Cause 9. Prolonged Exercise: The Unexpected Athletic Route to Hyponatremia
Prolonged exercise, particularly endurance sports like marathons or triathlons, can surprisingly lead to hyponatremia. This seems counterintuitive, as we often associate exercise with health and wellbeing, but intense, prolonged exercise can stress the body in ways that disrupt sodium balance.
One of the primary reasons for exercise-induced hyponatremia is excessive fluid intake. During prolonged exercise, athletes often drink large amounts of water to prevent dehydration. However, drinking too much water can lead to an overhydration condition called water intoxication, which can dilute the sodium in the bloodstream, leading to hyponatremia.
Sweating also plays a role. When we exercise, we sweat, and sweat contains sodium. If an athlete sweats profusely over a long period and replaces the lost fluid with water but not the lost sodium, hyponatremia can occur.
Moreover, prolonged exercise can stimulate the release of ADH. This hormone, as we’ve already discussed, causes the kidneys to retain water, which can dilute the sodium in the blood. This effect can be exacerbated if the athlete is also drinking excessive amounts of water.(9)
