Hydration in Runners

As the warm weather approaches, we should raise our awareness about the proper hydration techniques that will help us perform at our best, and avoid injury or illness. There are many different factors that come into play with regard to hydration. Most of the factors relate to individual sweat rates. Body size, ambient temperature, length of workout, type and amount of clothing, humidity, air movement, and exercise intensity, are some of the more important ones (Godek, Bartolozzi, Godek, BJSM, 2005). What we need to do is replace our fluid losses adequately, without overhydrating, which can be very dangerous. As most runners are well aware, hyponatremia (low total body sodium), is a problem that can be life threatening, and is caused by overhydration with plain water.

An easy way to estimate one’s sweat rate, is to take weight before and after runs (long training runs and marathons). If one has gained weight, they have overhydrated, and should not drink any more until they have urinated. If one has lost weight, they should try to replace their losses with water, or, a sports drink, if it was an endurance event. Another way to monitor hydration status, roughly, is to use the color of the urine. If urine is pale yellow, one is generally adequately hydrated. If urine is dark yellow, this is an indication of dehydration. On the contrary, clear urine, is a sign of overhydration, and one should stop replacing fluids until urine color returns.

Hydrating before an event is also important. However, one must not overhydrate. Use the above cues to guide whether you are hydrating appropriately. Before the event begins, a moderate amount of fluid should be ingested. This will vary according to body size.

As far as marathon running, or other endurance events, thirst should dictate the amount of fluid ingested, not to exceed 400-800ml per hour. This is especially true for slower runners, who will be out on the course for 4 hours or more. Elite athletes will drink less than this, and will tolerate this well.

Knowing your body and ambient conditions are the most important factors in proper hydration. Short events, in hot temperatures, with increased humidity pose the biggest threat for heat illness and/or dehydration. Also, larger runners that run slow are at increased risk. There is no longer the push to drink as much as possible.

Drinking plain water is still the drink of choice in most situations. For endurance events, one can drink a sports drink, but we still have to be careful of the amount of fluid ingested. These drinks will still cause hyponatremia if ingested in large quantities.