ACSM Exercise Physiology 2 — Questions and Answers
Question 1: Which energy system predominantly fuels a 400-meter sprint run?
- Phosphagen (ATP-PCr) system
- Glycolytic (lactic acid) system (Correct answer)
- Oxidative phosphorylation
- Beta-oxidation
Correct answer: Glycolytic (lactic acid) system
The 400-meter sprint (~45–60 seconds) relies primarily on fast glycolysis (lactic acid system) for ATP production.
Question 2: During incremental exercise to exhaustion, blood lactate concentration begins to rise sharply at the lactate threshold because:
- Muscle oxygen stores are depleted
- Lactate production exceeds clearance capacity (Correct answer)
- Mitochondrial ATP production ceases
- Glycogen stores are fully exhausted
Correct answer: Lactate production exceeds clearance capacity
At the lactate threshold, fast-twitch fiber recruitment and accelerated glycolysis cause lactate production to exceed peripheral clearance.
Question 3: Stroke volume typically reaches its plateau during upright cycle ergometry at approximately what percentage of VO2max?
- 20–30%
- 40–60% (Correct answer)
- 70–80%
- 90–100%
Correct answer: 40–60%
Stroke volume plateaus at roughly 40–60% of VO2max during upright exercise, after which further cardiac output increases rely on heart rate.
Question 4: The primary role of 2,3-bisphosphoglycerate (2,3-BPG) during prolonged exercise is to:
- Increase hemoglobin's affinity for oxygen
- Facilitate oxygen release from hemoglobin to muscles (Correct answer)
- Enhance carbon dioxide transport
- Stimulate erythropoietin production
Correct answer: Facilitate oxygen release from hemoglobin to muscles
2,3-BPG binds to deoxyhemoglobin, reducing oxygen affinity and promoting O2 unloading in metabolically active tissues.
Question 5: Which muscle fiber type has the highest oxidative capacity and fatigue resistance?
- Type IIx
- Type IIa
- Type I (Correct answer)
- Type IIb
Correct answer: Type I
Type I (slow-twitch) fibers have the most mitochondria and oxidative enzymes, making them highly resistant to fatigue.
Question 6: Excess post-exercise oxygen consumption (EPOC) is primarily attributed to which of the following?
- Continued muscle contraction after exercise
- Restoration of oxygen stores, removal of lactate, and elevated body temperature (Correct answer)
- Increased intestinal absorption of nutrients
- Sustained peripheral vasoconstriction
Correct answer: Restoration of oxygen stores, removal of lactate, and elevated body temperature
EPOC reflects elevated metabolism needed to replenish oxygen stores, restore ATP-PCr, clear lactate, and return body temperature to baseline.
Question 7: Which hormone primarily stimulates fat mobilization from adipose tissue during prolonged moderate-intensity exercise?
- Insulin
- Cortisol
- Epinephrine (Correct answer)
- Glucagon
Correct answer: Epinephrine
Epinephrine activates hormone-sensitive lipase in adipocytes, dramatically increasing free fatty acid release during exercise.
ACSM Exercise Physiology 2
Which energy system predominantly fuels a 400-meter sprint run?