CSN Hydration & Fluid Balance 1 — Questions and Answers
Question 1: Which electrolyte is lost in the greatest concentration through sweat and must be prioritized in a sports hydration plan?
- Potassium
- Sodium (Correct answer)
- Magnesium
- Calcium
Correct answer: Sodium
Sodium is the predominant electrolyte in sweat, with losses ranging from 460–1840 mg per liter, making it the primary electrolyte to replace during and after exercise.
Question 2: A urine specific gravity of 1.020–1.030 in an athlete prior to competition most likely indicates:
- Optimal hydration
- Mild dehydration (Correct answer)
- Severe dehydration
- Overhydration
Correct answer: Mild dehydration
A urine specific gravity above 1.020 indicates the kidneys are concentrating urine due to inadequate fluid intake, reflecting mild to moderate dehydration.
Question 3: At what level of body weight loss from sweat does aerobic exercise performance begin to measurably decline?
- 1%
- 2% (Correct answer)
- 4%
- 6%
Correct answer: 2%
Research consistently shows that a body weight loss of approximately 2% from sweat leads to measurable decreases in aerobic performance, thermoregulation, and cognitive function.
Question 4: Which of the following best describes the condition of hyponatremia in athletes?
- Elevated blood sodium due to excessive salt intake
- Low blood sodium typically caused by excessive plain water intake during prolonged exercise (Correct answer)
- Sodium depletion from insufficient dietary salt
- An electrolyte imbalance caused by potassium excess
Correct answer: Low blood sodium typically caused by excessive plain water intake during prolonged exercise
Exercise-associated hyponatremia occurs when serum sodium drops below 135 mEq/L, most commonly from drinking excessive amounts of plain water that dilute blood sodium levels.
Question 5: According to ACSM guidelines, how much fluid should an athlete consume in the 2–4 hours before exercise to ensure pre-hydration?
- 2–3 oz per pound of body weight
- 5–7 mL per kg of body weight (Correct answer)
- 500–1,000 mL as a flat dose
- 16 oz immediately before activity
Correct answer: 5–7 mL per kg of body weight
ACSM recommends consuming 5–7 mL of fluid per kg of body weight in the 2–4 hours before exercise to achieve adequate pre-exercise hydration.
Question 6: An athlete's sweat rate is best estimated using which method?
- Counting perceived thirst episodes per hour
- Measuring body weight before and after exercise accounting for fluid intake and urine output (Correct answer)
- Calculating total fluid consumed during exercise divided by exercise time
- Using heart rate variability as a proxy for fluid loss
Correct answer: Measuring body weight before and after exercise accounting for fluid intake and urine output
Sweat rate is calculated by comparing pre- and post-exercise body weight, adding fluid consumed, and subtracting any urine output, then dividing by exercise duration.
Question 7: Which urine color on the urine color chart (1–8 scale) is generally considered to indicate adequate hydration for athletes?
- Color 1 (nearly clear)
- Colors 1–3 (pale yellow to light yellow) (Correct answer)
- Colors 4–5 (yellow to dark yellow)
- Colors 6–8 (amber to brown)
Correct answer: Colors 1–3 (pale yellow to light yellow)
A urine color of 1–3 (pale to light yellow) is the target range for adequate hydration; colors above 3 typically suggest increasing dehydration.
CSN Hydration & Fluid Balance 1
Which electrolyte is lost in the greatest concentration through sweat and must be prioritized in a sports hydration plan?