Two key considerations for electrolyte supplementation during prolonged exercise.

• A. Sodium is not important; focus on potassium.
• B. Calcium should be the primary electrolyte during prolonged exercise.
• C. Sodium is crucial to prevent hyponatremia; tailor intake to duration, sweat rate, and GI tolerance.
• D. Magnesium is the only electrolyte needed.

Answer: (C)

During long-duration exercise, sodium replacement is essential because sodium helps maintain blood volume and plasma osmolality, supporting fluid balance and muscle-nerve function. The key is to tailor how much sodium you take in to how long you’re exercising, how much you sweat (which varies with temperature, humidity, and effort), and what your gut can tolerate without causing GI distress. If you replace sodium in line with these factors, you reduce the risk of hyponatremia, a dangerous drop in blood sodium that can impair performance and safety. While other electrolytes like potassium, calcium, and magnesium matter for muscle function, sodium is the main concern for preventing hyponatremia and preserving volume during extended activity, so focus your plan on adjusting sodium intake to duration, sweat rate, and GI tolerance.