Hydration is important for everyone, but especially for runners and triathletes. On an everyday basis, the water you drink moistens tissues (like those of the eyes and mouth), lubricates joints, maintains the correct body temperature, prevents constipation, and more. And during training and events, proper hydration helps reduce the risk of two undesirable situations – dehydration and hyponatremia.
Everyday Hydration – How Much Should You Drink? What Should You Drink?
Before you get into exercise-specific hydration, it’s important to pay attention to your daily needs outside of physical activity. Each day you lose water through breathing, sweating, and using the bathroom, and it’s important to replace these losses.
Properly addressing everyday hydration also helps prepare you for training and races – if you show up to the starting line dehydrated, it’s much more likely that you’ll suffer a dehydration-related drop in performance during your road race or tri.
How much fluid a day? There’s no one perfect answer, and it likely depends on your body composition, but the Institute of Medicine has made the following recommendations:
- Men: 3 liters (about 13 cups) of fluid from beverages
- Women: 2.2 liters (about 9 cups) of fluid from beverages
Water is obviously the preferred choice of fluid here, but you can count other beverages (yes, including a daily cup of coffee) in this count. If you want variety from plain water, try unsweetened teas (I’m a huge fan of tazo passion tea), flavored seltzer water, or fruit-infused waters to mix it up.
Hydration During Exercise – What Should You Drink?
When it comes to hydration during exercise, the choice of fluid depends on how long you’re training. If you’re exercising for less than an hour, plain water is all you need.
If you’re training for over an hour, then you’ll want to choose a drink that contains electrolytes. (You’ll also want a carbohydrate source for fuel for exercise over 60-90 minutes – whether that’s coming from your sports drink or another source like a gu is up to you).
Keep in mind if it’s very hot outside, or if you’re a heavy salt sweater, you may want a drink that provides higher levels of sodium compared to standard sports drinks. {This is very individualized, since different people lose different amounts of salt in sweat.}
Hydration During Exercise – How Much Should You Drink?
Your most important goal with hydration during endurance exercise is to prevent both dehydration and hyponatremia.
Dehydration occurs when you lose too much fluid and aren’t replacing it, and can lead to declining performance and increased risk of heat injury.
Hyponatremia occurs when you take in too much fluid and dilute your blood’s sodium levels. Hyponatremia can cause serious side effects, including nausea, vomiting, and disorientation in mild forms, and life-threatening complications like respiratory arrest, coma, and death in severe cases.
Dehydration is much more common among runners than hyponatremia, but hyponatremia generally presents more serious concerns and complications.
The goal here is balance. Ideally, you want to replace enough fluid so that you only lose about 2-3% of your body weight. You want to avoid losing much more than that, or you start to risk performance impairment.
You also don’t want to gain weight, as this increases your risk of hyponatremia.
For example, let’s say you are a 170 pound athlete. A 2 percent loss in body weight would be the equivalent of losing about 3.5 pounds. During exercise, we would want you to avoid losing much more than 3.5 pounds (risk of dehydration impairing performance) as well as avoid gaining any weight (risk of hyponatremia).
Because of this careful balance, there’s no one “right” amount to drink during exercise. It depends on many factors, including your weight, training level, speed, sweat rate, sweat composition, and more.
Estimating Your Fluid Needs During Runs
The best way to estimate your needs for hydration during exercise is using a combination of two methods:
First, conduct a sweat test during a training session, ideally under the conditions that you expect for race day (so if you expect the race weather to be hot, get out there on a hot day). Weigh yourself before and after training, and be sure you note how much you were drinking during your training session. If you’ve gained weight, you’re likely drinking too much. If you’ve lost more than 2-3% of your body weight, you probably want to drink a bit more. If you’ve lost around 2% of your body weight, you’re likely right on track.
Second, pay attention to your body’s thirst cues. Drinking to thirst is a very successful strategy for many athletes, however I’d disagree with those who say that it is the only strategy anyone ever needs to use. Why? Some people don’t pay attention to their thirst; the aid stations may be spaced at a distance that don’t allow you to drink to your thirst; and older athletes have a decreased thirst mechanism.
For these reasons, I recommend conducting the sweat test to get an estimate of your hydration needs and develop a loose plan for hydrating during exercise. This may indicate that you need to carry a fuel belt, or may guide you towards drinking at certain aid stations.
Then, during the event, you have your plan in place and ready to execute – but you can (and should) defer to your body’s physiologic cues when in question of whether to drink or not. If you feel dry mouth or thirsty, drink. If you feel nauseous or sloshing, slow down the fluid intake.
There you have it – my best advice on hydration for runners and triathletes!
Share with me: Do you get concerned about hydration during exercise? How do you handle hydration on runs or rides?
Chrissy Carroll
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I definitely struggle with drinking enough water while exercising. On the other hand I’m usually pretty good at drinking water throughout the day when I’m not working out.
I’m the opposite – I actually don’t have a huge problem drinking during events and feel like I’m always thirsty while exercising. But I struggle much more with remembering to drink enough on a daily basis.
I struggle with staying hydrated!! I made it one of my goals this year to drink more water pre and post workouts!!
That sounds like an awesome goal for the year!
Great post! I seem to struggle more in the winter with drinking enough!
I have heard half your body weight in OZ is what you should drink. When I follow that I stay well hydrated!
Thanks for the great reminder to drink up!
Glad you found the post helpful! And I think it can be tough in the winter because the heat in the summer might make us feel thirstier.
I always feel like I never drink enough water! I’m ALWAYS thirsty!
I’m the opposite; I don’t feel thirsty that often during the day so I have to remember to drink enough!
Hydration is crucial on a daily basis, especially when working out. Great and useful tips, Chrissy!
Yes, definitely important to remember both the everyday hydration as well as that during workouts!