NSCA-CPT Biomechanics 4 — Questions and Answers
Question 1: During a deadlift, excessive forward lean increases the lumbar extensor moment arm. This MOST directly increases:
- Compressive forces on the cervical spine
- Shear forces at the glenohumeral joint
- Compressive and shear forces on the lumbar spine (Correct answer)
- Tensile forces on the Achilles tendon
Correct answer: Compressive and shear forces on the lumbar spine
A greater horizontal distance between the barbell and the lumbar spine increases the torque demand on lumbar extensors, raising both compressive and shear spinal loads.
Question 2: Which of the following BEST describes the angle of pull of a muscle?
- The angle between the muscle's line of action and the long axis of the bone it moves (Correct answer)
- The angle between the muscle and the vertical
- The curvature of the muscle belly at peak contraction
- The angle between two adjacent limb segments
Correct answer: The angle between the muscle's line of action and the long axis of the bone it moves
The angle of pull determines how much of the muscle force is directed toward rotation versus compression/distraction of the joint.
Question 3: What happens to angular velocity when a rotating object's moment of inertia decreases (assuming no external torque)?
- Angular velocity decreases
- Angular velocity remains constant
- Angular velocity increases (Correct answer)
- Angular momentum decreases
Correct answer: Angular velocity increases
Conservation of angular momentum (L = Iω) means that if moment of inertia (I) decreases, angular velocity (ω) must increase to keep L constant.
Question 4: Ground reaction force (GRF) during running is typically how many times greater than during walking?
- 0.5–1 times body weight
- 1–1.5 times body weight
- 2–3 times body weight (Correct answer)
- 5–8 times body weight
Correct answer: 2–3 times body weight
Running produces vertical GRFs of approximately 2–3 times body weight, compared to roughly 1.1–1.5 times during normal walking.
Question 5: The sarcomere length at which maximal active force is produced corresponds to:
- Maximum overlap between thin filaments only
- Optimal actin–myosin cross-bridge overlap (Correct answer)
- Full extension with no filament overlap
- Complete thick-filament compression
Correct answer: Optimal actin–myosin cross-bridge overlap
Peak active force occurs at the sarcomere length where actin and myosin filaments have the greatest number of available cross-bridge binding sites.
Question 6: Which movement is produced by the hip flexors acting concentrically in the sagittal plane?
- Hip abduction
- Hip extension
- Hip flexion (Correct answer)
- Hip external rotation
Correct answer: Hip flexion
Concentric hip flexor action brings the femur anteriorly toward the trunk, which is hip flexion occurring in the sagittal plane.
Question 7: Compared to a wide grip, a narrower grip on a barbell bench press typically:
- Shifts emphasis toward the pectorals and away from the triceps
- Increases pectoral moment arm length
- Shifts emphasis toward the triceps and reduces pectoral stretch (Correct answer)
- Decreases elbow joint stress
Correct answer: Shifts emphasis toward the triceps and reduces pectoral stretch
A closer grip reduces the horizontal adduction range at the shoulder, decreasing pectoral contribution while increasing triceps demand.
NSCA-CPT Biomechanics 4
During a deadlift, excessive forward lean increases the lumbar extensor moment arm.
This MOST directly increases: