CSSD Exercise Physiology & Energy Metabolism 5 — Questions and Answers
Question 1: Which metabolic adaptation MOST distinguishes skeletal muscle of a highly trained endurance athlete compared to an untrained individual?
- Increased fast-twitch fiber proportion
- Greater intramuscular triglyceride (IMTG) stores and enhanced lipid oxidation capacity (Correct answer)
- Elevated resting muscle glycogen with no change in oxidative capacity
- Decreased capillary density around muscle fibers
Correct answer: Greater intramuscular triglyceride (IMTG) stores and enhanced lipid oxidation capacity
Endurance training increases IMTG content and upregulates lipid oxidative enzymes, enabling the athlete to oxidize fat at higher absolute workloads and spare glycogen.
Question 2: Excess post-exercise oxygen consumption (EPOC) after high-intensity exercise is PRIMARILY driven by:
- Resynthesis of phosphocreatine, lactate clearance, elevated temperature, and hormonal effects (Correct answer)
- Continued fat oxidation only
- Glycogen re-synthesis requiring extra oxygen
- Protein synthesis in the post-exercise window
Correct answer: Resynthesis of phosphocreatine, lactate clearance, elevated temperature, and hormonal effects
EPOC results from multiple oxygen-consuming processes: PCr resynthesis, lactate-to-glycogen conversion, elevated core temperature, and catecholamine-driven elevation of metabolic rate.
Question 3: During altitude acclimatization, which metabolic shift occurs that affects carbohydrate and fat utilization?
- Fat oxidation increases dramatically and carbohydrate use drops immediately
- Initial increased reliance on carbohydrate due to hypoxia-induced AMPK activation and PDH upregulation (Correct answer)
- Protein becomes the dominant fuel within 24 hours
- No metabolic substrate shift occurs at altitude
Correct answer: Initial increased reliance on carbohydrate due to hypoxia-induced AMPK activation and PDH upregulation
Hypoxia activates AMPK and pyruvate dehydrogenase, shifting substrate preference toward carbohydrate oxidation because fat oxidation requires more oxygen per ATP produced.
Question 4: Which concept explains why athletes performing concurrent training (strength + endurance) may see blunted strength gains compared to strength training alone?
- Substrate competition between fat and glucose during resistance exercise
- AMPK-mTOR interference, where AMPK activated by endurance work suppresses mTORC1-driven hypertrophy signaling (Correct answer)
- Excessive protein intake during concurrent training
- Greater EPOC suppressing testosterone release
Correct answer: AMPK-mTOR interference, where AMPK activated by endurance work suppresses mTORC1-driven hypertrophy signaling
Endurance exercise activates AMPK, which can phosphorylate and inhibit mTORC1, the primary anabolic signaling hub for muscle protein synthesis and hypertrophy.
Question 5: A female soccer player in a prolonged energy deficit shows blunted resting metabolic rate (RMR). This adaptation is MOST consistent with:
- Increased thyroid hormone production compensating for low intake
- Metabolic adaptation (adaptive thermogenesis) reducing RMR below predicted values (Correct answer)
- Improved mitochondrial efficiency unrelated to energy availability
- Increased brown adipose tissue activation
Correct answer: Metabolic adaptation (adaptive thermogenesis) reducing RMR below predicted values
Chronic low energy availability triggers adaptive thermogenesis, suppressing RMR below predictions based on lean mass, consistent with Relative Energy Deficiency in Sport (RED-S).
Question 6: Which measure BEST reflects an athlete's anaerobic power output capacity during a single explosive effort?
- VO2max
- Lactate threshold pace
- Peak power output on a Wingate test (Watts/kg) (Correct answer)
- Fat oxidation rate at 60% VO2max
Correct answer: Peak power output on a Wingate test (Watts/kg)
Peak power on the Wingate anaerobic test represents maximal short-duration power output and reflects phosphocreatine and early glycolytic energy system capacity.
Question 7: During resistance exercise, the primary energy system supporting a 3-set hypertrophy protocol (8–12 reps, 60–75% 1RM, 60-second rest) is:
- Exclusively oxidative phosphorylation
- A combination of phosphocreatine and glycolysis with limited aerobic contribution (Correct answer)
- Beta-oxidation of intramuscular triglycerides
- Gluconeogenesis from amino acids
Correct answer: A combination of phosphocreatine and glycolysis with limited aerobic contribution
The relatively short set duration and incomplete rest recovery characteristic of hypertrophy protocols rely predominantly on PCr resynthesis between sets supplemented by rapid glycolysis during sets.
CSSD Exercise Physiology & Energy Metabolism 5
Which metabolic adaptation MOST distinguishes skeletal muscle of a highly trained endurance athlete compared to an untrained individual?