CSCS Exercise Science & Anatomy 2 — Questions and Answers

Question 1: Which muscle fiber type is characterized by high oxidative capacity, slow contraction speed, and fatigue resistance?

Type IIx fibers
Type IIa fibers
Type I fibers (Correct answer)
Type IIb fibers

Correct answer: Type I fibers

Type I (slow-twitch) fibers have high mitochondrial density, rely on oxidative phosphorylation, and are highly fatigue-resistant, making them ideal for endurance activities.

Type I muscle fibers contain abundant mitochondria and myoglobin, giving them high oxidative capacity. They contract slowly (low myosin ATPase activity) and are extremely fatigue-resistant due to their aerobic energy production. Type IIx fibers are fast-glycolytic with low oxidative capacity, and Type IIa fibers are intermediate. Strength and conditioning specialists target Type I fibers through sustained aerobic training and muscular endurance protocols.

Question 2: The sliding filament theory of muscle contraction states that shortening occurs when:

Actin and myosin filaments shorten in length
Actin filaments slide over myosin filaments toward the M-line
Myosin cross-bridges pull actin filaments toward the center of the sarcomere (Correct answer)
Z-discs move apart to increase sarcomere length

Correct answer: Myosin cross-bridges pull actin filaments toward the center of the sarcomere

During contraction, energized myosin cross-bridges attach to actin and pivot, pulling actin filaments toward the M-line (center of sarcomere), reducing sarcomere length without the filaments themselves shortening.

The sliding filament theory (Huxley and Hanson, 1954) explains that sarcomere shortening results from myosin cross-bridges binding actin and undergoing a power stroke, drawing actin toward the center. ATP provides the energy for cross-bridge cycling. Filament lengths remain constant; it is the degree of overlap that changes. This mechanism explains the length-tension relationship critical for understanding exercise mechanics and how muscle force varies with joint angle.

Question 3: What is the primary role of the Golgi tendon organ (GTO)?

Detect changes in muscle length
Monitor joint position and proprioception
Detect changes in muscle tension and inhibit excessive force (Correct answer)
Facilitate stretch reflexes during plyometric training

Correct answer: Detect changes in muscle tension and inhibit excessive force

GTOs are mechanoreceptors in tendons that respond to increased muscle tension by sending inhibitory signals (via Ib afferents) to reduce motor neuron activation, protecting muscles and tendons from excessive force.

Golgi tendon organs are encapsulated sensory receptors at the muscle-tendon junction that respond to changes in tension. Sufficient tension sends Ib inhibitory signals via interneurons to homonymous motor neurons, reducing muscle activation (autogenic inhibition). This differs from muscle spindles, which detect length changes and facilitate stretch reflexes. Understanding GTOs is important in PNF stretching — the contract-relax technique exploits GTO inhibition to allow greater ROM.

Question 4: During pressing movements like the bench press, which rotator cuff muscle is most at risk of impingement injury due to its passage under the acromion?

Subscapularis
Teres minor
Infraspinatus
Supraspinatus (Correct answer)

Correct answer: Supraspinatus

The supraspinatus passes under the acromion and is susceptible to impingement and rotator cuff tears during pressing movements, especially with improper scapular positioning.

The supraspinatus originates on the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus. It initiates the first 15-30 degrees of shoulder abduction and stabilizes the humeral head in the glenoid fossa. During bench press, improper technique or excessive load can cause supraspinatus impingement under the coracoacromial arch. CSCS candidates must understand proper scapular retraction cues — maintaining retracted scapulae during pressing protects the supraspinatus and supports shoulder stability.

Question 5: Which energy system predominantly fuels a 400-meter sprint lasting approximately 45-60 seconds?

Phosphagen (ATP-PCr) system
Fast glycolysis (anaerobic glycolysis) (Correct answer)
Oxidative phosphorylation (aerobic system)
Beta-oxidation of fats

Correct answer: Fast glycolysis (anaerobic glycolysis)

Activities lasting approximately 45-60 seconds rely predominantly on fast glycolysis (anaerobic glycolysis), which rapidly produces ATP from glucose without oxygen, resulting in lactate accumulation.

The phosphagen system (ATP-PCr) dominates up to approximately 10 seconds; fast glycolysis predominates from about 10 seconds to 2 minutes. A 400m sprint falls squarely in the glycolytic window. Glucose is broken down to pyruvate, which is converted to lactate under anaerobic conditions to regenerate NAD+ and sustain ATP production. The oxidative system contributes increasingly after approximately 2 minutes. CSCS training design must match energy system demands to the sport's metabolic profile when designing conditioning programs.

Question 6: What is the primary physiological basis for the rapid phase of EPOC (Excess Post-exercise Oxygen Consumption) in the first 2-3 minutes after intense exercise?

Restoration of muscle glycogen stores
Re-synthesis of phosphocreatine and oxygen debt repayment in blood/muscle (Correct answer)
Rebuilding of damaged muscle proteins
Sustained elevation of growth hormone secretion

Correct answer: Re-synthesis of phosphocreatine and oxygen debt repayment in blood/muscle

The rapid (alactacid) phase of EPOC is primarily due to PCr resynthesis (approximately 70% complete in 30 sec, complete in 3 min) and restoration of oxymyoglobin and oxyhemoglobin levels depleted during exercise.

EPOC has two phases. The rapid phase (first 2-3 minutes) restores phosphocreatine (approximately 50% in 30 sec, complete in 3 min), re-saturates myoglobin and hemoglobin with oxygen, and begins lactate clearance. The slow phase (lasting hours) involves elevated body temperature, elevated catecholamine and glucocorticoid levels, substrate cycling, and elevated cardiac and respiratory work. Strength and conditioning specialists use EPOC knowledge when designing conditioning programs and explaining post-exercise caloric expenditure to athletes following high-intensity training.

CSCS Exercise Science & Anatomy 2

Which muscle fiber type is characterized by high oxidative capacity, slow contraction speed, and fatigue resistance?