Chapter 23 — Self-Check Quiz

20 questions. Answers with explanations at the end. Aim for 16+.

Questions

1. Total glycogen stores in a trained athlete are approximately:

• a) 100–150 g
• b) 400–500 g (~1,600–2,000 kcal)
• c) 1,500 g
• d) Unlimited

2. The top of §23.1's hierarchy is:

• a) Supplements
• b) Adequate energy availability
• c) Protein timing
• d) Hydration

3. Energy availability is calculated as:

• a) Energy intake ÷ body mass
• b) (Energy intake − exercise energy expenditure) ÷ fat-free mass
• c) Energy intake − total daily expenditure
• d) Calories burned per session

4. In RED-S, performance decline is:

• a) The first sign to appear
• b) One of the last things to go, after bone, endocrine and immune effects
• c) Not a feature
• d) Only seen in women

5. An endurance athlete training 1–3 hours daily should aim for approximately:

• a) 2–3 g/kg carbohydrate
• b) 6–10 g/kg carbohydrate
• c) 15 g/kg carbohydrate
• d) Carbohydrate is not important

6. Muscle glycogen cannot be exported to the bloodstream because muscle lacks:

• a) Glycogen synthase
• b) Glucose-6-phosphatase
• c) Hexokinase
• d) Insulin receptors

7. "The bonk" — lightheadedness and confusion — primarily reflects depletion of:

• a) Muscle glycogen
• b) Liver glycogen and falling blood glucose
• c) Intramuscular triglyceride
• d) Creatine phosphate

8. The ~60 g/hour ceiling on carbohydrate absorption exists because:

• a) The stomach cannot empty faster
• b) The SGLT1 glucose transporter saturates
• c) Insulin cannot respond fast enough
• d) The liver limits it

9. Glucose-plus-fructose mixtures allow higher oxidation rates because fructose uses:

• a) The same transporter, more efficiently
• b) GLUT5, a separate transporter
• c) Passive diffusion only
• d) The lymphatic system

10. A carbohydrate mouth rinse improves performance in ~1 hour efforts via:

• a) Rapid absorption providing fuel
• b) Oral receptors signalling centrally, not by supplying fuel
• c) Improved hydration
• d) It does not work

11. The "30–60 minute anabolic window" is best described as:

• a) Well supported
• b) Overstated — the window is hours, and total daily protein and distribution matter more
• c) Irrelevant in every circumstance
• d) Applicable only to endurance athletes

12. The race-walker study found that LCHF diets:

• a) Improved race performance
• b) Increased fat oxidation and impaired exercise economy, without improving performance
• c) Had no metabolic effects
• d) Were impossible to adhere to

13. Fat oxidation is a performance penalty at competitive intensities because:

• a) Fat cannot be stored in muscle
• b) It requires more oxygen per unit ATP, and oxygen delivery is the constraint
• c) It produces lactate
• d) It depletes glycogen faster

14. Programmed over-drinking during endurance events risks:

• a) Nothing
• b) Exercise-associated hyponatremia, which has killed athletes
• c) Dehydration
• d) Hyperglycaemia

15. Sweat sodium concentration between individuals varies by roughly:

• a) 10%
• b) Tenfold (~200–2,000 mg/L)
• c) It is identical in everyone
• d) Twofold

16. Beta-alanine and sodium bicarbonate are most useful for efforts lasting:

• a) Under 10 seconds
• b) Roughly 1–10 minutes
• c) Over 3 hours
• d) Any duration equally

17. Nitrate (beetroot juice) shows effects that are:

• a) Largest in elite endurance athletes
• b) Smaller or absent in highly trained endurance athletes — the inverse of who buys it
• c) Identical across training status
• d) Only present in team sports

18. For a recreational athlete training 4 hours/week, in-session carbohydrate is:

• a) Essential in every session
• b) Almost never needed under 75 minutes
• c) Required above 30 minutes
• d) Needed only in winter

19. Under anti-doping strict liability:

• a) Intent is a valid defence
• b) You are responsible for what is in your body regardless of how it got there
• c) Contamination voids a positive test
• d) Only prescription drugs are covered

20. The five supplements with good evidence are worth approximately:

• a) 15–20% improvement
• b) 1–3%, larger in less-trained people and smaller in elite ones
• c) 50% improvement
• d) No measurable effect

Answers

1. b) 400–500 g. Muscle ~300–400 g plus liver ~80–100 g, ≈1,600–2,000 kcal. ⚠️ A marathon for a ~55 kg runner costs ~2,400–2,800 kcal — the tank holds less than the race costs. That's the whole of "the wall," and it's arithmetic, not willpower. §23 hook.

2. b) Adequate energy availability. ⚠️ Everything else is built on it — get it wrong and nothing above it matters. And attention flows almost exactly in reverse: supplements and timing get the podcasts; rows 1 and 2 decide the race. §23.1.

