Running Myth 10 – Is Dehydration one of The most Common Complications from Running?


It is important to drink often, even when not thirsty, to avoid hyperthermia* during an endurance activity.


Surprisingly, hyponatremia** is one of the main causes of serious complications in endurance sports. There is no solid scientific evidence suggesting that it is important to drink before feeling thirsty in order to prevent hyperthermia.



In a world where proper hydration is said to cure most – it is valid to point out that hyponatremia is one of the most frequent and serious complications during marathons. Often associated with an excessive intake of water, it is an interesting topic in the endurance sports community. Women tend to be more concerned about rehydrating during longer runs, and, to no surprise, hyponatremia is more common in women.

Again, your body will adapt to everything. When you are used to a smaller intake of water your body will adapt by sweating less and signalling thirst more appropriately. Some elite runners do not drink at all during a longer run or a marathon. Think ancestor out for a full-day run hunting for the fam. That being said, we are far from adapted to that lifestyle today, so please read on…


A general guideline is to drink 150-200 ml of fluid every 15-20 min during an endurance activity that lasts longer than 60 min. However, that is pushing it close to the recommended intake of no more than 800 ml of liquid per hour in order to minimize the risk of hyponatremia. A smarter approach would be to weigh yourself before and after a run to determine fluid requirements. A water loss of 3-4% starts to impair performance. Remember that your fluid loss will vary in different climates, so if you are looking to optimize your fluid intake you need to measure your loss in that specific climate.


  • Do not drink water just because
  • Too much water is as harmful as too little
  • Get to know yourself and your fluid loss to be more accurate!

* Elevated body temperature when the body produces or absorbs more heat than it dissipates.
** A decrease in the level of sodium in the blood – often caused by excessive intake of water. 

Now that is the last Running Myth BLASTED!! @jeanlewispt and I hope that you have picked up some goodies and we are always available for questions!

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References: “New Trends in the Prevention of Running Injuries” – Blaise Dubois BScPT; based on several scientific publications available on demand.

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