CSCS CSCS: Biomechanics of Resistance 5 — Questions and Answers
Question 1: An athlete performs a bench press with a wide versus narrow grip. The wide grip primarily changes which biomechanical variable?
- Barbell load path trajectory
- Moment arm at the shoulder joint (Correct answer)
- Pectoralis major physiological cross-sectional area
- Maximum motor unit recruitment
Correct answer: Moment arm at the shoulder joint
A wider grip reduces the horizontal distance the bar travels and alters the shoulder moment arm, shifting emphasis toward the pectorals over the triceps.
Question 2: The coefficient of static friction between an athlete's shoe and the floor is 0.8, and the athlete weighs 800 N. What is the maximum horizontal force the athlete can exert without sliding?
- 1000 N
- 640 N (Correct answer)
- 800 N
- 160 N
Correct answer: 640 N
Maximum static friction = μs × Normal force = 0.8 × 800 N = 640 N.
Question 3: Which type of muscle contraction produces the greatest peak force at a given velocity?
- Concentric at high speed
- Isometric
- Eccentric (Correct answer)
- Concentric at low speed
Correct answer: Eccentric
Eccentric contractions can generate 20–50% more force than isometric contractions because cross-bridges are forcibly stretched, allowing greater tension per bridge.
Question 4: What is the primary reason the deadlift generates higher lumbar compressive forces compared to many other resistance exercises?
- The lifter is in a standing rather than seated position
- The load is held far from the body's center of mass, increasing the spinal moment arm (Correct answer)
- The hamstrings apply excessive posterior shear to the lumbar spine
- The exercise is performed bilaterally, doubling load on each vertebra
Correct answer: The load is held far from the body's center of mass, increasing the spinal moment arm
When the barbell is positioned anterior to the spine, its large moment arm relative to the lumbar joints requires enormous erector spinae forces to maintain posture, increasing compressive load.
Question 5: During a sprint start, an athlete pushes backward and downward against the blocks. According to Newton's third law, the resulting ground reaction force is directed:
- Backward and downward into the blocks
- Forward and upward on the athlete (Correct answer)
- Directly upward with no horizontal component
- Backward and upward on the athlete
Correct answer: Forward and upward on the athlete
Newton's third law states that the reaction force is equal in magnitude and opposite in direction; pushing backward-downward produces a forward-upward ground reaction force on the athlete.
Question 6: Which of the following best explains why Bulgarian split squats produce high hip flexor (iliopsoas) eccentric demand on the rear leg?
- The rear leg is in terminal knee extension, maximizing quadriceps stretch
- The rear leg's hip is in an extended and internally rotated position, elongating the iliopsoas (Correct answer)
- The front leg creates a posteriorly directed reaction force that pulls the rear hip into flexion
- Knee flexion of the rear leg compresses the iliopsoas against the anterior hip capsule
Correct answer: The rear leg's hip is in an extended and internally rotated position, elongating the iliopsoas
With the rear foot elevated, the hip is driven into extension and slight internal rotation, placing the iliopsoas on maximal stretch and creating a large eccentric demand.
Question 7: When analyzing projectile motion of a thrown medicine ball, ignoring air resistance, the horizontal component of velocity:
- Decreases due to gravity throughout flight
- Increases as the ball accelerates downward
- Remains constant throughout the flight (Correct answer)
- Varies with the vertical velocity component
Correct answer: Remains constant throughout the flight
In projectile motion without air resistance, there is no horizontal force, so horizontal velocity remains constant by Newton's first law.
CSCS CSCS: Biomechanics of Resistance 5
An athlete performs a bench press with a wide versus narrow grip.
The wide grip primarily changes which biomechanical variable?