Fitness Research

How to Grab the Right Drink and Properly Hydrate for Exercise

by Katie Mark

I used to force myself to hydrate during training, and I learned (the hard way) that hydration is crucial to an athlete’s optimal performance. As a tennis player, road cyclist, and recreational boxer, I’ve found a major difference in my ability to sustain endurance and intensity during workouts when properly hydrated. There’s nothing worse than quitting a marathon, getting dropped on a ride, or stopping practice because of dehydration. Why? Because you can prevent it. 

When I competitively played tennis in hot and humid Miami, dehydration constantly hit me during tournaments and practice, especially while practicing six hours during a summer day. In my Bike w Waterearly days of road cycling, I used to get dropped on rides because I was too busy in the back of the group struggling with the consequences of dehydration.

For years I had trouble staying hydrated, which always led to cramping and fatigue. I work out two hours per day when I’m in Boston (high intensity interval training and boxing). When I’m in Miami, I do three hours per day of tennis and/or road cycling. There’s no excuse for me not to properly hydrate, especially since I am an athlete and my career focus is sports nutrition.

Proper hydration controls body temperature, and electrolyte and fluid balance – so staying hydrated requires replacement of electrolytes—not just fluid. Dehydration results when fluids lost by the body through sweat or urine are not replaced, which leads to hypohydration. This leads to greater heat storage in the body, which lowers the ability to tolerate outside heat.

Dehydration tackles athletes even when they think they are hydrated. Yet, it’s preventable. Keep in mind, sports have different—and specific—hydration protocols. Below is general guidance on how to properly hydrate and choose the right fluid for sport performance. Even if you don’t road cycle 50 miles a day or run marathons, you can still soak up the details below and apply them to your workouts.

Detect Dehydration to Avoid the Consequences

The severity of impaired sport performance increases as the severity of dehydration increases. For dehydration to negatively affect sport performance, it takes as little as 2% loss in body weight (~1.4 kg, or 3 lb, in a 68 kg, or 150 lb, athlete). A loss larger than 2% leads to an increased risk for nausea, vomiting, and other GI problems. Dehydration during high-intensity or anaerobic activities can lead to 3-5% loss in body weight. Therefore, hydration during these activities is even more critical.

Symptoms of dehydration include:

  • Muscle cramps
  • Nausea and vomiting
  • Weakness and lightheadedness
  • Decreased urination
  • Dry mouth
  • Chills and lack of sweat

Consequences of dehydration include a reduction of:

  • Sweat rate
  • Blood volume, which thickens blood
  • Skin blood flow
  • Heat loss

And an increase in:

  • Body temperature
  • Rate of muscle glycogen use
  • Difficulty oxygenating the body

Hydration Strategies

Optimal performance starts with proper hydration before exercise. This is especially important for hot and humid environments and exercise lasting longer than 30-60 minutes. Pre-, during and post-exercise tactics are outlined below:

Days Before Competition:

  • Drink an extra cup or two of fluid. This can help make up for any potential shortcomings during pre-competition training.
  • Increase sodium intake. Extra sodium in water will help increase fluid uptake in the blood. This can be done by adding electrolytes to your drink or putting a little bit of salt on your food.
  • Calculate your sweat rate. This is important to determine the amount you should be drinking during training. Sweat rates, depending on intensity, duration, fitness level and environmental conditions, can range between 0.3-2.4 L/hr. Knowing the amount of fluid you need to drink will keep comfortable for optimal performance. Drinking too much during competition may lead to GI distress. Here’s how to calculate your sweat rate to personalize your fluid replacement plan:
  1. Right before training. Empty your bladder, and weigh yourself with little to no clothing.
  2. After training. Wipe off extra sweat on your body and weight yourself again.
  3. Calculate your new weight. Subtract the after exercise weight from the before exercise weight. The new weight reflects your weight change during training (change in weight = sweat loss – fluid intake). This is primarily water loss as opposed to fat loss.
  4. Convert to ounces. Multiply the new weight (in pounds) by 16.
  5. Calculate the total amount of fluid. Add the amount of fluid (ounces) you drank during training to what you calculated as your change in weight.
  6. Divide by number of hours you trained. If you trained for two hours then take the number from step 5 and divide it by 2. This gives you the amount of ounces of fluid you need to replace per hour, or sweat rate.
  7. Monitor this sweat loss. Your sweat rate is the amount of fluid you need to consume during training and competitions.

Calculate Sweat Rate Graphic

Pre-Exercise or Competition:

  • Check urine color. Clear to pale-yellow colored urine is good hydration status. This is a basic—yet helpful—indicator of hydration because urine color can be affected by riboflavin (B vitamin), vitamin C, and some medications.
  • Drink 2-4 hours before. Drink 5-10 ml/kg of body weight, or 2-4 ml/lb before exercise.

During Exercise or Competition:

  • Prepare your water bottle. Options for fluids are discussed below so make sure your bottle is ready.
  • Make your fluid cold. Cold beverages can help reduce your body temperature, which helps in hot and humid conditions.
  • Follow your sweat rate. Calculate this (described above) during your training sessions.
  • Grab your water bottle before you get thirsty. Thirst indicates that you need to drink and not that you are dehydrated.
  • Drink the suggested amount. If you don’t know your sweat rate, drink 6-12 oz (150-350 mL) every 15-20 minutes. Keep in mind, the amount will vary depending on the:
    1. Intensity of the sport
    2. Environmental conditions
    3. Amount of fluid you can handle
  • Listen to your body. The body does an exceptional job maintaining fluid balance. That’s why you drink when you’re thirsty. Follow your body’s message to drink.
  • Pinch your skin. This is not a 100% reliable method, but it still helps to detect hydration. Pinch the skin on the back of your hand using your pointer finger and thumb. Hold for a few seconds. If your skin takes a bit of time to return to normal position then you need to drink more.
  • Check urine color. Make sure urine is a pale color. If it looks dark like apple juice then drink up.
  • Sense dry mouth. A dry mouth is one of the first signs of dehydration. Grab the water bottle!

