Types of muscle contraction

The figure shows an athlete performing a squat. Which one of the following best describes the action of the quadriceps muscle group as the athlete lowers into the squat?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

As the athlete lowers into the squat, the quadriceps muscle group is lengthening while controlling the descent, which is an eccentric contraction. This allows for a smooth and controlled movement.

During a bicep curl, which of the following best describes the action of the biceps brachii as the weight is lowered back to the starting position?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

As the weight is lowered during a bicep curl, the biceps brachii lengthens while still under tension, which is an eccentric contraction. This allows for controlled movement and helps to prevent injury.

In a push-up, which 2 muscles are primarily responsible for the eccentric phase as the body is lowered towards the ground?

• Pectoralis major

• Triceps brachii

• Bicep brachii

• Latissimus dorsi

Answer explanation

During the eccentric phase of a push-up, the pectoralis major and triceps brachii control the lowering of the body. The pectoralis major helps in chest muscle engagement, while the triceps brachii stabilizes the elbow joint.

Which of the following best describes the action of the gastrocnemius during the downward phase of a squat?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During the downward phase of a squat, the gastrocnemius lengthens while controlling the descent, which is an eccentric contraction. This helps to stabilize the movement and prevent injury.

During a push-up, which of the following best describes the action of the triceps brachii as the body is pushed up from the ground?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During a push-up, the triceps brachii contracts concentrically to extend the elbow and push the body upward. This is the primary action as the muscle shortens to generate force against gravity.

During a leg extension exercise, which of the following best describes the action of the quadriceps as the leg is extended?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During leg extension, the quadriceps contract concentrically to extend the leg at the knee joint, generating force to lift the weight. This is the primary action of the quadriceps in this exercise.

Which of the following best describes the action of the deltoid muscle during the upward phase of a shoulder press?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During the upward phase of a shoulder press, the deltoid muscle is responsible for lifting the weight. This action involves the muscle contracting concentrically, meaning it shortens to generate force and move the arm upward.

During a plank exercise, which of the following best describes the action of the core muscles?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During a plank, the core muscles engage to maintain stability, which is best described as contracting isometrically. This means they hold a position without changing length, providing support throughout the exercise.

Which of the following best describes the action of the pectoralis major during the downward phase of a bench press?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During the downward phase of a bench press, the pectoralis major lengthens while controlling the weight, which is an eccentric contraction. This means it is contracting eccentrically to manage the load safely.

Which of the following best describes the action of the latissimus dorsi during the upward phase of a pull-up?

• Contracting concentrically

• Contracting eccentrically

• Contracting isometrically

• Relaxing as the antagonist

Answer explanation

During the upward phase of a pull-up, the latissimus dorsi contracts concentrically to pull the body upward. This means it shortens while generating force, making 'contracting concentrically' the correct choice.