CSCS Resistance Training Biomechanics 2 — Questions and Answers
Question 1: Which joint action occurs at the hip during the concentric phase of a back squat?
- Hip flexion
- Hip extension (Correct answer)
- Hip abduction
- Hip adduction
Correct answer: Hip extension
During the concentric (rising) phase of the back squat, the hip extensors (glutes and hamstrings) produce hip extension to return the body to standing.
Question 2: What is the moment arm in a lever system?
- The length of the bone acting as the lever
- The perpendicular distance from the axis of rotation to the line of force application (Correct answer)
- The total force applied by the muscle
- The angle of the joint at peak force production
Correct answer: The perpendicular distance from the axis of rotation to the line of force application
The moment arm is the perpendicular distance from the joint's axis of rotation to the line of action of the applied force, and it determines the torque generated.
Question 3: During a standing barbell curl, which phase produces an eccentric contraction of the biceps brachii?
- Lifting the bar from the thighs to shoulder height
- Holding the bar at the top position
- Lowering the bar back to the starting position (Correct answer)
- Gripping the bar before initiating the lift
Correct answer: Lowering the bar back to the starting position
The biceps brachii lengthens under load during the lowering (eccentric) phase of the curl as elbow extension occurs against gravity.
Question 4: A longer resistance arm in a lever system will:
- Decrease the torque produced by the resistance
- Increase the torque produced by the resistance (Correct answer)
- Have no effect on torque
- Decrease the mechanical advantage of the effort force
Correct answer: Increase the torque produced by the resistance
Torque equals force multiplied by its moment arm, so a longer resistance arm increases the torque the resistance creates about the joint.
Question 5: Which type of muscle action produces the greatest force output?
- Concentric
- Isometric
- Eccentric (Correct answer)
- Isotonic
Correct answer: Eccentric
Eccentric muscle actions can produce approximately 20–50% more force than concentric contractions due to passive elastic contributions from titin and connective tissue.
Question 6: In a first-class lever, where is the fulcrum located relative to the effort and resistance?
- At the same end as the effort force
- Between the effort force and the resistance (Correct answer)
- At the same end as the resistance
- At the midpoint of the resistance arm only
Correct answer: Between the effort force and the resistance
A first-class lever has its fulcrum (axis) positioned between the effort (muscle force) and the resistance (load), as seen with neck extension against gravity.
Question 7: What is the primary mechanical disadvantage of the human musculoskeletal system compared to machines?
- Muscles attach far from joints, reducing speed
- Muscles attach close to joints, requiring large forces to move loads (Correct answer)
- Bones are too light to transmit force effectively
- Tendons store no elastic energy
Correct answer: Muscles attach close to joints, requiring large forces to move loads
Most muscles attach very close to the joint (short effort arm), creating poor mechanical advantage and requiring the muscle to produce much greater force than the external load.
CSCS Resistance Training Biomechanics 2
Which joint action occurs at the hip during the concentric phase of a back squat?