Ivan
Eats Squid
Thanks for the link, some good reading to be found there.
Avoiding dehydration
- Thread starter Ivan
- Start date
Sugars is what sports drinks are full of. They tend to be either glucose, fructose, sucrose or maltodextrin or combinations of these . Fructose has a fairly low GI (is absorbed slowly). Glucose has a high GI, Maltodextrin has the same GI as glucose as it is converted almost immediately by the body into glucose.
Some studies have shown mixing glucose or maltodextrin at a 2:1 ratio with fructose or sucrose can enable carbohydrates to consumed at a higher rate than just glucose by itself.
The main advantage of using Maltodextrin over glucose is that it is not as sweet.
longxc
Likes Bikes
More on sugar
Exceeding these values will actually result in the body flooding the intestine with water to aid in its digestion, which is why people end up with their guts feeling bad. This is also why manufacturers recommend consuming water when eating gels and bars, this also applies to bananas and any other sugary food you consume out on trail.
More on sugars:
2:1 works because frutose and glucose are absorbed by 2 different mechanisms so more sugar can be absorbed through the gut wall than just consuming one sugar alone.
Maltidextrin an glucose use the same mechanism and are absorbed quickly and can be used by the body straight away.
Glucose has a Gi of 100 and Matlidextrin 110 and because of this Maltidextrin produces a greater insulin release than glucose thus allowing more sugar(glycogen) to be transported in the blood.
Frutose is low Gi as the body can not use it straight away, it is broken down in the liver into sugars the body can use(glycogen).
Sucrose is frutose and glucose joined together so has to be broken down before being absorbed, which means it sits in the gut for longer.
Sugar is important as it also allows the body to absorb water via the same osmotic process that electrolites so a sugary drink is better than water alone, however, there is a fine balance as the sugar water mix must not exceed 8-9% sugar(glucose) or upto 15% using a maltidextrin/fructose 2:1 mix (as previously mentioned).
Exceeding these values will actually result in the body flooding the intestine with water to aid in its digestion, which is why people end up with their guts feeling bad. This is also why manufacturers recommend consuming water when eating gels and bars, this also applies to bananas and any other sugary food you consume out on trail.
More on sugars:
2:1 works because frutose and glucose are absorbed by 2 different mechanisms so more sugar can be absorbed through the gut wall than just consuming one sugar alone.
Maltidextrin an glucose use the same mechanism and are absorbed quickly and can be used by the body straight away.
Glucose has a Gi of 100 and Matlidextrin 110 and because of this Maltidextrin produces a greater insulin release than glucose thus allowing more sugar(glycogen) to be transported in the blood.
Frutose is low Gi as the body can not use it straight away, it is broken down in the liver into sugars the body can use(glycogen).
Sucrose is frutose and glucose joined together so has to be broken down before being absorbed, which means it sits in the gut for longer.
Bushranger
Likes Dirt
Actual Science doesn't support most of the myths people keep repeating
Some points:
http://www.sportsscientists.com/search/label/hyponatremia
So much of what people believe about hydration and electrolyes is simply a rehash of marketing campaings and slogans from the sports drink companies. There are some main players in that industry that practically get laughed off stage whenever they attempt to talk to real scientists at conferences. There simply isn't the science to back up their claims.
don't believe the hype people - you are not going to pass out and shrivel up if you get thirsty. Thirst is the best indicator and it isn't too late. Water is still fine to drink.
I've not used a sports drink for a long, long time since "seeing the light". I eat bananas and bars and drink water - and heaven forbid - I drink very diluted cordial for longer events.
The best prevention of cramping is preparation. The fittest won't cramp. If you have specifically prepared well for an event, you won't cramp - unless the event takes you beyond anything you've done in your preparation.
