Training

A Quick Guide to Workout Hydration

It's not just about what fluids you're drinking, but when. Learn the proper way to hydrate and get the most out of your workouts.

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What—and when—you drink matters. The type of fluids you take in should be chosen according to your sport and the duration of the workout, as well as the weather and particular needs of your body. Often, water or an electrolyte drink with low carb content is sufficient. Sugar-bomb energy drinks and isotonic beverages (i.e., high in carbs), on the other hand, should be limited. When you’re well hydrated going into a workout or race, you’re off to a great start to perform at your best. But as you go harder, your blood and muscles use more water and you lose it through sweat, so your hydration level drops off. To combat this, drink up during and after your workout, too, so that your body can get the water and nutrients it needs to keep going strong.

Sweat It Out

Sweat removes not only water but also electrolytes such as sodium, chlorine, potassium, and magnesium and in smaller amounts, calcium, iron, copper, bicarbonates, phosphates, sulfates, amino acids, and some vitamins. Of course, the rate of excretion of sweat is individually variable. Sometimes athletes and coaches think heavy sweating is undesirable, but in fact, in a well-trained athlete, it’s a sign not of weakness but of an efficiently functioning thermoregulatory system. If physical exercise is performed in a hot or humid environment, heat dissipation is very difficult. The release of 1 liter of sweat causes the loss of 2.9 grams of sodium chloride, so athletes training intensely lose about 15 grams of salt with every 5 liters of sweat. (Some recommendations for daily salt intake among the general population are therefore lower than what’s best for an athlete.)

Take It Back In

The sensation of thirst prompts the body to supplement about half the volume of lost fluids. However, thirst appears only after you’ve lost 1–2 percent of your fluids, which seems small but can significantly reduce athletic performance. Using thirst as an indicator of fluid demand, then, can be misleading. And just as the feeling of thirst doesn’t reflect the exact moment of fluid loss (it’s too late, in fact), drinking enough to quench your thirst doesn’t mean you’ve fully hydrated your body.

Follow the guidelines in this table to be sure your body is well hydrated for your effort and recovery. Note that after a workout, you should drink more than the amount of body weight lost. Then, below, learn more about hitting that “just right” balance of carbs, water, and electrolytes from your sports drink.

Workout hydration plan from pre- to post-workout
Weigh yourself before and after your workout to get the most accurate measure of fluids lost. 500 mL = 2 cups. Your weight in kilograms = [your weight in lbs.] x 0.453

Get the Right Mix of Carbs and Electrolytes

Your body operates under undeniable laws of chemistry. Just because you pounded a pair of energy gels before a workout, it doesn’t mean your intervals will be any faster than last time. It takes the right balance of nutrients and water to actually get into your system and deliver the ingredients your cells need to power you through a workout. So the composition of your food and drink will have a big influence on how your body performs.

Sports and energy drinks contain different proportions of electrolytes and carbohydrates compared to the blood’s composition of the same compounds—think sugar, salt, and other minerals. How the drink and your blood compare will affect the body’s hydration and nutrient balance: Some will enhance the hydration process while others will actually draw water out of your bloodstream, hindering muscular performance.

A drink that has a lower concentration of compounds than the concentration in the body is called hypotonic. A drink with higher concentrations is hypertonic. And when the beverage and blood have the same concentrations, the drink is isotonic. Each of these are appropriate for an athlete, but the quantity and time of consumption matters.

Depending on their ingredients, sports drinks could fall into any of these three categories. Some are labeled, but many are not. Most of the more common drinks fall into the isotonic category, but check the nutrition label to know how many carbs are in a serving.

Hypotonic Drinks Deliver Water with a Hint of Other Essentials

Hypotonic liquids encourage the fastest transfer of water into the body. These drinks include water and other diluted drinks that contain lower concentrations of minerals and other ingredients than the concentration in the body. Equally important, these liquids contain only a small amount of carbohydrates (less than 4 grams per 100 milliliters). Gatorade’s G2 Low Sugar is one example.

Because these drinks are quickly absorbed through the gastrointestinal tract, if consumed in high quantities they can dilute the plasma and prompt more frequent urination, thereby decreasing overall hydration levels. Drinking plain water during a long, intense effort is not enough to properly hydrate and fuel the body, as some of the body’s electrolytes can move into the gastrointestinal tract, causing hyponatremia. On hot days, sweat losses are high, and while the body needs more water, it’s important to add in electrolytes, too. . . which leads us to isotonic drinks.

Isotonic Drinks Are Ideal for Maintaining Energy and Nutrients During Exercise

Isotonics have a nearly identical composition as our body fluids. The carbohydrate content is in the range of 4–8 grams per 100 milliliters, and the minerals are close to the composition of sweat. Isotonic drinks provide electrolytes and glucose, which lets you save or supplement muscle glycogen. Therefore, these types of beverages are recommended during training lasting over 60 minutes or immediately afterward, to compensate for such losses. They are especially important if your workout involves a lot of high-intensity effort, when glycogen and electrolytes are lost quickly. Finally, isotonic drinks should not be consumed as a substitute for other drinks during the day, such as tea or juices. Keep them just for your workout and perhaps recovery time. Skratch Labs powders mixed according to the instructions or Gatorade Original fall into this category.

Hypertonic Drinks Might Taste Good (They’re Sweet) but Cause Problems

Hypertonic liquids include fruit juices and other highly sweetened beverages (think Coke). The concentration of minerals and vitamins is higher than in body fluids, and the carbohydrate content exceeds 8 grams per 100 milliliters. They are helpful because they provide many nutrients that were lost during exercise, but they draw water from the body and into the intestines, and they reduce the rate of rehydration. This means that your cells, which need water, have in fact lost some hydration.

Hypertonic drinks taken during intense physical exercise may cause gastrointestinal distress, nausea, and diarrhea. These types of drinks cause a rapid increase in blood sugar levels, leading to hyperglycemia. The pancreas then jump into action, releasing insulin and reducing blood-sugar levels, almost causing a hypoglycemic condition. This is something to avoid.


 

Adapted from Sports Nutrition Handbook by Justyna Mizera, MA, and Krzysztof Mizera, PhD, with permission of VeloPress.