The marathoner's most important nutrient is water. Adequate fluid intake before, during & after runs helps the body to regulate temperature, prevent heat exhaustion & helps to transport nutrients & energy to the muscle tissue.
It is not uncommon for runners to lose 2-5 pounds of water weight after long runs, especially in Austin's hot & humid climate. Dehydration will cause shivers, nausea & significantly affect your performance potential. It is very important to follow the guidelines below to ensure adequate fluid intake.
General Hydration Guidelines Before - You should be drinking fluids continuously throughout the day. A minimum 10, 8 oz. glasses of water per day should be consumed. Thirst is not an accurate indicator of hydration level, you should drink before you find yourself thirsty. As a part of your pre-run meal, you should consume 3-4 cups of fluid. Though water is the most important source of fluid intake other appropriate beverage choices include fruit & vegetable juices, skim milk & electrolyte replacement sports drinks. Prior to your races you should strive to drink 2 cups of fluid per hour up to an hour before run time. This will help to reduce the risk for dehydration during the race.
During - For run under 90 minutes, cool water is the most appropriate replacement fluid. Water is preferred because it empties out of the stomach almost instantly & begins its job of transporting nutrients & energy throughout the body. You should try to consume ½ to 1 cup of water every 15 minutes. After 90 minutes the body will begin to run out of glycogen stores & will need quick sugar sources to spare the dreaded effect of "hitting the wall." The best beverages for this are sports beverages like Powerade & Gatorade, a watered down (½ original concentration) fruit juice or a de-carbonated soft drink. If choosing a drink with a high sugar content, it is best to use this beverage in practice & long run sessions to ensure it does not aversely effect the stomach & cause nausea.
After - Immediately after runs is the key time to replace fluids & glycogen stores. For every pound of body weight lost, you should drink 2 cups of fluid. Research has shown that the body has a 15 minute window of time in which it "superstores" replacement fluids & helps prevent muscle tissue breakdown. It will take 2-3 times longer to replace these fluids 30 minutes to an hour after exercise. It is important to recognize this window & be prepared to get 50 grams of liquid carbohydrate into your body as soon after running as possible.
There are some basic, self-regulating habits that you should begin to add into your daily regimen.
1. Check yourself: You can quickly assess your hydration level by checking the color of your urine. If the color is lighter you are better hydrated.
2. Joe to go: Coffee has, for years, been much maligned as a diuretic, however, new research has revealed that marathoners have much to gain from the old black lively. Some laboratory tests have shown that coffee has the ability to enhance endurance up to 15%. By lowering the runner's perceived exertion, caffeine causes your nerves to more effectively drive your muscles. In other words, it feels like you are not running as hard. There are some health concerns that need to be considered with regards to caffeine, but most are not a serious concern if the intake is limited to 2 cups per day. Those with high blood pressure, women who are pregnant, those who have osteoporosis, heartburn or ulcers need to limit their consumption. For more information check out this link: http://www.runnersworld.com/cda/article/0,5033,s6-53-0-0-2199,00.html.
3. Test your fluid loss: It is easy to determine how much the environmental conditions affect your fluid loss. Without any clothes on, weigh yourself before & after training runs of different durations, intensities & heat & humidity conditions. If 30 minutes of running under specific set of environmental conditions results in a 1 pound weight loss, you can figure what will happen after an hour or more under similar conditions. Each individual will have a different rate of perspiration & therefore a different dehydration point. It is very important to determine how much water you need personally.