Exercise-associated hyponatremia is defined by a serum sodium concentration less than what value during or within 24 hours of physical activity?

Exercise-associated hyponatremia is defined by a serum sodium concentration less than what value during or within 24 hours of physical activity?

• A. 135 mmol/L
• B. 130 mmol/L
• C. 125 mmol/L
• D. 140 mmol/L

Answer: (A)

The key idea here is that hyponatremia means the blood sodium level is below the normal lower limit. For exercise-associated hyponatremia, the concern is that this drop occurs during or within 24 hours after physical activity. The standard cutoff used to define this condition is the lower limit of the normal sodium range, which is about 135 mmol/L. So “less than 135” describes the threshold at which hyponatremia is defined in the context of exercise. Values at or above that are not hyponatremic, while lower values indicate increasing severity. In the context of the question, recognizing that 135 mmol/L marks the boundary is why this choice is the best answer.

The key idea here is that hyponatremia means the blood sodium level is below the normal lower limit. For exercise-associated hyponatremia, the concern is that this drop occurs during or within 24 hours after physical activity. The standard cutoff used to define this condition is the lower limit of the normal sodium range, which is about 135 mmol/L. So “less than 135” describes the threshold at which hyponatremia is defined in the context of exercise. Values at or above that are not hyponatremic, while lower values indicate increasing severity. In the context of the question, recognizing that 135 mmol/L marks the boundary is why this choice is the best answer.