CSCS CSCS: Bioenergetics of Exercise & Training 4 — Questions and Answers
Question 1: Which of the following training adaptations most directly increases the lactate threshold as a percentage of VO2max?
- Increased fast-twitch fiber recruitment
- Greater mitochondrial density and oxidative enzyme activity in slow-twitch fibers (Correct answer)
- Increased anaerobic enzyme concentrations
- Higher resting glycogen stores
Correct answer: Greater mitochondrial density and oxidative enzyme activity in slow-twitch fibers
Greater mitochondrial density and oxidative capacity allow muscle to clear lactate more efficiently and rely less on glycolysis at a given intensity.
Question 2: Approximately how many ATP molecules are produced per mole of palmitate (a 16-carbon fatty acid) during complete beta-oxidation and Krebs cycle oxidation?
- 38
- 96
- 129 (Correct answer)
- 180
Correct answer: 129
Complete oxidation of palmitate yields approximately 129 ATP through combined beta-oxidation, Krebs cycle, and oxidative phosphorylation.
Question 3: What is the primary regulatory role of AMP in skeletal muscle bioenergetics?
- AMP inhibits glycolysis to preserve glucose
- AMP stimulates phosphofructokinase and AMP kinase, signaling low energy status (Correct answer)
- AMP activates the electron transport chain directly
- AMP inhibits mitochondrial respiration
Correct answer: AMP stimulates phosphofructokinase and AMP kinase, signaling low energy status
Rising AMP signals energy deficit, activating PFK (glycolysis) and AMPK (promoting fat oxidation and mitochondrial biogenesis) to restore ATP.
Question 4: Which energy system is MOST responsible for ATP production during a 400-meter race run at maximal effort (~45–60 seconds)?
- Phosphagen system exclusively
- Glycolytic system predominantly, with phosphagen contribution early (Correct answer)
- Oxidative system predominantly
- Equal contribution from all three systems
Correct answer: Glycolytic system predominantly, with phosphagen contribution early
The 400m race relies primarily on anaerobic glycolysis for most of its duration, with the phosphagen system dominant in the first seconds and some aerobic contribution.
Question 5: Ketone bodies (acetoacetate and beta-hydroxybutyrate) become a significant fuel source primarily during:
- High-intensity sprinting
- Prolonged low-carbohydrate states such as fasting or very-low-carb diets (Correct answer)
- Post-exercise recovery periods of less than one hour
- The immediate onset of moderate-intensity exercise
Correct answer: Prolonged low-carbohydrate states such as fasting or very-low-carb diets
Ketone bodies are produced by the liver from fatty acids during prolonged carbohydrate restriction or fasting and serve as an alternative fuel for brain and muscle.
Question 6: Which statement best describes excess post-exercise oxygen consumption (EPOC)?
- EPOC is exclusively caused by lactate removal from the blood
- EPOC represents elevated oxygen consumption after exercise used to restore physiological homeostasis (Correct answer)
- EPOC duration is the same regardless of exercise intensity
- EPOC only occurs after anaerobic exercise
Correct answer: EPOC represents elevated oxygen consumption after exercise used to restore physiological homeostasis
EPOC reflects elevated VO2 after exercise used for PCr resynthesis, lactate clearance, elevated temperature/hormones, and other recovery processes.
Question 7: A runner competing in a 10 km race primarily uses which combination of energy systems?
- Phosphagen system and glycolysis equally
- Oxidative system predominantly with glycolytic contributions at higher intensities (Correct answer)
- Glycolytic system exclusively
- Phosphagen system only during the final sprint
Correct answer: Oxidative system predominantly with glycolytic contributions at higher intensities
A 10 km race lasting ~28–45 minutes is primarily aerobic (oxidative), though anaerobic glycolysis contributes during surges and the finishing sprint.
CSCS CSCS: Bioenergetics of Exercise & Training 4
Which of the following training adaptations most directly increases the lactate threshold as a percentage of VO2max?