CSSD Macronutrient Timing 3 — Questions and Answers
Question 1: Which branched-chain amino acid acts as the primary leucine-sensing trigger for mTORC1 activation and subsequent muscle protein synthesis?
- Isoleucine
- Valine
- Leucine (Correct answer)
- Lysine
Correct answer: Leucine
Leucine is the key anabolic trigger that activates the mTORC1 signaling pathway, making it the most critical BCAA for initiating muscle protein synthesis.
Question 2: A cyclist completing a 3-hour race consumes carbohydrate only in the final 30 minutes. What is the primary consequence of this poorly timed intake?
- Hyperinsulinemia causing early fatigue
- Suboptimal glycogen sparing in the first two hours (Correct answer)
- Reactive hypoglycemia immediately post-race
- Excessive fat oxidation reducing power output
Correct answer: Suboptimal glycogen sparing in the first two hours
Without early carbohydrate supplementation, muscle glycogen is depleted faster in the first two hours, impairing performance well before the late intake can counteract it.
Question 3: In the context of pre-exercise nutrition, why is a low-glycemic index meal preferred 3–4 hours before competition compared to a high-GI meal?
- It provides more total calories
- It sustains blood glucose and avoids pre-exercise hyperinsulinemia (Correct answer)
- It delays gastric emptying to prevent GI issues
- It increases fat availability for aerobic metabolism
Correct answer: It sustains blood glucose and avoids pre-exercise hyperinsulinemia
A low-GI pre-exercise meal maintains steady blood glucose without an insulin spike that could suppress fat mobilization and cause rebound hypoglycemia at exercise onset.
Question 4: Which protein source has the highest leucine content per 100g of protein, making it particularly effective for post-exercise MPS?
- Soy protein isolate
- Casein
- Whey protein (Correct answer)
- Egg white protein
Correct answer: Whey protein
Whey protein contains approximately 10–11% leucine by amino acid content, the highest of commonly used protein supplements, supporting rapid and robust MPS activation.
Question 5: Carbohydrate ingestion immediately post-resistance training primarily benefits which physiological process?
- Increasing testosterone levels
- Blunting cortisol and replenishing muscle glycogen (Correct answer)
- Enhancing fat oxidation during recovery
- Increasing growth hormone secretion
Correct answer: Blunting cortisol and replenishing muscle glycogen
Post-resistance exercise carbohydrates blunt cortisol-induced catabolism and replenish muscle glycogen, supporting recovery even though glycogen use during resistance training is modest.
Question 6: An athlete undergoing two-a-day training sessions should prioritize carbohydrate intake within what timeframe after the first session to maximize glycogen resynthesis before the second session?
- Within 15 minutes (Correct answer)
- Within 30 minutes
- Within 60 minutes
- Within 2 hours
Correct answer: Within 15 minutes
Glycogen synthase activity is highest in the first 15–30 minutes post-exercise; consuming carbohydrates immediately (within 15–30 minutes) maximizes resynthesis rates when recovery windows are short.
Question 7: Which condition most significantly impairs the anabolic response to post-exercise protein intake in an endurance athlete?
- Consuming protein within 30 minutes of finishing
- Training in a carbohydrate-depleted state without subsequent carb intake (Correct answer)
- Using whey rather than casein protein post-exercise
- Consuming protein with a high-fat meal
Correct answer: Training in a carbohydrate-depleted state without subsequent carb intake
Severe glycogen depletion without carbohydrate recovery diverts amino acids toward gluconeogenesis rather than MPS, blunting the anabolic response to protein.
CSSD Macronutrient Timing 3
Which branched-chain amino acid acts as the primary leucine-sensing trigger for mTORC1 activation and subsequent muscle protein synthesis?