One of the main differences between living in the Northeast and the South is the humidity. Not to sound like a total dad but it's not the heat.... it's the humidity that gets you. It would get up to 90 degrees in Massachusetts, but it was a comfortable 90. You could still go outside without it being completely miserable. Down in Virginia you better be done with outside activities by 10am otherwise you're waiting until past dinnertime to go back out. I tried cutting the grass last week during the heat wave and I was soaked by the time I was done. Shirt was just saturated with sweat; I could see the salt rings around the chest area from where I was sweating so much. I downed about four bottles of water post cutting the grass. This got me thinking.... how much water should have I drank? So, like any good sports scientist I researched it.
This is what I found
It varies. I know right.... sound science right there. I know what you're thinking way to put that Master's degree at work Tom! hold on let me explain. Adult males the acceptable intake (AI) is 3.7 L or in back-to-back World War Champs talk that's 125oz or in Gatorade bottle measurements that's 6.25 bottles or nearly a gallon. See a southern dude can do math! For woman the acceptable limit that's 2.7L. I did the math once you can do for 2.7L. I'll give you a hint. typical Gatorade bottles are 20z.
For kids that weight 88 pounds that are practicing outside the recommended intake is 5oz every 20 minutes. You can substitute flavored, salted beverage (more on this later) instead. For a kid that weights 132 pounds its 9oz per 20 minutes. These are recommended dosages. It might be more depending on environment (humidity versus no humidity), altitude, clothing (dark colors versus lighter colors), equipment (pads in football versus shorts and a T-Shirt) and weight (larger person's sweat more than a smaller person). Another fun fact is that a loss of 2% of body weight during practice or game situation detracts from performance. Drinking water turns into a delicate balance between hydration and overhydration or in scientific terms preventing hypohydration.
Hypohydration is the dilution of electrolytes within the body. Electrolytes perform several functions within the body-for exercise purposes electrolytes are essential for muscle contraction and nerve conduction. Keep in mind that muscles are attached to the nervous system and that one nerve innervates several muscle fibers at once. If the nerve that attaches to the thigh muscle is down or not working at full capacity does bode well for running. Electrolytes are broken down into sodium chloride (salt), potassium, magnesium and calcium. Salt helps your body retain water and calcium is needed for muscle contraction (look into the Sliding filament theory for the role of calcium in muscle contraction). Most of your sports drinks contain those elements. One thing to keep in mind when selecting a sports drink is the amount of carbs within those drinks. Anything within 6%-8% carb ratio and your good (check nutrition facts label for amount of carbs and serving size). Above 8% delays gastric emptying or how fast your body processes those carbs. Slow emptying and it could possibly cause GI issues and stomach cramping. Another aspect of carbs to look for is the type. You want multiple types of carbs to rehydrate. A single source of carb ingested blocks other types of carbs from being processed. Think a traffic jam in the highway. The best way to drink a sports drink is chilled but not cold as to aid in ingestion. If you're not a fan of sports drinks, then adding salt to water is acceptable or adding additional salt to foods will do the trick.
Back to the original question. How much water or fluid should I drink? Ideally, you would calculate your sweat rate which involves weighing yourself before and after practice. Take out the fluid consumed and fluid loss through urine and that is your sweat rate. Each pound lost is equal to 16oz of water consumed. If you plan to exercise again later that day, then a more aggressive approach is needed which calls for 1.5 L per pound lost.
Thirst is a poor indicator of drinking water. Once you are thirsty then you are already dehydrated. Water should be consumed throughout the day to combat the heat. One of the simpler ways to measure hydration levels is your urine. Clear urine means hydration, darker more yellow urine indicates dehydration. So, in the words of my people, "Drink Water!"
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