COKO COKO Anatomy and Biomechanics 2 — Questions and Answers
Question 1: The rotator cuff is composed of which four muscles?
- Supraspinatus, infraspinatus, teres minor, subscapularis (Correct answer)
- Deltoid, pectoralis major, teres major, latissimus dorsi
- Biceps brachii, triceps, coracobrachialis, brachialis
- Rhomboids, trapezius, serratus anterior, levator scapulae
Correct answer: Supraspinatus, infraspinatus, teres minor, subscapularis
The rotator cuff (SITS muscles) — supraspinatus, infraspinatus, teres minor, and subscapularis — stabilize the glenohumeral joint by compressing the humeral head into the glenoid.
Question 2: In biomechanics, the 'lever arm' (moment arm) is defined as:
- The perpendicular distance from the axis of rotation to the line of force application (Correct answer)
- The length of the bone acting as a lever
- The mass of the segment multiplied by gravity
- The velocity of limb movement during contraction
Correct answer: The perpendicular distance from the axis of rotation to the line of force application
The moment arm is the perpendicular distance between the joint axis and the force vector, determining the torque produced by a muscle or external load.
Question 3: Which type of muscle contraction occurs when the muscle produces force while lengthening?
- Eccentric contraction (Correct answer)
- Concentric contraction
- Isometric contraction
- Isokinetic contraction
Correct answer: Eccentric contraction
Eccentric contractions occur when a muscle generates force while being elongated, such as the quadriceps controlling descent during a squat.
Question 4: The lumbar spine's natural curvature is called:
- Lordosis (Correct answer)
- Kyphosis
- Scoliosis
- Hyperlordosis
Correct answer: Lordosis
Lordosis is the normal inward (anterior) curvature of the lumbar spine; excessive lordosis is termed hyperlordosis and can contribute to low back pain.
Question 5: Which muscle is primarily responsible for dorsiflexion of the ankle?
- Tibialis anterior (Correct answer)
- Gastrocnemius
- Soleus
- Peroneus longus
Correct answer: Tibialis anterior
The tibialis anterior, located on the anterolateral shin, is the primary dorsiflexor of the ankle, pulling the foot upward toward the shin.
Question 6: The term 'center of mass' in human movement refers to:
- The point at which the body's total mass is theoretically concentrated and balance is maintained (Correct answer)
- The geometric center of the largest muscle group
- The axis around which all rotational movements occur
- The midpoint of the spine at the L3 vertebra
Correct answer: The point at which the body's total mass is theoretically concentrated and balance is maintained
The center of mass is the average location of all mass in the body; its position relative to the base of support determines postural stability.
COKO COKO Anatomy and Biomechanics 2
The rotator cuff is composed of which four muscles?