Post-Exercise or Competition:

  • Replace your fluid deficit. You will continue to lose fluid even after exercise. Over two to six hours, replace about 150% of the fluid you lost because a larger volume of fluid is needed for the continued sweat losses and urine losses after exercise. Generally, replace 16-24 ounces of fluid for every pound lost. If you have a hard time doing this, an easy tactic/reminder is to drink fluids with your recovery meals.
  • Do not restrict sodium. Athletes usually have large sodium losses during exercise so sodium intake should not be restricted.
  • Plan for next practice or competition. If you felt dehydrated, go back to the drawing board. Revaluate the amount of fluid you need.

Note on over-hydration: there is no benefit to drinking more than what you need. Over-hydration is especially seen in recreational athletes because they may believe that they need to drink more when their exercise intensity and sweat rate are not that as high as competitive athletes. Drinking more than needed could dilute important electrolytes necessary for cell communication, nerve pulses, and muscle contraction. Drinking more can also increase urination and leave you feeling bloated.

Water’s Best Friend: Electrolytes

Electrolytes are critical for cell communication, nerve impulses and muscle contraction. Sodium, potassium, and magnesium are important electrolytes. For instance, the body needs to maintain 135-145 mmol/l of sodium in the blood for optimal body function. This is why drinking too much water should be avoided because dilution can lead to sodium depletion, or hyponatremia. Urination increases with the more you drink, and this causes additional sodium excretion. Even if this is mild, it can lead to fatigue, headaches and confusion.

Exercise at a high intensity—at least 70% of your max heart rate—or for greater than 90 minutes calls for electrolyte replacement. Read on for options on how to replace electrolytes.

How to Pick the Right Fluid

Plain Water

Plain water is the best choice in majority of exercise conditions. Sports drinks provide carbohydrate and electrolytes, but are only intended for those exercising more than 90 minutes and/or at a high intensity. In contrast, water is ideal for those who are just doing short duration and/or low intensity (i.e., the elliptical) exercise. The carbohydrate (simple sugar) only adds unnecessary calories.

Sports Drinks

Research suggests that sports drinks like Gatorade and Powerade can help sport performance. Sports drinks contain carbohydrates (6-8% of solution), water, and electrolytes. Avoid sports drinks with high fructose corn syrup or sugar alcohols because these ingredients can lead to upset stomach.

Consider your sport and intensity to determine if the extra carbohydrates from sports drinks is necessary because it’s added sugar. If you are worried about added calories, but you want the flavor of a sports drink, you can dilute the sports drink with water. If you use a sports drink, avoid drinking one that you’ve never used before on the day of competition. Make sure the drink is tolerable to your stomach during a few training sessions.

Electrolyte Sources

Some alternatives for electrolyte sources are coconut water, water-enhancing electrolyte tablets (i.e., Nuun), or fruit-infused water. Coconut water comes from the fluid inside the coconut—which is different from coconut milk—and it’s a natural way to replenish electrolytes, especially potassium and magnesium. There are sweetened and unsweetened versions—so no sugar, artificial sweeteners, or dyes that sports drinks contain. Water-enhancing electrolytes will give you the electrolytes you need without the sugar. Simply adding fruit or citrus (i.e., berries and lemon slices) can also do the trick.

A large sweat sodium loss calls for replacing sodium during exercise. Do this by using electrolyte tablets or adding salt to your beverage. Sodium should be replaced if:Electrolytes Graphic

  • Athlete has a high sweat rate (>1.2 L/hr)
  • “Salty sweat” is present. Signs to look for include sweat stings the eyes, sweat tastes salty and white streaks on your face, skin or clothes
  • Exercise is longer than 2 hours

Note on the electrolytes that not all products have the same amount of electrolytes. A tablet of Nuun may have more magnesium than the amount found in coconut water. You may need to use multiple electrolyte tablets depending on the intensity of your exercise.

You need to compare products. Look at serving size and the electrolytes you’re getting for that serving size. For instance, I know my diet lacks magnesium, and I will not drink a sports drink (even if I’m riding 50 or 100 miles). I searched for electrolyte sources that have the highest amount of magnesium per serving. And I found electrolyte tablets were the best option for my exercise conditions and my personal preferences and needs. I add more tablets to my water bottle depending on the intensity and duration of training.

Bottom line: If you’re a gym rat exercising at low or moderate intensity or for less than 90 minutes then skip the sports drink. For those exercising at a higher intensity and/or for at least 90 minutes, consider if the added calories from sugar are unnecessary based on your training session or competition. Skipping the sports drink means you need to consider alternatives for electrolyte sources so you can sustain optimal performance.

Katie Mark is a second year MS Nutrition Communication and Master of Public Health candidate. She carries tubes of electrolyte tablets in her cycling jersey pocket and a dollar for Cuban coffee.

The Friedman Sprout is a monthly student run newspaper that aims to serve the student population at the Friedman School of Nutrition Science and Policy, prospective students, and alumni. Our mission is to report on newsworthy information that affects the Friedman community including nutrition research, food policy, internship and volunteer opportunities, as well as school events. Our editorial slant is that of sustainability in food and nutrition.

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