NSCA-CPT Biomechanics 3 — Questions and Answers
Question 1: What does the term 'moment arm' refer to in biomechanics?
- The length of a muscle's belly
- The perpendicular distance from the line of force to the axis of rotation (Correct answer)
- The distance a limb travels during movement
- The velocity of joint rotation
Correct answer: The perpendicular distance from the line of force to the axis of rotation
The moment arm is the shortest (perpendicular) distance between the axis of rotation and the line of action of the applied force.
Question 2: Which axis of rotation is associated with transverse plane movements?
- Frontal axis
- Sagittal axis
- Vertical (longitudinal) axis (Correct answer)
- Diagonal axis
Correct answer: Vertical (longitudinal) axis
Transverse plane movements such as rotation occur around the vertical (longitudinal) axis running head to toe.
Question 3: An increase in base of support (BOS) typically results in:
- Decreased dynamic balance
- Increased stability (Correct answer)
- Higher center of mass
- Reduced muscle activation
Correct answer: Increased stability
A wider BOS lowers the likelihood that the center of gravity will move outside the support base, increasing stability.
Question 4: During a push-up, which joint action occurs at the shoulder during the upward phase?
- Shoulder extension
- Shoulder flexion
- Horizontal adduction (Correct answer)
- Horizontal abduction
Correct answer: Horizontal adduction
The upward phase of a push-up involves horizontal adduction (pressing the arms together in the transverse plane) at the glenohumeral joint.
Question 5: Newton's third law states that for every action there is:
- An equal and proportional reaction in the same direction
- An equal and opposite reaction (Correct answer)
- A greater reaction due to friction
- A smaller reaction scaled by mass
Correct answer: An equal and opposite reaction
Newton's third law (law of reaction) states that forces come in pairs: equal in magnitude but opposite in direction.
Question 6: What is the term for the resistance a body has to changes in its rotational motion?
- Linear momentum
- Moment of inertia (Correct answer)
- Angular impulse
- Static friction
Correct answer: Moment of inertia
Moment of inertia is the rotational analog of mass and depends on both mass and the distribution of that mass relative to the axis of rotation.
Question 7: Which anatomical term describes movement of a limb away from the midline of the body?
- Adduction
- Flexion
- Abduction (Correct answer)
- Circumduction
Correct answer: Abduction
Abduction is movement away from the body's midline, occurring in the frontal plane (e.g., raising the arm laterally).
NSCA-CPT Biomechanics 3
What does the term 'moment arm' refer to in biomechanics?