ACE Exercise Science & Application 2 — Questions and Answers
Question 1: Which energy system is the PRIMARY source during a 400-meter sprint?
- Phosphagen (ATP-PC) system
- Glycolytic system (Correct answer)
- Oxidative system
- Combined phosphagen and oxidative
Correct answer: Glycolytic system
The glycolytic system dominates efforts lasting roughly 30–120 seconds, such as a 400-meter sprint.
Question 2: The sliding filament theory describes how muscle contraction occurs when:
- Myosin heads pull actin filaments toward the M-line (Correct answer)
- Actin filaments elongate during contraction
- Titin proteins shorten to produce force
- Tropomyosin binds to calcium to initiate contraction
Correct answer: Myosin heads pull actin filaments toward the M-line
Cross-bridges form when myosin heads attach to actin and pull actin toward the center of the sarcomere (M-line), shortening the muscle.
Question 3: Which of the following BEST describes the Fick equation for oxygen consumption?
- VO2 = HR × SV × (a-vO2 difference) (Correct answer)
- VO2 = RQ × VCO2 production
- VO2 = cardiac output × blood lactate
- VO2 = tidal volume × respiratory rate
Correct answer: VO2 = HR × SV × (a-vO2 difference)
The Fick equation states VO2 = cardiac output (HR × SV) multiplied by the arteriovenous oxygen difference.
Question 4: A client's respiratory exchange ratio (RER) is 0.85. This MOST likely indicates they are primarily using:
- Carbohydrate as the primary fuel
- Fat as the primary fuel
- Protein as the primary fuel
- An equal mix of carbohydrate and fat (Correct answer)
Correct answer: An equal mix of carbohydrate and fat
An RER of 0.85 falls between the pure-fat value (~0.70) and pure-carbohydrate value (1.00), indicating a mixed substrate blend.
Question 5: Which muscle action occurs when the biceps brachii lengthens while producing force during the lowering phase of a curl?
- Concentric
- Isometric
- Eccentric (Correct answer)
- Isokinetic
Correct answer: Eccentric
Eccentric contractions occur when a muscle produces force while lengthening, as when controlling the lowering of a weight.
Question 6: During high-intensity exercise, lactate threshold is BEST defined as the exercise intensity at which:
- Blood lactate begins to accumulate faster than it can be cleared (Correct answer)
- Muscle glycogen is fully depleted
- Cardiac output reaches its maximum
- The phosphagen system becomes the sole energy source
Correct answer: Blood lactate begins to accumulate faster than it can be cleared
Lactate threshold marks the point where lactate production exceeds clearance, causing blood lactate to rise exponentially.
Question 7: Type II muscle fibers differ from Type I fibers in that they have:
- Greater mitochondrial density and fatigue resistance
- Higher myosin ATPase activity and faster contraction speed (Correct answer)
- Lower glycolytic capacity and more capillaries
- Greater reliance on oxidative phosphorylation
Correct answer: Higher myosin ATPase activity and faster contraction speed
Type II (fast-twitch) fibers have higher myosin ATPase activity, enabling faster cross-bridge cycling and rapid force production.
ACE Exercise Science & Application 2
Which energy system is the PRIMARY source during a 400-meter sprint?