CSN Hydration & Fluid Balance 2 — Questions and Answers
Question 1: During prolonged endurance exercise lasting more than 60 minutes, what is the general fluid intake guideline to prevent significant dehydration?
- Drink only when thirsty, regardless of intake volume
- Consume 400–800 mL (14–27 oz) of fluid per hour (Correct answer)
- Drink 1 liter every 30 minutes
- Avoid fluid intake to minimize GI distress
Correct answer: Consume 400–800 mL (14–27 oz) of fluid per hour
The ACSM recommends consuming 400–800 mL per hour during prolonged exercise to replace sweat losses without risking overhydration or hyponatremia.
Question 2: What is the primary function of including carbohydrates in a sports drink during exercise lasting more than 60–90 minutes?
- To increase urine output and promote detoxification
- To maintain blood glucose, spare glycogen, and support fluid absorption in the gut (Correct answer)
- To increase gastric emptying rate above plain water
- To replace muscle glycogen immediately during exercise
Correct answer: To maintain blood glucose, spare glycogen, and support fluid absorption in the gut
Carbohydrate-electrolyte beverages help sustain blood glucose levels, spare muscle glycogen, and enhance intestinal fluid and electrolyte absorption during prolonged activity.
Question 3: A sports nutritionist recommends a beverage with 6–8% carbohydrate concentration for an endurance athlete. What is the rationale for this specific range?
- Higher concentrations are absorbed faster and provide more energy
- This range optimizes both fluid delivery and carbohydrate oxidation without slowing gastric emptying (Correct answer)
- Below 6% provides insufficient energy for performance
- Above 8% causes hyperglycemia in most athletes
Correct answer: This range optimizes both fluid delivery and carbohydrate oxidation without slowing gastric emptying
A 6–8% carbohydrate concentration balances rapid gastric emptying, optimal intestinal absorption, and adequate carbohydrate delivery to working muscles.
Question 4: Which sign or symptom is most indicative of severe dehydration (>5% body weight loss) in an exercising athlete?
- Slight thirst and darker urine
- Muscle cramps and reduced endurance
- Confusion, dizziness, and inability to continue exercise (Correct answer)
- Mild headache and reduced sweat rate
Correct answer: Confusion, dizziness, and inability to continue exercise
Severe dehydration (>5% body weight loss) produces central nervous system symptoms including confusion, extreme dizziness, and incapacitation, requiring immediate medical attention.
Question 5: Osmolality of a sports drink is most relevant because it affects:
- The flavor intensity and palatability of the beverage
- The rate at which fluid moves from the gut into the bloodstream (Correct answer)
- The total caloric density of the product
- The shelf life and product stability
Correct answer: The rate at which fluid moves from the gut into the bloodstream
Osmolality determines the osmotic gradient across the intestinal wall; hypotonic and isotonic solutions (below ~290 mOsm/kg) are absorbed more rapidly than hypertonic solutions.
Question 6: Post-exercise rehydration is most complete when an athlete consumes approximately how much fluid relative to their sweat losses?
- 50% of body weight lost
- 100% of body weight lost
- 125–150% of body weight lost (Correct answer)
- 200% of body weight lost
Correct answer: 125–150% of body weight lost
Consuming 125–150% of estimated fluid losses accounts for ongoing urinary losses during recovery, ensuring full rehydration within a few hours after exercise.
Question 7: Which mineral co-consumed with water post-exercise is most effective at promoting fluid retention and restoration of plasma volume?
- Magnesium
- Potassium
- Calcium
- Sodium (Correct answer)
Correct answer: Sodium
Sodium is the primary driver of fluid retention after exercise; its osmotic effect reduces urinary output and promotes reabsorption of water in the kidneys to restore plasma volume.
CSN Hydration & Fluid Balance 2
During prolonged endurance exercise lasting more than 60 minutes, what is the general fluid intake guideline to prevent significant dehydration?