CSSD Exercise Physiology & Energy Metabolism 4 — Questions and Answers
Question 1: What is the approximate ATP yield from the complete oxidation of one mole of palmitate (16-carbon saturated fatty acid)?
- 38 ATP
- 96 ATP
- 129 ATP (Correct answer)
- 56 ATP
Correct answer: 129 ATP
Palmitate oxidation yields approximately 129 ATP through combined beta-oxidation (producing NADH and FADH2) and subsequent oxidative phosphorylation of resulting acetyl-CoA in the TCA cycle.
Question 2: An athlete complains of 'hitting the wall' at mile 20 of a marathon. This phenomenon is primarily attributed to:
- Dehydration exceeding 5% body weight
- Near-depletion of liver and muscle glycogen stores (Correct answer)
- Excessive ketone body production causing acidosis
- Lactic acid accumulation in slow-twitch fibers
Correct answer: Near-depletion of liver and muscle glycogen stores
The 'wall' corresponds to glycogen depletion forcing greater reliance on fat oxidation, which cannot sustain race pace, resulting in a dramatic reduction in running speed.
Question 3: Which statement BEST describes muscle fiber recruitment during progressive increases in exercise intensity?
- Type II fibers are recruited first to maximize power output
- Type I fibers are recruited first, with Type IIa and IIx added as intensity increases (size principle) (Correct answer)
- All fiber types are recruited simultaneously regardless of intensity
- Type IIx fibers are exclusively used at submaximal intensities
Correct answer: Type I fibers are recruited first, with Type IIa and IIx added as intensity increases (size principle)
Henneman's size principle dictates that smaller, fatigue-resistant Type I motor units are recruited first, with larger Type II units added as force demands increase.
Question 4: During prolonged exercise in the heat, which combination of stressors MOST compromises muscle glycogen sparing?
- Alkalosis and hyperinsulinemia
- Hyperthermia and dehydration (Correct answer)
- Hyperoxia and low ambient temperature
- Caffeine ingestion and altitude
Correct answer: Hyperthermia and dehydration
Hyperthermia accelerates glycogenolysis and dehydration increases circulating catecholamines and reduces hepatic glucose output, together accelerating glycogen depletion.
Question 5: What is the primary nutritional strategy to maximize muscle glycogen supercompensation before an endurance event?
- High-fat diet for 7 days followed by one day of carbohydrate loading
- 3–4 days of high carbohydrate intake (8–12 g/kg/day) combined with exercise taper (Correct answer)
- Fasting for 24 hours to upregulate GLUT-4 expression
- Protein loading at 3 g/kg/day with moderate carbohydrate intake
Correct answer: 3–4 days of high carbohydrate intake (8–12 g/kg/day) combined with exercise taper
Current evidence supports 3–4 days of high carbohydrate intake (8–12 g/kg/day) paired with exercise tapering to maximize glycogen stores prior to competition.
Question 6: The lactate threshold (LT1) is physiologically defined as the exercise intensity at which:
- Blood lactate exceeds 4 mmol/L
- Lactate production first exceeds lactate clearance, causing a sustained rise above resting levels (Correct answer)
- VO2max is reached
- Respiratory exchange ratio equals 1.0
Correct answer: Lactate production first exceeds lactate clearance, causing a sustained rise above resting levels
LT1 marks the intensity where lactate production begins to outpace clearance, resulting in the first sustained elevation above baseline (~1–2 mmol/L).
Question 7: A sports dietitian notes that a cyclist's fat max (FATmax) occurs at 55% VO2max. How should this information guide fueling recommendations?
- Recommend fat-only fueling for all training below 55% VO2max
- Use this intensity as the upper anchor for low-carbohydrate recovery rides and fat-adaptation training blocks (Correct answer)
- Advise carbohydrate loading before every session above 55% VO2max regardless of duration
- Ignore FATmax because it has no practical relevance to performance nutrition
Correct answer: Use this intensity as the upper anchor for low-carbohydrate recovery rides and fat-adaptation training blocks
FATmax identifies the optimal intensity for maximal fat oxidation, informing periodized fueling strategies where lower-carbohydrate availability during recovery or base rides can enhance fat-burning adaptations.
CSSD Exercise Physiology & Energy Metabolism 4
What is the approximate ATP yield from the complete oxidation of one mole of palmitate (16-carbon saturated fatty acid)?