CSCS CSCS: Bioenergetics of Exercise & Training 5 — Questions and Answers
Question 1: Which of the following accurately describes the fate of lactate during low-to-moderate intensity exercise in trained athletes?
- Lactate is exclusively converted to glucose in the liver
- Lactate is oxidized directly as a fuel by heart, slow-twitch fibers, and liver (Correct answer)
- Lactate is converted to fatty acids and stored
- Lactate accumulates linearly with exercise intensity
Correct answer: Lactate is oxidized directly as a fuel by heart, slow-twitch fibers, and liver
Trained muscles and the heart can oxidize lactate directly via the intracellular lactate shuttle, using it as an aerobic substrate.
Question 2: How does carnitine facilitate fat metabolism in skeletal muscle?
- Carnitine activates fatty acids in the cytoplasm for beta-oxidation
- Carnitine transports activated fatty acids (acyl-CoA) across the inner mitochondrial membrane (Correct answer)
- Carnitine is the enzyme that catalyzes beta-oxidation
- Carnitine inhibits malonyl-CoA to increase fat transport
Correct answer: Carnitine transports activated fatty acids (acyl-CoA) across the inner mitochondrial membrane
Carnitine acyltransferase enzymes use carnitine to shuttle long-chain acyl-CoA molecules across the inner mitochondrial membrane for beta-oxidation.
Question 3: Which of the following best explains the 'slow component' of VO2 kinetics observed during heavy exercise?
- Delayed activation of the phosphagen system
- Progressive recruitment of less efficient fast-twitch fibers as fatigue sets in (Correct answer)
- Decreased cardiac output over time
- Reduced mitochondrial oxygen affinity at high work rates
Correct answer: Progressive recruitment of less efficient fast-twitch fibers as fatigue sets in
The VO2 slow component arises from progressive recruitment of less efficient type II fibers, increasing the oxygen cost of maintaining a given power output.
Question 4: Training-induced mitochondrial biogenesis is primarily regulated by which signaling molecule?
- mTOR
- PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) (Correct answer)
- IGF-1
- Myostatin
Correct answer: PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha)
PGC-1α is the master regulator of mitochondrial biogenesis, activated by endurance training signals such as AMPK and calcium-calmodulin kinase.
Question 5: During the transition from rest to moderate-intensity exercise, what is the PRIMARY source of ATP during the first 1–2 seconds before other systems ramp up?
- Stored ATP in the muscle cell (Correct answer)
- Glycolysis
- Oxidative phosphorylation
- Beta-oxidation
Correct answer: Stored ATP in the muscle cell
The muscle cell has a small but immediately available pool of free ATP that is the very first energy source used at exercise onset.
Question 6: Which training intervention is MOST effective for maximally increasing muscle glycolytic enzyme (e.g., PFK, LDH) activity?
- Long slow distance running at 60% VO2max
- High-intensity interval training (HIIT) or sprint training (Correct answer)
- Low-load high-repetition resistance training
- Yoga and flexibility training
Correct answer: High-intensity interval training (HIIT) or sprint training
High-intensity interval and sprint training create the greatest upregulation of glycolytic enzymes due to repeated demand on anaerobic glycolysis.
Question 7: An athlete's RER value measured at rest is 0.78. This indicates that approximately what percentage of energy is coming from fat?
- 0%
- 33%
- 67% (Correct answer)
- 100%
Correct answer: 67%
An RER of 0.78 corresponds to approximately 67% fat and 33% carbohydrate contribution based on non-protein RER tables.
CSCS CSCS: Bioenergetics of Exercise & Training 5
Which of the following accurately describes the fate of lactate during low-to-moderate intensity exercise in trained athletes?