3. b) (Intake − exercise expenditure) ÷ fat-free mass. ⚠️ It's the energy left for everything that isn't the training session — hormones, bone, immune function, menstrual cycling, repair. ~45 kcal/kg FFM supports full function; below ~30 is where consequences are consistently observed. §23.2.

4. b) One of the last things to go. ⚠️ By the time the times slow, bone, hormones and immune function have been in deficit for months — which is why "my times are fine" is not reassurance, and why §23.2's warning-sign list matters more than performance data. §23.2, Ch 21 CS2.

5. b) 6–10 g/kg. ⚠️ And note the boundary: this does NOT mean everyone needs a high-carbohydrate diet. The dose is a function of the load — a person training three hours a week doesn't need 8 g/kg. "Carbs are good for athletes" isn't the answer; the table is. §23.3.

6. b) Glucose-6-phosphatase. ⚠️ So muscle glycogen fuels only the muscle storing it and can never be shared or exported. Liver has the enzyme, which is exactly why liver glycogen's job is maintaining blood glucose. §23.3.

7. b) Liver glycogen and falling blood glucose. ⚠️ Different tank, different symptom. "The wall" is a muscle glycogen event — legs fine, pace gone. "The bonk" is a blood glucose event — lightheaded, confused, can't do arithmetic. In-race carbohydrate addresses both. §23.3.

8. b) SGLT1 saturates. At roughly 60 g/hour, regardless of how much more you drink. §23.5.

9. b) GLUT5, a separate transporter. ⚠️ Recruiting both pathways permits oxidation rates well above 60 g/h and causes less GI distress — because unabsorbed carbohydrate sitting in the gut is what causes the distress. This is Chapter 15's ORS co-transport logic, deliberately exploited a second time. §23.5.

10. b) Oral receptors signalling centrally. ⚠️ Not by supplying fuel — the effect appears too fast for that, and rinsing-and-spitting works. A genuinely odd, replicated finding. §23.5.

11. b) Overstated — hours, not minutes. ⚠️ Muscle stays sensitized to protein feeding for at least 24 hours after resistance exercise, and total daily protein plus distribution matter considerably more. 🟢 the distribution is real: ~0.3 g/kg across 3–5 meals beats the same total in one or two. (Exception: fasted training, or another session within ~8 hours — that's a refuelling problem.) §23.6.

12. b) Increased fat oxidation, impaired economy, no performance improvement. ⚠️ The high-carbohydrate and periodized groups improved race performance; the LCHF group did not — despite the metabolic adaptation occurring exactly as predicted. §23.7.

13. b) More oxygen per unit ATP. ⚠️ At submaximal intensities that's irrelevant — there's oxygen to spare. At competitive intensities, where oxygen delivery is the constraint, a less oxygen-efficient fuel is a direct penalty. "Fat-adapted" is real, and it is a trade, not an upgrade. §23.7.

14. b) Exercise-associated hyponatremia. ⚠️ Chapter 15's Priya Achterberg. Chapter 15 §15.3's asymmetry is why drink-to-thirst replaced schedules: under-drinking has an alarm, over-drinking doesn't. §23.8.

15. b) Tenfold. Roughly 200–2,000 mg/L, ⚠️ and largely a fixed personal characteristic rather than something you train. Which is why blanket electrolyte recommendations fail and why the free indicators — salt crusting, stinging eyes — are worth knowing. §23.8.

16. b) Roughly 1–10 minutes. ⚠️ Both work on buffering capacity, so they share a duration window. Neither helps a marathon. Both can help an 800 m, a 2 km row, or a hard interval set. §23.9.

17. b) Smaller or absent in highly trained endurance athletes. ⚠️ The inverse of who buys it — it's most useful for recreational and moderately-trained people. §23.9.

18. b) Almost never needed under 75 minutes. ⚠️ And the calories in a sports drink taken during a 45-minute run frequently exceed those burned in the last 20 minutes of it. The most common error in recreational sport is importing elite fuelling into a non-elite training load — which reliably produces weight gain that then gets blamed on the training. §23.12.

19. b) You are responsible regardless of how it got there. ⚠️ "It was contaminated" is not a defence that returns your result. Which is why only batch-certified products (NSF Certified for Sport, Informed Sport) are usable, why proprietary blends are the worst risk, and why you keep the tub. The five supplements are worth 1–3%; a sanction costs years — the arithmetic is not close. §23.10.

20. b) 1–3%. ⚠️ For an elite athlete that's a final versus a heat. For everyone else it's smaller than the variation between two Tuesdays — and the recreational athlete buying the elite stack is buying the smallest available intervention while leaving rows 1–4 untouched. §23.9.

Scoring

Three items worth checking regardless of score.

Question 2. ⚠️ If the hierarchy didn't land, you'll optimize row 7 and wonder why nothing changes — which is the most common outcome in recreational sport.

Question 4. ⚠️ Performance declining last is why athletes present late. If you take one thing from this chapter into a coaching or clinical setting, take this.

Question 18. ⚠️ Most readers are not elite. The recreational correction in §23.12 is the section that applies to you.