In the fifth nutrition article of our year-long Build A Better Athlete series, we focus on what might be the most important topic as we start to get into warmer weather -- hydration. University of Michigan director of sports nutrition Caroline Mandel, a registered dietitian, says the goals of hydration are to delay fatigue, maintain mental focus, regulate body temperature (especially in hot environments), satisfy thirst and to improve the ability to recover from training and competition.
Yet, for how important staying hydrated is, Mandel says that research shows that most athletes typically only drink half of what they need.
ESPNHS: What's the ideal amount of fluid an adolescent athlete should consume during training and competition?
Mandel: Fluid needs depend on the intensity and duration of the activity as well as the environmental conditions and the types of clothing/equipment worn. In general, high school athletes require 10 to 12 cups of fluid (water, fruit juice, milk, etc.) per day consumed at meals and snacks so they start exercise in a hydrated state. During exercise, athletes require 4 to 8 ounces of fluid every 15 to 20 minutes. Fluid intake can then be adjusted based on weight change and monitoring urine color and volume before and after exercise. An athlete is hydrated if he/she produces urine in a sufficient volume and that is light in color. If less than two hours prior to training or competition the athlete does not produce urine or if the urine is dark in color, they are not hydrated and should slowly drink more fluids. I recommend that athletes weigh themselves before and after training and competition at least two times per season to gauge their specific fluid needs. The goal is to start exercise in a hydrated state and drink adequately during exercise to prevent weight loss.
What types of fluids should you avoid while training? Which do you recommend?
Mandel: According to the American Academy of Pediatrics, energy drinks have no place in the diets of children and adolescents. The best fluid choices for young athletes are water and sports drinks. Water is a great hydrator and is fine for exercise that lasts less than an hour and exercise on cool days. For intense exercise that lasts longer than an hour and for exercise on hot and humid days, a sports drink that contains carbohydrate (no more than 14 grams per 8 fluid oz.) and electrolytes like sodium and potassium has been shown to improve voluntary hydration and prevent dehydration better than water alone. Milk, chocolate milk and fruit juices should be avoided during training or competition because their carbohydrate content is too high and causes an upset stomach. It also slows the rate of gastric emptying and fluid absorption.
ESPNHS: Are there any foods that can help keep you hydrated and can also provide essential nutrients?
Mandel: We consume around 80 percent of our daily fluid from beverages and around 20 percent from foods. Hydrating foods include fruits, vegetables and yogurt and even cooked beans, rice, pastas and cereals since they are cooked in water or other liquids. During exercise, blood is shunted away from the GI track to working muscles. Most solid foods are not well tolerated during intense exercise, so athletes should practice with hydrating foods during practices to find what works best for them.
ESPNHS: What are the warning signs of dehydration?
Mandel: Heat illness occurs in three stages:
• Heat cramps, which are categorized by excess sweating, fatigue, thirst and cramps, usually in the stomach, arms or legs. This condition is common in very hot weather or with moderate to heavy physical activity. You can usually treat heat cramps by drinking water or fluids containing electrolytes (such as sports drinks), resting and getting to a cool spot, like a shaded or air-conditioned area.
• Heat exhaustion occurs when you don't act on the signs and symptoms of heat cramps and your condition worsens. Signs and symptoms of heat exhaustion include a headache, dizziness or lightheadedness, nausea, skin that feels cool and moist, and muscle cramps. Often with heat exhaustion, you can treat the condition yourself by following the same measures used to treat heat cramps, such as drinking cool beverages, getting into an air-conditioned area or taking a cool shower. If symptoms persist, seek medical attention immediately.
• Heat stroke. A body temperature of 104 degrees Fahrenheit or higher is the main sign of heatstroke. In heat stroke brought on by hot weather, your skin will feel hot and dry to the touch. However, in heatstroke brought on by strenuous exercise, your skin may feel moist. You may feel sick to your stomach or vomit. Your skin may turn red as your body temperature increases. Your breathing may become rapid and shallow. Your pulse may significantly increase because heat stress places a tremendous burden on your heart to help cool your body. You may experience a throbbing headache. You may have seizures, hallucinate, or have difficulty speaking or understanding what others are saying. You may pass out or fall into a state of deep unconsciousness (coma). Your muscles may feel tender or cramped in the early stages of heatstroke, but may later go rigid or limp.
ESPNHS: Is there ever such a thing as being over-hydrated while training?
Mandel: Hyponatremia is a potentially deadly disorder that results from over-consumption of fluids where the sodium content of the blood is diluted to dangerous levels. It is extremely rare in high athletes but has been seen in endurance events that last longer than 4 hours, such as marathons and triathlons, when participants consume large amounts of water over several hours without adequate sodium intake. Affected individuals may experience disorientation, altered mental status, headache, lethargy and seizures. Suspected hyponatremia is a medical emergency and is diagnosed by testing blood sodium levels. Treatment is through administering intravenous fluids containing sodium.