ACSM Exercise Physiology 5 — Questions and Answers
Question 1: During prolonged exercise lasting 2+ hours, hypoglycemia can impair performance primarily because:
- The liver cannot release glycogen
- The central nervous system relies heavily on glucose as fuel (Correct answer)
- Fatty acid oxidation shuts down without glucose
- Muscle glycogen resynthesis stops without blood glucose
Correct answer: The central nervous system relies heavily on glucose as fuel
The brain depends almost exclusively on glucose; hypoglycemia impairs CNS function, leading to fatigue, confusion, and cessation of exercise.
Question 2: Which of the following best describes the effect of dehydration equivalent to 2% of body weight on aerobic exercise performance?
- No measurable effect on VO2max
- Up to 20% decrease in aerobic performance capacity (Correct answer)
- Improved fat oxidation partially offsetting any deficit
- Increased stroke volume compensating for reduced plasma volume
Correct answer: Up to 20% decrease in aerobic performance capacity
A 2% body weight deficit from dehydration can reduce aerobic performance by approximately 10–20% due to decreased plasma volume and cardiac output.
Question 3: Muscle glycogen resynthesis after prolonged exercise is maximized when carbohydrate is consumed:
- At least 4 hours post-exercise to allow blood flow normalization
- Within 30–60 minutes after exercise ends (Correct answer)
- Only with simultaneous high-fat intake
- Immediately before sleep the same night
Correct answer: Within 30–60 minutes after exercise ends
Glycogen synthase activity and muscle insulin sensitivity are highest immediately post-exercise, making early carbohydrate intake critical for rapid resynthesis.
Question 4: Which phenomenon explains why trained endurance athletes oxidize more fat and less carbohydrate at a given absolute submaximal workload compared to untrained individuals?
- Lower mitochondrial density in trained muscle
- Greater reliance on phosphocreatine at submaximal intensities
- Training-induced increase in mitochondrial density and fat oxidation enzymes (Correct answer)
- Higher muscle glycogen stores forcing obligate carbohydrate oxidation
Correct answer: Training-induced increase in mitochondrial density and fat oxidation enzymes
Aerobic training increases mitochondrial density and enzymes such as citrate synthase, enabling greater fat oxidation at the same absolute workload.
Question 5: What is the primary mechanism by which beta-blockers limit exercise performance?
- They reduce blood glucose availability during exercise
- They blunt the catecholamine-mediated increase in heart rate, limiting maximal cardiac output (Correct answer)
- They decrease respiratory drive and reduce VE at maximal effort
- They inhibit free fatty acid mobilization from adipose tissue
Correct answer: They blunt the catecholamine-mediated increase in heart rate, limiting maximal cardiac output
Beta-blockers block beta-1 adrenergic receptors on the heart, preventing the catecholamine-driven heart rate increase and thus limiting maximal cardiac output.
Question 6: The crossover concept in exercise metabolism states that as exercise intensity increases:
- Fat becomes the exclusive fuel above the lactate threshold
- Carbohydrate oxidation progressively increases while fat oxidation decreases (Correct answer)
- Protein contribution to energy expenditure exceeds fat at high intensities
- Fat and carbohydrate are always oxidized in a fixed 50:50 ratio
Correct answer: Carbohydrate oxidation progressively increases while fat oxidation decreases
The crossover concept describes the shift from fat-dominant to carbohydrate-dominant energy supply as exercise intensity increases toward VO2max.
Question 7: Which of the following is a primary long-term skeletal muscle adaptation to high-intensity interval training (HIIT)?
- Conversion of Type I fibers to Type IIx fibers
- Increased mitochondrial biogenesis and oxidative enzyme activity (Correct answer)
- Decreased muscle capillary density due to reduced volume
- Reduced buffering capacity for hydrogen ions
Correct answer: Increased mitochondrial biogenesis and oxidative enzyme activity
HIIT stimulates mitochondrial biogenesis (via PGC-1α activation) and upregulates oxidative enzymes similar to continuous endurance training.
ACSM Exercise Physiology 5
During prolonged exercise lasting 2+ hours, hypoglycemia can impair performance primarily because: