Fluid overload is the primary factor leading to hyponatremia, especially in events lasting less than 4 hours. During normal everyday hydration, your body can typically adjust for excessive hydration by increasing urine production. During exercise, however, this physiological mechanism is less effective and you aren’t able to get rid of excess fluid as quickly (ACSM, 2007).
Now, before you get scared of drinking water during a race – dehydration is much more common among athletes than hyponatremia. For example, among Boston Marathon runners from 2001-2008, those ending up in the medical tent were almost 6 times more likely to have dehydration compared to hyponatremia (Siegel et al, 2009). Moderate dehydration can impair aerobic performance by increasing body temperature and heart rate, as well as increasing perceived exertion – aka making the exercise feel more difficult.
However, the medical side effects associated with hyponatremia are much more concerning than mild dehydration. So to help you out, here are a few tips on preventing this condition…
2) Listen to your body. A sweat test provides you with a great plan going into training/races in terms of how much fluid to carry and a general idea of how much to drink – but above all, follow your body’s signals for thirst/overdrinking. If you’re feeling thirsty or have dry mouth, drink something. If you’re feeling nauseous or have a sloshing in the stomach, cut back a bit.
3) Remember electrolytes. In events over 4 hours, fluid overload is still a primary cause but a lack of sodium intake can also play a role (Montain et al, 2006). This is especially true on hot & humid days. Be sure that your beverage of choice contains adequate sodium. If it doesn’t, you can easily adjust by adding a pinch of salt or an electrolyte fizzy tab.
4) Skip the NSAIDs. Non-steroidal anti-inflammatory drugs – or NSAIDs – like Aleve, Ibuprofin, or Motrin have been associated with an increased risk of hyponatremia during exercise (Wharam et al, 2006). Some athletes unknowingly pop these pills in advance of a long race because they think it will ward off pain/cramps, but this is a dangerous strategy. NSAIDs affect renal function and water/sodium balance, which can play a role in hyponatremia development.
5) When in doubt, get help. If you are experiencing nausea, vomiting, and disorientation on the course during a race, you may want to ask for a medic in case of hyponatremia. Sometimes nausea and vomiting can occur for other reasons – like trying a new food or drink on the course – but if you feel like something just isn’t right with your body, ask for help.