Water for the Long Run

By: Douglas R. Dirschl, MD, Orthopaedic Surgeon

What a winter, right? Now that the weather is warming (finally!) and training season for endurance events is ramping up for many of us, this is the perfect time to talk about hydration for endurance training. Fluids are paramount, as both chronic and acute dehydration directly affect performance. The most common method for estimating hydration status is via measuring body weight, although most athletes can learn to estimate their hydration status just from how they feel. Even a small change in your body’s hydration status (1 to 2% of body weight) can increase your sense of effort, cause nausea, decrease appetite, lead to irritability, and reduce performance. The vast majority of athletes are at least slightly dehydrated day to day and during training activities. So, what should we do about this?

Staying hydrated throughout the day is one’s best defense against dehydration. While recommendations for how much water to drink vary, one simple estimate is that one should drink as many ounces of water each day as one’s weight in kilograms. So, if you weigh 150 pounds (about 70 kg), you should drink about 70 ounces of water each day – and this is at baseline and does not include the additional fluids you require to replace fluid losses from training. Unfortunately, coffee, tea, and soda do not count (since the caffeine in these drinks can be dehydrating) and water with electrolytes is best. Finally, for optimal effect, you should spread the fluid consumption throughout the day – it’s not a good idea to drink a large amount of water to “catch up” just prior to your training run, as your stomach will be full of fluid it can’t absorb very well (your entire GI tract slows down during intense physical activity).

What about fluids during training? Anytime you’re training for more than 60 minutes, hydrating during training is recommended. If you are training for 60 minutes or less, you can likely get by with no hydration as long as you are well-hydrated at baseline. In high heat or humidity, you must hydrate while training—no matter the duration. When you sweat, you lose both free fluids and electrolytes. Consuming water during the training will replace the fluids, but not the electrolytes. This is the reason that most endurance athletes consume an electrolyte beverage during training. Over-hydration can occur, but it is really too little electrolytes compared to the amount of fluid intake. It’s not the fluid that is the problem, but the lack of electrolytes.

Please keep in mind that many electrolyte beverages also have calories in them. These beverages are intended to provide an athlete with ‘full nutrition’ during their training activity. While this may be perfect for you, it can also lead to two problems. First, if weight loss is one of your main training goals, you may not desire the added calories in the ‘full nutrition’ beverages. If this is you, you might consider adding electrolyte tablets (NUUN, Hammer Fizz, Camelback elixir, etc.) to your water so that you get electrolytes without the calories. Second, many athletes find that some full nutrition beverages upset their stomach during training; unfortunately, trial and error is the only way to assess what beverage will be best tolerated by your stomach.

If you want to most accurately estimate your fluid needs during training, you should weigh yourself immediately before and after training, in the buff or in only underwear if possible. Weighing yourself in your running clothes can lead to inaccuracies because your clothing can absorb significant amounts of sweat, leaving them heavier after the run. Calculate every pound lost as 16 fluid ounces. Then, add in any fluid you consumed during training. This is the amount of fluid you lost during that specific exercise session. Plan to hydrate proactively for the next one.

Unless you have a support crew following you on your training runs, the only way for you to hydrate during a run is to carry your fluids yourself. While this seems like a burden, you will get used to it after a while. For small amounts of fluid, carrying a water bottle is pretty simple (check out one of the runners in the book “Born to Run”, who believes carrying the bottle in your armpit is the most efficient way to do so – seriously!) For larger amounts of fluid, there are a variety of belt and backpack devices that can assist you in carrying the fluid and electrolytes you need to replace while training. (Maybe it looks weird to run with a Camelback on, but I do it regularly; meeting my fluid and electrolyte needs trumps looking weird – and I have much better training runs when I hydrate properly.)

So, think about your fluid and electrolyte needs during training. Hydrate appropriately every day, remember to replace electrolytes as well as free fluids, and consider weighing yourself before and after training. Most importantly, learn to listen to your body so you can learn how you feel when you are getting dehydrated. Finally, don’t be afraid to experiment a bit with various amounts and types of fluids and electrolytes during training until you find just the right recipe for you to feel better and train better for your next endurance event.