May 17, 2018
Fully Hydrated
Susan Kundrat

Optimal hydration is the nutrition cornerstone for enhancing training and maximizing performance. As an athlete builds a “nutrition toolbox,” fluids should be the main tool, while pre-exercise nutrition, post-exercise nutrition, and overall sound eating help fine-tune the gears. Without proper hydration, it’s impossible for athletes to reach their potential, and they are at risk for heat-related problems like heat exhaustion.

Helping athletes understand how much fluid their bodies need and providing opportunities to hydrate before, during, and after workouts and competitions is critical. Setting up a hydration plan can make a major difference for athletes, especially at the end of a game or competition.

A person’s body is made up of about 60 percent fluids, so the first step in maximizing performance is maintaining a good balance of fluids in compared to fluids out. Although athletes don’t need to keep their weight stable to optimize performance, many studies have found that sports performance can be impaired if an athlete’s bodyweight changes by two percent or more during exercise.

For example, for a 150-pound athlete, losing three or more pounds during practice or a game could result in a drop in performance. Sweat rates in players can vary greatly, but it’s not difficult to lose a significant amount of fluid in a short amount of time, especially in hot, humid environments.

Potential consequences of dehydration include decreased endurance, decreased strength and power, a lesser ability to cool the body, less blood flow to the working muscles, lack of concentration, slowed recovery from workouts and competitions, increased risk of injury, and increased risk of heat cramping and other heat illnesses. Sweat losses greater than three percent of bodyweight have been noted to lead to heat illness, heat stroke, or worse: death from severe dehydration.

In some cases, fluid losses may exceed 10 liters a day, so knowing individual fluid losses for players is an important step in understanding specific needs. Typically, athletes lose between one-half to two liters per hour (or between two and eight cups per hour) of fluid during heavy training.

Athletes may not realize they are losing this much, as fluids are lost not only through sweat athletes can see, but also through evaporation, which is the main way a body dissipates heat and tries to cool itself. For example, evaporation can account for 80 percent or more of heat losses in warm, humid environments and over 95 percent in hot, dry environments.

It’s critical for athletes to replace not only fluids, but sodium as well. Typical sodium losses are estimated at 460 to 1,840 milligrams of sodium per liter of sweat lost, but athletes who are salty sweaters or high-volume sweaters can lose even more. These athletes often need to consume three to four times the recommended sodium compared to the general population.

Although some coaches and sports professionals continue to recommend bananas or high-potassium foods to ward off heat cramps, potassium losses are generally very small (160 to 390 milligrams of potassium per liter). That is only about three to eight percent of the recommended daily intake.

If athletes keep a few key points in mind before, during, and after training and competition, staying hydrated will come naturally. These keys include the following:

Stay well hydrated all day. It’s important for athletes to come to workouts and competitions hydrated — that’s why “pre-hydrating” is so important. Drinking fluids all day long can help ensure that an athlete is ready to practice. To do this, athletes can grab water, juice, milk, sports drinks, or other fluids first thing in the morning. Then, they should continue to drink fluids throughout the day, using water fountains, coolers, and cafeteria beverages as easy sources for drinking. Soup and some water-rich foods (like watermelon, grapes, and tomatoes) can also contribute to proper daily hydration.

Because athletes wake up dehydrated (their weight is often two to three pounds lower in the morning), athletes should to drink at least 32 ounces of fluid during the first two hours they are awake. This will help them rehydrate from the previous night.

Have a pre-game/training hydration plan. Athletes should aim for at least 16 ounces (two cups) of fluid two to three hours before practices and competitions. They should consume an additional eight ounces (one cup) 10 to 20 minutes prior to getting on the field.

Drink on a schedule during workouts and competitions. Perhaps one of the most important things sports professionals can do is set up a hydration schedule for athletes when they are training and competing. During activity, athletes should begin drinking early and at regular intervals to ensure they are getting enough fluids. Most athletes will not naturally take in enough fluid if left to their own devices, as thirst is not a good indicator of fluid needs. Athletes are distracted during workouts and competitions, and by the time they are thirsty, they are generally already dehydrated. When feasible, athletes should drink six to eight ounces of fluids (or as much as they can tolerate) every 15 to 20 minutes during hard exercise or competition to maximize hydration.

Sports drinks can help ward off dehydration and muscle cramps because they help replenish both fluid and electrolytes (sodium and potassium) lost through sweat. For workouts and competitions lasting an hour or longer, sports drinks containing six to eight percent carbohydrate can aid in rehydration and boost sodium intake. In addition, the sodium and flavoring in a sports drink can provide better taste over water, which may drive an athlete to drink more. Sports drinks with more than eight percent carbohydrate can be difficult to digest and slow down the rate at which carbohydrates reach the muscles to provide energy. In addition, they can cause gastrointestinal distress.

Monitor hydration status. All athletes can monitor their own hydration status from the time they wake up to the time they go to bed by being in tune with their urine status. Are they going to the bathroom every couple of hours? Do they have ample urine? Is it relatively clear? If the answers are all “yes,” then the athlete is probably well hydrated. The three keys to proper hydration are going often, going enough, and having clear urine.

There are also clear signs if severe dehydration and heat illness start to occur. They include: headache, nausea, loss of coordination, dizziness, fainting, profuse sweating, persistent muscle cramps, diarrhea, stomach or intestinal cramps, vomiting, and increased heart rate. In cases of exertional heat stroke, additional signs may include: increased body temperature, inability to focus or communicate, confusion, altered consciousness, or seizures.

Image by Werner100359.

Susan Kundrat, MS, RD, CSSD, is a Clinical Assistant Professor of Kinesiology and the Nutritional Sciences Program Director at the University of Wisconsin-Milwaukee. She's also the co-founder of RK Team Nutrition.

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