role of the deep longitudinal subsystem (DLS) during gait?
- Hip abduction in swing phase
- Force transmission from the foot through the ipsilateral posterior chain (Correct answer)
- Trunk rotation during arm swing
- Maintaining lateral pelvic stability
Correct answer: Force transmission from the foot through the ipsilateral posterior chain
The DLS (biceps femoris, sacrotuberous ligament, erector spinae) transmits ground reaction forces from the foot up through the posterior kinetic chain.
Question 5: During a squat, excessive forward lean of the torso is most likely caused by which limitation?
- Weak deltoids
- Limited ankle dorsiflexion (Correct answer)
- Tight shoulder external rotators
- Weak wrist flexors
Correct answer: Limited ankle dorsiflexion
Limited ankle dorsiflexion forces the trunk to lean forward excessively to keep the center of mass over the base of support during a squat.
Question 6: Which law states that a bone will remodel along the lines of mechanical stress placed upon it?
- Hooke's Law
- Wolff's Law (Correct answer)
- Newton's Third Law
- Davis's Law
Correct answer: Wolff's Law
Wolff's Law states that bone adapts its internal architecture and external shape in response to the mechanical loads applied to it.
Question 7: In a first-class lever system, where is the fulcrum located relative to the effort and resistance?
- At the same end as the effort
- At the same end as the resistance
- Between the effort and the resistance (Correct answer)
- Outside both the effort and resistance
Correct answer: Between the effort and the resistance
In a first-class lever, the fulcrum (joint) lies between the effort (muscle force) and the resistance (load), like a seesaw.
PAS Biomechanical Analysis & Movement 3
In biomechanical analysis, what does the term 'moment arm' refer to?