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dehydration and heat exhaustion

 
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PostPosted: Mon Oct 24, 2005 12:12 am GMT +0000    Post subject: dehydration and heat exhaustion Reply with quote

BikeDoc,
several weeks ago I suffered dehydration and heat exhaustion while racing in 107 degree weather. I went to the ER for iv fluids and bloodwork. i was given two bags of fluids and released two hours later. I am still feeling a little fatigued on the mtb towards the end of my races, and I then feel very nauseated and have a headache after my race. Am I verging on dehydration at these races? Or do I still have some effects from the H.E./dehydration? What could I do prior to the race and during the race to hopefully prevent from feeling totally like crap afterwards? Thanks for your time!
Josh
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The Bike Doc
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Joined: 08 May 2003
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Location: Corpus Christi and Warda, Texas

PostPosted: Mon Oct 24, 2005 5:50 am GMT +0000    Post subject: Reply with quote

Guest:

Significant dehydration actually takes several weeks to recover fully from. Though the fluid within your blood vessels, the intravascular volume, can be rapidly replace with IV or oral fluids after an episode of severe dehydration, the intracellur fluids can take two or more weeks to fully be restored to normal balance. Therefore, subsequent dehydration is more likely to occur. Your symptoms of nausea, fatigue and headache are signs of dehydration.

What should you do right now? First of all take it easy for the next 2-3 three weeks, allow your body to fully recover. Drink plenty of fluids, do not be afraid of the salt shaker and eat/drink fluids that are high in potassium such as dairy products, citrus fruits and juices, tomatoes and tomato juice. Second, when you work out, replace what you are loosing. When it is cool and you are working out you can loose up to 1 quart per hour of sweat. When it is hot you can loose up to 2 quarts an hour of sweat. You need to be drinking a fluid that will replace the sodium, chloride and potassium in your sweat. Fortunately, there are several commercially available sport drinks that help you do just that. I am a big fan of Gatorade because it is inexpensive, and is readily available in many palatable flavors. Use a hydration system like a CamelBak which makes it much easier for you to drink while you are on the ride or run. Check your weight (in the buff is best) prework out or race and again immediately afterwards. For every pound you are down post workout or race, you were deficient in your fluid replacement by 16 ounces. So if you drank 1 quart (32 ounces) of fluid while racing and you are down 2 pounds at the end, you need to increase your fluid intake 32 ounces more on top of the 32 ounces you consumed while racing.

Disclaimer: I have no financial connections with Gatorade or CamelBak. I recommend them because they work and are readily available.

Thanks,
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Paul K. Nolan, MD
AKA: The Bike Doc
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PostPosted: Mon Oct 24, 2005 10:33 pm GMT +0000    Post subject: Reply with quote

thanks for the advice. i will definitely be purchasing a scale to monitor my fluid intake. never thought about it that way. thanks again.
josh
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Gumby
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PostPosted: Tue Jan 31, 2006 7:56 am GMT +0000    Post subject: Fluid Calculator Reply with quote

Try using this fluid calculator... http://www.eload.net/Calculator/FluidCalc.htm
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littlemike
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PostPosted: Wed Mar 01, 2006 7:34 am GMT +0000    Post subject: Reply with quote

Doc,

I have done simple measurements and found that I can actually lose up to 3.5 liters per hour in high heat, high intensity exercise. Yeah, I know everyone says 2 liters, but that's way less than I sweat in the heat. I sweat more than anyone I know. Fluid loss in the 3.5 liters per hour range has only happened for me when running, not while biking.

As for the calculator, I don't bring out the computer. A liter of water is about two pounds, and I weigh before and after. Divide the weight loss (in pounds) by two and add the number of liters you drank -- seems like easy math to me.

My question is also about one of those things "everyone says" which is that your body can only utilize about 1 liter per hour of water during exercise. Based purely on empirical evidence, it feels like my number is closer to a liter and a half. Any thoughts/comments?

FWIW, I am a kinda big and somewhat muscular guy (over 200 pounds).
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The Bike Doc
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Joined: 08 May 2003
Posts: 1370
Location: Corpus Christi and Warda, Texas

PostPosted: Wed Mar 01, 2006 10:58 am GMT +0000    Post subject: Reply with quote

littlemike:

You should try to target your intake for what you loose. If your measurements are 3.5 litters and hour for running in the heat, then that is what you should tarket your hourly intake. Adjust your intake accordingly for your weight measurements when bicycling. Try drinking your sport drink at 1/2 to 3/4 strength to see if you can tolerate the higher volume per hour. The poor tolerance of full strength sport drinks which typically have 6 to 8% carbohydrates (60-80 grams per liter) is often due to exceeding the 100 gram of carbohydrate an hour that the gut can digest. By going to half to 3/4 strength you may improve the tolerance of the higher volume by decreasing the carbohydrate amount.

Thanks,
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Paul K. Nolan, MD
AKA: The Bike Doc
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