Weighing yourself before and after to work out "sweat rates" doesn't work. When you exercise you burn stored energy. That energy is stored with accompanying water. Let's say you lose 200 to 300 grams of stored carbohydrate. You will lose around a kilo of water stored with it. Yes you do need to drink, but not equal to your weight lost, and certainly don't use it as a firm guide to how much you should be drinking whilst exercising. I know it's a common practice, but it's just not as good as claimed and doesn't work the way people claim. Sure, use it as a guide, but just be aware that you are not only losing water and all the water you do lose wasn't just floating around bathing your cells.
"Replacing what the sweat takes out" is a perfect argument for drinking your own urine!
As for headaches - perhaps tension in the upper shoulders/neck or issues with helmet. I know that I get more of a head ache after 2 hours of riding than I do after 2 hours of running, yet I drink more when riding (simply because it's convenient).
Some points:
http://www.sportsscientists.com/search/label/hyponatremia
So much of what people believe about hydration and electrolyes is simply a rehash of marketing campaings and slogans from the sports drink companies. There are some main players in that industry that practically get laughed off stage whenever they attempt to talk to real scientists at conferences. There simply isn't the science to back up their claims.
don't believe the hype people - you are not going to pass out and shrivel up if you get thirsty. Thirst is the best indicator and it isn't too late. Water is still fine to drink.
I've not used a sports drink for a long, long time since "seeing the light". I eat bananas and bars and drink water - and heaven forbid - I drink very diluted cordial for longer events.
The best prevention of cramping is preparation. The fittest won't cramp. If you have specifically prepared well for an event, you won't cramp - unless the event takes you beyond anything you've done in your preparation.
Weighing yourself before and after to work out "sweat rates" doesn't work. When you exercise you burn stored energy. That energy is stored with accompanying water. Let's say you lose 200 to 300 grams of stored carbohydrate. You will lose around a kilo of water stored with it. Yes you do need to drink, but not equal to your weight lost, and certainly don't use it as a firm guide to how much you should be drinking whilst exercising. I know it's a common practice, but it's just not as good as claimed and doesn't work the way people claim. Sure, use it as a guide, but just be aware that you are not only losing water and all the water you do lose wasn't just floating around bathing your cells.
"Replacing what the sweat takes out" is a perfect argument for drinking your own urine!
As for headaches - perhaps tension in the upper shoulders/neck or issues with helmet. I know that I get more of a head ache after 2 hours of riding than I do after 2 hours of running, yet I drink more when riding (simply because it's convenient).
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cha_cha_
Likes Dirt
i can think of 1 reason: because magnesium is a laxative. o/d and you'll be pissing out your arsehole for the rest of the day and end up more dehydrated than you would have been otherwise...
DaGonz
Eats Squid
Be careful what you read on the internet
http://www.sportsscientists.com/2007/10/fluid-intake-debate-comments-from.html
clearly someone disagrees with them. I thought some of their conclusions and inferences, while clearly based on proper reasearch, were "interesting". Equally, I'm not sure about your glycogen v water loss argument.
Thing is, most people who train regularly, do so in a glycogen depleted state. There for the weight loss of a "sweat study" due to glycogen depletion is probably not that significant in reality, and will depend on your length of ride and intensity of ride. A short fast ride is unlikely to deplete glycogen stores at all! 4-5hr ride at a lower intensity and you're probably spent it very early. I'm not sure how eating on a ride affects things on top of this.
I guess my comment is, and my general opinion, be careful with the conclusions of others and papers (especially on the internet). Sometimes they're a very specific view point or left field completely.
I do know, for the a similar ride at similar effort, my weight loss after a 4-5hr ride has ranged from 2-300g/hr at 10degC to 600g/hr at 20degC to 1.2kg/hr at 30degC. There's a kg/hr of something lost there for a very similar ride between 10deg and 30deg. Assuming there is a base amount in there for Glycogen loss that would be similar across the board, some high school maths would suggest we're still talking 1L/hr for fluids.
Maybe it can only be used as a guide, but it'll still put the OP in the right ball park. The longer the training rides you use to get the data, I'd dare suggest the closer to the money it's going to get.
*shrug*
Cheers
Spoonie